While the global supply of available freshwater is more than adequate to meet all current and foreseeable water demands, its spatial and temporal distributions are not. There are many regions where our freshwater resources are inadequate to meet domestic, economic development and environmental needs. In such regions, the lack of adequate clean water to meet human drinking water and sanitation needs is indeed a constraint on human health and productivity and hence on economic development as well as on the maintenance of a clean environment and healthy ecosystems.
All of us involved in research must find ways to remove these constraints. We face multiple challenges in doing that, especially given a changing and uncertain future climate, and a rapidly growing population that is driving increased social and economic development, globalization, and urbanization. How best to meet these challenges requires research in all aspects of water management. Since , the journal Water Resources Research has played an important role in reporting and disseminating current research related to managing the quantity and quality and cost of this resource.
This paper identifies the issues facing water managers today and future research needed to better inform those who strive to create a more sustainable and desirable future. Throughout the world, demographic, economic, and technological trends have accelerated our ability to knowingly and unknowingly modify the environment we live in and that sustains us. We humans have become the principal driver of environmental change.
Our actions are impacting our global environment, including our climate. This in turn impacts the amounts and spatial and temporal distributions of precipitation that falls on watersheds and the timing of its runoff. Coupled with changes in landscapes, due to growth in food and energy production and from the movement of people into urban centers, we are altering the quantity and quality of our freshwater resources on which we depend to survive, both physically and economically.
We depend on water not only for life itself, but indeed for our economic wellbeing as well. Water plays a role in the creation of everything we produce. There are no substitutes and while it is renewable there is only a finite amount of it. In the past, we have made decisions regarding the management of our water resources that have not always helped us become more secure or sustainable.
We have disrupted and overallocated river flow regimes—sometimes to the point of drying them up, along with their downstream lakes. We have overdrawn groundwater aquifers; polluted many, if not most of our water bodies including estuaries, coastal zones and even oceans; and degraded ecosystems. Our planet no longer functions in the way it once did. Earth is currently confronted with a relatively new situation, the ability of humans to transform the atmosphere, degrade the biosphere, and alter the lithosphere and hydrosphere. These challenges to effective planetary stewardship must be addressed and soon.
The various parts of the Earth system — rock, water, and atmosphere — are all involved in interrelated cycles where matter is continually in motion and is used and reused in the various planetary processes.
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Without interlocked cycles and recycling, the components of our Earth could not function as an integrated system. In the last 50 years or so we have come to recognize the movements in all Earth's layers, including the plates at the surface, the mantle and the core as well as the atmosphere and ocean.
The momentum and acceleration of the impacts of business as usual threaten to tip the complex Earth System out of the environment in which everything living on this Earth has evolved and developed. Some call this new geological period the Anthropocene [ Crutzen , ; Williams et al.
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Water is becoming a central issue in this new period. This applies not only to freshwater systems but also to the oceans, their levels and what lives in them. The interdependency between social or human ambitions on the one hand, and availability and quality of our natural resources and the environment on the other, is obvious; it determines the kind of development that is realistic and stable.
The expansion in the production and supply of goods and services in the recent past has meant more jobs, income, and, generally, greater possibilities for a better life. It has also meant an increase in the use and pollution of natural resources.
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The adverse effects on water and other vital components of the Earth System are evident. An estimated 1. There is no escape from the fact that the need and demand for finite and vulnerable water will continue to expand and so will competition for it.
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More uncertainty in water availability, higher frequency of extreme weather events, and more rapid return flows of water to the atmosphere are expected in the future. Given the changes in the hydrologic cycle as a result of land use and climate changes and the closed character of many basins, allocations to, and patterns of future water use, will deviate from past trends.
Research is needed to better understand how these complex interactions may develop over the coming decades and the associated social, political, and environmental implications. Clearly, water issues will become even more important in the lives and activities of people [ Cosgrove and Rijsberman , ; Grayman et al. The Global Risk Perception Survey conducted among recognized experts by the World Economic Forum reports that the highest level of societal impact over the next 10 years will be from water crises.
In recent decades the percentage increase in water use on a global scale has exceeded twice that of population growth. This has led to more, and larger, regions in the world being subject to water stress where the current restricted rates of water use and consumption, let alone the desired rates, are unsustainable. Water demands and supplies are changing. What they will be in the future is uncertain, but it is certain that they will change.
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Demands are driven in part by population growth and higher per capita water consumption in growing urban, domestic, and industrial water sectors. By , the world will have to feed and provide energy for an additional 2—2. To meet the nutritional needs of this additional population, we should consider the amount of water that is consumed in the production of different goods and, in particular, energy and food. Energy and food security are demands that are particularly critical to water managers.
Energy production, water, food security, and climate change are all connected through interactions and feedbacks. For example, the growing, transportation, processing, and trading of food products require large amounts of water and energy. Per capita water use varies considerably over the globe. In developed regions one can assume an average value of L per person per day.
The value adopted internationally for basic human water needs is about 50 L per person per day [ Gleick , ]. The amount of water each person in the USA uses is on average is much higher depending on a number of factors, in particular diet, but also in all the water required to make all the energy and nonagricultural products consumed.
A recent report on water consumption in the USA shows reductions in all sectors: including agriculture; municipal and industrial; and thermoelectric power. But the report concludes that while substantial progress has been made, current water use trends are not sustainable in the face of population growth and climate change [ Donnelly and Cooley , ]. Water is increasingly becoming a priority policy issue at the international level. Both economic development and security are placed at risk by poor water management.
That is why the concern about a global energy crisis has recently begun to be accompanied by a concern about a looming global water crisis. The energy and water nexus expressed both by the effects of water use on energy consumption and by the effects of energy production on water consumption, is gaining increasing attention [see e.
Increasing globalization is motivating the implementation of new rules and procedures for the international trade of goods and services, reflecting the increasing influence of multinational firms engaged indirectly in water use and transfers. While bulk water is not commonly traded, except for relatively limited quantities in bottles, the water used to produce the goods that are traded across borders, called virtual water, can have a major impact on water balances in basins and regions.
The US is the world's largest exporter of virtual water [ Hoekstra and Chapagain , ]. The impact of globalization on water may be considered from two other perspectives: the negative effects on water of the growing integration of the world economy, in particular concerning water contamination and associated environmental degradation; and water itself as an object of global trade policies. Some natural resources, such as oil, natural gas, wood, agricultural products, or fish have, for a long time, been traded in international markets without becoming a political issue.
Not so with regard to water. Water is different than many other natural resources that are traded because the costs of transport are very significant in comparison to the understated economic value of water and, perhaps more importantly, because of perceptions about the human right to water, and objections to the commodification of the resource [ Gleick et al.
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International projects involving water transfer often raise concern and controversy. This transaction is normally ruled by political agreements, rather than trade agreements. In practice, only a comparatively small number of agreements for the long distance trade of raw water have been concluded. Water transportation is expensive and usually pursued only in rare cases where other practices, such as desalination, are not possible or economic. Trade in high water consumptive goods from water scarce regions may be economically profitable in the short term but it is not viable in the long term and is a threat to meeting other water related goals.