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Article

Johanna Brühl, Leonard le Roux, Martine Visser, and Gunnar Köhlin

The water crisis that gripped Cape Town over the 2016–2018 period gained global attention. For a brief period of time in early 2018, it looked as if the legislative capital of South Africa would become the first major city in the world to run out of water. The case of Cape Town has broad implications for how we think about water management in a rapidly urbanizing world. Cities in the global South, especially, where often under-capacitated urban utilities need to cope with rapid demographic changes, climate change, and numerous competing demands on their tight budgets, can learn from Cape Town’s experience. The case of Cape Town draws attention to the types of decisions policymakers and water utilities face in times of crisis. It illustrates how these decisions, while being unavoidable in the short term, are often sub-optimal in the long run. The Cape Town drought highlights the importance of infrastructure diversification, better groundwater management, and communication and information transparency to build trust with the public. It also shows what governance and institutional changes need to be made to ensure long-term water security and efficient water management. The implementation of all of these policies needs to address the increased variability of water supplies due to increasingly erratic rainfall and rapidly growing urban populations in many countries. This necessitates a long-term planning horizon.

Article

Claudia Sadoff, David Grey, and Edoardo Borgomeo

Water security has emerged in the 21st century as a powerful construct to frame the water objectives and goals of human society and to support and guide local to global water policy and management. Water security can be described as the fundamental societal goal of water policy and management. This article reviews the concept of water security, explaining the differences between water security and other approaches used to conceptualize the water-related challenges facing society and ecosystems and describing some of the actions needed to achieve water security. Achieving water security requires addressing two fundamental challenges at all scales: enhancing water’s productive contributions to human and ecosystems’ well-being, livelihoods and development, and minimizing water’s destructive impacts on societies, economies, and ecosystems resulting, for example, from too much (flood), too little (drought) or poor quality (polluted) water.

Article

Manuel Pulido-Velazquez and Amaury Tilmant

The management of water resources systems involves influencing and improving the interaction among three subsystems: natural (biophysical), economic, and legal-institutional frameworks. In this sense, hydroeconomic models have the advantage of analyzing water management problems through models that explicitly represent these interactions. The combination of economic, engineering, and environmental aspects of management provides better-informed results for decision making in the complex environment in which water management operates. Hydroeconomic models (HEMs) are spatially distributed management models of a river basin or system in which both water supply and demands are economically and hydrologically characterized. This definition is sometimes relaxed to refer in general to water resources management models that include the economic component. In HEMs, the management and allocation of water is either driven by the economic value of water or economically assessed, which contributes to policy analysis and reveals opportunities for better economic management. The traditional view of water demand as a fixed requirement to be satisfied is modified by a view of demand that adapts to the changes in the scarcity of water. The integration of economics in HEMs allows the identification of the best combination of water supply and demand management options within a consistent framework. As water scarcity increases worldwide, water managers will increasingly turn to tools that reveal solutions to increase efficiency in water use, fostering improved economic development through better-informed policy choices.

Article

This is an immersive journey through different water management concepts. The conceptual attractiveness of concepts is not enough; they must be applicable in the real and fast-changing world. Thus, beyond the concepts, our long-standing challenge remains increasing water security. This is about stewardship of water resources for the greatest good of societies and the environment. It is a public responsibility requiring dynamic, adaptable, participatory, and balanced planning. It is all about coordination and sharing. Multi-sectoral approaches are needed to adequately address the threats and opportunities relating to water resources management in the context of climate change, rapid urbanization, and growing disparities. The processes involved are many and need consistency and long-term commitment to succeed. Climate change is closely related to the problems of water security, food security, energy security and environment sustainability. These interconnections are often ignored when policy-makers devise partial responses to individual problems. They call for broader public policy planning tools with the capacity to encourage legitimate public/collective clarification of the trade-offs and the assessment of the potential of multiple uses of water to facilitate development and growth. We need to avoid mental silos and to overcome the current piecemeal approach to solving the water problems. This requires a major shift in practice for organizations (governmental as well as donor organizations) accustomed to segregating water problems by subsectors. Our experience with integration tells us that (1) we need to invest in understanding the political economy of different sectors; (2) we need new institutional arrangements that function within increasing complexity, cutting across sectoral silos and sovereign boundaries; (3) top down approaches for resources management will not succeed without bottom-up efforts to help people improve their livelihoods and their capacity to adapt to increasing resource scarcity as well as to reduce unsustainable modes of production. Political will, as well as political skill, need visionary and strong leadership to bring opposing interests into balance to inform policy- making with scientific understanding, and to negotiate decisions that are socially accepted. Managing water effectively across a vast set of concerns requires equally vast coordination. Strong partnerships and knowledge creation and sharing are essential. Human civilization – we know- is a response to challenge. Certainly, water scarcity can be a source of conflict among competing users, particularly when combined with other factors of political or cultural tension. But it can also be an inducement to cooperation even in high tension areas. We believe that human civilization can find itself the resources to respond successfully to the many water challenges, and in the process make water a learning ground for building the expanded sense of community and sharing necessary to an increasingly interconnected world.

Article

Ronald van Nooijen, Demetris Koutsoyiannis, and Alla Kolechkina

Humanity has been modifying the natural water cycle by building large-scale water infrastructure for millennia. For most of that time, the principles of hydraulics and control theory were only imperfectly known. Moreover, the feedback from the artificial system to the natural system was not taken into account, either because it was too small to notice or took too long to appear. In the 21st century, humanity is all too aware of the effects of our adaptation of the environment to our needs on the planetary system as a whole. It is necessary to see the environment, both natural and hman-made as one integrated system. Moreover, due to the legacy of the past, the behaviour of the man-madeparts of this system needs to be adapted in a way that leads to a sustainable ecosystem. The water cycle plays a central role in that ecosystem. It is therefore essential that the behaviour of existing and planned water infrastructure fits into the natural system and contributes to its well-being. At the same time, it must serve the purpose for which it was constructed. As there are no natural feedbacks to govern its behaviour, it will be necessary to create such feedbacks, possibly in the form of real-time control systems. To do so, it would be beneficial if all persons involved in the decision process that establishes the desired system behaviour understand the basics of control systems in general and their application to different water systems in particular. This article contains a discussion of the prerequisites for and early development of automatic control of water systems, an introduction to the basics of control theory with examples, a short description of optimal control theory in general, a discussion of model predictive control in water resource management, an overview of key aspects of automatic control in water resource management, and different types of applications. Finally, some challenges faced by practitioners are mentioned.

Article

Water scarcity has long been recognized as a key issue challenging China’s water security and sustainable development. Economically, China’s water scarcity can be characterized by the uneven distribution of limited water resources across space and time in hydrological cycles that are inconsistent with the rising demand for a sufficient, stable water supply from rapid socioeconomic development coupled with a big, growing population. The limited water availability or scarcity has led to trade-offs in water use and management across sectors and space, while negatively affecting economic growth and the environment. Meanwhile, inefficiency and unsustainability prevail in China’s water use, attributable to government failure to account for the socioeconomic nature of water and its scarcity beyond hydrology. China’s water supply comes mainly from surface water and groundwater. The nontraditional sources, wastewater reclamation and reuse in particular, have been increasingly contributing to water supply but are less explored. Modern advancement in solar and nuclear power development may help improve the potential and competitiveness of seawater desalination as an alternative water source. Nonetheless, technological measures to augment water supply can only play a limited role in addressing water scarcity, highlighting the necessity and importance of nontechnological measures and “soft” approaches for managing water. Water conservation, including improving water use efficiency, particularly in the agriculture sector, represents a reasonable strategy that has much potential but requires careful policy design. China’s water management has started to pay greater attention to market-based approaches, such as tradable water rights and water pricing, accompanied by management reforms. In the past, these approaches have largely been treated as command-and-control tools for regulation rather than as economic instruments following economic design principles. While progress has been made in promoting the market-based approaches, the institutional aspect needs to be further improved to create supporting and enabling conditions. For water markets, developing regulations and institutions, combined with clearly defining water use rights, is needed to facilitate market trading of water rights. For water pricing, appropriate design based on the full cost of water supply needs to be strengthened, and policy implementation must be enforced. An integrated approach is particularly relevant and greatly needed for China’s water management. This approach emphasizes integration and holistic consideration of water in relation to other resource management, development opportunities, and other policies across scales and sectors to achieve synergy, cost-effectiveness, multiple benefits, and eventually economic efficiency. Integrated water management has been increasingly applied, as exemplified by a national policy initiative to promote urban water resilience and sustainability. While economics can play a critical role in helping evaluate and compare alternative measures or design scenarios and in identifying multiple benefits, there is a need for economic or social cost–benefit analysis of China’s water policy or management that incorporates nonmarket costs and benefits.

Article

Groundwater overdraft is an issue faced by urban and rural water users worldwide. With climate change making efforts to meet global water demands even more challenging, improving water security and resilience is of paramount importance. Managed aquifer recharge efforts are being deployed globally to further achieve water management goals, such as helping to reduce groundwater overdraft at a local level. Artificial recharge or managed aquifer recharge (MAR) is a concept that has been applied to describe diverse methods with the aim of both augmenting groundwater resources during times when water is available and recovering the water from the same aquifer in the future when it is needed. MAR projects are distributed in almost every continent. An extensive study published in 2018 identified that 15 countries and regions account for 76% of the installed MAR capacity (Australia, China, France, Finland, India, Israel, Italy, Jordan, Netherlands, Qatar, Southern Africa, Spain, United States, and United Kingdom). MAR is considered a viable tool to face the negative impacts of climate change and to increase public water supply at a local level. In arid and semiarid regions, MAR plays an important role because it allows the storage of large volumes of water without the risk of evaporation. MAR is used to provide water for agricultural activities in groundwater-dependent countries and regions. Increasingly, at least in India, many MAR projects are designed to protect domestic water supply. MAR is also used as a water source for maintaining environmental services, although this use is still incipient.

Article

Cathy Rubiños and Maria Bernedo Del Carpio

Adequate water governance is necessary for the world’s sustainability. Because of its importance, a growing literature has studied ways to improve water governance, beginning in the early 2000s. Institutions, which refer to the set of shared rules, codes, and prescriptions that regulate human actions, are a particularly important element of sustainable water governance. Evidence shows that to design institutions that will generate sustainable economic, ecological, and cultural development, it is necessary to consider ecosystems and socioeconomic-cultural systems as social-ecological systems (SESs). In the past, practitioners and international agencies tried to find the government-led panaceas, but this search has been largely unsuccessful. Current views support efforts to move towards addressing complexity (e.g., Integrated Water Resources Management), and search for the fit between the institutional arrangements and SESs’ attributes. The literature on institutional fit in SESs encourages planners to design institutions by carefully considering the defining features of the problems they are meant to address and the SES context in which they are found. This literature has been developing since the 1990s and has identified different types of misfits. A comprehensive fitness typology that includes all the different types of fitness (ecological, social, SES, and intra-institutional fit) helps organize existing and future work on institutional fit and provides a checklist for governments to be used in the problem-solving process for increasing fitness. The water governance and institutional fitness literature provide examples of management practices and mechanisms for increasing institutional fit for each fitness type. Future research should focus on improving the methodologies to measure different types of fit and testing the effect of introducing fit on SES outcomes.

Article

Mattia Grandi

The lack of a settled definition for hydropolitics—a prismatic concept that acquires specific meanings according to both the disciplinary boundaries within which it is used and the theoretical perspectives of those employing it—is consistent with the disagreement over its nomenclature (hydro-politics vs. hydropolitics). The term has had many meanings and idiosyncratic usages over time, and there has been hardly any attempt to advance a clear definition for it. The strength of the concept of hydropolitics, its inter-disciplinary conceptual heterogeneity, is also its weakness. While the crystallization of some of the core features of hydropolitics in the literature—especially with regard to scale (namely, the focus on the inter-state level and the range of issues covered, that is, the politics of international water basins)—has anchored hydropolitics to “standard cases” of the concept, its theoretical underpinnings are still blurred. The study of hydropolitics has substantially delved into trans-boundary, not just any, waters. Yet, both the ontology and epistemology of the concept are debatable, so few eclectic definitions for hydropolitics have emerged. Hence, by addressing the relationships between knowledge, theory, and action of hydropolitics, the scientific community, in particular scholars of international relations, political geography, and critical geopolitics, has struggled for theoretical coherence as well as for conceptual clarity over the use of the term. This is not an easy task, though, because the fluid essence of hydropolitics escapes not only definition but also easy classification.

Article

Luis S. Pereira and José M. Gonçalves

Surface irrigation is the oldest and most widely used irrigation method, more than 83% of the world’s irrigated area. It comprises traditional systems, developed over millennia, and modern systems with mechanized and often automated water application and adopting precise land-leveling. It adapts well to non-sloping conditions, low to medium soil infiltration characteristics, most crops, and crop mechanization as well as environmental conditions. Modern methods provide for water and energy saving, control of environmental impacts, labor saving, and cropping economic success, thus for competing with pressurized irrigation methods. Surface irrigation refers to a variety of gravity application of the irrigation water, which infiltrates into the soil while flowing over the field surface. The ways and timings of how water flows over the field and infiltrates the soil determine the irrigation phases—advance, maintenance or ponding, depletion, and recession—which vary with the irrigation method, namely paddy basin, leveled basin, border and furrow irrigation, generally used for field crops, and wild flooding and water spreading from contour ditches, used for pasture lands. System performance is commonly assessed using the distribution uniformity indicator, while management performance is assessed with the application efficiency or the beneficial water use fraction. The factors influencing system performance are multiple and interacting—inflow rate, field length and shape, soil hydraulics roughness, field slope, soil infiltration rate, and cutoff time—while management performance, in addition to these factors, depends upon the soil water deficit at time of irrigation, thus on the way farmers are able to manage irrigation. The process of surface irrigation is complex to describe because it combines surface flow with infiltration into the soil profile. Numerous mathematical computer models have therefore been developed for its simulation, aimed at both design adopting a target performance and field evaluation of actual performance. The use of models in design allows taking into consideration the factors referred to before and, when adopting any type of decision support system or multicriteria analysis, also taking into consideration economic and environmental constraints and issues. There are various aspects favoring and limiting the adoption of surface irrigation. Favorable aspects include the simplicity of its adoption at farm in flat lands with low infiltration rates, namely when water conveyance and distribution are performed with canal and/or low-pressure pipe systems, low capital investment, and low energy consumption. Most significant limitations include high soil infiltration and high variability of infiltration throughout the field, land leveling requirements, need for control of a constant inflow rate, difficulties in matching irrigation time duration with soil water deficit at time of irrigation, and difficult access to equipment for mechanized and automated water application and distribution. The modernization of surface irrigation systems and design models, as well as models and tools usable to support surface irrigation management, have significantly impacted water use and productivity, and thus competitiveness of surface irrigation.

Article

Water is essential to life and development in terms of both quantity and quality. Water resources continue to face various pressures brought about by climate change, growing population, and increased economic demand for water. Managing this unique and precious resource has become a global challenge. The conflicts over water issues often arise not only among stakeholders facing limited water resources but also from social and political aspects of the design, operation, and management of water supply projects. A fair and sustainable system of sharing water resources, therefore, is one of the greatest challenges we face in the 21st century. In the absence of negotiation and lack of clear property rights, water is a source for human conflicts. Game theory as strategic analysis has provided powerful tools and been applied to many fields, including water resources management. The basic assumptions of game theory emphasize that rational players who pursue well-defined objectives and assume knowledge of others would accordingly form expectations of other decision makers’ behavior. Hence, game theory is used to predict agents’ behaviors toward fulfilling their own interests during the interactive decision-making process with other agents. Since the 1950s, game theory has become an important tool for analyzing important aspects of water resource management. Yet despite the rapid increase in the application of game theoretical approaches to water resource management, many challenges remain. The challenges of the early 21st century, including resource constraints, financial instability, inequalities within and between countries, and environmental degradation, present opportunities to address and reach resolutions on how water is governed and managed to ensure that everyone has sufficient access to water.

Article

Indigenous rights to water follow diverse trajectories across the globe. In Asia and Africa even the concept of indigeneity is questioned and peoples with ancient histories connected to place are defined by ethnicity as opposed to sovereign or place-based rights, although many seek to change that. In South America indigenous voices are rising. In the parts of the globe colonized by European settlement, the definition of these rights has been in a continual state of transition as social norms evolve and indigenous capacity to assert rights grow. From the point of European contact, these rights have been contested. They have evolved primarily through judicial rulings by the highest court in the relevant nation-state. For those nation-states that do address whether indigenous rights to land and water exist, the approach has ranged from the 18th- and 19th-century doctrines of terra nullius (the land (and resources) belonged to no one) to a recognized right of “use and occupancy” that could be usurped under the doctrine of “discovery” by the conquering power. In the 20th and 21st centuries the evolution of the recognition of indigenous rights remains uneven, reflecting the values, judicial doctrine, and degree to which the contested water resource is already developed in the relevant nation-state. Thus, indigenous rights to water range from the recognition of cultural and spiritual rights that would have been in existence at the time of European contact, to inclusion of subsistence rights, rights sufficient for economic development, rights for homeland purposes, and rights as guardian for a water resource. At the forefront in this process of recognition is the right of indigenous peoples as sovereign to control, allocate, develop and protect their own water resources. This aspirational goal is reflected in the effort to create a common global understanding of the rights of indigenous peoples through declaration and definition of the right of self-determination articulated in the UN Declaration on the Rights of Indigenous Peoples.

Article

Jazmin Zatarain Salazar, Andrea Castelletti, and Matteo Giuliani

Shared water resource systems spark a number of conflicts related to their multi sectorial, regional, and intergenerational use. They are also vulnerable to a myriad of uncertainties stemming from changes in the hydrology, population demands, and climate change. Planning and management under these conditions are extremely challenging. Fortunately, our capability to approach these problems has evolved dramatically over the last few decades. Increased computational power enables the testing of multiple hypotheses and expedites the results across a range of planning alternatives. Advances in flexible multi-objective optimization tools facilitate the analyses of many competing interests. Further, major shifts in the way uncertainties are treated allow analysts to characterize candidate planning alternatives by their ability to fail or succeed instead of relying on fallible predictions. Embracing the fact that there are indeterminate uncertainties whose probabilistic descriptions are unknown, and acknowledging relationships whose actions and outcomes are not well-characterized in planning problems, have improved our ability to perform diligent analysis. Multi-objective robust planning of water systems emerged in response to the need to support planning and management decisions that are better prepared for unforeseen future conditions and that can be adapted to changes in assumptions. A suite of robustness frameworks has emerged to address planning and management problems in conditions of deep uncertainty. That is, events not readily identified or that we know so little about that their likelihood of occurrence cannot be described. Lingering differences remain within existing frameworks. These differences are manifested in the way in which alternative plans are specified, the views about how the future will unfold, and how the fitness of candidate planning strategies is assessed. Differences in the experimental design can yield diverging conclusions about the robustness and vulnerabilities of a system. Nonetheless, the means to ask a suite of questions and perform a more ambitious analysis is available in the early 21st century. Future challenges will entail untangling different conceptions about uncertainty, defining what aspects of the system are important and to whom, and how these values and assumptions will change over time.

Article

The importance of groundwater has become particularly evident in the late 20th and early 21st centuries due to its increased use in many human activities. In this time frame, vertical wells have emerged as the most common, effective, and controlled system for obtaining water from aquifers, replacing other techniques such as drains and spring catchments. One negative effect of well abstraction is the generation of an inverted, conically shaped depression around the well, which grows as water is pumped and can negatively affect water quantity and quality in the aquifer. An increase in the abstraction rate of a specific well or, as is more common, an uncontrolled increase of the number of active wells in an area, could lead to overexploitation of the aquifer’s long-term groundwater reserves and, in some specific contexts, impact water quality. Major examples can be observed in arid or semi-arid coastal areas around the world that experience a high volume of tourism, where aquifers hydraulically connected with the sea are overexploited. In most of these areas, an excessive abstraction rate causes seawater to penetrate the inland part of the aquifer. This is known as marine intrusion. Another typical example of undesirable groundwater management can be found in many areas of intensive agricultural production. Excessive use of fertilizer is associated with an increase in the concentration of nitrogen solutions in groundwater and soils. In these farming areas, well design and controlled abstraction rates are critical in preventing penetrative depression cones, which ultimately affect water quality. To prevent any negative effects, several methods for aquifer management can be used. One common method is to set specific abstraction rules according to the hydrogeological characteristics of the aquifer, such as flow and chemical parameters, and its relationship with other water masses. These management plans are usually governed by national water agencies with support from, or in coordination with, private citizens. Transboundary or international aquifers require more complex management strategies, demanding a multidisciplinary approach, including legal, political, economic, and environmental action and, of course, a precise hydrogeological understanding of the effects of current and future usage.

Article

Economics conceptualizes harmful effects to the environment as negative externalities that can be internalized through implementation of policies involving regulatory and market-based mechanisms, and behavioral economic interventions. However, effective policy will require knowledge and understanding of intended and unintended stakeholder behaviors and consequences and the context in which the policy will be implemented. This mandate is nontrivial since policies once implemented can be hard to reverse and often have irreversible consequences in the short and/or long run, leading to high social costs. Experimental economics (often in combination with other empirical evaluation methods) can help by testing policies and their impacts prior to modification of current policies, and design and implementation of new ones. Such experimental evaluation can include lab and field experiments, and choice experiments. Additionally, experimental policy evaluation should pay attention to scaling up problems and the ethical ramifications of the treatment. This would ensure that the experimental findings will remain relevant when rolled out to bigger populations (hence retaining policy makers’ interest in the method and evidence generated by it), and the treatment to internalize the externality will not create or exacerbate societal disparities and ethical challenges.

Article

Water resources represent an essential input to most human activities, but harnessing them requires significant infrastructure. Such water control allows populations to cope with stochastic water availability, preserving uses during droughts while protecting against the ravages of floods. Economic analysis is particularly valuable for helping to guide infrastructure investment choices, and for comparing the relative value of so called hard and soft (noninfrastructure) approaches to water management. The historical evolution of the tools for conducting such economic analysis is considered. Given the multimillennial history of human reliance on water infrastructure, it may be surprising that economic assessments of its value are a relatively recent development. Owing to the need to justify the rapid deployment of major public-sector financing outlays for water infrastructure in the early 20th century, government agencies in the United States—the Army Corps of Engineers and the Bureau of Reclamation—were early pioneers in developing these applications. Their work faced numerous technical challenges, first addressed in the drafting of the cost-benefit norms of the “Green Book.” Subsequent methodological innovation then worked to address a suite of challenges related to nonmarket uses of water, stochastic hydrology, water systems interdependencies, the social opportunity cost of capital, and impacts on secondary markets, as well as endogenous sociocultural feedbacks. The improved methods that have emerged have now been applied extensively around the world, with applications increasingly focused on the Global South where the best infrastructure development opportunities remain today. The dominant tools for carrying out such economic analyses are simulation or optimization hydroeconomic models (HEM), but there are also other options: economy wide water-economy models (WEMs), sociohydrological models (SHMs), spreadsheet-based partial equilibrium cost-benefit models, and others. Each of these has different strengths and weaknesses. Notable innovations are also discussed. For HEMs, these include stochastic, fuzz, and robust optimization, respectively, as well as co-integration with models of other sectors (e.g., energy systems models). Recent cutting-edge work with WEMs and spreadsheet-based CBA models, meanwhile, has focused on linking these tools with spatially resolved HEMs. SHMs have only seen limited application to infrastructure valuation problems but have been useful for illuminating the paradox of flood management infrastructure increasing the incidence and severity of flood damages, and for explaining the co-evolution of water-based development and environmental concerns, which ironically then devalues the original infrastructure. Other notable innovations are apparent in multicriteria decision analysis, and in game-theoretic modeling of noncooperative water institutions. These advances notwithstanding, several issues continue to challenge accurate and helpful economic appraisal of water infrastructure and should be the subject of future investigations in this domain. These include better assessment of environmental and distributional impacts, incorporation of empirically based representations of costs and benefits, and greater attention to the opportunity costs of infrastructure. Existing tools are well evolved from those of a few decades ago, supported by enhancements in scientific understanding and computational power. Yet, they do appear to systematically produce inflated estimations of the net benefits of water infrastructure. Tackling existing shortcomings will require continued interdisciplinary collaboration between economists and scholars from other disciplines, to allow leveraging of new theoretical insights, empirical data analyses, and modeling innovations.