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Food & Water Stories

Solutions to Address Water Scarcity in the U.S.

More than half the nation has regularly experienced droughts since 2000.

February 13, 2020 | Last updated March 31, 2022

• Agriculture
• Groundwater

Freshwater is essential for all life on Earth. Yet, only 2.5 percent of Earth’s vast water resources are fresh, and less than 1 percent of that is easily accessible for people and nature. This limited resource must be man­aged wisely, particularly in the face of climate change, growing populations, and increasing demands from multiple sectors. To meet this challenge, The Nature Conservancy works to reduce demands for water among the biggest users, improve the flexibility of water governance and management, and advance financial incentives and tools that enable users—like irrigation districts and cities—to transfer water, which will provide water security for the environment as well.

The benefits of healthy, sustainable water resources:

• Supply clean drinking water.
• Grow our food and are used to raise livestock.
• Produce the goods we use.
• Drive economic and social benefits.
• Sustain healthy rivers, lakes, springs and associated habitats that support diverse wildlife.
• Provide for recreation and tourism. And can be harnessed to produce clean hydroelectric power.

Freshwater Challenges in the U.S.

More than half the continental U.S. has regularly experienced drought conditions over the past two decades.

Because of climate change, experts predict precipitation will likely decline 20 to 25 percent by 2100 in much of the West.

Since 2000, the Colorado River Basin— which supplies water to 40 million people—has experienced historic drought conditions.

Water scarcity isn’t limited to Western states. In 2014, 40 of 50 state water managers expected shortages in some portion of their states over the next 10 years.

Our Freshwater Conservation Strategies

Our approach to protecting freshwater involves a combination of water funds, promoting incentives, collaborating with water users, and advancing sound water policies and funding.

We invest in water markets and water transactions with cities, irrigation districts and other water users to demonstrate flexible water use and transfers that include water for environmental needs.

We promote and incentivize innovative approaches that reduce demands and improve infrastructure to move and store water more efficiently.

We collaborate with farmers, ranchers and corporations to reduce water use at all levels in the agricultural supply chain.

We advance local, state and federal policies that enable water managers to effectively meet the needs of people and nature. We also work to secure state and federal funding that supports sustainable water practices and agreements.

We demonstrate our work through more than 70 projects across the nation. Currently, approximately 90 percent of these are located in the western U.S., including TNC’s Colorado River Program . The remaining projects are located east of the Mississippi River in regions that are beginning to experience water scarcity more frequently and intensely.

Finding Solutions to Water Scarcity in  Agriculture

Agriculture accounts for 70 percent of the planet’s freshwater withdrawals annually. This presents a tremendous opportunity to work with farmers and agriculture supply chain companies to ensure the sustainability of the food we eat and the water upon which it relies. In the U.S., irrigation accounts for more than 80 percent of total water consumptive use and up to 94 percent of con­sumption in regions most prone to water scarcity. Below are two case studies that demonstrate how TNC is working with farmers to help reduce water use. 

Case Study 1: Saving Water, Securing the Nation's Food

Agricultural irrigation accounts for 90 percent of the consumptive water use in Nebraska. There are 7 million acres of irrigated land in the Platte River Valley alone. Here, The Nature Conservancy recognized a chance to conserve water at a large scale and reached out to land­owners interested in new water-saving irrigation technologies. These efforts evolved into a collaboration with Coca-Cola, John Deere, McDonalds and the World Wildlife Fund to launch the Western Nebraska Irrigation Project in 2014.

TNC connected 11 farmers who collectively manage 8,000 acres with tech­nology providers to install soil moisture probes, pivot telemetry and weather stations to help reduce water use. The farmers were then provided support that enabled them to micromanage irrigation and reduce the amount of water pumped from the underlying aquifer by 20 percent. The project site included quality historic water-use records, which enabled researchers to measure change. Over a three-year period, the farmers saved over a billion gallons of water—enough to fill more than 110,000 semi tanker trucks.

Less groundwater pumping not only helps secure the resiliency of the underlying aquifer, it also saves the farmers time and money. One participating farmer reported “the probes paid for themselves easily each year,” while another noted the technology saved time because he didn’t have to drive to his field to check conditions.

The project’s success spurred interest in Central Nebraska, where TNC teamed with Nestlé Purina and Cargill to launch a  second irrigation project  in 2018. Here, researchers estimated that 20 participating farmers saved at least 120 million gallons of water in the first year. In March 2020, the project reached its enrollment target of 50 farmers, with many reporting that the technology and training has helped them save time and money because of less pumping.

Case Study 2: Price River, Utah—Water Wise Solutions for People and Nature

TNC is working with a wide range of partners in the Price River watershed to enhance water use in ways that benefit agricultural operations while improving flows. Since 2016, TNC has worked with farmers to test water-saving methods that could inform drought contin­gency plans in the Colorado River’s Upper Basin. Working with farmers and other partners, TNC is exploring temporary, voluntary and compensated measures—like water banking—to help reduce the risk of water shortages for all.

Quote : Kevin Cotner

My family has farmed here for three generations. Working with TNC gives me a chance to help improve my agricultural operations and the wildlife habitat here that I care so much about.

Kevin Cotner

Agriculture uses about 80 percent of the water in the Colorado River Basin, with large flows moving from rivers to fields through irrigation ditches, canals and other structures. The infrastructure that moves irrigation water is often old, leaky and inefficient. To address this challenge, TNC works with water users to improve the delivery and timing of irrigation water through updated canal lining and piping. On the Price River, TNC has negotiated an innovative water-management agreement with a canal company to enhance flows and agriculture. The agreement upgrades the company’s infrastructure and benefits six rare fish species in the lower Price. Water that isn’t delivered to shareholders is stored in an adjacent reservoir for strategic releases in late summer when levels in the river typically drop. While these measures increase water for the environment, they can also benefit farm productivity and help enhance the security of water for agriculture.

Take Action

You can advance TNC’s efforts to secure clean fresh water around the world. Make a difference today!

More Water Stories

Groundwater: Our Most Valuable Hidden Resource

Though it's out of sight, groundwater is critical for biodiversity, growing food and other needs for a healthy planet. See what The Nature Conservancy is doing to safeguard this hidden resource.

Demand Management in the Colorado River Basin

State Drought Contingency Plans in the Colorado River Basin are using demand management to reduce water use at critical times and compensate users for saving water.

Western Nebraska Irrigation Project

A three-year pilot project with Nebraska farmers has yielded big water savings on the Platte River.

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Peer-reviewed

Research Article

Water resource management: IWRM strategies for improved water management. A systematic review of case studies of East, West and Southern Africa

Roles Conceptualization, Formal analysis, Investigation, Methodology, Writing – original draft, Writing – review & editing

* E-mail: [email protected]

Affiliations Soil, Crop, and Climate Sciences, University of the Free State, Bloemfontein, South Africa, School of Engineering, University of KwaZulu-Natal, Pietermaritzburg, South Africa, Varmac Consulting Engineers, Scottsville, Pietermaritzburg, South Africa

Roles Conceptualization, Formal analysis, Methodology, Writing – original draft, Writing – review & editing

Affiliation Department of Civil & Structural Engineering, Masinde Muliro University of Science and Technology, Kakamega, Kenya

Roles Conceptualization, Methodology, Supervision, Writing – review & editing

Affiliation Soil, Crop, and Climate Sciences, University of the Free State, Bloemfontein, South Africa

Roles Writing – review & editing

Affiliation Department of Agriculture and Engineering Services, Irrigation Engineering Section, Ministry of Agriculture and Natural Resources, Ilorin, Kwara State, Nigeria

• Tinashe Lindel Dirwai, 
• Edwin Kimutai Kanda, 
• Aidan Senzanje, 
• Toyin Isiaka Busari

• Published: May 25, 2021
• https://doi.org/10.1371/journal.pone.0236903
• Reader Comments

The analytical study systematically reviewed the evidence about the IWRM strategy model. The study analysed the IWRM strategy, policy advances and practical implications it had, since inception on effective water management in East, West and Southern Africa.

The study adopted the Preferred Reporting Items for Systematic Review and Meta-analysis Protocols (PRISMA-P) and the scoping literature review approach. The study searched selected databases for peer-reviewed articles, books, and grey literature. DistillerSR software was used for article screening. A constructionist thematic analysis was employed to extract recurring themes amongst the regions.

The systematic literature review detailed the adoption, policy revisions and emerging policy trends and issues (or considerations) on IWRM in East, West and Southern Africa. Thematic analysis derived four cross-cutting themes that contributed to IWRM strategy implementation and adoption. The identified four themes were donor effect, water scarcity, transboundary water resources, and policy approach. The output further posited questions on the prospects, including whether IWRM has been a success or failure within the African water resource management fraternity.

Citation: Dirwai TL, Kanda EK, Senzanje A, Busari TI (2021) Water resource management: IWRM strategies for improved water management. A systematic review of case studies of East, West and Southern Africa. PLoS ONE 16(5): e0236903. https://doi.org/10.1371/journal.pone.0236903

Editor: Sergio Villamayor-Tomas, Universitat Autonoma de Barcelona, SPAIN

Received: July 12, 2020; Accepted: May 2, 2021; Published: May 25, 2021

Copyright: © 2021 Dirwai et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the paper.

Funding: This study was supported by the National Research Foundation (NRF) in the form of a grant awarded to TLD (131377) and VarMac Consulting Engineers in the form of a salary for TLD. The specific roles of the authors are articulated in the ‘author contributions’ section. The funders had no additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have read the journal’s policy and have the following potential competing interests: TLD is a paid employee of VarMac Consulting Engineers. This does not alter our adherence to PLOS ONE policies on sharing data and materials. There are no patents, products in development or marketed products associated with this research to declare.

1 Introduction

Integrated Water Resources Management (IWRM) is a concept that is meant to foster effective water resource management. GWP [ 1 ] defined it as “the process which promotes the coordinated development and management of water, land and related resources, to maximise the resultant economic and social welfare equitably without compromising the sustainability of vital systems”. A holistic approach, in the form of the Dublin statement on Water and Sustainable Development (DSWSD), emerged and it became the backbone of IWRM principles.

According to Solanes and Gonzalez-Villarreal [ 2 ] the Dublin priciples are: “ (1) Freshwater is a finite and vulnerable resource , essential to sustain life , development and the environment; (2) Water development and management should be based on a participatory approach , involving users , planners and policy-makers at all levels , (3) Women play a central part in the provision , management , and safeguarding of water , and (4) Water has an economic value in all its competing uses , and should be recognised as an economic good .” The seamless conflation of the DSWSD and the Agenda 21 at the United Nations Conference on Environment and Development (UNCED) in 1992 further strengthened the IWRM discourse and facilitated the policy approach of IWRM [ 3 , 4 ]. Since its inception the IWRM policy has been the holy grail of water resource management in Africa, Asia, and Europe to mention a few. For policy diffusion, countries were required to develop an IWRM policy blueprints for effective water use [ 5 ].

This review sought to unveil the innovative IWRM strategy approach by critically examining its genesis, implementation, adoption and the main drivers in in East, Southern and West Africa. Secondary to this, the study endeavoured to determine whether the IWRM implementation has been a success or failure. The choice of East, West and Southern Africa was influenced by the regional dynamics of Sub-Saharan Africa which have unique problems in water resources management and the hydropolitical diversity in this region. The isolated cases provide a holistic representation t the implementation dynamics of IWRM. In addition, sub-Sahara Africa was the laboratory for IWRM with Zimbabwe and South Africa being the early implementers [ 6 ]. Apart from the IWRM strategy being a social experiment in sub-Sahara, there exists a gap on an overarching review on the performance and aggregated outcomes of the IWRM adopters in the continent. The selection of the countries of interest was based on the authors geo-locations and their expert experiences with the IWRM strategy in their respective localities. The study sought to draw trends, similarities, and potential differences in the drivers involved in achieving the desired IWRM outcome.

IWRM strategy approach and implementation are ideally linked to individual country’s developmental policies [ 7 ]. Southern Africa (Zimbabwe and South Africa) is the biggest adopter of the water resource management strategy and produced differed uptake patterns [ 8 ]. In East Africa, Tanzania,Uganda and Kenya also adopted the IWRM strategy, whilst in West Africa, Burkina Faso latently adopted the IWRM strategy in 1992 [ 4 ] and in Ghana, customary and traditional water laws transformed into latent IWRM practices [ 9 ].

Various initiatives were put in place to aid the adoption of IWRM in sub-Sahara Africa. For example, Tanzania benefited from donor funds and World Bank programmes that sought to alleviate poverty and promote environmental flows. The World Bank radically upscaled and remodelled IWRM in Tanzania through the River Basin Management—Smallholder Irrigation Improvement Programme (RBM-SIIP) [ 10 ]. The government of Uganda’s efforts of liberalising the markets, opening democratic space and decentralising the country attracted donor funds that drove the IWRM strategy agenda. The long-standing engagement between Uganda and the Nordic Fresh Water initiative helped in the diffusion of IWRM strategy in the country. Finally, in West Africa, Burkina Faso and Ghana made significant strides in operationalising the IWRM strategy by adopting the West Africa Water Resources Policy (WAWRP). A massive sense of agency coupled with deliberate government efforts drove the adoption status of Burkina Faso.

Total policy diffusion can be achieved when the practice or idea has supporting enablers. Innovation is key in developing plocies that altersocietal orthodox policy paths that fuel hindrance and consequently in-effective water governance [ 11 ]. Acknowledging the political nature of water (water governance and transboundary catchments issues) is the motivation to legislate water-driven and people-driven innovative policy [ 12 ]. Water policy reform should acknowledge the differing interests’ groups of the water users and its multi-utility nature; thus, diffusion channels should be tailored accordingly, avoiding the ‘one size fits all’ fallacy. IWRM as an innovative strategy approach diffused from the global stage to Africa and each regional block adopted the approach at different times under different circumstances.

The rest of this paper is outlined as follows; section 2 presents the conceptual framework adopted and the subsequent methodology. Section 3 presents the results and discussion. The discussion is structured around innovation driver in each respective region. Thereafter, sub-section 3.4 presents the prospect of IWRM in the East, West and Southern Africa regions. Lastly, the paper presents the conclusion.

2 Methodology

2.1 conceptual framework and methodology.

The analytical framework applied in the study is based on the water innovation frames by the United Nations Department of Economic and Social Affairs (UNDESA) [ 13 ]. The UNDESA [ 13 ], classified water frames into three distinct categories namely water management strategies (e.g., IWRM), water infrastructure and water services. The former partly involves IWRM strategies and the latter encompasses economic water usage such as agriculture, energy production and industrial applications [ 12 ].

The literature review identified research gaps that informed the employed search strategy. The literature that qualified for inclusion was thoroughly analysed and discussed. The aggregated outcomes were used for excerpt extraction in the thematic analysis.

2.2 Literature handling

The study performed a systematic review as guided by the Arksey and O’Malley [ 14 ] approach. The approach details methods on how to scope, gather, screen and report literature. The study further employed a constructionist thematic analysis to extract common recurring themes amongst the regions.

2.2.1 Eligibility criteria.

Eligibility criteria followed an adapted SPICE (Setting, Perspective, Intervention, Comparison and Evaluation) structure ( Table 1 ). The SPICE structure informed the study’s search strategy ( Table 2 ) and the subsequent formulation of the inclusion-exclusion criteria ( Table 3 ). The evidence search was conducted from the following databases: Scopus, Web of Science, Google Scholar, UKZN-EFWE, CABI, JSTOR, African Journals Online (AJOL), Directory of Open Access Journals (DOAJ), J-Gate, SciELO and WorldCat for peer-reviewed articles, books, and grey literature. The study did not emphasize publication date as recommended by Moffa, Cronk [ 15 ]. Databases selection was based on their comprehensive and over-arching nature in terms of information archiving. It is worth mentioning that the search strategy was continuously revised by trial and error until the databases yielded the maximum number of articles for screening.

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https://doi.org/10.1371/journal.pone.0236903.t001

https://doi.org/10.1371/journal.pone.0236903.t002

https://doi.org/10.1371/journal.pone.0236903.t003

2.2.2 Search strategy.

The search strategy or query execution [ 16 ] utilised Boolean operators ( OR & AND ). The dynamic nature of the search strategy required the authors to change the search terms and strategy, for example, if digital databases did not yield the expected search items the study would manually search for information sources. The search queries included a string of search terms summarised in Table 2 .

2.2.3 Selection process.

DistillerSR © software was used for article screening. Online data capturing forms were created in the DistillerSR © software and two authors performed the article scoring process that eventully led to article screening. The screening was based on the article title, abstract and locality. The study employed a two-phase screening process [ 17 ], the first phase screened according to title and the second phase screened according to abstract and keywords. During the screening process, studies that the matched information in the left column of Table 3 we included in the literature review syntheses, whilst those that matched the exclusion list were discarded.

2.3 Thematic analysis

The review also adopted the thematic analysis approach by Braun and Clarke [ 18 ] to extract, code, and select candidate converging themes for the systematic review. The selected lieterature was subjected to qualitative analysis to capture recurring themes amongst the selected regions (East, West and Southern Africa). Data extracts from the respective regional analysis were formulated into theoretical themes. Thereafter, the extracted data was coded according to the extracted patterns from the information source to constitute a theme. It is worth mentioning that the authors used their discretion to extract and code for themes.

3 Results and discussion

Data charting comprised of the PRISMA flow-chart ( Fig 1 ). The study utilised 80 out of 183 records (n = 37, 46%) for East Africa, (n = 37, 46%) for Southern Africa, and (n = 6, 8%) for West Africa.

https://doi.org/10.1371/journal.pone.0236903.g001

3.1 Case studies

The introduction of IWRM in the East African region was initiated in 1998 by the water ministers in the Nile basin states due to the need for addressing the concerns raised by the riparian states. These water sector reforms revolved around the Dublin principles initiated by the UN in 1992 [ 20 ]. In 1999, Kenya developed the national water policy and the enabling legislation, the Water Act 2002 was enacted [ 21 ]. The Act was replaced by the Water Act 2016 which established the Water Resources Authority (WRA) as the body mandated to manage water resources in line with the IWRM principles and Water Resource Users Association (WRUA) as the lowest (local) level of water management [ 22 ].

Similarly, Uganda developed the national water policy in 1999 to manage, and develop the available water resources in an integrated and sustainable manner [ 23 ]. The National Water Policy further provides for the promotion of water supply for modernized agriculture [ 24 ]. Tanzania’s water policy of 2002 espouses IWRM principles, and its implementation is based on a raft of legal, economic, administrative, technical, regulatory and participatory instruments [ 25 ]. The National Irrigation Policy (NIP), 2010 and the National Irrigation Act, 2013 provides the legal basis for the involvement of different actors on a private-public partnership basis [ 26 ].

West Africa possesses an unregistered IWRM strategy that is espoused in the West Africa Water Resources Policy (WAWRP) of 2008. The WAWRP is founded on the following legal principles; (a) “promote, coordinate and ensure the implementation of a regional water resource policy in West Africa, in accordance with the mission and policies of Economic Community of West African States (ECOWAS)and (b) “harmonization and coordination of national policies and the promotion of programmes, projects and activities, especially in the field of agriculture and natural resources”. The founding legal basis resonates with the Dublin principles.

The WAWRP design actors were ECOWAS, Union Economique et Monétaire Ouest Africaine (UEMOA), and Comité Permanent Inter-État de Llutte Contre la Sécheresse au Sahel (CILSS). CILSS is the technical arm of ECOWAS and UEMOA. The institutional collaboration was driven by the fact that West Africa needed a sound water policy for improved regional integration and maximised economic gains. ECOWAS established the Water Resources Coordination Centre (WRCC) to (a) oversee and monitor the region’s water resources and management activities and (b) to act as an executive organ of the Permanent Framework for Coordination and Monitoring (PFCM) of IRWM [ 27 ].

The inception and triggers of IWRM in West Africa can be traced back to the General Act of Berlin in 1885 which, among other things, dictated water resources use of the Congo and Niger rivers [ 28 ]. A multiplicity of agreements around shared watercourses in West Africa led to the realisation of the IWRM policy approach. For example, the Senegal River Basin (SRB) Development Mission facilitated collaboration between Senegal and Mauritania in managing the SRB. Another noteworthy agreement was Ruling C/REG.9/7/97, a regional plan to fight floating plants in the ECOWAS countries [ 28 ]. GWP (2003) categorised the West African countries according to the level of adoption into three distinct groups namely; (a) Group A comprised of countries with the capacity to develop and adopt the IWRM approach (Burkina Faso and Ghana), (b) Group B comprised of countries needing “light support” to unroll the IWRM plan (Benin, Mali, Nigeria, and Togo), and (3) Group C comprised of laggards which needed significant support to establish an IWRM plan (Cape Verde, Ivory Coast, Gambia, Guinea, Guinea Bissau, Liberia, Mauritania, Niger, Senegal and Sierra Leone).

Southern African Development Community (SADC) regional bloc has over 15 shared transboundary river basins (For detailed basin and catchment arrangement in SADC see [ 29 ]). SADC member states established the Protocol on Shared Water Systems (PSWS) which meant to encourage sustainable water resources utilisation and management. The PSWS was perceived to strengthen regional integration [ 30 ]. The regional bloc formulated the Regional Strategic Action Plans (RSAPs) that sought to promote an integrated water resources development plan. The action initiative mimicked IWRM principles and the shared water resources initiatives acted as a catalyst for the genesis of IWRM in Southern Africa [ 31 ]. SADC houses the Waternet and the GWP-SA research and innovation hubs upon which SADC’s IWRM adoption was anchored on. Besides the availability of trained water experts in the region who were willing to experiment with the IWRM policy approach, water scarcity fuelled by climate change prompted the region’s adoption of the IWRM policy approach at the local level.

3.2 Diffusion drivers of IWRM in East, West and Southern Africa

3.2.1 water scarcity..

The adoption of IWRM in East Africa was necessitated by water scarcity which is experienced by the countries in the region, which formed the need for adoption of prudent water resources management strategies as envisaged under the Dublin principles which was championed indirectly, according to Allouche [ 5 ], by the World Bank. Specifically, the need to give incentives and disincentives in water use sectors to encourage water conservation.

Kenya is a water-scarce country with per capita water availability of 586 m 3 in 2010 and projected to 393 m 3 in 2030 [ 32 ]. Uganda is endowed with water resources, however, it is projected that the country will be water-stressed by 2020 which could be compounded by climate variability and change, rapid urbanization, economic and population growth [ 33 ].

Using water scarcity was in essence coercing countries to adopt the IWRM principles with the irrigation sector, the contributor of the largest proportion of water withdrawals, becoming the major culprit [ 5 ]. The researchers opine that the effects of water scarcity in the region can be countered by adopting IWRM strategy, but adaptively to suit the local context and thus, persuasive rather than coercive, is the appropriate term. Indeed, as put forward by Van der Zaag [ 34 ], IWRM is not an option but it is a necessity and therefore, countries need to align their water policies and practices in line with it.

West African climatic conditions pose a threat on the utilisation of the limited water resource. Water resource utilisation is marred by erratic rainfalls and primarily a lack of water resources management know-how [ 27 ]. Countries in the Sahelian regions are characterised by semi-arid climatic conditions. Thus, dry climatic conditions account as an IWRM strategy driver to ensure maximised water use efficiency. Although the region acknowledges the need for adopting the IWRM strategy, they have varied adoption statuses (GWP, 2003).

Southern African countries also face serious water scarcity problems. Rainfall in South Africa is low and unevenly distributed with about 9% translating to useful runoff making the country one of the most water scarce countries in the world [ 35 ]. Generally, SADC countries experience water scarcity resulting in conflicts due to increasing pressure on the fresh water resources [ 36 ]. Thus, the researched opine that water scarcity pushed the region to adopt the IWRM strategy inorder to mitigate the looming effects of climate change on surface water availainility.

3.2.2 Trans-boundary water resources.

Water resources flow downstream indiscriminately across villages, locations, regions and nations/states and therefore necessitates co-operation. The upstream and downstream relationships among communities, people and countries created by the water is asymmetrical in that the actions upstream tend to affect the downstream riparian and not the other way round [ 34 ]. In East Africa, the Nile Basin Initiative (NBI) and the Lake Victoria Basin Commission (LVBC) plays a critical component in promoting the IWRM at regional level [ 20 ].

The Nile River system is the single largest factor driving the IWRM in the region. Lake Victoria, the source of the Nile River is shared by the three East African states of Kenya, Uganda and Tanzania. Irrigation schemes in Sudan and Egypt rely exclusively on the waters of River Nile and are therefore apprehensive of the actions of upstream states notably Ethiopia, Kenya, Uganda, Tanzania, Rwanda and Burundi. The source of contention is the asymmetrical water needs and allocation which was enshrined in the Sudan–Egypt treaty of 1959 [ 37 ]. All the riparian countries in the Nile basin have agricultural-based economies and thus irrigation is the cornerstone of food security [ 38 ]. Therefore, there was the need for the establishment of basin-wide co-operation which led to the formation of NBI in 1999 with a vision to achieve sustainable socio-economic development through the equitable utilisation of the Nile water resources [ 39 ].

The Mara River is another trans-boundary river which is shared between Tanzania and Kenya and the basin forms the habitat for the Maasai Mara National Reserve and Serengeti National Park in Kenya and Tanzania, respectively, which is prominent for the annual wildlife migration. Kenya has 65% of the upper part of the basin, any development on the upstream, such as hydropower or water diversion, will reduce the water quantities and therefore affect the Serengeti ecosystem and the livelihoods of people in Tanzania [ 40 ]. The LVBC, under the East African Community, developed the Mara River Basin-wide—Water Allocation Plan (MRB-WAP) to help in water demand management and protection of the Mara ecosystem [ 41 ]. The mandate of the LVBC is to implement IWRM in Lake Victoria Basin riparian countries [ 20 ].

Other shared water basins include the Malakisi-Malaba-Sio River basin shared between Uganda and Kenya and the Kagera River basin traversing Burundi, Rwanda, Tanzania and Uganda. The two river basins form part of the Upper Nile system and are governed through the LVBC and the NBI.

The universal transboundary nature of water creates dynamics that warrant cooperation for improved water use. West Africa has 25 transboundary watercourses and only 6 are under agreed management and regulation. The situation is compounded by the fact that 20 watercourses lack strategic river-basin management instruments [ 28 ]. Unregistered rules and the asymmetrical variations associated with watercourses warranted the introduction of the IWRM principle to set equitable water sharing protocols and promote environmental flows (e-flows). The various acts signed represent an evolutionary treaty development that combines th efforts of riparian states to better manage the shared water resources (for detailed basin configuration in West Africa see [ 42 ]). Hence, adoption of the IWRM strategy driven WAWRP of 2008 ensured the coordinanted and harmonised regional water usage mechanisms.

The SADC region has 13 major transboundary river basins which calls for development of agreements on how to handle the shared water resources with the contraints of varying levels of economic development and priorities among the member states. The multi-lateral and bi-lateral agreeements on shared water resources in the SADC is hampered by the hydropolitics where economic power dynamics favour South Africa as in the case of the Orange-Senqu basin [ 43 ].

3.2.3 Donor influence.

The World Bank has been pushing for IWRM principles in the East Africa through the NBI and by pressurising Egypt to agree to co-operate with the upstream riparian countries in the Nile basin [ 38 ]. In the early 1990s, the World Bank had aligned its funding policies to include sustainable water resources management [ 44 ].

In Tanzania, Norway, through NORAD, played a key role in implementing IWRM by promoting water projects including hydropower schemes [ 45 ]. Indeed the transformation of the agricultural sector in Tanzania through Kilimo Kwanza policy of 2009 which emphasised on the commercialization of agriculture including irrigation was driven by foreign donors such as the USAID and UK’s DFID [ 26 ].

In Uganda, however, the reforms in the water sector were initiated devoid of external influence [ 46 ]. However, this assertion is countered by Allouche [ 5 ] who pointed that Uganda had become a ‘darling’ of the donor countries in the early 1990s and that DANIDA helped to develop the Master Water Plan and the country was keen to show a willingness to develop policy instruments favourable to the donor. East African countries are developing economies and therefore most of their development plans are supported by external agencies, which to some extent come with subtle ‘conditions’ such as free-market economies. In fact imposition of tariffs and other economic instruments used to implement IWRM in water supply and irrigation is a market-based approach which was favoured by the World Bank and other development agencies.

Donor aid cannot be downplayed in pushing for IWRM diffusion in low-income aid-dependent countries of West Africa. GoBF [ 47 ] reported that from the period 1996–2001, more than 80% of water-related projects were donor funded. Cherlet and Venot [ 48 ] also found that almost 90% of the water investments in Mali were funded outside the government apparatus. It can, therefore, be argued that donor-aid plays a pivotal and central role in diffusing policy and innovation in aid-depended countries because of the incentive nature it provides for the low-income countries in the sub-Sahara region.

Southern Africa’s experience with western donors including the World Bank in terms of IWRM adoption favoured the urban areas and neglected rural areas (see [ 8 ]). The National Water Act drafting process in South africa was a multi-stakeholder and intersectoral activity that brought in international consultancies. Notable IWRM drivers were Department of International Development—UK (DFID), Danish Danida, and Deustsche Gesellschaft fur Zusammernarbeit (GIZ). The DFID was instrumental in water reform allocation law whilst the GIZ and Danida were active in experimental work in the catchments [ 3 ]. On the contrary, in Zimbabwe, a lack of access to international funding and fleeting donor aid exacerbated the policy uptake as such the anticipated implementation, operationalisation and continuous feedback mechanism for policy revision and administering process was never realised.

3.2.4 Government intervention and pro-active citizenry.

This was predomint in West Africa. For example the Burkinabe government exhibited political goodwill such that in 1995 the government brought together two separate ministries into one ministry of Environment and Water thus enabling coherent policy formulation and giving the ministry one voice to speak on water matters. The dynamic innovation arena (where policy players interact) allows continuous policy revision and redesign thus water policy reform diffusion, and policy frameworks are in a perpetual state of shifting. For example, in the 1990s the Burkinabe government was engaged in several water-related projects and was continuously experimenting with local governance and privatization (from donors) [ 1 ]. This policy shift according to Gupta [ 49 ] qualifies as an innovation driver.

Burkina Faso and Mali’s adoption story is accentuated by heightened agency, the individual enthusiasm on influencing the outcome facilitated policy diffusion and can be argued to be a potential innovation diffusion driver for the IWRM policy approach in the region. The individual policy diffusion fuelled by an enthusiastic citizenry was a sure method that effectively diffused awareness around the IWRM innovation and acted as a driver of the IWRM practices in the region. Individual strategies were honed in smallholder farming institutions to diffuse the IWRM practice and drawing from the Sabatier and Jenkins-Smith [ 50 ] advocacy coalition theory, having individuals with common agendas promoted the transfer and diffusion of water reforms in parts of West Africa.

3.2.5 Legal, political and institutional incoherence.

This was a major factor which dictated the pace of IWRM implementation in Southern Africa. For example, the Fast Track Land Reform (FTLR) programme in Zimbabwe disaggregated the large-scale commercial farms and created smallholder farming [ 51 ], consequently influencing and dictating IWRM policy path. The FTLR programme had a negative impact on the spread and uptake of IWRM. A series of poor economic performance and poor policy design compounded the limited diffusion and the adoption of IWRM practices at local levels in Zimbabwe. The FTLR programme compounded the innovation diffusion process as the Zimbabwe National Water Authority (ZINWA) lost account of who harvested how much at the newly created smallholder farms. Thus, water access imbalance ensured, and ecological sustainability was compromised.

Policy incoherence was a major factor in poor IWRM diffusion and adoption, for example, the government did not synchronise the land and water reforms thus it meant at any given point in time there was a budget for one reform agenda [ 8 ] and the land reform agenda would take precedence because of political rent-seeking. IWRM in its nature couples growth to the coordinated consumption of finite resources, hence the circular approach cannot be easily realised because finte resources are at the core of the strategy’s existence.

South Africa’s transition from Integrated Catchment Management (ICM) strategies to the IWRM strategy, hindered the operationalisation and diffusion of the IWRM strategy [ 52 ]. Despite acknowledging the “integration”, researchers argued that the word lacked a clear-cut definition thus failing to establish a common ground for water’s multi-purpose use [ 53 ]. For maximised adoption of a practice, incremental innovation is required, which was Danida’s agenda in the quest to drive IWRM in South Africa. According to Wehn and Montalvo [ 54 ] incremental innovation “is characterised by marginal changes and occurs in mature circumstances”,

Land reform in South Africa is characterised by (a) redistribution which seeks to transfer land from the white minority on a willing buyer willing seller basis, (b) restitution which rights the discriminatory 1913 land laws that saw natives evicted from their ancestral land, and (c) land tenure that provides tenure to the occupants of the homelands. This new pattern created a new breed of smallholder farmers that are, more often than not, excluded from diffusion and water governance channels [ 55 ]. In addition, researchers argue that a farm once owned by one white farmer is owned by multiple landowners with different cultural backgrounds and, more often than not, IWRM strategy is met with resistance [ 56 ]. Another challenge posed by multi-cultural water users is the interpretation and translation of innovations.

To foster water as an economic good aspect of IWRM the licensing system was enacted in South Africa. The phenomenon was described by van Koppen (2012) as paper water precedes water, thus the disadvantaged black smallholder farmers could not afford paper water which consequently limits access to water. The licensing system can be interpreted as stifling the smallholder sector and hence negative attitudes develop and hinder effective policy diffusion. Another issue that negatively impacted adoption was that issuing a license was subject to farmers possessing storage facilities. The smallholder farmers lack resources hence the requirement for obtaining a license excluded the small players in favour of the large-scale commercial farmers. This consequently maintains the historically skewed status-quo, where “big players” keep winning. Van Koppen [ 57 ] and Denby, Movik [ 58 ] argue the shift from local water rights system to state-based water system have created bottlenecks making it hard for smallholder farmers to obtain “paper water” and subsequently “wet water”. The state-based system is characterised by bureaucracies and local norms are in perpetual change, hence denying the IWRM innovation policy approach stability efficiency.

A lack of political will and pragmatism amplified the poor adoption and operationalisation of IWRM, a poorly performing economy and fleeing donor agencies resulted in less funding for water-related project. Political shenanigans created an imbalance that resulted in two forms of water i.e., water as an economic good vs. water as a social good [ 59 ]. Manzungu [ 60 ] argued post-colonial Zimbabwe continuously failed to develop a peoples-oriented water reform policy. In a bid to correct historical wrongs by availing subsidised water to the vulnerable and support the new social order, the initiative goes against the neo-liberalism approach that defines the “water as an economic good” [ 61 ] which is a founding principle of IWRM.

Water redistribution in South Africa has been fraught with political and technical issues, for example, the Water Allocation Reform of 2003 failed to reconcile the apartheid disparity hence the equity component of IWRM was compromised. IWRM suffered another setback caused by the governing party when they introduced radical innovations that sought to shift from the socialist to neoliberal water resource use approach. The radical innovation through the government benefited the large-scale commercial farmers at the expense of the black smallholder farming community [ 53 ].

3.3 Systematic comparison of findings on East, West and Southern Africa

Data extracts from the respective regional analysis were formulated into theoretical candidate themes. The thematic analysis extracted recurring themes common to all the three regions. An independent reviwer performed the subjective thematic analysis and the authors performed the review on the blind thematic analysis outcome. The analysis performed a data extraction exercise and formulated codes ( Fig 2 ). Themes were then generated from the coded data extracts to create a thematic map. It is worth mentioning that the data extracts were phrases/statement from with in the literature review.

https://doi.org/10.1371/journal.pone.0236903.g002

3.3.1 Donor aid and policy approach.

Donor activity invariably influenced the policy path that individual countries took. The three regions had significant support from donors to drive the IWRM strategy. Zimbabwe experienced a different fate. The political climate caused an exodus of donor support from the nation, which consequently caused a laggard. The absence of donor support was at the backdrop of the two formulated water acts namely National Water Act [ 62 ] and the Zimbabwe National Water Authority Act of 1998 [ 63 ], which were meant to promote equitable water provision amongst the population. This highlights the latent adoption of IWRM strategy. The 2008/2009 cholera outbreak raised alarm and facilitated the return of donor activity in Zimbabwe’s water sector. The availability of donor support motivated the redrafting of a water clause in the 2013 constitution that espoused the IWRM strategy to water management [ 64 ].

Whilst Mehta, Alba [ 64 ] argue that South Africa enjoyed minimal donor support it cannot be downplayed how much donor influence impacted the IWRM strategy adoption. For instance, the Water Allocation Reform (WAR) was drafted with the aid of the UK Department of International Development. The WAR fundamentals are informed by IWRM principles. The economic structural programmes spearheaded by The World Bank and the IMF were active in facilitating the diffusion of the IWRM strategy in Kenya and Uganda. Uganda made strides because of a long-standing relationship with donor nations. The Uganda—donor relationship dates back to early 1990 where Uganda was elected to be the NBI secretariat, this in itself evidence of commitment to water policy reform [ 4 , 65 ]. Donor aid acts as an incentive and augments the low African goverments’ budgets, as such proper accountability and usage of the funds ensures that more funds come in for projected water related projects.

3.3.2 Transboundary water resources.

The Nile River system is the single largest factor driving the IWRM in the region since it is shared across several upstream and downetream nations. Irrigation schemes in Sudan and Egypt rely exclusively on the waters of River Nile and are therefore apprehensive of the actions of upstream states notably Ethiopia, Kenya, Uganda, Tanzania, Rwanda and Burundi. The source of contention is the asymmetrical water needs and allocation which was enshrined in the Sudan–Egypt treaty of 1959 [ 37 ]. Over time, the upstream countried demanded equitable share of the Nile waters and this led to the establishment of NBI. In Eastern Africa, the Nile Basin Initiative (NBI) and the Lake Victoria Basin Commission (LVBC) plays a critical component in promoting the IWRM at regional level [ 20 ]. The LVBC is deeply intertwined with the East African Community (EAC) and thus has more political clout to implement policies regarding utilization of the Lake Victoria waters [ 66 ]. This, therefore, implies that for NBI to succeed, it must have a mandate and political goodwill from the member countries.

The conflicts around the utilization of the Nile water resources persists due to the treaty of 1959 which led to the signing of Cooperative Framework Agreement (CFA) by a number of the Nile basin countries, with the notable exceptions of Egypt, Sudan and South Sudan [ 67 ]. The CFA was signed between 2010 and 2011 and establishes the principle that each Nile Basin state has the right to use, within its territory, the waters of the Nile River Basin, and lays down some factors for determining equitable and reasonable utilization such as the contribution of each state to the Nile waters and the proportion of the drainage area [ 68 ]. The construction of the Grand Ethiopian Renaissance Dam has been a source of concern and conflict among the three riparian countries of Ethiopia, Sudan and Egypt [ 67 ]. The asymmetrical power relations (Egypt is the biggest economy) in the Nile Basin is a big hindrance to the co-operation among the riparian countries [ 69 ] and thus a threat to IWRM implementation in the shared watercourse. While Ethiopia is using its geographical power to negotiate for an equitable share in the Nile water resources, Egypt is utilizing both materials, bargaining and idealistic power to dominate the hydro politics in the region and thus the former can only succeed if it reinforces its geographical power with material power [ 70 ].

Therefore, IWRM implementation at the multi-national stage is complex but necessary to forestall regional conflicts and war. The necessity of co-operation rather than conflict in the Nile Basin is paramount due to the water availability constraints which is experienced by most countries in the region. The transboundary IWRM revolves around water-food- energy consensus where the needs of the riparian countries are sometimes contrasting, for example, Egypt and Sudan require the Nile waters for irrigation to feed their increasing population while Ethiopia requires the Nile waters for power generation to stimulate her economy. The upstream riparian States could use their bargaining power to foster co-operation and possibly force the hegemonic downstream riparian States into the equitable and sustainable use of Nile waters [ 71 ].

The SADC region has 13 major transboundary river basins (excluding the Nile and Congo) of Orange, Limpopo, Incomati, Okavango, Cunene, Cuvelai, Maputo, Buzi, Pungue, Save-Runde, Umbeluzi, Rovuma and Zambezi [ 72 ]. The Revised Protocol on Shared Watercourses was instrumental for managing transboundary water resources in the SADC. The overall aim of the Protocol was to foster co-operation for judicious, sustainable and coordinated management, the protection and utilization of shared water resources [ 73 ].

Ashton and Turton [ 74 ] argue that the transboundary water issues in Southern Africa revolved around the key roles played by pivotal States and impacted States and their corresponding pivotal basins and impacted basins. In this case, pivotal States are riparian states with a high level of economic development (Botswana, Namibia, South Africa, and Zimbabwe) and a high degree of reliance on shared river basins for strategic sources of water supply while impacted States are riparian states (Angola, Lesotho, Malawi, Mozambique, Swaziland, Tanzania, and Zambia) that have a critical need for access to water from an international river basin that they share with a pivotal state, but appear to be unable to negotiate what they consider to be an equitable allocation of water and therefore, their future development dreams are impeded by the asymmetrical power dynamics with the pivotal states. Pivotal Basins (Orange, Incomati, and Limpopo) are international river basins that face closure but are also strategically important to anyone (or all) of the pivotal states by virtue of the range and magnitude of economic activity that they support. Impacted basins (Cunene, Maputo, Okavango, Cuvelai, Pungué, Save-Runde, and Zambezi) are those international river basins that are not yet approaching a point of closure, and which are strategically important for at least one of the riparian states with at least one pivotal State.

The transboundary co-operation under IWRM in Southern Africa is driven mainly by water scarcity which is predominant in most of the SADC countries which may imply the use of inter-basin transfers schemes [ 74 ]. Further, most of the water used for agriculture, industry and domestic are found within the international river basins [ 75 ] which calls for collaborative water management strategies. The tricky feature hindering the IWRM is the fact that States are reluctant to transfer power to River Basin Commissions [ 76 ]. Indeed most of the River Basin Organizations (RBO) in Southern region such as the Zambezi Commission, the Okavango River Basin Commission, and the Orange-Sengu River Basin Commission have loose links with SADC and therefore lack the political clout to implement the policies governing the shared water resources [ 66 ]. Power asymmetry, like in Eastern Africa, is also a bottleneck in achieving equitable sharing of water resources as illustrated by the water transfer scheme involving Lesotho and South Africa [ 77 ]. The hydro-hegemonic South Africa is exercising control over any negotiations and agreements in the Orange-Senqu basin [ 43 ]. Limited data sharing among the riparian States is another challenge which affects water management in transboundary river basins e.g. in the Orange-Senqu basin [ 78 ].

West Africa has 25 transboundary watercourses and only 6 are under agreed management and regulation. The situation is compounded by the fact that 20 watercourses lack strategic river-basin management instruments [ 28 ]. Unregistered rules and the asymmetrical variations associated with watercourses warrant the introduction of the IWRM principle to set equitable water sharing protocols and promote environmental flows (e-flows). The various acts signed represent an evolutionary treaty development that combines the efforts of riparian states to better manage the shared water resources. It is important to note that evolutionary treaties are incremental innovation. Water Resources Coordination Centre (WRCC) was established in 2004 to implement an integrated water resource management in West Africa and to ensure regional coordination of water resource related policies and activities [ 79 ].

The Niger River basin covers 9 Countries of Benin, Burkina, Cameroon, Chad, Côte d’Ivoire, Guinea, Mali, Niger and Nigeria. The Niger River Basin Authority (NBA) was established to promote co-operation among the member countries and to ensure basin-wide integrated development in all fields through the development of its resources, notably in the fields of energy, water resources, agriculture, livestock, forestry exploitation, transport and communication and industry [ 80 ]. The Shared Vision and Sustainable Development Action Programme (SDAP) was developed to enhance co-operation and sharing benefits from the resources of River Niger [ 81 ]. The Niger Basin Water Charter together with the SDAP are key instruments which set out a general approach to basin development, an approach negotiated and accepted not only by all member states but also by other actors who utilize the basin resources [ 82 ].

The main agreement governing the transboundary water resource in River Senegal Basin is the Senegal River Development Organization, OMVS (Organisation pour la mise en valeur du fleuve Sénégal) with its core principle being the equitably shared benefits of the resources of the basin [ 82 ]. The IWRM in the Senegal River Basin is hampered by weak institutional structures and lack of protocol on how shared waters among the States as well as conflicting national and regional interests [ 83 , 84 ]. The Senegal River Basin, being situated in the Sudan-Sahelian region, is faced by the threat of climate change which affects water availability [ 84 ] The Senegal River Basin States have high risks of political instability.

3.4 Prospects of IWRM Africa

The countries in the three regions are at different stages of implementation ( Table 4 ). In East Africa, Uganda and Kenya are at medium-high level while Tanzania is medium-low. Majority of the countries in the Southern Africa region are at medium low. Comoros Islands is the only country at low level of implementation in the region. West African countries are evenly spread between low, medium-low and medium-high levels of implementation. Generally, East Africa is ranked as medium-high level with average score of 54% while Southern Africa and West Africa are ranked as medium low-level at 46% and 42% respectively. However if you include, medium low countries of Rwanda, Burundi, Ethiopia and South Sudan and the low-level Somalia, then East Africa’s score drops to 39% (medium-low).

https://doi.org/10.1371/journal.pone.0236903.t004

The implementation of IWRM in the continent, and more so the inter dependent and multi purpose water use sectors, will continue to evolve amid implementation challenges. The dynamics of water policies, increased competition for finite water resources from rapid urbanization, industrialization and population growth will continue to shape IWRM practices in the region. Trans-boundary water resources management will possibly take centre stage as East African countries move towards full integration and political federation as envisaged in the four pillars of the EAC treaty. Decision support tools such as the Water—Energy—Food (WEF) nexus appraoch will be very relevant in the trans-boundary water resources such as the Nile system, Mara and Kagera river basins. The approach can potentially ameliorate the after effects of the devolved governance system in Kenya that consequently created a multiplicity of transboundary sectors.

Adoption of the IWRM policy in West Africa is fraught with many challenges. For example, despite having significant water resources, the lack of a collective effort by the governments to train water experts at national level presents a challenge for adoption. Unavailability of trained water experts (who in any case are diffusion media) results in a lack of diffusion channels that facilitate policy interpretation, translation and its subsequent implementation. Helio and Van Ingen [ 27 ] pointed out how political instability possesses a threat to current and future implantation initiatives. The future collaboration projects and objective outlined by ECOWAS, CILSS, and UEMO highlight a major effort to bring the region to speed with the IWRM policy approach. The WAWRP objectives can potentially set up the region on an effective IWRM trajectory which can be mimicked and upscaled in other regions. Positives drawn from the region are the deliberate institutional collaborations. Burkina Faso and Mali have the potential to operationalise and facilitate policy diffusion to other neighbouring states. Donor driven reform is essential and national ownership is critical in ensuring the water reform policies and innovation diffusion processes are implemented at the national level.

The IWRM policy approach and practice in South Africa was government-driven whereas in Zimbabwe external donors were the main vehicles for diffusion. For both countries, the water and land reform agenda has a multiplicity of overlapping functionaries; however, they are managed by separate government departments. The silo system at national level prevents effective innovation diffusion and distorts policy interpretation and the subsequent dissemination at the local level.i.

Water affairs are politicised and often, the water reform policy fails to balance the Dublin’s principles which form the backbone of the IWRM innovation policy approach. Failure by national governments to address unequal water access created by former segregationist policies is perpetuated by the lack of balance between creating a new social order and recognising the “water as an economic good” principle.

4 Conclusion

Africa as a laboratory of IWRM produced varied aggregated outcomes. The outcomes were directly linked to various national socio-economic development agendas; thus, the IWRM policy took a multiplicity of paths. In East Africa, Kenya is still recovering from the devolved system of government to the County system which created new transboundary sectors with the country. Water scarcity, trans-boundary water resource and donor aid played a critical role in driving the IWRM policy approach in the three regions. Southern Africa’s IWRM experience has been fraught with policy clashes between the water and land reforms. Similar to Africa, the transboundary issue in Europe and Asia and the subsequent management is a major buy-in for formulating water resources strategies that are people centric and ecologically friendly. Global water scarcity created fertile grounds for IWRM adoption in Asia, specifically India. Thus, we postulate that some of the drivers that influenced the uptake and diffusion in Africa are not only unique to the continent.

For the future, IWRM policy approach can be implemented in Africa and the continent has the potential to implement and adopt the practice. Endowed with a significant number of water bodies, Africa must adopt a blend of IWRM strategy and the water energy food nexus (WEF) for maximising regional cooperation and subsequent economic gains. WEF nexus will help combat a singular or silo approach to natural resources management. WEF nexus and IWRM is a fertile area for future research as it brings a deeper understanding of the trade-offs and synergies exsisting in the water sector across and within regions. In addition, the WEF nexus approach can potentially facilitate a shift to a circular approach that decouples over dependence on one finte resource for development.

Supporting information

S1 checklist..

https://doi.org/10.1371/journal.pone.0236903.s001

S1 Table. Data extracts with the applied codes.

https://doi.org/10.1371/journal.pone.0236903.s002

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Ground Water Vulnerability Assessment: Predicting Relative Contamination Potential Under Conditions of Uncertainty (1993)

Chapter: 5 case studies, 5 case studies, introduction.

This chapter presents six case studies of uses of different methods to assess ground water vulnerability to contamination. These case examples demonstrate the wide range of applications for which ground water vulnerability assessments are being conducted in the United States. While each application presented here is directed toward the broad goal of protecting ground water, each is unique in its particular management requirements. The intended use of the assessment, the types of data available, the scale of the assessments, the required resolution, the physical setting, and institutional factors all led to very different vulnerability assessment approaches. In only one of the cases presented here, Hawaii, are attempts made to quantify the uncertainty associated with the assessment results.

Introduction

Ground water contamination became an important political and environmental issue in Iowa in the mid-1980s. Research reports, news headlines, and public debates noted the increasing incidence of contaminants in rural and urban well waters. The Iowa Ground water Protection Strategy (Hoyer et al. 1987) indicated that levels of nitrate in both private and municipal

wells were increasing. More than 25 percent of the state's population was served by water with concentrations of nitrate above 22 milligrams per liter (as NO 3 ). Similar increases were noted in detections of pesticides in public water supplies; about 27 percent of the population was periodically consuming low concentrations of pesticides in their drinking water. The situation in private wells which tend to be shallower than public wells may have been even worse.

Defining the Question

Most prominent among the sources of ground water contamination were fertilizers and pesticides used in agriculture. Other sources included urban use of lawn chemicals, industrial discharges, and landfills. The pathways of ground water contamination were disputed. Some interests argued that contamination occurs only when a natural or human generated condition, such as sinkholes or agricultural drainage wells, provides preferential flow to underground aquifers, resulting in local contamination. Others suggested that chemicals applied routinely to large areas infiltrate through the vadose zone, leading to widespread aquifer contamination.

Mandate, Selection, and Implementation

In response to growing public concern, the state legislature passed the Iowa Ground water Protection Act in 1987. This landmark statute established the policy that further contamination should be prevented to the "maximum extent practical" and directed state agencies to launch multiyear programs of research and education to characterize the problem and identify potential solutions.

The act mandated that the Iowa Department of Natural Resources (DNR) assess the vulnerability of the state's ground water resources to contamination. In 1991, DNR released Ground water Vulnerability Regions of Iowa , a map developed specifically to depict the intrinsic susceptibility of ground water resources to contamination by surface or near-surface activities. This assessment had three very limited purposes: (1) to describe the physical setting of ground water resources in the state, (2) to educate policy makers and the public about the potential for ground water contamination, and (3) to provide guidance for planning and assigning priorities to ground water protection efforts in the state.

Unlike other vulnerability assessments, the one in Iowa took account of factors that affect both ground water recharge and well development. Ground water recharge involves issues related to aquifer contamination; well development involves issues related to contamination of water supplies in areas where sources other than bedrock aquifers are used for drinking water. This

approach considers jointly the potential impacts of contamination on the water resource in aquifers and on the users of ground water sources.

The basic principle of the Iowa vulnerability assessment involves the travel time of water from the land surface to a well or an aquifer. When the time is relatively short (days to decades), vulnerability is considered high. If recharge occurs over relatively long periods (centuries to millennia), vulnerability is low. Travel times were determined by evaluating existing contaminants and using various radiometric dating techniques. The large reliance on travel time in the Iowa assessment likely results in underestimation of the potential for eventual contamination of the aquifer over time.

The most important factor used in the assessment was thickness of overlying materials which provide natural protection to a well or an aquifer. Other factors considered included type of aquifer, natural water quality in an aquifer, patterns of well location and construction, and documented occurrences of well contamination. The resulting vulnerability map ( Plate 1 ) delineates regions having similar combinations of physical characteristics that affect ground water recharge and well development. Qualitative ratings are assigned to the contamination potential for aquifers and wells for various types and locations of water sources. For example, the contamination potential for wells in alluvial aquifers is considered high, while the potential for contamination of a variable bedrock aquifer protected by moderate drift or shale is considered low.

Although more sophisticated approaches were investigated for use in the assessment, ultimately no complex process models of contaminant transport were used and no distinction was made among Iowa's different soil types. The DNR staff suggested that since the soil cover in most of the state is such a small part of the overall aquifer or well cover, processes that take place in those first few inches are relatively similar and, therefore, insignificant in terms of relative susceptibilities to ground water contamination. The results of the vulnerability assessment followed directly from the method's assumptions and underlying principles. In general, the thicker the overlay of clayey glacial drift or shale, the less susceptible are wells or aquifers to contamination. Where overlying materials are thin or sandy, aquifer and well susceptibilities increase. Vulnerability is also greater in areas where sinkholes or agricultural drainage wells allow surface and tile water to bypass natural protective layers of soil and rapidly recharge bedrock aquifers.

Basic data on geologic patterns in the state were extrapolated to determine the potential for contamination. These data were supplemented by databases on water contamination (including the Statewide Rural Well-Water Survey conducted in 1989-1990) and by research insights into the transport, distribution, and fate of contaminants in ground water. Some of the simplest data needed for the assessment were unavailable. Depth-to-bedrock information had never been developed, so surface and bedrock topographic

maps were revised and integrated to create a new statewide depth-to-bedrock map. In addition, information from throughout the state was compiled to produce the first statewide alluvial aquifer map. All new maps were checked against available well-log data, topographic maps, outcrop records, and soil survey reports to assure the greatest confidence in this information.

While the DNR was working on the assessment, it was also asked to integrate various types of natural resource data into a new computerized geographic information system (GIS). This coincident activity became a significant contributor to the assessment project. The GIS permitted easier construction of the vulnerability map and clearer display of spatial information. Further, counties or regions in the state can use the DNR geographic data and the GIS to explore additional vulnerability parameters and examine particular areas more closely to the extent that the resolution of the data permits.

The Iowa vulnerability map was designed to provide general guidance in planning and ranking activities for preventing contamination of aquifers and wells. It is not intended to answer site-specific questions, cannot predict contaminant concentrations, and does not even rank the different areas of the state by risk of contamination. Each of these additional uses would require specific assessments of vulnerability to different activities, contaminants, and risk. The map is simply a way to communicate qualitative susceptibility to contamination from the surface, based on the depth and type of cover, natural quality of the aquifer, well location and construction, and presence of special features that may alter the transport of contaminants.

Iowa's vulnerability map is viewed as an intermediate product in an ongoing process of learning more about the natural ground water system and the effects of surface and near-surface activities on that system. New maps will contain some of the basic data generated by the vulnerability study. New research and data collection will aim to identify ground water sources not included in the analysis (e.g., buried channel aquifers and the "salt and pepper sands" of western Iowa). Further analyses of existing and new well water quality data will be used to clarify relationships between aquifer depth and ground water contamination. As new information is obtained, databases and the GIS will be updated. Over time, new vulnerability maps may be produced to reflect new data or improved knowledge of environmental processes.

The Cape Cod sand and gravel aquifer is the U.S. Environmental Protection Agency (EPA) designated sole source of drinking water for Barnstable County, Massachusetts (ca. 400 square miles, winter population 186,605 in 1990, summer population ca. 500,000) as well as the source of fresh water for numerous kettle hole ponds and marine embayments. During the past 20 years, a period of intense development of open land accompanied by well-reported ground water contamination incidents, Cape Cod has been the site of intensive efforts in ground water management and analysis by many organizations, including the Association for the Preservation of Cape Cod, the U.S. Geological Survey, the Massachusetts Department of Environmental Protection (formerly the Department of Environmental Quality Engineering), EPA, and the Cape Cod Commission (formerly the Cape Cod Planning and Economic Development Commission). An earlier NRC publication, Ground Water Quality Protection: State and Local Strategies (1986) summarizes the Cape Cod ground water protection program.

The Area Wide Water Quality Management Plan for Cape Cod (CCPEDC 1978a, b), prepared in response to section 208 of the federal Clean Water Act, established a management strategy for the Cape Cod aquifer. The plan emphasized wellhead protection of public water supplies, limited use of public sewage collection systems and treatment facilities, and continued general reliance on on-site septic systems, and relied on density controls for regulation of nitrate concentrations in public drinking water supplies. The water quality management planning program began an effort to delineate the zones of contribution (often called contributing areas) for public wells on Cape Cod that has become increasingly sophisticated over the years. The effort has grown to address a range of ground water resources and ground water dependent resources beyond the wellhead protection area, including fresh and marine surface waters, impaired areas, and water quality improvement areas (CCC 1991). Plate 2 depicts the water resources classifications for Cape Cod.

Selection and Implementation of Approaches

The first effort to delineate the contributing area to a public water supply well on Cape Cod came in 1976 as part of the initial background studies for the Draft Area Wide Water Quality Management Plan for Cape

Cod (CCPEDC 1978a). This effort used a simple mass balance ratio of a well's pumping volume to an equal volume average annual recharge evenly spread over a circular area. This approach, which neglects any hydrogeologic characteristics of the aquifer, results in a number of circles of varying radii that are centered at the wells.

The most significant milestone in advancing aquifer protection was the completion of a regional, 10 foot contour interval, water table map of the county by the USGS (LeBlanc and Guswa 1977). By the time that the Draft and Final Area Wide Water Quality Management Plans were published (CCPEDC 1978a, b), an updated method for delineating zones of contribution, using the regional water table map, had been developed. This method used the same mass balance approach to characterize a circle, but also extended the zone area by 150 percent of the circle's radius in the upgradient direction. In addition, a water quality watch area extending upgradient from the zone to the ground water divide was recommended. Although this approach used the regional water table map for information on ground water flow direction, it still neglected the aquifer's hydrogeologic parameters.

In 1981, the USGS published a digital model of the aquifer that included regional estimates of transmissivity (Guswa and LeBlanc 1981). In 1982, the CCPEDC used a simple analytical hydraulic model to describe downgradient and lateral capture limits of a well in a uniform flow field (Horsley 1983). The input parameters required for this model included hydraulic gradient data from the regional water table map and transmissivity data from the USGS digital model. The downgradient and lateral control points were determined using this method, but the area of the zone was again determined by the mass balance method. Use of the combined hydraulic and mass balance method resulted in elliptical zones of contribution that did not extend upgradient to the ground water divide. This combined approach attempted to address three-dimensional ground water flow beneath a partially penetrating pumping well in a simple manner.

At about the same time, the Massachusetts Department of Environmental Protection started the Aquifer Lands Acquisition (ALA) Program to protect land within zones of contribution that would be delineated by detailed site-specific studies. Because simple models could not address three-dimensional flow and for several other reasons, the ALA program adopted a policy that wellhead protection areas or Zone IIs (DEP-WS 1991) should be extended upgradient all the way to a ground water divide. Under this program, wells would be pump tested for site-specific aquifer parameters and more detailed water table mapping would often be required. In many cases, the capture area has been delineated by the same simple hydraulic analytical model but the zone has been extended to the divide. This method has resulted in some 1989 zones that are 3,000 feet wide and extend 4.5

miles upgradient, still without a satisfactory representation of three-dimensional flow to the well.

Most recently the USGS (Barlow 1993) has completed a detailed subregional, particle-tracking three-dimensional ground water flow model that shows the complex nature of ground water flow to wells. This approach has shown that earlier methods, in general, overestimate the area of zones of contribution (see Figure 5.1 ).

In 1988, the public agencies named above completed the Cape Cod Aquifer Management Project (CCAMP), a resource-based ground water protection study that used two towns, Barnstable and Eastham, to represent the more and less urbanized parts of Cape Cod. Among the CCAMP products were a GIS-based assessment of potential for contamination as a result of permissible land use changes in the Barnstable zones of contribution (Olimpio et al. 1991) and a ground water vulnerability assessment by Heath (1988) using DRASTIC for the same area. Olimpio et al. characterized land uses by ranking potential contaminant sources without regard to differences in vulnerability within the zones. Heath's DRASTIC analysis of the same area, shown in Figure 5.2 , delineated two distinct zones of vulnerability based on hydrogeologic setting. The Sandwich Moraine setting, with deposits of silt, sand and gravel, and depths to ground water ranging from 0 to more than 125 feet, had DRASTIC values of 140 to 185; the Barnstable Outwash Plain, with permeable sand and fine gravel deposits with beds of silt and clay and depths to ground water of less than 50 feet, yielded values of 185 to 210. The DRASTIC scores and relative contributions of the factors are shown in Tables 5.1 and 5.2 . Heath concluded that similar areas of Cape Cod would produce similar moderate to high vulnerability DRASTIC scores. The CCAMP project also addressed the potential for contamination of public water supply wells from new land uses allowable under existing zoning for the same area. The results of that effort are shown in Plate 4 .

In summary, circle zones were used initially when the hydrogeologic nature of the aquifer or of hydraulic flow to wells was little understood. The zones improved with an understanding of ground water flow and aquifer characteristics, but in recognition of the limitations of regional data, grossly conservative assumptions came into use. Currently, a truer delineation of a zone of contribution can be prepared for a given scenario using sophisticated models and highly detailed aquifer characterization. However, the area of a given zone still is highly dependent on the initial assumptions that dictate how much and in what circumstances a well is pumped. In the absence of ability to specify such conditions, conservative assumptions,

FIGURE 5.1 Contributing areas of wells and ponds in the complex flow system determined by using the three-dimensional model with 1987 average daily pumping rates. (Barlow 1993)

such as maximum prolonged pumping, prevail, and, therefore, conservatively large zones of contribution continue to be used for wellhead protection.

The ground water management experience of Cape Cod has resulted in a better understanding of the resource and the complexity of the aquifer

FIGURE 5.2 DRASTIC contours for Zone 1, Barnstable-Yarmouth, Massachusetts.

system, as well as the development of a more ambitious agenda for resource protection. Beginning with goals of protection of existing public water supplies, management interests have grown to include the protection of private wells, potential public supplies, fresh water ponds, and marine embayments. Public concerns over ground water quality have remained high and were a major factor in the creation of the Cape Cod Commission by the Massachusetts legislature. The commission is a land use planning and regulatory agency with broad authority over development projects and the ability to create special resource management areas. The net result of 20 years of effort by many individuals and agencies is the application of

TABLE 5.1 Ranges, Rating, and Weights for DRASTIC Study of Barnstable Outwash Plain Setting (NOTE: gpd/ft 2 = gallons per day per square foot) (Heath 1988)

TABLE 5.2 Ranges, Rating, and Weights for DRASTIC Study of Sandwich Moraine Setting (NOTE: gpd/ft 2 = gallons per day per square foot) (Heath 1988)

higher protection standards to broader areas of the Cape Cod aquifer. With some exceptions for already impaired areas, a differentiated resource protection approach in the vulnerable aquifer setting of Cape Cod has resulted in a program that approaches universal ground water protection.

Florida has 13 million residents and is the fourth most populous state (U.S. Bureau of the Census 1991). Like several other sunbelt states, Florida's population is growing steadily, at about 1,000 persons per day, and is estimated to reach 17 million by the year 2000. Tourism is the biggest industry in Florida, attracting nearly 40 million visitors each year. Ground water is the source of drinking water for about 95 percent of Florida's population; total withdrawals amount to about 1.5 billion gallons per day. An additional 3 billion gallons of ground water per day are pumped to meet the needs of agriculture—a $5 billion per year industry, second only to tourism in the state. Of the 50 states, Florida ranks eighth in withdrawal of fresh ground water for all purposes, second for public supply, first for rural domestic and livestock use, third for industrial/commercial use, and ninth for irrigation withdrawals.

Most areas in Florida have abundant ground water of good quality, but the major aquifers are vulnerable to contamination from a variety of land use activities. Overpumping of ground water to meet the growing demands of the urban centers, which accounts for about 80 percent of the state's population, contributes to salt water intrusion in coastal areas. This overpumping is considered the most significant problem for degradation of ground water quality in the state. Other major sources of ground water contaminants include: (1) pesticides and fertilizers (about 2 million tons/year) used in agriculture, (2) about 2 million on-site septic tanks, (3) more than 20,000 recharge wells used for disposing of stormwater, treated domestic wastewater, and cooling water, (4) nearly 6,000 surface impoundments, averaging one per 30 square kilometers, and (5) phosphate mining activities that are estimated to disturb about 3,000 hectares each year.

The Hydrogeologic Setting

The entire state is in the Coastal Plain physiographic province, which has generally low relief. Much of the state is underlain by the Floridan aquifer system, largely a limestone and dolomite aquifer that is found in both confined and unconfined conditions. The Floridan is overlain through most of the state by an intermediate aquifer system, consisting of predominantly clays and sands, and a surficial aquifer system, consisting of predominantly sands, limestone, and dolomite. The Floridan is one of the most productive aquifers in the world and is the most important source of drinking water for Florida residents. The Biscayne, an unconfined, shallow, limestone aquifer located in southeast Florida, is the most intensively used

aquifer and the sole source of drinking water for nearly 3 million residents in the Miami-Palm Beach coastal area. Other surficial aquifers in southern Florida and in the western panhandle region also serve as sources of ground water.

Aquifers in Florida are overlain by layers of sand, clay, marl, and limestone whose thickness may vary considerably. For example, the thickness of layers above the Floridan aquifer range from a few meters in parts of west-central and northern Florida to several hundred meters in south-central Florida and in the extreme western panhandle of the state. Four major groups of soils (designated as soil orders under the U.S. Soil Taxonomy) occur extensively in Florida. Soils in the western highlands are dominated by well-drained sandy and loamy soils and by sandy soils with loamy subsoils; these are classified as Ultisols and Entisols. In the central ridge of the Florida peninsula, are found deep, well-drained, sandy soils (Entisols) as well as sandy soils underlain by loamy subsoils or phosphatic limestone (Alfisols and Ultisols). Poorly drained sandy soils with organic-rich and clay-rich subsoils, classified as Spodosols, occur in the Florida flatwoods. Organic-rich muck soils (Histosols) underlain by muck or limestone are found primarily in an area extending south of Lake Okeechobee.

Rainfall is the primary source of ground water in Florida. Annual rainfall in the state ranges from 100 to 160 cm/year, averaging 125 cm/year, with considerable spatial (both local and regional) and seasonal variations in rainfall amounts and patterns. Evapotranspiration (ET) represents the largest loss of water; ET ranges from about 70 to 130 cm/year, accounting for between 50 and 100 percent of the average annual rainfall. Surface runoff and ground water discharge to streams averages about 30 cm/year. Annual recharge to surficial aquifers ranges from near zero in perennially wet, lowland areas to as much as 50 cm/year in well-drained areas; however, only a fraction of this water recharges the underlying Floridan aquifer. Estimates of recharge to the Floridan aquifer vary from less than 3 cm/year to more than 25 cm/year, depending on such factors as weather patterns (e.g., rainfall-ET balance), depth to water table, soil permeability, land use, and local hydrogeology.

Permeable soils, high net recharge rates, intensively managed irrigated agriculture, and growing demands from urban population centers all pose considerable threat of ground water contamination. Thus, protection of this valuable natural resource while not placing unreasonable constraints on agricultural production and urban development is the central focus of environmental regulation and growth management in Florida.

Along with California, Florida has played a leading role in the United

States in development and enforcement of state regulations for environmental protection. Detection in 1983 of aldicarb and ethylene dibromide, two nematocides used widely in Florida's citrus groves, crystallized the growing concerns over ground water contamination and the need to protect this vital natural resource. In 1983, the Florida legislature passed the Water Quality Assurance Act, and in 1984 adopted the State and Regional Planning Act. These and subsequent legislative actions provide the legal basis and guidance for the Ground Water Strategy developed by the Florida Department of Environmental Regulation (DER).

Ground water protection programs in Florida are implemented at federal, state, regional, and local levels and involve both regulatory and nonregulatory approaches. The most significant nonregulatory effort involves more than 30 ground water studies being conducted in collaboration with the Water Resources Division of the U.S. Geological Survey. At the state level, Florida statutes and administrative codes form the basis for regulatory actions. Although DER is the primary agency responsible for rules and statutes designed to protect ground water, the following state agencies participate to varying degrees in their implementation: five water management districts, the Florida Geological Survey, the Department of Health and Rehabilitative Services (HRS), the Department of Natural Resources, and the Florida Department of Agriculture and Consumer Services (DACS). In addition, certain interagency committees help coordinate the development and implementation of environmental codes in the state. A prominent example is the Pesticide Review Council which offers guidance to the DACS in developing pesticide use regulation. A method for screening pesticides in terms of their chronic toxicity and environmental behavior has been developed through collaborative efforts of the DACS, the DER, and the HRS (Britt et al. 1992). This method will be used to grant registration for pesticide use in Florida or to seek additional site-specific field data.

Selecting an Approach

The emphasis of the DER ground water program has shifted in recent years from primarily enforcement activity to a technically based, quantifiable, planned approach for resource protection.

The administrative philosophy for ground water protection programs in Florida is guided by the following principles:

Ground water is a renewable resource, necessitating a balance between withdrawals and natural or artificial recharge.

Ground water contamination should be prevented to the maximum degree possible because cleanup of contaminated aquifers is technically or economically infeasible.

It is impractical, perhaps unnecessary, to require nondegradation standards for all ground water in all locations and at all times.

The principle of ''most beneficial use" is to be used in classifying ground water into four classes on the basis of present quality, with the goal of attaining the highest level protection of potable water supplies (Class I aquifers).

Part of the 1983 Water Quality Assurance Act requires Florida DER to "establish a ground water quality monitoring network designed to detect and predict contamination of the State's ground water resources" via collaborative efforts with other state and federal agencies. The three basic goals of the ground water quality monitoring program are to:

Establish the baseline water quality of major aquifer systems in the state,

Detect and predict changes in ground water quality resulting from the effects of various land use activities and potential sources of contamination, and

Disseminate to local governments and the public, water quality data generated by the network.

The ground water monitoring network established by DER to meet the goals stated above consists of two major subnetworks and one survey (Maddox and Spicola 1991). Approximately 1,700 wells that tap all major potable aquifers in the state form the Background Network, which was designed to help define the background water quality. The Very Intensively Studied Area (VISA) network was established to monitor specific areas of the state considered highly vulnerable to contamination; predominant land use and hydrogeology were the primary attributes used to evaluate vulnerability. The DRASTIC index, developed by EPA, served as the basis for statewide maps depicting ground water vulnerability. Data from the VISA wells will be compared to like parameters sampled from Background Network wells in the same aquifer segment. The final element of the monitoring network is the Private Well Survey, in which up to 70 private wells per county will be sampled. The sampling frequency and chemical parameters to be monitored at each site are based on several factors, including network well classification, land use activities, hydrogeologic sensitivity, and funding. In Figure 5.3 , the principal aquifers in Florida are shown along with the distribution of the locations of the monitoring wells in the Florida DER network.

The Preservation 2000 Act, enacted in 1990, mandated that the Land Acquisition Advisory Council (LAAC) "provide for assessing the importance

FIGURE 5.3 Principal aquifers in Florida and the network of sample wells as of March 1990 (1642 wells sampled). (Adapted from Maddox and Spicola 1991, and Maddox et al. 1993.)

of acquiring lands which can serve to protect or recharge ground water, and the degree to which state land acquisition programs should focus on purchasing such land." The Ground Water Resources Committee, a subcommittee of the LAAC, produced a map depicting areas of ground water significance at regional scale (1:500,000) (see Figure 5.4 ) to give decision makers the basis for considering ground water as a factor in land acquisition under the Preservation 2000 Act (LAAC 1991). In developing maps for their districts, each of the five water management districts (WMDs) used the following criteria: ground water recharge, ground water quality, aquifer vulnerability, ground water availability, influence of existing uses on the resource, and ground water supply. The specific approaches used by

FIGURE 5.4 General areas of ground water significance in Florida. (Map provided by Florida Department of Environmental Regulation, Bureau of Drinking Water and Ground Water Resources.)

the WMDs varied, however. For example, the St. Johns River WMD used a GIS-based map overlay and DRASTIC-like numerical index approach that rated the following attributes: recharge, transmissivity, water quality, thickness of potable water, potential water expansion areas, and spring flow capture zones. The Southwest Florida WMD also used a map overlay and index approach which considered four criteria, and GIS tools for mapping. Existing databases were considered inadequate to generate a DRASTIC map for the Suwannee River WMD, but the map produced using an overlay approach was considered to be similar to DRASTIC maps in providing a general depiction of aquifer vulnerability.

In the November 1988, Florida voters approved an amendment to the Florida Constitution allowing land producing high recharge to Florida's aquifers to be classified and assessed for ad valorem tax purposes based on character or use. Such recharge areas are expected to be located primarily in the upland, sandy ridge areas. The Bluebelt Commission appointed by the 1989 Florida Legislature, studied the complex issues involved and recommended that the tax incentive be offered to owners of such high recharge areas if their land is left undeveloped (SFWMD 1991). The land eligible

for classification as "high water recharge land" must meet the following criteria established by the commission:

The parcel must be located in the high recharge areas designated on maps supplied by each of the five WMDs.

The high recharge area of the parcel must be at least 10 acres.

The land use must be vacant or single-family residential.

The parcel must not be receiving any other special assessment, such as Greenbelt classification for agricultural lands.

Two bills related to the implementation of the Bluebelt program are being considered by the 1993 Florida legislation.

THE SAN JOAQUIN VALLEY

Pesticide contamination of ground water resources is a serious concern in California's San Joaquin Valley (SJV). Contamination of the area's aquifer system has resulted from a combination of natural geologic conditions and human intervention in exploiting the SJV's natural resources. The SJV is now the principal target of extensive ground water monitoring activities in the state.

Agriculture has imposed major environmental stresses on the SJV. Natural wetlands have been drained and the land reclaimed for agricultural purposes. Canal systems convey water from the northern, wetter parts of the state to the south, where it is used for irrigation and reclamation projects. Tens of thousands of wells tap the sole source aquifer system to supply water for domestic consumption and crop irrigation. Cities and towns have sprouted throughout the region and supply the human resources necessary to support the agriculture and petroleum industries.

Agriculture is the principal industry in California. With 1989 cash receipts of more than $17.6 billion, the state's agricultural industry produced more than 50 percent of the nation's fruits, nuts, and vegetables on 3 percent of the nation's farmland. California agriculture is a diversified industry that produces more than 250 crop and livestock commodities, most of which can be found in the SJV.

Fresno County, the largest agricultural county in the state, is situated in the heart of the SJV, between the San Joaquin River to the north and the Kings River on the south. Grapes, stone fruits, and citrus are important commodities in the region. These and many other commodities important to the region are susceptible to nematodes which thrive in the county's coarse-textured soils.

While agricultural diversity is a sound economic practice, it stimulates the growth of a broad range of pest complexes, which in turn dictates greater reliance on agricultural chemicals to minimize crop losses to pests, and maintain productivity and profit. Domestic and foreign markets demand high-quality and cosmetically appealing produce, which require pesticide use strategies that rely on pest exclusion and eradication rather than pest management.

Hydrogeologic Setting

The San Joaquin Valley (SJV) is at the southern end of California's Central Valley. With its northern boundary just south of Sacramento, the Valley extends in a southeasterly direction about 400 kilometers (250 miles) into Kern County. The SJV averages 100 kilometers (60 miles) in width and drains the area between the Sierra Nevada on the east and the California Coastal Range on the west. The rain shadow caused by the Coastal Range results in the predominantly xeric habitat covering the greater part of the valley floor where the annual rainfall is about 25 centimeters (10 inches). The San Joaquin River is the principal waterway that drains the SJV northward into the Sacramento Delta region.

The soils of the SJV vary significantly. On the west side of the valley, soils are composed largely of sedimentary materials derived from the Coastal Range; they are generally fine-textured and slow to drain. The arable soils of the east side developed on relatively unweathered, granitic sediments. Many of these soils are wind-deposited sands underlain by deep coarse-textured alluvial materials.

From the mid-1950s until 1977, dibromochloropropane (DBCP) was the primary chemical used to control nematodes. DBCP has desirable characteristics for a nematocide. It is less volatile than many other soil fumigants, such as methylbromide; remains active in the soil for a long time, and is effective in killing nematodes. However, it also causes sterility in human males, is relatively mobile in soil, and is persistent. Because of the health risks associated with consumption of DBCP treated foods, the nematocide was banned from use in the United States in 1979. After the ban, several well water studies were conducted in the SJV by state, county and local authorities. Thirteen years after DBCP was banned, contamination of well waters by the chemical persists as a problem in Fresno County.

Public concern over pesticides in ground water resulted in passage of the California Pesticide Contamination Prevention Act (PCPA) of 1985. It is a broad law that establishes the California Department of Pesticide Regulation

as the lead agency in dealing with issues of ground water contamination by pesticides. The PCPA specifically requires:

pesticide registrants to collect and submit specific chemical and environmental fate data (e.g., water solubility, vapor pressure, octanol-water partition coefficient, soil sorption coefficient, degradation half-lives for aerobic and anaerobic metabolism, Henry's Law constant, hydrolysis rate constant) as part of the terms for registration and continued use of their products in California.

establishment of numerical criteria or standards for physical-chemical characteristics and environmental fate data to determine whether a pesticide can be registered in the state that are at least as stringent as those standards set by the EPA,

soil and water monitoring investigations be conducted on:

pesticides with properties that are in violation of the physical-chemical standards set in 2 above, and

pesticides, toxic degradation products or other ingredients that are:

contaminants of the state's ground waters, or

found at the deepest of the following soil depths:

2.7 meters (8 feet) below the soil surface,

below the crop root zone, or

below the microbial zone, and

creation of a database of wells sampled for pesticides with a provision requiring all agencies to submit data to the California Department of Pesticide Regulation (CDPR).

Difficulties associated with identifying the maximum depths of root zone and microbial zone have led to the establishment of 8 feet as a somewhat arbitrary but enforceable criterion for pesticide leaching in soils.

Selection and Implementation of an Approach

Assessment of ground water vulnerability to pesticides in California is a mechanical rather than a scientific process. Its primary goal is compliance with the mandates established in the PCPA. One of these mandates requires that monitoring studies be conducted in areas of the state where the contaminant pesticide is used, in other areas exhibiting high risk portraits (e.g., low organic carbon, slow soil hydrolysis, metabolism, or dissipation), and in areas where pesticide use practices present a risk to the state's ground water resources.

The numerical value for assessments was predetermined by the Pesticide Use Report (PUR) system employed in the state. Since the early

1970s, California has required pesticide applicators to give local authorities information on the use of restricted pesticides. This requirement was extended to all pesticides beginning in 1990. Application information reported includes names of the pesticide(s) and commodities, the amount applied, the formulation used, and the location of the commodity to the nearest section (approximately 1 square mile) as defined by the U.S. Rectangular Coordinate System. In contrast to most other states that rely on county pesticide sales in estimating pesticide use, California can track pesticide use based on quantities applied to each section. Thus, the section, already established as a political management unit, became the basic assessment unit.

The primary criteria that subject a pesticide to investigation as a ground water pollutant are:

detection of the pesticide or its metabolites in well samples, or

its failure to conform to the physical-chemical standards set in accordance with the PCPA, hence securing its position on the PCPA's Ground Water Protection List of pesticides having a potential to pollute ground water.

In either case, relatively large areas surrounding the original detection site or, in the latter case, high use regions are monitored via well surveys. Positive findings automatically increase the scope of the surveys, and since no tolerance levels are specified in the PCPA, any detectable and confirmed result establishes a pesticide as a contaminant.

When a pesticide or its degradation products is detected in a well water sample and the pesticide is judged to have contaminated the water source as a result of a legal agricultural use, the section the well is in is declared a Pesticide Management Zone (PMZ). Further application of the detected pesticide within PMZ boundaries may be prohibited or restricted, depending on the degree of contamination and subject to the availability of tried and tested modifications in management practices addressing environmental safety in use of the pesticide. PMZs are pesticide-specific—each contaminant pesticide has its own set of PMZs which may or may not overlap PMZs assigned another pesticide. Currently, consideration is being given to the extension of PMZs established for one chemical to other potential pesticide pollutants. In addition to monitoring activities in PMZs, protocols have been written to monitor ground water in sections adjacent to a PMZ. Monitoring of adjacent sections has resulted in many new PMZs. Currently, California has 182 PMZs involving five registered pesticides.

California has pursued this mechanical approach to assessing ground water vulnerability to pesticides for reasons that cover a spectrum of political, economic, and practical concerns. As noted earlier, the scale of the assessment unit was set at the section level because it is a well-defined

geopolitical unit used in the PUR system. Section boundaries frequently are marked by roads and highways, which allows the section to be located readily and makes enforcement of laws and regulations more practical. California law also requires that well logs be recorded by drillers for all wells in the state. Well-site information conforms to the U.S. Rectangular Coordinate System's township, range, and section system.

The suitability and reliability of databases available for producing vulnerability assessments was a great concern before passage of the PCPA in 1985. Soil survey information holds distinct advantages for producing assessments and developing best management practices strategies, but it was not available in a format that could work in harmony with PUR sections. To date, several areas of the SJV are not covered by a modern soil survey; they include the western part of Tulare County, which contains 34 PMZs. Other vadose zone data were sparse, it available at all.

The use of models was not considered appropriate, given the available data and because no single model could cope with the circumstances in which contaminated ground water sources were being discovered in the state. While most cases of well contamination were associated with the coarse-textured soils of the SJV and the Los Angeles Basin, several cases were noted in areas of the Central Valley north of the SJV, where very dense fine-textured soils (vertisols and other cracking clays) were dominant.

The potential vagaries and uncertainties associated with more scientific approaches to vulnerability assessment, given the tools available when the PCPA was enacted, presented too large a risk for managers to consider endorsing their use. In contrast, the basic definition of the PMZ is difficult to challenge (pesticide contamination has been detected or not detected) in the legal sense. And the logic of investing economic resources in areas immediately surrounding areas of acknowledged contamination are relatively undisputable. The eastern part of the SJV contains more than 50 percent of the PMZs in the state. Coarse-textured soils of low carbon content are ubiquitous in this area and are represented in more than 3,000 sections. The obvious contamination scenario is the normal scenario in the eastern SJV, and because of its size it creates a huge management problem. While more sophisticated methods for assessing ground water vulnerability have been developed, a question that begs to be asked is "How would conversion to the use of enhanced techniques for evaluating ground water vulnerability improve ground water protection policy and management in the SJV?"

More than 90 percent of the population of Hawaii depends on ground water (nearly 200 billion gallons per day) for their domestic supply (Au 1991). Ground water contamination is of special concern in Hawaii, as in other insular systems, where alternative fresh water resources are not readily available or economically practical. Salt water encroachment, caused by pumping, is by far the biggest source of ground water contamination in Hawaii; however, nonpoint source contamination from agricultural chemicals is increasingly a major concern. On Oahu, where approximately 80 percent of Hawaii's million-plus population resides, renewable ground water resources are almost totally exploited; therefore, management action to prevent contamination is essential.

Each of the major islands in the Hawaiian chain is formed from one or more shield volcanoes composed primarily of extremely permeable thin basaltic lava flows. On most of the Hawaiian islands the margins of the volcanic mountains are overlapped by coastal plain sediments of alluvial and marine origin that were deposited during periods of volcanic quiescence. In general, the occurrence of ground water in Hawaii, shown in Figure 5.5 , falls into three categories: (1) basal water bodies floating on and displacing salt water, (2) high-level water bodies impounded within compartments formed by impermeable dikes that intrude the lava flows, and (3) high-level water bodies perched on ash beds or soils interbedded with

FIGURE 5.5 Cross section of a typical volcanic dome showing the occurrence of ground water in Hawaii (After Peterson 1972. Reprinted, by permission, from Water Well Journal Publishing Company, 1972.)

thin lava flows on unconformities or on other relatively impervious lava flows (Peterson 1972).

A foundation of the tourist industry in Hawaii is the pristine environment. The excellent quality of Hawaii's water is well known. The public has demanded, and regulatory agencies have adopted, a very conservative, zero-tolerance policy on ground water contamination. The reality, however, is that past, present, and future agricultural, industrial, and military activities present potentially significant ground water contamination problems in Hawaii.

Since 1977 when 1,874 liters of ethylene dibromide (EDB) where spilled within 18 meters of a well near Kunia on the island of Oahu, the occurrence and distribution of contaminants in Hawaii's ground water has been carefully documented by Oki and Giambelluca (1985, 1987) and Lau and Mink (1987). Before 1981, when the nematocide dibromochloropropane (DBCP) was found in wells in central Oahu, the detection limit for most chemicals was too high to reveal the low level of contamination that probably had existed for many years.

Concern about the fate of agriculture chemicals led the Hawaii State Department of Agriculture to initiate a large sampling program to characterize the sources of nonpoint ground water contamination. In July 1983, 10 wells in central Oahu were closed because of DBCP and EDB contamination. The public has been kept well informed of possible problems through the publication of maps of chemicals detected in ground water in the local newspaper. Updated versions of these maps are shown in Figures 5.6a , b , c , and d .

In Hawaii, interagency committees, with representation from the Departments of Health and Agriculture, have been formed to address the complex technical and social questions associated with ground water contamination from agricultural chemicals. The Hawaii legislature has provided substantial funding to groups at the University of Hawaii to develop the first GIS-based regional scale chemical leaching assessment approach to aid in pesticide regulation. This effort, described below, has worked to identify geographic areas of concern, but the role the vulnerability maps generated by this system will play in the overall regulatory process is still unclear.

Agrichemicals are essential to agriculture in Hawaii. It is not possible to maintain a large pineapple monoculture in Hawaii without nematode control using pesticides. Pineapple and sugar growers in Hawaii have generally employed well controlled management practices in their use of fertilizers, herbicides, and insecticides. In the early 1950s, it was thought that organic chemicals such as DBCP and EDB would not leach to ground water

FIGURE 5.6a The occurrence and distribution of ground water contamination on the Island of Oahu. (Map provided by Hawaii State Department of Health.)

FIGURE 5.6b The occurrence and distribution of ground water contamination on the Island of Hawaii. (Map provided by Hawaii State Department of Health.)

FIGURE 5.6c The occurrence and distribution of ground water contamination on the Island of Maui. (Map provided by Hawaii State Department of Health.)

FIGURE 5.6d The occurrence and distribution of ground water contamination on the Island of Kauai. (Map provided by Hawaii State Department of Health.)

because (1) the chemicals are highly sorbed in soils with high organic carbon contents, (2) the chemicals are highly volatile, and (3) the water table is several hundred meters below the surface. Measured concentrations of DBCP and EDB down to 30 meters at several locations have shown the original assessment to be wrong. They have resulted in an urgent need to understand processes such as preferential flow better and to predict if the replacement chemicals used today, such as Telon II, will also leach to significant depths.

Leaching of pesticides to ground water in Hawaii could take decades. This time lag could lead to a temporary false sense of security, as happened in the past and potentially result in staggering costs for remedial action. For this reason, mathematical models that permit the user to ask ''what if" questions have been developed to help understand what the future may hold under certain management options. One needs to know what the fate of chemicals applied in the past will be and how to regulate the chemicals considered for use in the future; models are now being developed and used to help make these vulnerability assessments.

Researchers have embarked on several parallel approaches to quantitatively assess the vulnerability of Hawaii's ground water resources, including: (1) sampling, (2) physically-based numerical modeling, and (3) vulnerability mapping based on a simple chemical leaching index. Taken together these approaches have provided insight and guidance for work on a complex, spatially and temporally variable problem.

The sampling programs (Wong 1983 and 1987, Peterson et al. 1985) have shown that the chemicals applied in the past do, in fact, leach below the root zone, contrary to the original predictions, and can eventually reach the ground water. Experiments designed to characterize the nuances of various processes, such as volatilization, sorption, and degradation, have been conducted recently and will improve the conceptualization of mathematical models in the future.

The EPA's Pesticide Root Zone Model (PRZM), a deterministic-empirical/conceptual fluid flow/solute transport model, has been tested by Loague and co-workers (Loague et al. 1989a, b; Loague 1992) against measured concentration profiles for DBCP and EDB in central Oahu. These simulations illustrate that the chemicals used in the past can indeed move to considerable depths. Models of this kind, once properly validated, can be used to simulate the predicted fate of future pesticide applications. One must always remember, however, that numerical simulations must be interpreted in terms of the limiting assumptions associated with model and data errors.

Ground water vulnerability maps and assessments of their uncertainty were pioneered at the University of Hawaii in the Department of Agriculture Engineering (Khan and Liang 1989, Loague and Green 1990a). These pesticide leaching assessments were made by coupling a simple mobility index to a geographic information system. Loague and coworkers have investigated the uncertainty in these maps owing to data and model errors (Loague and Green 1988; Loague et al. 1989c, 1990; Loague and Green 1990b, 1990c; Loague 1991; Kleveno et al. 1992; Yost et al. 1993). The Hawaiian database on soils, climate, and chemicals is neither perfect nor poor for modeling applications; it is typical of what exists in most states—major extrapolations are required to estimate the input parameters required for almost any chemical fate model.

Sampling from wells in Hawaii has shown the concentrations of various chemicals, both from agriculture and industrial sources, which have leached to ground water in Hawaii. These concentrations, in general, are low compared to the levels detected in other states and for the most part are below health advisory levels established by EPA. In some instances contamination has not resulted from agriculture, but rather from point sources such as chemical loading and mixing areas and possibly from ruptured fuel lines. The widespread presence of trichloropropane (TCP) in Hawaii's ground water and deep soil cores at concentrations higher than DBCP was totally unexpected. TCP was never applied as a pesticide, but results from the manufacture of the fumigant DD, which was used until 1977 in pineapple culture. The occurrence of TCP illustrates that one must be aware of the chemicals applied as well as their components and transformation products.

Wells have been closed in Hawaii even though the measured contaminant concentrations have been below those considered to pose a significant health risk. At municipal well locations in central Oahu, where DBCP, EDB, and/or TCP have been detected, the water is now passed through carbon filters before it is put into the distribution system. The cost of this treatment is passed on to the water users, rather than to those who applied the chemicals.

The pesticide leaching assessment maps developed by Khan and Liang (1989) are intended for incorporation into the regulatory process. Decisions are not made on the basis of the red and green shaded areas for different chemicals (see Plate 3 ), but this information is considered. The uncertainty analysis by Loague and coworkers has shown some of the limitations of deterministic assessments in the form of vulnerability maps and provided initial guidance on data shortfalls.

APPLICATION OF A VULNERABILITY INDEX FOR DECISION-MAKING AT THE NATIONAL LEVEL

Need for a vulnerability index.

A vulnerability index for ground water contamination by pesticides has been developed and used by USDA as a decision aid to help attain the objectives of the President's Water Quality Initiative (see Box 1.1 ). A vulnerability index was needed for use in program management and to provide insight for policy development. Motivation for the development of the vulnerability index was provided by two specific questions:

Given limited resources and the geographic diversity of the water quality problems associated with agricultural production, what areas of the country have the highest priority for study and program implementation?

What policy implications emerge from the spatial patterns of the potential for conamination from a national perspective, given information currently available about farming practices and chemical use in agriculture?

Description of the Vulnerability Index

A vulnerability index was derived to evaluate the likelihood of shallow ground water contamination by pesticides used in agriculture in one area compared to another area. Because of the orientation of Initiative policies to farm management practices, it was necessary that the vulnerability measure incorporate field level information on climate, soils, and chemical use. It also needed to be general enough to include all areas of the country and all types of crops grown.

A Ground Water Vulnerability Index for Pesticides (GWVIP) was developed by applying the Soil-Pesticide Interaction Screening Procedure (SPISP) developed by the Soil Conservation Service to the National Resource Inventory (NRI) land use database for 1982 and the state level pesticide use database created by Resources for the Future (Gianessi and Puffer 1991). Details of the computational scheme and databases used are described by Kellogg et al. (1992). The 1982 NRI and the associated SOIL-5 database provide information on soil properties and land use at about 800,000 sample points throughout the continental United States. This information is sufficient to apply the SPISP to each point and thus obtain a relative measure of the soil leaching potential throughout the country. The RFF pesticide use database was used to infer chemical use at each point on the basis of the crop type recorded in the NRI database. By taking advantage of the statistical properties of the NRI database, which is based on a statistical survey

sampling design, the GWVIP score at each of the sample points can be statistically aggregated for making comparisons among regions.

Since the GWVIP is an extension of a screening procedure, it is designed to minimize the likelihood of incorrectly identifying an area as having a low potential for contamination—that is, false negatives are minimized and false positives are tolerated. The GWVIP is designed to classify an area as having a potential problem even if the likelihood is small.

GWVIP scores were graphically displayed after embedding them in a national cartographic database consisting of 13,172 polygons created by overlaying the boundaries of 3,041 counties, 189 Major Land Resource Areas (MLRAs), 2,111 hydrologic units, and federal lands.

Three caveats are especially important in using the GWVIP and its aggregates as a decision aid:

Land use data are for 1982 and do not represent current cropping patterns in some parts of the country. Although total cropland acreage has remained fairly stable over the past 10 years, there has been a pronounced shift from harvested cropland to cropland idled in government programs.

The approach uses a simulation model that predicts the amount of chemical that leaches past the root zone. In areas where the water table is near the surface, these predictions relate directly to shallow ground water contamination. In other areas a time lag is involved. No adjustment was made for areas with deep water tables.

No adjustment in chemical use is made to account for farm management factors, such as chemical application rates and crop rotations. The approach assumes that chemical use is the same for a crop grown as part of a rotation cropping system as for continuous cropping. Since the chemical use variable in the GWVIP calculation is based on acres of land treated with pesticides, application rates are also not factored into the analysis.

Application to Program Management

By identifying areas of the country that have the highest potential for leaching of agrichemicals, the GWVIP can serve as a basis for selecting sites for implementation of government programs and for more in-depth research on the environmental impact of agrichemical use. These sites cannot be selected exclusively on the basis of the GWVIP score, however, because other factors, such as surface water impacts and economic and demographic factors, are also important.

For example, the GWVIP has been used as a decision aid in selecting sites for USDA's Area Study Program, which is designed to provide chemical use and farming practice information to aid in understanding the relationships among farming activities, soil properties, and ground water quality.

The National Agricultural Statistics Service interviews farm operators in 12 major watersheds where the U.S. Geological Survey is working to measure the quality of surface and ground water resources under its National Water Quality Assessment Program. At the conclusion of the project, survey information will be combined with what is learned in other elements of the President's Water Quality Initiative to assess the magnitude of the agriculture-related water quality problem for the nation as a whole and used to evaluate the potential economic and environmental effects of Initiative policies of education, technical assistance, and financial assistance if implemented nationwide.

To meet these objectives, each Area Study site must have a high potential for ground water contamination relative to other areas of the country. A map showing the average GWVIP for each of the 13,172 polygons comprising the continental United States, shown in Plate 3 , was used to help select the sites. As this map shows, areas more likely to have leaching problems with agrichemicals than other areas of the country occur principally along the coastal plains stretching from Alabama and Georgia north to the Chesapeake Bay area, the corn belt states, the Mississippi River Valley, and the irrigated areas in the West. Sites selected for study in 1991 and 1992 include four from the eastern coastal plain (Delmarva Peninsula, southeastern Pennsylvania, Virginia and North Carolina, and southern Georgia), four from the corn belt states (Nebraska, Iowa, Illinois, and Indiana), and two from the irrigated areas in the West (eastern Washington and southeastern Idaho). Four additional sites will be selected for study in 1993.

Application to Policy Analysis and Development

The GWVIP has also been used by USDA to provide a national perspective on agricultural use of pesticides and the potential for ground water contamination to aid in policy analysis and development.

The geographic distribution of GWVIP scores has shown that the potential for ground water contamination is diverse both nationally and regionally. Factors that determine intrinsic vulnerability differ in virtually every major agricultural region of the country. Whether an impact is realized in these intrinsically vulnerable areas depends on the activities of producers—such as the type of crop planted, chemical use, and irrigation practices—which also vary both nationally and regionally. High vulnerability areas are those where a confluence of these factors is present. But not all cropland is vulnerable to leaching. About one-fourth of all cropland has GWVIP scores that indicate very low potential for ground water contamination from the use of agrichemicals. Nearly all agricultural states have significant acreage that meets this low vulnerability criterion. Areas of the country identified as being in a high vulnerability group relative to potential

for agrichemical leaching also have significant acreages that appear to have low vulnerability.

This mix of relative vulnerabilities both nationally and regionally has important policy implications. With the potential problem so diverse, it is not likely that simple, across-the-board solutions will work. Simple policies—such as selective banning of chemicals—may reduce the potential for ground water contamination in problem areas while imposing unnecessary costs on farming in nonproblem areas. The geographic diversity of the GWVIP suggests that the best solutions will come from involvement of both local governments and scientists with their state and national counter-parts to derive policies that are tailored to the unique features of each problem area.

In the future, USDA plans to use vulnerability indexes, like the GWVIP, in conjunction with economic models to evaluate the potential for solving agriculture-related water quality problems with a nationwide program to provide farmers with the knowledge and technical means to respond voluntarily to water quality concerns.

These six case studies illustrate how different approaches to vulnerability assessment have evolved under diverse sets of management requirements, data constraints, and other technical considerations. In addition, each of these examples shows that vulnerability assessment is an ongoing process through which information about a region's ground water resources and its quality can be organized and examined methodically.

In Iowa, the Iowa DNR staff elected to keep their vulnerability characterization efforts as simple as possible, and to use only properties for which data already existed or could be easily checked. They assumed that surficial features such as the soil are too thin and too disrupted by human activities (e.g., tillage, abandoned wells) to provide effective ground water protection at any particular location and sought to identify a surrogate measure for average travel time from the land surface to the aquifer. Thus, a ground water vulnerability map was produced which represents vulnerability primarily on the basis of depth to ground water and extent of overlying materials. Wells and sinkholes are also shown. The results are to be used for informing resource managers and the public of the vulnerability of the resource and to determine the type of information most needed to develop an even better understanding of the vulnerability of Iowa's ground water.

The Cape Cod approach to ground water vulnerability assessment is perhaps one of the oldest and most sophisticated in the United States. Driven by the need to protect the sole source drinking water aquifer underlying this sandy peninsula, the vulnerability assessment effort has focused on the identification

and delineation of the primary recharge areas for the major aquifers. This effort began with a simple mass balance approach which assumed even recharge within a circular area around each drinking water well. It has since evolved to the development of a complex, particle-tracking three-dimensional model that uses site-specific data to delineate zones of contribution. Bolstered by strong public concern, Cape Cod has been able to pursue an ambitious and sophisticated agenda for resource protection, and now boasts a sophisticated differential management ground water protection program.

In Florida, ground water resource managers rely on a combination of monitoring and vulnerability assessment techniques to identify high recharge areas the develop the state ground water protection program. Overlay and index methods, including several modified DRASTIC maps were produced to identify areas of ground water significance in support of decision making in state land acquisition programs aimed at ground water protection. In addition, several monitoring networks have been established to assess background water quality and monitor actual effects in areas identified as highly vulnerable. The coupling of ground water vulnerability assessments with monitoring and research efforts, provides the basis of an incremental and evolving ground water protection program in Florida.

The programs to protect ground water in California's intensely agricultural San Joaquin Valley are driven largely by compliance with the state Pesticide Contamination Prevention Act. The California Department of Pesticide Regulation determined that no model would be sufficient to cover their specific regulatory needs and that the available data bases were neither suitable nor reliable for regulatory purposes. Thus, a ground water protection program was built on the extensive existing pesticide use reporting system and the significant ground water monitoring requirements of the act. Using farm sections as management units, the state declares any section in which a pesticide or its degradation product is detected as a pesticide management zone and establishes further restrictions and monitoring requirements. Thus, the need to devise a defensible regulatory approach led California to pursue a mechanistic monitoring based approach rather than a modeling approach that would have inherent and difficult to quantify uncertainties.

In contrast, the approach taken in Hawaii involves an extensive effort to understand the uncertainty associated with the assessment models used. The purpose of this is to provide guidance to, but not the sole basis for, the pesticide regulation program. The combined use of sampling, physically-based numerical modeling, and a chemical leaching index has led to extensive improvements in the understanding of the fate of pesticides in the subsurface environment. Uncertainty analyses are used to determine where additional information would be most useful.

Finally, USDA's Ground Water Vulnerability Index for Pesticides illustrates a national scale vulnerability assessment developed for use as a decision aid and analytical tool for national policies regarding farm management and water quality. This approach combines nationally available statistical information on pesticide usage and soil properties with a simulation model to predict the relative likelihood of contamination in cropland areas. USDA has used this approach to target sites for its Area Study Program which is designed to provide information to farmers about the relationships between farm management practices and water quality. The results of the GWVIP have also indicated that, even at the regional level, there is often an mix of high and low vulnerability areas. This result suggests that effective ground water policies should be tailored to local conditions.

Au, L.K.L. 1991. The Relative Safety of Hawaii's Drinking Water. Hawaii Medical Journal 50(3): 71-80.

Barlow, P.M. 1993. Particle-Tracking Analysis of Contributing Areas of Public-Supply Wells in Simple and Complex Flow Systems, Cape Cod, Massachusetts. USGS Open File Report 93-159. Marlborough, Massachusetts: U.S. Geological Survey.

Britt, J.K., S.E. Dwinell, and T.C. McDowell. 1992. Matrix decision procedure to assess new pesticides based on relative ground water leaching potential and chronic toxicity. Environ. Toxicol. Chem. 11: 721-728.

Cape Cod Commission (CCC). 1991. Regional Policy Plan. Barnstable, Massachusetts: Cape Cod Commission.

Cape Cod Planning and Economic Development Commission (CCPEDC). March 1978a. Draft Area Wide Water Quality Management Plan for Cape Cod. Barnstable, Massachusetts: Cape Cod Commission.

Cape Cod Planning and Economic Development Commission (CCPEDC). September 1978b. Final Area Wide Water Quality Management Plan for Cape Cod. Barnstable, Massachusetts: Cape Cod Commission.

Department of Environmental Protection, Division of Water Supply (DEP-WS). 1991. Guidelines and Policies for Public Water Supply Systems. Massachusetts Department of Environmental Protection.

Gianessi, L.P., and C.A. Puffer. 1991. Herbicide Use in the United States: National Summary Report. Washington, D.C.: Resources for the Future.

Guswa, J.H., and D.R. LeBlanc. 1981. Digital Models of Ground water Flow in the Cape Cod Aquifer System, MA. USGS Water Supply Paper 2209. U.S. Geological Survey.

Heath, D.L. 1988. DRASTIC mapping of aquifer vulnerability in eastern Barnstable and western Yarmouth, Cape Cod, Massachusetts. In Appendix D, Cape Cod Aquifer Management Project, Final Report, G.A. Zoto and T. Gallagher, eds. Boston: Massachusetts Department of Environmental Quality Engineering.

Horsely, S.W. 1983. Delineating zones of contribution of public supply wells to protect ground water . In Proceedings of the National Water Well Association Eastern Regional Conference, Ground-Water Management, Orlando, Florida.

Hoyer, B.E. 1991. Ground water vulnerability map of Iowa. Pp. 13-15 in Iowa Geology, no. 16. Iowa City, Iowa: Iowa Department of Natural Resources.

Hoyer, B.E., J.E. Combs, R.D. Kelley, C. Cousins-Leatherman, and J.H. Seyb. 1987. Iowa Ground water Protection Strategy. Des Moines: Iowa Department of Natural Resources.

Kellogg, R.L., M.S. Maizel, and D.W. Goss. 1992. Agricultural Chemical Use and Ground Water Quality: Where Are the Potential Problems? Washington, D.C.: U.S. Department of Agriculture, Soil Conservation Service.

Khan, M.A., and T. Liang. 1989. Mapping pesticide contamination potential. Environmental Management 13(2):233-242.

Kleveno, J.J., K. Loague, and R.E. Green. 1992. An evaluation of a pesticide mobility index: Impact of recharge variation and soil profile heterogeneity. Journal of Contaminant Hydrology 11(1-2):83-99.

Land Acquisition Advisory Council (LAAC). 1991. Ground Water Resources Committee Final Report: Florida Preservation 2000 Needs Assessment. Tallahassee, Florida: Department of Environmental Regulation. 39 pp.

Lau, L.S., and J.F. Mink. 1987. Organic contamination of ground water: A learning experience. J. American Water Well Association 79(8):37-42.

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Loague, K. 1992. Simulation of organic chemical movement in Hawaii soils with PRZM: 3. Calibration. Pacific Science 46(3):353-373.

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Since the need to protect ground water from pollution was recognized, researchers have made progress in understanding the vulnerability of ground water to contamination. Yet, there are substantial uncertainties in the vulnerability assessment methods now available.

With a wealth of detailed information and practical advice, this volume will help decision-makers derive the most benefit from available assessment techniques. It offers:

• Three laws of ground water vulnerability.
• Six case studies of vulnerability assessment.
• Guidance for selecting vulnerability assessments and using the results.
• Reviews of the strengths and limitations of assessment methods.
• Information on available data bases, primarily at the federal level.

This book will be indispensable to policymakers and resource managers, environmental professionals, researchers, faculty, and students involved in ground water issues, as well as investigators developing new assessment methods.

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Case study: strengthening a city's water resources and flood management capacity.

Keeping a city safe from flood and waterborne diseases requires a holistic approach to water resources management.

The protection of water resources is necessary for sustainable economic growth and better living conditions in cities. This is what the residents of Jiaozhou, a city in the People’s Republic of China, realized in the late 1990s when they started experiencing flooding and a high incidence of waterborne diseases.

The city government had already implemented water conservation and management projects, such as centralized wastewater treatment. However, they recognized the need to further improve their environmental management strategies to sustain their initial efforts.

A project supported by the Asian Development Bank (ADB) helped Jiaozhou take an integrated water management approach to reduce pollution and sustain river and coastal ecosystems.

Project information

• 40017-013: China, People's Republic of: Qingdao Water Resources and Wetland Protection

Jiaozhou, one of the five county-cities of Qingdao municipality, lies above Jiaozhou Bay, southeast of Shandong Peninsula. Qingdao (dubbed as “Eastern Switzerland”) surrounds Jiaozhou Bay in the Yellow Sea. This city has experienced rapid economic growth, averaging about 20% per annum in real terms since 2004, well above the national average. In 2007, the city’s population was 891,800—estimated to be increasing at an average annual rate of 1.12%. Rapid growth has resulted in considerable environmental stresses which threatened to erode progress in the area.

Development Challenges

Jiaozhou has faced flooding every 3 years, costing the city an average of more than CNY200 million (about US$28.7 million) in damages. The rate of waterborne diseases due to untreated wastewater and poor sanitation in the city is above the national average.

Jiaozhou Bay’s wetlands are seriously degraded, deteriorating by about 0.9% every year. These coastal wetlands are the most important marine ecosystem in the Qingdao coastal region and the Shandong Peninsula. They provide breeding grounds for fish and shellfish and temporary shelter for migratory birds. They are also important for coastal biodiversity preservation, nutrients absorption to prevent eutrophication in the bay, and flood and coastal protection—which is increasingly significant to coastal cities as sea levels continue to rise as a result of global warming.

Moreover, water management efforts were fragmented. Strategies and implementation activities were uncoordinated as the different tasks (water supply, wastewater management, and drainage) associated with water management were handled by different agencies.

Through the ADB-funded Qingdao Water Resources and Wetland Protection Project , Jiaozhou City adopted a holistic and integrated approach to water management of river basins and coastal zones, reduced land-based pollution sources particularly from industrial and urban sources, and reformed institutional and financial management to facilitate sustainable environmental management.

Reduced flooding and more sustainable flood management

The project aimed to integrate water and ecosystem management through structural and non-structural measures. Through the project, 18.4 km of river courses were rehabilitated through river dredging, embankment works, and greening (Yunxi River 8.3 km, Hucheng River 3.9 km, Wushui River 3.2 km, and Hucheng River branch 3.0 km). A river monitoring and administration center was established to provide data on water quality and real-time river flow to facilitate the operation of control gates for flood prevention. The Erli'he flood retention facilities were upgraded from 0.20 million cubic meters (m3) to 0.80 million m3. Storm sewerage facilities comprising 11.4 km were also constructed. The water quality of the rivers within Jiaozhou City has improved compared to pre-project levels. The operation and maintenance of the river works is the responsibility of the Jiaozhou City Construction Bureau. The city government levies a flood control management fee on all enterprises in the city, and this, together with wastewater collection fees are more than adequate to cover the operation and maintenance costs of the infrastructure constructed under the project.

Riverbank walkways, cycle paths, and other public amenity areas were constructed. Riverbank greening was also implemented. These complemented the rehabilitation of river embankments transforming the area into a place of interest in the urban city.

The project protected over 480,000 residents from flooding and associated loss of assets and livelihoods and hazards resulting from poor drainage.

Improvements in the project area led to an increase in the construction or improvement of residential and commercial buildings, influx of people, more business activities, and higher land and property value

Reduced water pollution and improved wastewater management

Interceptor sewers, 27.7 km long along river embankments, were installed to collect and transport sewerage to the existing wastewater trunk sewerage system (15.9 km along the embankments of the Yunxi River, Hucheng River, and Hucheng River tributaries, plus 11.8 km expanding the existing trunk sewerage system). In addition, a 1.7 km interceptor sewer was constructed on the Hucheng River branch.

The project incorporated a public-private partnership (PPP) model in wastewater treatment through a build-operate-transfer (BOT) arrangement with a 20-year contract. Wastewater services were also converted into commercial companies. This expanded the capacity of the existing wastewater treatment plant from 50,000 m3 to 100,000 m3. The treatment level was upgraded from class II to class IB and adapted to treat stormwater flows. This improved the water quality in the local river systems.

Improved wastewater and sewage treatment contributed to better sanitation. According to the Jiaozhou City Center for Disease Control and Prevention, the incidence of water-borne diseases decreased by 96% from 0.2888 per 10,000 people in 2008 to 0.01142 per 10,000 people in 2016 because of the project.

Moreover, the project reduced the extent of environmental degradation in the coastal wetlands. An assessment in 2018 revealed that 72% of Jiaozhou Bay has improved its water quality⁠—6 percentage points higher than 2015’s.

Improved capacity for integrated water and ecosystem management

Aside from flood protection infrastructure, artificial wetlands (Shaohai National Wetland Park, Erle’hi River Southwest Wetland Park, Yunxi Downstream Wetland Park) were constructed to enhance the coastal ecosystem. A Handbook for the Shaohai Lake Ecosystem Management and Operation was developed to help the Shaohai Lake Management Office in their monitoring efforts.

An integrated information system for flood, water, and wastewater management was also launched in 2017.

Staff from the city government and project management office were trained on environmental protection and management and flood control. The same training was conducted for 413 participants from 9 villages, of which 161 (39%) were men and 252 (61%) were women. Likewise, public awareness and consultation were held in 8 villages with 196 participants, of which 73 (37%) were men and 123 (63%) were women.

The path to sustainable cities requires an integrated approach to water resources and environmental protection. Though it is an internationally accepted framework, this approach in practice has plenty of room for innovation. One is involving the people who benefited from project outcomes in the operation and recovery of costs for new investments.

Having reliable projections about local development scenarios based on careful project planning and analysis can help local governments in maximizing the potential of a water resource or environmental management investment particularly in fast-growing areas like Qingdao.

ADB. 2008. Report and Recommendation of the President to the Board of Directors: Proposed Loan to the People’s Republic of China for the Qingdao Water Resources and Wetland Protection Project . Manila.

ADB. 2019. Completion Report: Qingdao Water Resources and Wetland Protection Project in the People’s Republic of China . Manila.

Ask the Expert

Rabindra P. Osti

Senior Water Resources Specialist, East Asia Department, Asian Development Bank

Mr. Osti has been working on water-related projects at ADB’s East Asia Department since 2015. Prior to his current role, he worked as a consultant for some of World Bank’s South Asia, South-East Asia, and East Asia projects. He also served in various capacities for the United Nations.

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• Published: 02 March 2023

Impact of the Russia–Ukraine armed conflict on water resources and water infrastructure

• Oleksandra Shumilova   ORCID: orcid.org/0000-0002-6270-7242 1 ,
• Klement Tockner 2 , 3 ,
• Alexander Sukhodolov   ORCID: orcid.org/0000-0002-6942-2098 1 ,
• Valentyn Khilchevskyi 4 ,
• Luc De Meester 1 , 5 , 6 ,
• Sergiy Stepanenko   ORCID: orcid.org/0000-0002-6343-3968 7 ,
• Ganna Trokhymenko   ORCID: orcid.org/0000-0002-0835-3551 8 ,
• Juan Antonio Hernández-Agüero   ORCID: orcid.org/0000-0001-6584-5774 2 &
• Peter Gleick 9  

Nature Sustainability volume  6 ,  pages 578–586 ( 2023 ) Cite this article

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• Environmental sciences
• Water resources

The armed conflict between Ukraine and Russia that began in late February 2022 has far-reaching environmental consequences, especially regarding water resources and management. Here we analysed the multifaceted impacts of the military actions on freshwater resources and water infrastructure during the first three months of the conflict. We identified the nature of the impacts, the kind of pressures imposed on the water sector and the negative consequences for the availability and quality of freshwater resources for the civilian population. Our results showed that many water infrastructures such as dams at reservoirs, water supply and treatment systems and subsurface mines have been impacted or are at risk from military actions. Continuation of the conflict will have multiple negative sustainability implications not only in Ukraine but also on a global scale, hampering achievement of clean water and sanitation, conservation and sustainable use of water resources, and energy and food security.

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Water is a fundamental and irreplaceable resource for life on Earth. Accordingly, it plays a pivotal role in the Sustainable Development Goals by securing societal and environmental well-being 1 . At the same time, freshwater as a resource 2 and related water infrastructure 3 are among the most vulnerable sectors during armed conflicts. This has led to increased attention to both the role of water as a driver of conflicts 4 and the impacts of armed conflicts on water and water systems 5 , 6 .

Reported violence associated with freshwater resources and water infrastructure, from 2500 bc to the present, is tracked by the open-source database Water Conflict Chronology (Pacific Institute 7 ). At present, the database consists of more than 1,300 entries, covering three separate categories: (1) water as a ‘trigger’ (the control of or access to water leads to violence), (2) water as a ‘weapon’ (water is used as a weapon during a conflict) and (3) water as a ‘casualty’ (direct attack on water systems) of violence. Over the past decade, the number of recorded conflicts has increased, particularly when water was used as a trigger and/or as a casualty of a conflict (Fig. 1 ). In addition to these, water resources are often threatened through collateral damage (for example, a pollution spill caused by military action).

Data from https://www.worldwater.org .

Despite its importance, there is a lack of academic research related to the multifaceted impacts of armed conflicts on the water sector. For example, a systematic review by Schillinger et al. 5 identified only 48 peer-reviewed studies on water in conflict settings. Geographically, the majority of studies have focused on the Middle East (in particular, Iraq, Syria and Israel), Africa and Asia.

The armed conflict between Ukraine and Russia (applying the agreed-upon definition of the International Committee of the Red Cross 8 ), which started on 24 February 2022, represents an exceptional case with regard to its impact on the environment 9 , 10 , 11 and particularly on water resources and water infrastructure. Unlike previously reported conflicts within the territories of the Global South and emerging economies 5 , the current armed conflict occurs in a region characterized by a heavily modified and industrialized water sector 6 , 12 . The extensive and critical water infrastructure of Ukraine includes large multi-purpose reservoirs, hydropower dams, cooling facilities for nuclear plants, water reservoirs used for industry and mining, and extensive water distribution canals and pipelines for irrigation and household purposes 13 . The majority of this water infrastructure is located in the eastern and southern parts of the country, areas of intense agricultural production and major industrial activities such as metallurgy, coal mining and chemical production.

Within the first three months of the conflict, it became clear that this conflict and its impact on freshwater resources and water infrastructure would impact both the livelihoods of local civilians and the global food supply 14 , reflecting the importance of water resources for the agriculture of the region 15 . The impacts of the armed conflict are further compounded by drought and heat waves across Europe and new constraints on water resources as a consequence of climate change 16 . All these factors argue for more detailed analyses and evaluation of possible consequences.

In this Analysis, we compile and analyse information about the multifaceted impacts of the armed conflict on freshwater resources and infrastructure on the basis of reported evidence during the first three months of the conflict. We discuss the key challenges that the water sector of Ukraine is facing due to the armed conflict and provide a retrospective view on previous catastrophes within the water sector of the country to highlight potential consequences of the current impacts. We aim to raise awareness of this problem and to provide evidence and information to help motivate the international community to both act to stop the conflict and develop mechanisms to prevent future water- and environment-related damages from conflicts.

Type and status of identified impacts

In total, we identified 64 reported impacts on the water sector, among them 49 realized and 15 potential (Fig. 2 ).

a , Locations of major river basins in Ukraine. b , Identified impacts on water resources and infrastructure in Ukraine (18 February 2022–24 May 2022). Red line corresponds to a front-line location after three months of the armed conflict 53 ; red area shows parts of Ukraine that are not under control of the Ukrainian government. See Source data for details.

Source data

The following types of realized impacts were identified: eight cases of water-transfer interruption, six cases of surface-water pollution due to military actions with four cases of sunken military objects and two due to release of chemicals as a result of shelling, five cases of damage to dams (four at reservoirs and one along the North Crimean canal), six cases of mines overflooding, one case of bacteriological pollution due to a mass poultry death and one case of interrupted operation of a hydroelectric station (HES) (Kakhovka HES).

Furthermore, we report impacts on water supply and wastewater treatment systems, including 12 cases of disrupted operation of water and wastewater treatment facilities, seven cases of disrupted centralized water supply and three cases of disrupted operation of wastewater treatment plants. For some regions, it was possible to obtain only pooled information, with a total number of settlements and inhabitants without water supply, and therefore these data are not presented in Fig. 2 but are provided in Supplementary Information 1 .

From realized impacts, 17 are the result of direct attacks, 13 are due to power-supply cut-offs, 8 are a combination of both, 4 instances of the pollution of surface waters are from sunken military objects, 1 is related to the indirect damage of the water supply system (the case of Mykolayiv, where connection to an alternative water supply source led to pipe corrosion and damage) and 1 is due to unusual operation condition (flooding in Nova Kakhovka).

With respect to water supply infrastructure, military actions affected 12 pumping stations, pipelines and dams were affected in 6 cases, damages to wastewater treatment plants were reported in 3 cases, and 2 filtering stations with water-intake facilities and 1 artesian well were affected. For a total of 12 settlements, such damages have caused the complete failure of the whole water supply and wastewater treatment system.

As potential threats, we identified 15 impacts, including 8 cases of flooding due to damage to dams (for example, missiles potentially targeting the dams of Kyiv and Kakhovka HESs, explosion of the road on the dam of Pechenizskiy Reservoir, 5 reservoirs are supposedly mined), 4 threats linked to nuclear power plants due to low-flying missiles (potential damage of cooling ponds, spread of radioactive dust), 2 cases of periodically flooded underground mines, 1 possible case of detonation of container with chlorine at the territory of wastewater treatment plant and explosion of nautical mines in the Danube River delta.

Geographical distribution of impacts and affected water bodies

Freshwater resources and water infrastructure were affected primarily in the Donetsk and Luhansk regions (17 and 13 realized impacts, respectively), where the conflict has been most intense. The number of incidents peaked within the Siverskyi Donets River basin ( Source data and Supplementary Information 2 ). There the river itself as well as demolished reservoirs located within its basin became a barrier for movement of troops (Supplementary Information 2 ). A shortage in electricity supply in the region led to interruption in long-distance water transfer (the main source of water supply) and caused uncontrolled rise of contaminated mine waters.

Several impacts on freshwater resources and water infrastructure were also recorded in the western regions of Ukraine far from active ground military operations. For example, an attack on the oil depot in Lviv led to the pollution of the Western Bug River, the tributary to the Narva River (Vistula River basin). North of the Ternopil region, shelling led to the damage of six reservoirs storing mineral fertilizers, causing the pollution of the Ikva River, the tributary of the Styr River (the Dnieper River basin). This resulted in a major increase in ammonia and nitrate concentrations, leading to a mass fish death. In the Odessa region in southern Ukraine, local authorities reported the presence of nautical mines in the Danube River delta, preventing fishing and constraining navigation.

Our results show that the most-affected types of infrastructure during the first three months of the armed conflict were dams and reservoirs, underground mines, urban water supply and wastewater treatment systems (overview of this infrastructure in Supplementary Information 2 ).

Ukraine’s critical water infrastructure at risk

Of special concern are large reservoirs along the Dnieper River, which are critical for energy production, cooling of nuclear power plants, sustaining agriculture and seasonal flow regulation. In addition, there is a high concentration of settlements along the Dnieper River, with flooding being an immediate threat if the dams would breach (Fig. 3a,b ). During World War II, intentional damage to the 800-m-wide dam of the Dnieper HES holding water in the Dnieper Reservoir, near the city of Zaporizhzhia, affected 20,000–100,000 civilians and retreating soviet soldiers crossing the river 17 (Fig. 3a ). Details on a quantitative flooding-risk assessment for the cascade of Dnieper reservoirs, including those based on hydrological conditions observed in 2022, are presented in Supplementary Information 2 .

a , The dam on the Dnieper River near the city of Zaporizhzhia after reportedly being blown up by Soviet special forces in 1941 in an attempt to delay the offence of German troops. b , Demolition of the dam on the Irpin River on 26 February 2022 caused flooding near the village of Demidov in the Vyshhorod district of Kyiv region. c , Craters formed by shells on the floodplain of the Irpin River. d , Water in the Kamyshevakha River polluted by mine waters (picture taken in 2021). e , Damaged pipe near Kiselevka village in the Kherson region (picture taken in April 2022). f , People in a line for drinking water in Mykolayiv (picture taken in April 2022). Panels adapted with permission from: a , ref. 54 , Taras Shevchenko National University of Kyiv; d , ref. 55 , Deutsche Welle; e , ref. 56 , Korabelov.info; f , ref. 57 , Novosti-N. Credit: photographs in b , c , Vincent Mundy.

Apart from flooding, breaching of dams along the Dnieper River poses a danger of secondary radioactive pollution due to uncontrolled release of radioactive material accumulated in the sediments and associated with colloidal materials in surface waters after the disaster at the Chernobyl nuclear power plant (NPP) in 1986 18 , 19 . Following the accident, the reservoirs of the Dnieper Cascade acted as sinks for radiocaesium, with extensive accumulation recorded in the Kyiv Reservoir. As for radiostrontium, about 43% of the dissolved form that entered the Dnieper system from 1987 to 1993 reached the Black Sea 20 . Zaporizhzhia NPP, the largest NPP in Europe, is located on the shore of the Kakhovka Reservoir, 40 km downstream from the dam of the Dnieper HES. A sudden loss of water needed for the reactor’s active cooling system can lead to a scenario analogous to the accident at the Fukushima Daiichi NPP in Japan in 2011 21 . The Kakhovka Reservoir also serves as a water source for the largest irrigation system in Ukraine and in Europe 22 (for details, see Supplementary Information 2 ). The conflict raises a risk of either intentional or unintentional bombing posing threats to regional agriculture, food production and international food trade.

Military actions and severe environmental pollution

As a result of the armed conflict, multiple Ukrainian communities have been left without wastewater treatment, resulting in pollution of surface waters. For example, remote-sensing images showed that polluted wastewater was released into the Kakhovka Reservoir when the wastewater treatment plant near Zaporizhzhia ceased operation 23 . Rivers and networks of irrigation channels that are natural barriers for movement of troops have also become a burial place for military objects (for example, Figure 3c ). The underwater decomposition of ammunition leads to release of heavy metals and toxic explosive compounds, with impacts that may last for decades 2 . This can be critical in the southern regions of Ukraine where an extensive network of irrigation channels exists. Low quality of irrigation water affects the agricultural cropping and the quality of food production 24 . In the pre-conflict period, the concentrations of heavy metals in waters of the Kakhovka Canal were in compliance with water-quality standards 25 , but there is concern that the conflict will lead to a deterioration of water quality.

In June–July 2022, for the first time, traces of oil products were reported within the area of the surface drinking water intake in the basin of the Siverkyi Donets River, together with exceeded concentrations of mercury, ammonium nitrogen, nitrites, polyaromatic carbons, heavy metals and the insecticide cypermethrin in some rivers within the basin 26 (for details on the state of the Siverskyi Donets River since 2014, see Supplementary Information 3 ). In addition, multiple electrical blackouts within Donbass region have increased the threat of pollution of water sources with mine waters because of failures in operation of pumping equipment. Overflooding of geologically connected mines, a problem present in the region for a long time (for details, see Supplementary Information 2 ), leads to increase in the concentration of salts in mine water up to 20–70% (except for chloride) and can double concentrations of organic substances and hydrocarbons 27 . High concentrations of sulfates, chlorides and heavy metals in mine waters pose severe risks for groundwater and surface-water quality (for example, the Kamyshevakha River has become severely polluted by mine waters since 2018; Fig. 3d ).

Access to safe water resources and the danger of epidemics

During the armed conflict, water supply infrastructure has been subjected to repeated attacks, with limited time and few opportunities for repair and recovery. By 20 April 2022, the United Nations reported that 6 million people in Ukraine were struggling every day to get access to drinking water, with 1.4 million people being reported to lack access to safe water in the east of the country and another 4.6 million people having only limited access 28 . For the period between March and December 2022, the UN estimates that some 16 million people in Ukraine will need water, sanitation and hygiene assistance 29 . In the city of Mariupol, more than 40% of the water supply system is reportedly damaged, and on 17 May 2022, the World Health Organization raised concerns about the danger of a cholera epidemic in the city due to mixing of sewage and drinking water 30 . In Mykolayiv, the population was left without a centralized water supply for more than a month (Fig. 3e,f ), and water supplied with interruptions from an alternative source later had excessive concentrations of chlorides, sulfates and other mineral salts even after treatment 31 . The population of Donetsk is reportedly receiving water for only two hours once every 3–4 days, and all specialists capable of addressing problems with the water system are mobilized in the armed conflict, limiting the ability to repair the system 32 . The Luhansk region, with a pre-conflict population of 2.1 million, was left completely without water supply in the beginning of May, and delivery of water was possible only externally through humanitarian organizations. The lack of access to clean water poses a serious threat of epidemic outbreaks, which was worsened by both extremely hot temperatures observed during the summer in 2022 and reduced capabilities of the medical system 33 . According to UNICEF, children living through prolonged conflicts are more likely to die from water-borne diseases than from the military conflict itself 34 .

Caveats and uncertainties

Expert evaluation of reported and projected impacts of armed conflict is limited in many cases by the lack of safe access to affected sites and by possible biases and discrepancies in reporting. However, to a certain extent, consequences of the use or targeting of water systems in conflicts can be estimated on the basis of retrospective analyses of similar impacts on freshwater resources and infrastructure. For example, catastrophic flooding due to damage to the Dnieper HES during World War II and the spread of radionuclides through water as a result of the catastrophe at Chernobyl NPP indicate the spatial extent of potential impacts in cases when large reservoirs or NPPs are affected by military actions. The long-lasting consequences of environmental pollution due to impacts on water infrastructure have been highlighted by an accident of a potash spill into the Dniester River due to overflooding of the Stebnik waste pond in the Lviv region in 1983 35 , 36 . In this event, more than 3.8 km 3 of highly concentrated waste salts were spilled, raising the salinity of the Dniester River to levels higher than seawater. This event disrupted water supply to millions of people in Odessa, Kishinev and the Tiraspol region, killed hundreds of tons of fish and heavily contaminated the sediments of the river 35 , 37 .

Although modern military technologies can allow precise destruction of localized objects, the damage to industrial targets is not always environmentally local, and many of the attacks have been not precise but general. In highly industrialized Ukraine 38 , targeting urban and industrial infrastructure leads inevitably to widespread and severe environmental consequences. By the beginning of June 2022, more than 25 big Ukrainian industrial companies were damaged or fully destroyed. Most prominent are the ammonia producer AZOT, the Coke and Chemistry concern in Avdievka and the centre of metallurgy AZOVSTAL in Mariupol 39 . Port infrastructures in the Black Sea and Azov Sea coastal areas were heavily bombed in Mykolayiv, Odessa and Mariupol.

Other impacts on water resources can be only roughly estimated at the moment, including the threat to regional biodiversity. It has been reported that 14 Ramsar wetland sites covering 400,000 hectares along the coastline and lower reaches of the Dnieper River are under threat 40 . Damage to reservoirs during spring spawning led to mass fish deaths (confirmed for the Oskil Reservoir) 41 .

The need for urgent action

Our study on the impacts of the armed conflict on freshwater resources and water infrastructure in Ukraine highlights diverse and long-lasting consequences not only for local populations and ecosystems, but also for progress towards the global Sustainable Development Goals 42 .

Catchments cut across political borders and pollutants released into the environment from armed conflicts can spread across national borders. Ninety-eight percent of the catchment area of Ukrainian rivers flows to the Black Sea and Azov Sea, and the remaining 2% to the Baltic Sea. Although the international community has already identified the risk of environmental pollution in the Donbass region in the eastern part of Ukraine since 2014 43 , military actions have dramatically intensified and are now taking place in the previously unaffected southern part of Ukraine. This area is important for agricultural activities that depend on an extensive network of irrigation channels. According to the World Food Programme, Ukraine contributed 50% of sunflower oil and 10% of wheat to the total global exports in 2021, being the first and the sixth global producer, respectively 44 . Due to the armed conflict, agricultural production has been substantially reduced, leading to food shortage on the global scale, with countries of Middle East and Africa most affected 11 .

A lack of access to safe water and the environmental threats urge prompt action. Priority activities should focus on providing safe drinking water for millions of civilians in the affected areas and protecting civilian water supply and treatment systems. A set of international rules related to protection of the environment and civilian water infrastructure during armed conflicts is defined by the Geneva List of Principles, including especially the 1977 Protocols to the Geneva Convention 4 , 45 . According to the recent resolution adopted by the United Nations Security Council on 27 April 2021, all parties of the armed conflict are obliged to protect civilians and civilian infrastructure, including water facilities 46 . Nevertheless, multiple cases of attacks on water technicians since the start of the conflict have been reported in Chernihiv, Kharkiv and Mykolayiv, adding to at least 35 water engineers who have been killed or injured in the Donetsk and Luhansk region since 2014 47 , 48 . We argue that protection of civilian water technicians should be ensured, providing the so-called ‘green corridors’ for safe access to water infrastructure.

Support by international agencies and partners is needed to provide water-treatment systems that can be used by individual households and to provide temporary access to safe drinking water or assistance in rebuilding and replacing destroyed civilian water infrastructure. For places without current access to safe drinking water, sustainable options should be investigated apart from the temporary and costly option of transporting bottled water. In particular, water-treatment systems should be installed at critical locations such as hospitals, schools and community centres. Individual households could be supplied with individual small-scale filtration systems. In the longer term, options such as desalination should be considered because most of the local surface waters in the southeastern parts of the country are characterized by high mineralization 49 (for example, the current water supply to Mykolayiv from the Southern Bug to replace the damaged supply system from the Dnieper 30 ). For settlements that were receiving water from the basin of the Siverskyi Donets River, the option for desalination is even more convincing due to both the proximity to alternative water supply sources and the fragility of water-transfer facilities as has been shown by this armed conflict.

Importantly, environmental monitoring and data collection efforts to better understand the environmental risks are urgently needed. Unfortunately, in March 2022, the Organization for Security and Cooperation in Europe, the official international conflict monitor, announced closure of its Special Monitoring Mission in Ukraine 50 . The mission was enabling the repair and maintenance of the critical civilian infrastructure facilities benefitting civilians on both sides of the contact line in eastern Ukraine since 2014.

The current crisis demands coordinated action from Ukraine and Russia, mediated and facilitated by other countries of the European Union and the United Nations. We recommend that science and management focus on assessing the dynamic state of the environment and water conditions in the zone of the conflict, with the aim to develop effective and prompt approaches for its post-war rebuilding. Although the conflict is still ongoing, freshwater resources and water infrastructure should be protected and maintained because of their central role in supporting basic human needs, health and well-being. Because access to the sites in the zone of conflict is limited, particular attention should be given to spatial mathematical and cartographic modelling using remote-sensing data, which allow efficient use of limited input information. Such an approach can be applied to simulating flooding due to dam breaching under different hydrological scenarios, spread of pollutants from sunken military monitions, effect of land mines on surface and groundwater, predicting quality of subsurface mine waters and their overflow to geologically connected areas, forecast of quantity and quality of water for drinking and irrigation purposes and assessment of the effect on freshwater biodiversity. From a management perspective, we recommend that future studies focus on assessing financial apparatus and the economic dimensions of sustainable water management, on the enforcement of water-related regulations and on identification and evaluation of current and post-conflict needs, facilitating the recovery of Ukrainian water resources and infrastructure.

Information about the effects of the armed conflict on water resources and infrastructure was collected between 18 February 2022 and 30 May 2022, covering the first three months of the armed conflict. Although the conflict started on 24 February 2022, we included information from one week before due to massive attacks on water infrastructure in the eastern part of Ukraine during this period. Furthermore, because the conflict area occupies almost the same territories, the main results reported here remain fairly actual.

To avoid biased presentation of the information, we cross checked data from governmental and media sources of Ukrainian, Russian and international origin. As a primary source of information, we used weekly reports of the Ministry of Ecology and Natural Resources of Ukraine, reports of the Ministry for Reintegration of the Temporary Occupied Territories and Internally Displaced Persons of Ukraine and reports of the Ukrainian regional war administrations. To search for information from media sources, we used keywords related to reported impacts in Ukrainian, Russian and English languages in Google Search. As a timeline for checking information sources, we defined the period between 15 February and 15 September 2022. We also included information not only reported by the Ukrainian governmental sources, but provided by media sources in different countries, including Russia. For most of the identified events (64 in total), the majority of the information was derived from Ukrainian official governmental and media sources (43 and 56, respectively); less information was available from sources of international and Russian origin (28 and 24, respectively). All references and sources are listed in the Source data file and can be assessed and evaluated by readers if required.

The database on impacts ( Source data ) consists of three information clusters. First, the cluster on location characteristics contains information about location (for example, name of the region, city, reservoir or mine), including coordinates and dates of impacts, together with information on affected hydrographic sub-basin and main basin, water body and water infrastructure. Second, the cluster related to the type of incident provides a short description of the impact and its status, defined as realized (with documented evidence) or potential (impacts for which high likelihood of the event was documented, but no evidence on irreversible damage had been reported). In addition, each impact is described according to the DPSIR framework (drivers, pressures, states, impacts, responses), which is commonly used to assess and manage environmental problems 51 . Thus, for each impact, we described related drivers, pressures and states and provided an impact description. Due to the ongoing nature of the current conflict and difficulties in obtaining reliable information on the state of water resources or infrastructure, we did not include the category ‘response’ proposed by the framework. Although other methodological approaches can be applied to analyse the impact of armed conflict on water resources, this framework provides a good balance between a need to collect complex information over a long-term period of conflict duration (for example, used in the social-ecological system framework 52 ) and the necessity to include certain analytical assumptions on the dynamic nature of conflict and the operation of water utility companies (for example, such as in the ISO 31000 standard for risk management 49 ) or generalize collected information (for example, when impacts on water resources are classified according to Sustainable Development Goals and their specific targets 44 ). Finally, the third cluster of the database provides references to Ukrainian governmental sources and media sources, Russian media sources and international sources used in data collection. Cases for which information in the respective informational source was not found are marked with ‘NA’. In addition, we collected information on regions of Ukraine left without water supply since the start of the armed conflict in February 2022 (Supplementary Information 1 ).

Although we aimed to collect and arrange a database that is as comprehensive as possible, it is clear that, given the difficult circumstances intrinsic to an armed conflict, the data that we collected might be incomplete, and our account is an underestimate of the extent of the problem. Certain territories of Ukraine were left without internet access, and therefore adequate data on impacts were not available, or impacts took place in areas where adequate tracking of consequences was not possible. In addition, certain potential impacts could not be confirmed with full confidence.

Reporting summary

Further information on research design is available in the Nature Research Reporting Summary linked to this article.

Acknowledgements

This research was partly supported by the grant SU 405/10-1 from the Deutsche Forschungsgemainschaft (DFG).

Open access funding provided by Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB) im Forschungsverbund Berlin e.V.

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Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany

Oleksandra Shumilova, Alexander Sukhodolov & Luc De Meester

Senckenberg Society for Nature Research, Frankfurt a.M., Germany

Klement Tockner & Juan Antonio Hernández-Agüero

Faculty of Biological Sciences, Goethe University, Frankfurt a. M., Germany

Klement Tockner

Department of Hydrology and Hydroecology, Taras Shevchenko National University of Kyiv, Kyiv, Ukraine

Valentyn Khilchevskyi

Institut für Biologie, Freie Universität Berlin, Berlin, Germany

Luc De Meester

Department of Biology, University of Leuven (KU Leuven), Leuven, Belgium

Odessa State Environmental University, Hydrometeorological Institute, Odessa, Ukraine

Sergiy Stepanenko

Department of Ecology and Environmental Technologies, Admiral Makarov National University of Shipbuilding, Mykolayiv, Ukraine

Ganna Trokhymenko

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O.S., K.T., A.S. and P.G. designed the study. O.S., A.S., V.K., K.T. and P.G. collected the information on impacts of freshwater resources and water infrastructure from media sources. P.G. provided additional data from the Water Conflict Chronology. J.A.H.-A. produced Figs. 2 and 3 presented in the manuscript. O.S. wrote the paper with contributions from K.T., A.S., V.K., L.D.M., P.G., G.T., S.S. and J.A.H.-A. All authors participated in reviewing and editing the full manuscript.

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Supplementary Information 1–3.

Reporting Summary

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Database of reported impacts of armed conflict between Russia and Ukraine on freshwater resources and water infrastructure.

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Shumilova, O., Tockner, K., Sukhodolov, A. et al. Impact of the Russia–Ukraine armed conflict on water resources and water infrastructure. Nat Sustain 6 , 578–586 (2023). https://doi.org/10.1038/s41893-023-01068-x

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Case Study Questions Chapter 3 Water Resources

Please refer to the Case Study Questions Chapter 3 Water Resources with answers provided for Class 10 Social Science. These solved case study based questions are expected to come in the Class 10 Economics exam in the current academic year. We have provided Case study for Class 10 Social Science for all chapters here. You should practise these solved case studies to get more marks in examinations.

Chapter 3 Water Resources Case Study Questions Class 10 Social Science

1. Read the source given below and answer the following questions:

Today, dams are built not just for irrigation but for electricity generation, water supply for domestic and industrial uses, flood control, recreation, inland navigation and fish breeding. Hence, dams are now referred to as multi-purpose projects where the many uses of the impounded water are integrated with one another. For example, in the Sutluj-Beas river basin, the Bhakra – Nangal project water is being used both for hydel power production and irrigation. Similarly, the Hirakud project in the Mahanadi basin integrates conservation of water with flood control. Multi-purpose projects, launched after Independence with their integrated water resources management approach, were thought of as the vehicle that would lead the nation to development and progress, overcoming the handicap of its colonial past. Jawaharlal Nehru proudly proclaimed the dams as the ‘temples of modern India’; the reason being that it would integrate development of agriculture and the village economy with rapid industrialisation and growth of the urban economy.

Answer the following MCQs by choosing the most appropriate option.

(i) Which of the following multipurpose projects is found in the Satluj-Beas river basin? (a) Hirakud project (b) Damodar Valley Corporation (c) Bhakra Nangal Project (d) Rihand Project

(ii) Hirakund dam is built on which river? (a) Chenab (b) Mahanadi (c) Krishna (d) Satluj

(iii) For which of the following purposes were dams traditionally built? (a) For generating electricity (b) For supplying water to industries (c) For Flood control (d) To impound river and rain water for irrigation

(iv) Which one of the following is not an adverse effect of dams? (a) Interstate water disputes (b) Excessive sedimentation of Reservoir (c) Displacement of population (d) Flood control

2. Read the source given below and answer the following questions:

Many thought that given the disadvantages and rising resistance against the multipurpose projects, water harvesting system was a viable alternative, both socio-economically and environmentally. In ancient India, along with the sophisticated hydraulic structures, there existed an extraordinary tradition of water-harvesting system. People had in-depth knowledge of rainfall regimes and soil types and developed wide ranging techniques to harvest rainwater, groundwater, river water and flood water in keeping with the local ecological conditions and their water needs. In hill and mountainous regions, people built diversion channels like the ‘guls’ or ‘kuls’ of the Western Himalayas for agriculture. ‘Rooftop rainwater harvesting’ was commonly practised to store drinking water, particularly in Rajasthan. In the flood plains of Bengal, people developed inundation channels to irrigate their fields. In arid and semi-arid regions, agricultural fields were converted into rain fed storage structures that allowed the water to stand and moisten the soil like the ‘khadins’ in Jaisalmer and ‘Johads’ in other parts of Rajasthan. In the semi-arid and arid regions of Rajasthan, particularly in Bikaner, Phalodi and Barmer, almost all the houses traditionally had underground tanks or tankas for storing drinking water.

(i) Agricultural fields which are used as rainfed storage structures are called: (a) Kuls (b) Khadins/Johads (c) Recharge pits (d) None of the above

(ii) In which of the following regions, people built ‘Guls’ and ‘Kuls’ for irrigation? (a) Northern Plains (b) Western Himalayas (c) Coastal areas (d) None of these

(iii) The diversion channels seen in the Western Himalayas are called: (a) Guls or Kuls (b) Khadins (c) Johads (d) Recharge pits

(iv) Underground tanks seen in Rajasthan to store rainwater for drinking is called: (a) Tankas (b) Khadis (c) Ponds (d) Kuls

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Case Study Questions Class 10 Social Science Geography Water Resources

Case study questions class 10 social science geography chapter 3 water resources.

CBSE Class 10 Case Study Questions Social Science Geography Water Resources. Important Case Study Questions for Class 10 Board Exam Students. Here we have arranged some Important Case Base Questions for students who are searching for Paragraph Based Questions Water Resources.

At Case Study Questions there will given a Paragraph. In where some Important Questions will made on that respective Case Based Study. There will various types of marks will given 1 marks, 2 marks, 3 marks, 4 marks.

Case Study 1:

Earth 3/4th surface is covered with water still there is water scarcity, though water is considered as renewable resource is availability is limited. A report by the NITI Aayog stated that around 2 lakh people die in India every year due to inadequate water supply. It is common perceptions that only dry states like Rajasthan face water problem but the myth is broken by the recent ground water crises in cities of Chennai and Delhi. Surprisingly lack of availability of water is also supplemented with quality of availability of water which is major source of many water prone diseases in India. Effective measures have to be taken by both state and central government to ensure water security to its citizens and problem should be resolved in time bound manner.

Q1 Water Water everywhere, not a drop to drink? Comment Mark 2

Answer Though 3/4th Earth surface is covered with water and it is natural resource most of the water is present in oceans which cannot be consume by human beings directly and consumption of water is water is more than its recharge rate hence there emerge a severe water scarcity problem in India.

Q2 Give reasons why rainfall rich states also face water scarcity problems?  Mark 1

Answer Over exploitation of ground water mainly for irrigation and other commercial purposes by big MNCs , over population and changing lifestyles of urban and rural population are the major causes of water scarcity in rainfall rich states.

Q3 Write some government initiatives to solve the problem of water crises. Mark 1

Answer Jal Jeevan Mission ensure that every rural household get tap water at a service level of 55 litres per capita per day regularly this will prevent many water prone diseases in rural area.

Case Study 2:

Since the ancient times our ancestors knows the importance of water and its conversation and for that purpose they build multiple structures popularly known as dams. Not surprisingly

India has continued this tradition by building various dams alongside many river basins. India has 4,407 large dams, the third highest number in the world after China (23,841) and the USA (9,263). Jawaharlal Nehru proudly proclaimed the dams as “temples of modern India ,not only as a water reservoir dams have various multipurpose role to play. Dams now had become one of the symbols of advancement of science and technology in modern India.

Q1) Give an account for water conservation efforts done in ancient India. Mark 2

Answer Many dams were constructed in ancient India time like for an example in reign of Chandragupta Maurya Sudarshan Lake in Junagarh was build. In 11th century Bhopal lake was build and it was one of the biggest artificial lake of that time. An account of 14th century work hauz khas by Iltutmish can also be seen.

Q2)  Apart from water reservoir what are the other purposes of building the dams?  Mark 2

Answer Dams also used to produce hydroelectricity as 22% of India electricity demands is meet by dams only , also they are used for many other purpose like channelizing water for irrigation

Act as a place of tourism and so on.

Case Study 3 :

The tragedy in Kerala has highlighted the risks of extra water accumulation in dams. Greater than 20 dams launched water that cascaded down the hills, leaving at the back of a trail of destruction. the opening of the gates of the Idukki dam, for instance, precipitated the Periyar river to swell rapidly and discharge seven lakh litres of water consistent with 2 days yet, the argument for dams — that they offer ingesting water and water for agriculture — is these days scientifically discredited. For independent geologists and hydrologists, dams represent a nightmare, an ephemeral triumph of engineering over common sense and the herbal sciences. Increasingly more, it is evident that dam proponents are ignoring critical decision-making records now to be had on patterns of rainfall, geology and climate change.

Q1) What are the various cons associated with dams? Mark 2

Ans Dams stops natural flow to water and hence create a migration problem for acquatic animals especially for spawning.

Large number of displacement for local area people take place and huge submerge of land and nearby area occurs which itself cause disruption in ecological balance. Also by alternating the very purpose of dam like giving priority to urban area create a resentment in local area people which ultimately leads to various social problem and movements like Narmada bachao Andolan.

Q2) Write about 5 dams and their respective rivers. Mark 2

Dams  River

Sardar sarovar Narmada

Hirakud Mahanadi

Nagararjuna Sagar Krishna

Mettur Kaveri

Kota Barrage Chambal

Case Study 4:

Flash floods all through this year’s monsoon season have precipitated unprecedented damage to both lives and assets in Himachal Pradesh. The death toll has crossed 150, and the anticipated total loss quantities to ₹10,000 crore. although weather exchange is anticipated to have played a hand in inflicting the high precipitation leading to these flash floods, human brought about screw ups resulting from planned development have played a massive role in causing such giant losses. in the last five years (earlier than 2022), 1,550 humans misplaced their lives and almost 12,444 houses had been broken.

The IPCC (Intergovernmental Panel on climate exchange) VI record has actually said that the Himalayas and coastal regions of India can be the hardest hit via climate exchange inside the Himalayas, there may be a major pattern of accelerated precipitation going on in shorter periods of time. The India Meteorological department facts suggests that the everyday rainfall all through this era is anticipated to be among 720mm and 750 mm. but, in positive times, it has surpassed 888 mm in 2010 and 926.nine mm in 2018. This 12 months, the precipitation to this point has been attributed to the combined effect of the south-west monsoon with western disturbances. the total rainfall from June to this point become 511 mm.

Q1) Why dams failed to control the floods? Mark 2

Answer Ironically, the dams that were constructed to control floods have triggered floods due to sedimentation in the

Reservoir. As dams stops natural flow of river it accumulated huge amount of sediments at its bottom which causes lower the water holding capacity and hence at time of excessive water gates of dams are required to be open causing a human aid to the magnitude of flood.

Q2) Write two do’s and don’t at time of flooding? Mark 2

Use Boiled and filter drinking water Don’t use wet electrical appliances

Use bleaching power and lime to disinfect the surrounding.

Don’t enter in flooded water

Case Study 5:

Rainwater harvesting must be seamlessly integrated into the each town’s climate resilience making plans. Huge progress has absolutely been made, the evolving landscape of Delhi, wherein urbanization and climate change intersect, amplifies the urgency of water conservation. The unwavering commitment of government concerned to this motive is as a result imperative. Rainwater harvesting must be seamlessly included into the town’s weather resilience planning.”

A chronic cognizance on teaching the general public and resident welfare institutions approximately the blessings of rainwater harvesting, together with sensible implementation guidance, can cause a shift in the direction of “sustainable water practices”. Introduction of water tariff rebates as incentives for rainwater harvesting and wastewater recycling structures serves as demonstration in their dedication to the purpose

Q1) What are the regional names given to rain water harvesting?

Answer In mountain regions people build many diversion channels knows and “kuls” and “guls”, ‘khadins’ in Jaisalmer and ‘Johads’ in other parts of Rajasthan. In Bikaner, Phalodi and Barmer, almost all the houses traditionally had underground tanks or tankas for storing drinking water.

Q2) How rainwater harvesting system works?

Step 1Rooftop rainwater is collected using a PVC pipe

Step 2 Filtered using sand and bricks

Step 3 Underground pipe takes water to sump for immediate usage

Step 4 Excess water from the sump is taken to the well

Step 5 Water from the well recharges the underground

Step 6 Take water from the well (later)

Also See: The Human Eye and Colourful World Case Study Question and answer

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ORIGINAL RESEARCH article

This article is part of the research topic.

Broadband Seafloor Sediment Acoustic Property and Multi-Parameter Geoacoustic Model

Correlation between acoustic velocity and physical parameters of sea floor sediments: A case study of the northern South China Sea Provisionally Accepted

• 1 Key Lab of Submarine Geosciences and Prospecting Techniques, College of Marine Geo Sciences, Ocean University of China, China
• 2 Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, China
• 3 National Engineering Research Center of Offshore Oil and Gas Exploration, China
• 4 Key Laboratory of Marine Geology and Metallogeny, First Institute of Oceanography, Ministry of Natural Resources, China

The final, formatted version of the article will be published soon.

As the interface between seawater and the seabed, superficial sediments on the seabed are an important part of the marine acoustic field environment and are indispensable for marine resource investigations. Studying sediments several meters to hundreds of meters below the seafloor is highly valuable and important. This study processes and analyses the water depth, topography and bottom data and obtains the shallow bottom profile and topographic map of the northern continental slope of the South China Sea (SCS). The study analyzes the influence of physical parameter (including density, porosity, and grain size) on the acoustic velocity in sediments. Single-parameter and dualparameter models are established to further examine this influence. The results show that porosity and density have greater influences on the acoustic velocity of sediments than does grain size. Finally, the acoustic properties of several typical stations with water depths are tested to analyze the variations in the acoustic properties of the shallow sediments in the northern SCS. The results show that the influence of each parameter on the prediction of the acoustic velocity of the sediment is in the following order: porosity>density>grain size. This study analyses and reveals the reason why the seafloor sediments in the local area cause the acoustic properties to change greatly. It may be caused by changes in the sediment type, lithology along with the depth. And the other reason is the development of interlayer in the land slope of the northern SCS.

Keywords: The northern South China Sea, Physical parameter, acoustic velocity, density, Porosity, Grain size

Received: 15 Dec 2023; Accepted: 12 Apr 2024.

Copyright: © 2024 Zhang, Xing, Zhou, Han, Li and Liu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Lei Xing, Key Lab of Submarine Geosciences and Prospecting Techniques, College of Marine Geo Sciences, Ocean University of China, Qingdao, 266100, Shandong Province, China

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