Sri Lanka's celebrated twelfth-century king Parakramabahu reportedly said, "not a single drop of water received from rain should be allowed to escape into the sea without being utilized for human benefit."
The concern to ensure a steady water supply was pervasive throughout South Asia in his time. Thousands of small dams created cascades of connected lakes (locally called "tanks") that made irrigation possible all year round, despite the vagaries of the monsoon climate. Comparable inventiveness produced aqueducts in Rome, elaborate systems of underground tunnels (qanats) in the Middle East and Northern Africa, and King Nebuchadnezzar II's irrigation systems for the hanging gardens of Babylon. The Babylonian irrigation worked, but Mesopotamian society apparently failed to control the slow build-up of salt in the soil, faced a water crisis, and ultimately collapsed.
Salinization remains a serious threat to irrigated lands, but we are now hearing warnings about something much more dangerous: a genuinely global scarcity of water. Reports describe majestic rivers such as the Yellow River in China no longer reaching the sea. Ships sit on the dry bed of the Aral Sea. Droughts such as those that have ravaged the Australian countryside in recent years appear to be increasing in frequency and severity. In 2006 the International Water Management Institute, which I directed at the time, reported that water scarcity affected a full third of world population. In 2007 the Intergovernmental Panel on Climate Change predicted that, due to climate change, the number of people facing water scarcity would grow. Others, too, say that there is a global water crisis, the availability of water is dwindling, the world is running out of water, water is the blue gold, and that future wars will be fought over water. In When the Rivers Run Dry (2006), Fred Pearce characterizes this emerging shortage as the defining crisis of the twenty-first century.
So, is the planet drying up? Not exactly, but a growing number of people are sharing a fixed amount of water, and that water is badly managed and increasingly polluted. Thanks largely to unsafe drinking water, more than 2 million children die of diarrhea each year. Six hundred million subsistence farmers lack irrigation water and are mired in poverty. Wetlands have been decimated in Europe, North America, and Asia, and fish populations are collapsing. Drought caused a more than 50 percent drop in Australia's wheat production in 2007 and sparked a ten-year peak in global wheat prices. Burgeoning African and Asian cities, from Dakar to Beijing, face severe water shortages. Water rationing in these cities, to several hours per day or several days per week, is the norm rather than the exception.
We can avoid a full-blown global disaster. Unfortunately, the water crisis is complicated, often misunderstood, rarely grasped holistically, accelerated by climate change that melts glaciers and icecaps, and exacerbated by biofuel expansion that further stresses scarce water supplies. Forestalling it will require a mix of sustained technological innovation and institutional reform, all guided by deeper understanding and some new thinking.
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Most of the earth's water is saline, located in seas and oceans. And most of the earth's fresh water is locked up in the ice caps around the poles. The rest is the water pumped around by the sun in the hydrological cycle: water that evaporates into the atmosphere, gathers in clouds, and falls as rain.
Every year roughly 100,000 cubic kilometers of rain fall on earth -- some 15,000 cubic meters per person per annum. Because the quantity of solar energy that reaches earth is more or less constant, the total amount of water that evaporates also is more or less constant. Population, however, is not constant. It has doubled in the last fifty years, resulting in a 50 percent decline in water availability per person. Climate change may alter that equation somewhat as glaciers and ice caps melt, but it is expected to have much larger impact on the seasonal distribution of rainfall -- dry periods will get drier, wet periods will get wetter, floods and droughts will worsen -- than on the total amount of water available.
Does the population increase mean there will not be enough water? That is not quite the right question. Water is only valuable to people if it is available at the right time, in the right place, and at the right level of quality. Rain does not fall in an even drizzle throughout the year, except in my native Holland. And it is distributed unevenly in space, with some 24 percent of the world's estimated renewable water resources falling in Canada every year, and no rain most years in arid areas or deserts. Rainfall is distributed unevenly in time as well, especially in monsoon areas such as India, where 90 percent of the annual rainfall is concentrated in just a few major storms that may occur in less than one hundred hours. Bangladesh is well known for destructive flooding but, like India, can suffer as much or more from droughts.
When we think about water scarcity, then, we should not be focusing on an absolute shortfall between the total needs of the earth's population and the available supply, but on where the usable water is and what it costs to bring enough clean water to where people are.
That means not only ensuring the accessibility of safe drinking water, but also the availability of enough water for growing food. The former alone is no trivial undertaking. More than a billion people in developing countries invest a significant share of their time and resources in securing drinking water. Available water supplies are so limited in quantity and poor in quality that, combined with poor sanitation and personal hygiene, they are associated with ill health. Diarrheal diseases, generally caused by drinking or handling biologically unsafe water -- water that has been in contact with human or animal feces -- account for an estimated 20 percent of deaths among children under age five.
In the 1980s the United Nations led a massive effort to bring safe water to all people. Aid agencies and UN bodies increased their water budgets significantly, and water was provided to a large number of previously underserved populations. Yet at the end of the "Water Decade," more than a billion people were left without access to safe and affordable drinking water and more than two billion still lacked safe sanitation. In 2000 the world's leaders adopted the Millennium Development Goals, which included a commitment to halve the number of people without access to safe and affordable drinking water by 2015. Two years later they added a target to halve the number of people without access to safe and affordable sanitation. Development organizations are renewing their efforts to reach these goals and have doubled their aid budgets for water supply and sanitation projects to about $6 billion per year. In Asia the targets are likely to be met. Unfortunately, in Africa, where the proportion of the underserved is highest, the development partners are not making great strides.
Safe drinking water in sufficient quantity, however, is not the whole story. Even the most water-scarce parts of the world -- Egypt, for example -- have renewable water resources on the order of 1000-1500 liters per inhabitant per day. The United Nations recommends access to at least twenty liters of safe water per person per day as the minimum for a healthy life. When they have access to affordable water conveniently piped into their homes, people tend to use a great deal more: 200 to 400 liters per person per day, depending on whether they water their lawns or use dishwashers and similar water-guzzling conveniences. But even at that higher level of consumption there is no real scarcity of drinking water.
However, water for drinking, cooking, bathing, and all other domestic needs is only a small fraction of the requisite supply. A much larger amount is needed to grow our food as well as the fibers, such as cotton, in our clothes. On average, growing a single calorie of food demands a liter of water. Plants need water for evapotranspiration, the process by which water evaporates from soil and leaves and transpirates from plants through the stomata, thereby transferring water from Earth's surface into the atmosphere. A healthy diet of 3000 calories requires at least 3000 liters of water to produce; a vegetarian diet requires the least amount of water, while a Western, meat-based diet rich in corn-fed beef can require as much as 15,000 liters of water per person per day. Roughly seventy times as much water is needed to grow the food that people eat as to serve domestic purposes.
Therefore, to understand the water crisis we need to distinguish two fundamentally different problems, which will require different solutions. The first, the drinking water problem, is about access to affordable water services: here we face a service crisis. The second is about the lack of the vastly greater water resources needed to grow food and maintain ecosystem services: here we face a problem of water scarcity, a resource crisis.
The most widely used indicator of water scarcity, the Falkenmark Water Stress Index (after the Swedish hydrologist Malin Falkenmark), defines water stress as less than 1700 cubic meters of renewable water resources in a country per person per annum. Countries with less than one thousand cubic meters such as Algeria, Israel, or Egypt, are said to be severely water-scarce. So when countries are water-scarce in terms of the Falkenmark indicator it does not mean they do not have enough water to drink, but rather that they do not have enough water to grow their own food.
Yet the Falkenmark indicator is a limited measure of whether a country has the water it needs, because it only counts the annual national availability of what is traditionally defined as "renewable" water resources. Rainfall that runs off into streams and rivers, plus the water that recharges the groundwater (and often reenters the streams and rivers later), is defined as renewable. But this water accounts for only about 40 percent of total rainfall. The other 60 percent -- the neglected part -- becomes soil moisture and from there evaporates back into the atmosphere as water vapor or is taken up by the roots of plants and eventually transpirated by the plants' stomata.
For drinking purposes, the 60 percent of rainfall that becomes soil moisture is indeed lost. But for plants, and for our food, soil moisture is crucial and needs to be taken into account -- it is renewable. In an effort to refocus the attention of water managers on the 60 percent of rainfall that is not usually counted in assessing water scarcity, Falkenmark distinguishes blue water from green water. Blue water comprises the traditional renewable water resources, while green water is soil moisture. Her efforts are gaining ground as experts increasingly see the key to solving the water crisis in tapping the productivity of the green water, not just the blue.
Paying attention to all the blue water is also essential. While groundwater is included in all definitions of water resources, it is often ignored in practical water management. Groundwater is bypassed in part because it is hard to find in all but the simplest geologies, such as homogenous deep sand layers, and in part because it is difficult to quantify. Large-scale public water projects, from Roman aqueducts to the great irrigation systems in India and China, have traditionally focused on the water in rivers. Groundwater was traditionally accessed by digging wells that provided people with small amounts of clean and reliable drinking water.
The development of small and affordable diesel and electric pumps in the 1960s initiated a revolution in groundwater use for irrigation. In just a few decades, groundwater irrigation in India has surpassed the use of river or surface water. Some 20 million boreholes, equipped with diesel or electric pumps and supported privately by farmers, have overtaken public canal irrigation systems in their impact on agricultural production. These humble devices have contributed to enormous economic growth in the Indian countryside, but they have also led to over-pumping and lowering of the groundwater tables. Farmers in Gujarat, who used oxen to pump water from wells at depths of less than ten meters in the 1970s, have engaged in a race to the bottom. They have invested in successively deeper boreholes and larger and larger pumps. Their wells now have to reach 200 meters deep and their pumps are massive fifty-five horsepower machines. Eventually the aquifers are tapped out and the wells run dry. Similar issues are affecting groundwater use in other parts of the world. Groundwater depletion is reducing supplies both for irrigation and drinking water, as well as industry in cities like Bangkok.
In addition to green as well as blue water, and ground as well as surface, hydrologists need to consider the quality of available water. Cities discharge large amounts of organic material and human waste into the surrounding streams and rivers, making them bacteriologically unsafe to drink. Time and oxygen tend to reduce these problems. But ever-larger cities overwhelm this self-cleaning capacity of rivers, leading to lower and lower oxygen levels until the rivers become black, anaerobic, and practically devoid of life, as is now true of rivers near many Chinese cities.
Industry discharges chemical waste such as heavy metals or solvents that pose a different set of challenges for downstream users. These pollutants are generally "conservative": they are not biodegradable and, at best, settle into the sediments on the riverbeds. Agriculture that uses chemicals, particularly pesticides and herbicides, but also excess fertilizer, provides yet another load of pollutants into surface and groundwater water. These are often persistent organic chemicals which build up in the tissues of the animals that drink the water or the larger predators that, in turn, feed on them. Because of current levels of population and economic activity, hardly a stream on the planet is now untouched by pollution. In fact, the concerns of water managers in many cities today focus on a class of pollutants most water engineers had not heard of fifteen years ago: endocrine disruptors, which form when prescription drugs pass through patient's bodies.
The water cycle is a complex system that we must understand well in order to find sustainable solutions to the crisis. The traditional supply-side approach to water management emphasizes engineering the development of enough "new" water resources -- displacing the current use of ecosystems of the same water -- to satisfy growing human demands in agriculture, homes, or industry. This water is made available to users at subsidized prices that tend not to reflect the cost of providing the water, let alone the scarcity value of the resource. This approach makes sense only if there is abundant water available in the system and the value of the current use is much lower than the value of the use for which the water will be "developed."
As growing population puts pressure on supplies, the supply-side approach needs to be complemented and ultimately replaced by a demand-side approach that encourages consumers to use water more efficiently. Peter Gleick, a prominent advocate of a demand-side approach to water in the United States, has shown that increased American demand due to population or economic growth can be covered by increased efficiency. However, because the cost of transporting water over distances larger than hundreds of kilometers is prohibitive, more efficient water use in California supports only the local environment -- it does not help provide water for low-income people in Africa.
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Addressing the water crisis -- the service crisis (water to drink) and the resource crisis (water for food and clothing) -- will require both technological and political innovation. Climate change will introduce additional challenges associated with increased climate variability in many parts of a world. But advances in water science in recent decades have led to a better understanding of the key issues that need to be addressed to solve the water crisis, and speedy innovation in water technology during the last decade or so looks promising.
A rapidly growing market for water technology, now estimated at $500 billion annually (compare this to the United Nation's $6 billion annual budget for water and sanitation projects), is producing a flood of new devices. These range from high-tech consumer-oriented ultra-filtration units to off-the-shelf community-level micro-utilities, available on the Internet for as little as $2-3,000 in countries such as the Philippines or Indonesia. This technical innovation facilitates a fast-growing, indigenous, small-scale water industry in many developing countries. The Bloomberg World Water Index has shown average returns of 35 percent per annum since its inception in 2003, outperforming oil and gas. And cutting-edge nanotechnology promises to reduce substantially the cost and energy use of water purification and even desalination. Let's consider these advances, and areas that need improvement, starting with the latter.
Desalination. As a reliable and affordable technology, desalination has come of age in the last two decades. For island cities such as Singapore, or for a new five-star hotel on a Pacific atoll, a desalination plant is now standard technology. The cost of desalination has come down rapidly and now ranges from $0.50-1.00 per cubic meter, depending on the price of energy. This is a reasonable price for drinking water in a developed urban area or hotel where the impact on room prices will be only a few dollars per day. For agriculture purposes, however, the value of water ranges from several cents per cubic meter to grow crops such as corn, wheat, rice, or sugar cane, to half a dollar for intensive flower or vegetable production. Desalination is clearly not an economical option. Desalination is similarly impractical for poor people who live on less than $1 or $2 per day.
Falling prices in membrane filtering technology (reverse osmosis) and advances in ultraviolet and ozone disinfection have led to a wide array of off-the-shelf water technologies. Large companies such as GE, Siemens, and Dow developed these technologies for consumer markets in industrial countries, spurred by the exploding market in bottled water, but they offer interesting spin-offs in developing countries.
As documented in the 2006 Human Development Report, a home-grown water industry is rapidly developing in many urban and peri-urban areas throughout Asia. Companies buy off-the-shelf water purification technology and sell bottled or packaged water in twenty-liter refillable bottles at rates affordable to even low-income groups. A 2005 World Bank paper reported that there were some ten thousand such local water companies, and today that is probably a low estimate given the rapid evolution of the industry. Progress in nanotechnology is leading to specialized membranes grown at molecular level that promise to reduce the financial and energy costs of desalination, water purification, and specialized waste-water treatment by another 3 to 5 times within a few years.
The new indigenous micro–water industry offers a challenge for government regulation as governments are tasked not with providing the service but rather monitoring its quality. Yet, among developments for providing drinking water services for the unserved in urban and peri-urban areas, it is the most promising in the last twenty years. It is demand-driven, locally owned, and therefore more likely to be scalable and sustainable.
More crop per drop. Concerned about the constraints of supply-side solutions and the limited impact of desalination, some water scientists and engineers have turned their attention to a more holistic view of water management. The Global Water Partnership, an international NGO, actively advocates integrated water resources management, which it defines as
a process which promotes the coordinated development and management of water, land and related resources in order to maximize the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems.
In practice, this means bringing the many different ministries and agencies that all supervise a sliver of water in each country together to find ways in which to manage demand, increase efficiency, and move water to higher-value uses: in essence, to do more with less.
The International Water Management Institute developed this approach in agriculture under the mantra "more crop per drop." A 2007 IWMI-led study concluded that there are indeed many avenues open to increasing the productivity of water in agriculture, and, surprisingly, the greatest potential is in the African savannahs, areas that hitherto have been considered unlikely to benefit from this kind of intervention.
The work of Falkenmark and Johan Rockström has contributed significantly to this shift in thinking. In Balancing Water for Humans and Nature, they explore the potential to increase the productivity of the green water. In practice this means developing opportunities for supplemental irrigation (limited irrigation to supplement rainfall during drought spells) through technologies that range from small scale irrigation to rainwater harvesting. While some in the scientific community view their work with skepticism, others see important supporting evidence in the success of Brazilian researchers and farmers who turned the Brazilian savannahs, the cerrados, into highly productive agricultural land in the second half of the twentieth century through active soil and water management as well as targeted plant breeding.
Other promising approaches to increase water productivity include breeding more drought-resistant crops or rice that does not need to be grown in standing water; safely reusing municipal waste water for agriculture; adapting systems to serve multiple uses from drinking to animal husbandry, vegetable production, and fishponds; managing food production in wetlands without damaging ecosystem services; and improving the capacity of water institutions for adaptive management.
Building storage. Generations of water engineers have been educated to solve water problems by developing "new" water resources. This usually involves capturing the water where it is available in nature, storing it to overcome temporal variability, and transporting it through canals or pipes to overcome spatial variability. Of course this water is not new -- all water on earth already serves some purpose, generally producing ecosystem services that are valuable in the aggregate. Water storage -- ranging from cisterns in residences to Lake Volta, formed by the Akosombo dam, the largest man-made lake in the world -- was the twentieth century's primary adaptation to variations in rainfall. Largely in the last century, the governments of the United States and Australia built between 5,000 and 6,000 cubic meters of storage per inhabitant.
These dams have displaced people, reduced and regulated the flow of rivers, and eliminated the natural rhythm that supported riverine ecosystems in general and wetlands and fisheries in particular. For these reasons, dams have become a controversial subject. Environmentalists in the American Northwest, for example, campaign to have dams decommissioned and removed to restore salmon runs. Throughout Europe, North America, and Asia, the most productive dam sites have been essentially used up, and many river basins are closed, or closing, because no more water can be developed without affecting existing human uses downstream.
But the debate should not focus on whether dams in general are bad or good. They need to be assessed in each specific context for their potential benefit as well as their full impact on the environment and the burden they may place on displaced people. Some of the dams built in the past would not pass such a test, though there are areas in which new dams are still worth the difficulties they create. In Ethiopia, for example, the current stock of water infrastructure is so low, less than 50 cubic meters per person (less than 1 percent of that in Australia or the United States), that dams should be considered. In large parts of Africa there are still environmentally viable and reasonably inexpensive opportunities to build even large dams that can offer significant social and economic benefits.
Dams and irrigation projects also acquired a bad reputation in the last few decades of the twentieth century because projected benefits were exaggerated in the planning phases of some high-profile, white-elephant projects built in Africa. But, while extravagant promises should be reined in, we need to stay focused on what truly matters: it is unlikely that water problems will be successfully addressed without new dam projects in some countries that face serious shortfalls.
Governance. Building dams is not simply a matter of technology and honest impact statements. Large water projects are also particularly prone to corruption. Water managers have access to information that is not available to the users, opening up opportunities for rent-seeking and fraud; specialized management services and equipment lead to one-off contracts, as opposed to standardized products, that are difficult to monitor; large public subsidies, generally provided as budgets devoid of performance requirements, lead to an accountability deficit; and water engineers who dominate the water sector tend to approach water problems as technical problems that require technical solutions, and they are unlikely to address the incentives for corruption that pervade the process.
Researchers Hector Malano and Paul van Hofwegen introduced the idea of looking at irrigation water not only as a resource and infrastructure problem, but as a service that can only work well with effective institutions and an alignment of stakeholder interests. Their emphasis on institutions and governance mirrors a broader discussion in global development on redesigning institutions in order to achieve greater transparency, design better policy, and improve incentives for compliance. The most significant institutional innovation in fighting corruption in water management has been the development of water-user associations that take responsibility for managing water and irrigation systems. Large numbers of such associations have emerged in Mexico, Turkey, the Philippines, Pakistan, India, and, more recently, Central Asia. This irrigation management transfer, or participatory irrigation management, has become standard World Bank policy even though its benefit is hard to prove.
Other attempts have focused on market approaches to service delivery. In most cases in which governments, advised by the World Bank, have given contracts to large French and British water companies to provide water supply services, the intent was to privatize the delivery of accountable water services, not water resources themselves. Still, such privatizations have proven highly controversial, leading to popular protests and even riots. Current, second-generation experiments with water-sector reform tend to emphasize decentralization from national to regional, district, or provincial water agencies, utilities, or companies. Unfortunately these efforts are hampered by a lack of information at the local level that would enhance the transparency of the reforms and resulting services. Consumers find it surprisingly difficult to assess the services they receive or are entitled to.
Making services work for the poor. Despite considerable efforts both by national governments and development agencies, public services -- including water services -- are failing to reach the poor. One reason is corruption, based, again, on an asymmetry of information between consumers and service providers.
Better information can also assist service providers in improving their service and help government decision-makers allocate resources or make investment decisions more effectively. In the cases of sanitation and drinking water, the only information available in most areas lacking service concerns exclusively infrastructure, which does not adequately represent the situation facing the poor. What knowledge is available focuses on the presence or absence of infrastructure improvements, but speaks to neither the amount and quality of water available to individuals (even in the aggregate, at a scale useful for planning, such as a district or province level) nor the correlation between water services and water-related diseases.
Therefore, large-scale investments to achieve the Millennium Development Goals for water are still based on making infrastructure available, rather than on putting a service in place or, better still, achieving health. Water utilities in developing countries lack information about their customers, and they also lack the practical information they need to benchmark their own performance. Poor consumers in the rapidly growing urban and peri-urban areas often live in informal settlements, which implies that they do not have a proper address, cannot open a bank account, and are practically invisible to the formal system.
NGOs such as WaterAid are experimenting with ways to achieve accountability by providing these oft-ignored consumers with scorecards to rate the service they receive. Following similar initiatives in the education sector, others analyze government budgets and reports from water utilities in order to inform communities of the resources that ought to be available to them. Development organizations have begun to produce benchmarking databases that water utilities use to share information on their performance and compare their work to that of their peers. UN-Habitat, in collaboration with the governments of Kenya and Uganda, carried out detailed household surveys in fifteen towns around lake Victoria in order to create a water-service level baseline and establish the relationship between water services and health.
To support promising developments such as these, Google.org has begun an initiative that aims to improve education and health-related water services through empowered citizens and communities, responsive providers, and informed decision-makers.
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How can the world be induced to act on the water crisis? It took almost thirty years of advocacy by the climate community before the world took the climate crisis seriously. The water community knows that the best time to get people's attention and force action is in the wake of a flood or drought. The recent Australian drought made water the country's political hot button. A California court order to drastically reduce pumping water from the Sacramento-San Joaquin River Delta -- the lynchpin of the large-scale water transfer to the southern part of the state -- may trigger a similar emergency. But floods and droughts are local events that allow the large majority of the world population to ignore their own vulnerability until a crisis hits home. In the end it may be Al Gore who opened the door to far-reaching water awareness. As people accept that climate change is real and here to stay, they are likely to realize that while reducing greenhouse gas emissions is all about energy, adapting to climate change will be all about water.
Solutions to the world water crisis will not be technological fixes of the sort attempted in the past. The water-service crisis is most likely to be resolved through a combination of much-improved, cheaper, small-scale, off-the shelf water purification technology, combined with better information; a reformed public water-sector; and large numbers of indigenous, small to medium-scale private water-service providers. People affected by the water-resource crisis and their allies need to increase water productivity in a manner that maintains ecosystem services -- particularly, but not exclusively, through increased green-water productivity in Africa's savannahs -- and buttresses the local capacity to manage climate risk. A tall order, perhaps, but the current world food crisis demonstrates what is at stake. While that crisis appears to have been triggered by the production of cereals-based biofuels, the next food crisis could easily be triggered by water scarcity.