Water - Economics and Policy

Water: Economics and Policy Water: Economics and Policy Water is the driving force of all nature. -- Leonardo da Vinci 1. GLOBAL SUPPLY AND DEMAND FOR WATER Water is a unique natural resource that forms the basis for life on Earth. Two thirds of the planet’s surface is covered by oceans. 97% of the Earth’s water is salt water and only 3% is freshwater – 70% of which is in solid form, captured by the polar ice caps and by glaciers (Fig. 1). Of the 30% of freshwater that is available in its liquid form, most is in underground aquifers. The freshwater that makes up all of the terrestrial sources such as rivers and lakes only represents 1% of the planet’s freshwater. Figure 1: The composition of the planet’s water Source: Getting the picture: our changing climate - http://gettingthepicture.info/3/; Water can be characterized as a renewable resource, since it can generally be reused indefinitely as long as it is not severely polluted. Also, water is continually purified in a process known as the hydrologic cycle (Fig. 2). Water evaporates from lakes, rivers, oceans, and through the evapotranspiration of living organisms, returning as precipitation that replenishes the freshwater sources, whether on the ground or underground. The flows of freshwater that are recycled in the hydrologic cycle are at times stocked in two types of natural reservoirs, bodies of surface water such as lakes and rivers, and stocks of groundwater, which are found in underground aquifers. While aquifers are 1 replenished as a result of infiltration, most aquifers have very long replenishment times, making them essentially nonrenewable resources on a human time scale. Aquifers under the Sahara, for example, are thousands of years old, and are sometimes referred to as “fossil water.” Thus the analysis of water systems combines elements of renewable and non-renewable resource theory. Figure 2: The Hydrologic Cycle Evaporation fueled by the sun’s energy lifts 500,000 cubic kilometers of moisture into the atmosphere each year—86 % from the oceans and 14 % from the land. An equal amount falls back to earth as rain, sleet, or snow, but it is distributed in different proportions: whereas the continents lose about 70,000 cubic kilometers through evaporation, they gain 110,000 through precipitation. As a result, roughly 40,000 cubic kilometers are transferred from the sea to the land each year. The total available supply of 40,000 cubic kilometers converts to about 5,700 cubic meters per person per year. Hydrologists have established that, considering the water needs of modern societies, a threshold of 2,000 cubic meters per person per year represents the level above which a population can be sustained comfortably.1 But while the total global water supply is sufficient to meet human needs, not all water can be captured for human use. As much as two-thirds of the total water supply runs off as floods. Some water must also be allocated to meet ecological demands, such as supplying wetlands and wildlife habitat. According to the United Nations, an area is said to be experiencing water stress when annual water supplies fall below 1,700 cubic meters per person per year. 2 A region is said to face water scarcity when supplies fall below 1,000 cubic meters per person, and absolute water scarcity when supplies drop below 500 cubic meters per person per year.3 1 Postel, 1992. Hydrology is the scientific study of the distribution and movement of water on the earth’s surface, underground, and in the atmosphere. 2 Center for Strategic and International Studies, 2005. 3 U.N. Food and Agriculture Organization (FAO), 2012. 2 Global water supplies are not evenly distributed geographically or seasonally. Some regions of the world have abundant water resources, while others suffer from a scarcity of water. The symptoms of physical water scarcity include severe environmental degradation, declining groundwater, and unequal water distribution, and they cause severe constraints on food production, economic development, and protection of natural systems. In addition to physical scarcity, the concept of economic water scarcity relates to situations where a lack of proper infrastructure in water distribution, water recycling and treatment, and sanitation, leads to inadequate water supply. This situation often causes the population to rely on unhealthy sources of water, with tragic health and mortality consequences, as is the case in large parts of Africa, where waterborne diseases are the leading cause of children mortality. Worldwide, 6000 children die each day as a result of diseases caused by ingestion of unsafe water.4 Figure 3 shows the countries that are already experiencing water stress or water scarcity in physical terms. The countries with the most limited water supplies are in North Africa and the Middle East. Water stressed countries include India, South Africa, and Poland. Figure 3: Global Freshwater Availability, 2007 Cubic&meters&per&person&per&year Water"scarce Water"stressed Data"not"available 0""""1000"""1700"""2500""6000""15000"70000" Source: UNEP, 2008. 4 UNICEF, http://www.unicef.org/media/media_21423.html. 3 Figure 4 presents a more precise picture of water scarcity by displaying not only physical scarcity but also economic scarcity, showing that many African countries which are not water scarce in physical terms, are experiencing water economic scarcity and low access to clean water. Figure 4 also shows regional variability inside countries – The United States and Australia are on average well above the threshold of 2000 cubic meters of water per capita per year, but entire regions such as the US Western States and the Southeastern part of Australia are experiencing physical water scarcity. Figure 4: Physical Water Scarcity vs. Economic Water Scarcity Reproduced by Worldwatch Institute, March 2013, http://vitalsigns.worldwatch.org/node/180. Some of the most populated areas of the world are experiencing increasing water stress and scarcity (see Table 1) and the problem will only intensify throughout the 21st century, under the growing pressures of population growth and climate change, which will worsen water availability in areas that are already arid and semi-arid. The Middle East and North Africa region is the most water scarce (average 500 cubic meters per person per year) with a population of 432 million in 2007, expected to increase to 692 million in 2050.5 Sub-Saharan Africa already suffers from water scarcity (1000 cubic meters per person per year) with a current population of 936 million in 2013, expected to double by 2050.6 5 6 Population Reference Bureau, 2008 http://www.prb.org/Publications/Articles/2008/menafertilitydecline.aspx. World Bank, http://data.worldbank.org/region/SSA; Population Reference Bureau http://www.prb.org/Publications/Datasheets/2013/2013-world-population-data-sheet/data-sheet.aspx 4 Table 1: Water Availability per region (2012) Region Middle East and North Africa Sub-Saharan Africa Caribbean Asia/Pacific Europe Latin America North America (including Mexico) Average water availability (cubic meters/person) 500 1,000 2,466 2,970 4,741 7,200 13,401 Source: FAO, Aquastat (2013), UNESCO (2012) – from vitalsigns.worldwatch.org To examine those challenges in more depth, we turn first to a more detailed analysis of the uses of water in modern human societies, and indicators that can be used to measure the impact of our water use. Uses of water When considering the use of water, it is useful to think of water along three critical dimensions: consumption, withdrawal, and quality. Consumption refers to water that disappears or is diverted from its source, for example by evaporation, incorporation into crops or industrial processes, drinking water, etc. The source may or may not eventually be replenished. If replenished, the process could potentially take many years— decades, centuries, or longer. Withdrawal refers to water that is essentially “sucked up” for a given use, but then returned to its source. The quality of the returned water may or may not be the same as it was prior to removal. Quality is a broad term that can refer to pollutants that enter the water; changes to oxygen content, salinity, and acidity; temperature changes; destruction of organisms that live in the water; and so on.7 Considering these three dimensions of water, scientists have proposed a decomposition of water into three categories of water that allow for a more precise analysis of human use of freshwater8: Green water: the water that exists in flux in natural ecosystems, as clouds, mist, rain, as well as the humidity that is captured by the soils and plants. 7 Definitions are adapted from Glassman, et al., 2011. http://www.nationalfoodhub.com/images/THE_WATER-ENERGY_NEXUS_REPORT.pdf>. 8 Hoekstra and Hung, 2002. 5 Blue water: the water withdrawn from water stocks, i.e. bodies of water such as lakes, reservoirs, and groundwater aquifers – and which is used as input in all human activities (irrigated agriculture, industry, domestic use) Gray water: the freshwater needed in order to dilute and flush away all the pollutants that result from all human activities. It is quantified as the volume of water that is required to assimilate pollutants to such an extent that the quality of the ambient water remains above agreed water quality standards. Figure 5 gives a representation of the three types of water as used in agriculture. Figure 5: Green, Blue, and Gray Water uses of Water for Agriculture Source: https://thelivinglabiesd.wordpress.com/2012/11/14/sustainable-water-the-concept-of-water-footprint/ Agriculture uses as inputs both green water (rain-fed crops) and blue water (irrigated crops). It also requires gray water, to flush and dilute the pollutants used in industrial fertilizers (nitrates) and pesticides and herbicides. Industry uses mostly blue water, which is withdrawn for many usages such as cooling (thermoelectric plants, nuclear plants, steel industry). Industries also use water for hydraulic pressure (enormous amounts of water are used in fracking the underground rocks imbibed with gas) or as an input in fabrication processes – for instance the production of paper. Green water is also an input of industrial processes since some rainfed agricultural goods are also used as major ingredients in industrial production. This is the case with biofuels, which come from crops (primarily corn and soy) produced to make ethanol. Additionally, large amounts of gray water are needed to dilute all the industrial chemical pollutants that result from the industrial water uses. 6 Domestic and municipal use of water comes strictly from blue water sources, used for sanitation, bathing and cooking, as well as recreational uses (swimming pools, watering lawns, etc.). Indicators of water use Traditionally, the indicator used to measure the impact of human activities on water resources is the amount of total freshwater withdrawal for the various sectors of the economy. These water withdrawals from lakes, rivers, dams, reservoirs and aquifers, correspond in the above classification to “blue water”. The largest water consuming sector of human activities is agriculture. Although 83 percent of the world’s cropland is rain-fed (green water), the 17 percent that requires irrigation (blue water) produces more than 40 percent of the world’s food supply.9 The water needed for this part of agriculture amounts to a total of 70 percent of global water withdrawals.10 19 percent of global water withdrawals (blue water) is for industrial demands, including electricity production. Only 11 percent of water is used to meet municipal and domestic demands. Figure 6 presents the shares of water use per sector at the global level. Figure 6: Global Water Withdrawals for Agricultural, Industrial and Municipal use 19% Agricultural 11% Municipal 70% Industrial Source: Aquastat, F.A.O. http://www.fao.org/nr/water/aquastat/water_use/index.stm. These percentages are global averages, but they vary significantly from country to country. In the United States for instance, irrigation amounts to 41% of the nation’s total freshwater withdrawals but industry uses up to 46% of water withdrawals, especially thermoelectric power generation, which needs enormous amounts of water cooling for the steam-driven turbine generators11. In the developing world, freshwater withdrawals are often mostly used for agriculture (86% in Egypt, 94% in Ethiopia, 95% in Vietnam).12 9 Postel, 1999, p. 42. Aquastat, Food and Agriculture Organization, http://www.fao.org/nr/water/aquastat/water_use/index.stm. 11 Gleick et al., 2014, p.227-235. 12 ibid. 10 7 Like energy consumption, water consumption per capita varies significantly across different countries, as shown in Figure 7. Unlike energy use, water use is not mainly a function of economic development. Some countries with relatively high water use, such as Turkmenistan and Iraq, are not high-income countries yet heavily rely upon water for agriculture. While China has a higher gross domestic product (GDP) per capita than India, India uses more water per person, with 90 percent of it for agricultural purposes. German water use per-capita is similar to that in China, but hardly any water in Germany is used for agriculture. Figure 7: Water Consumption per Capita, Select Countries Source: World Bank Development Indicators, accessed on 8/21/15 While water itself is seldom traded, water is often used to produce goods that are traded. Countries can import goods produced with water coming from somewhere else, rather than with their own water resources. To capture the impact of trade and total water consumption, two other indicators have been proposed: virtual water and water footprint. 1) Virtual water is the amount of water that is embedded in every single good or service, and which accounts for all of the water used as input at every step of the production process, either for agricultural goods, industrial goods, or services. 13 13 Concept and term coined by Tony Allan. 8 2) Water footprint builds on the concept of virtual water, aggregating actual and virtual water consumption to calculate the total water impact of a sector of activity, or of an individual, household, city, or country. It takes into account all types of water impacted – green, blue, and gray. 14 Virtual Water In every good produced, there is a hidden quantity of water that has been used throughout the production process. Agricultural goods need water to grow plants and fruits, or water to raise cattle and other livestock. For instance, the production of an apple requires 70 liters of water, and the production of a glass of milk requires 200 liters of water (see Table 2). Industrial goods also require water from the raw material stage to the final production stage. One sheet of paper requires 10 liters of water to be produced, and a leather pair of shoes requires 800 liters. This hidden amount of water that is invisibly carried by any goods or products consumed is what we have defined as virtual water.15 Table 2: Virtual Water embedded in a selection of products, per unit of product (in liters: 1 gallon = 3.78 liters) Product Virtual-water content (liters) 1 sheet of paper (80 g/m2) 1 tomato (70 g) 1 slice of bread (30 g) 1 orange (100 g) 1 apple (100 g) 1 glass of beer (250 ml) 1 glass of wine (125 ml) 1 egg (40 g) 1 glass of orange juice (200 ml) 1 bag of potato crisps (200 g) 1 glass of milk (200 ml) 1 hamburger (150 g) 1 pair of shoes (bovine leather) Source: Hoekstra and Chapagain, 2008, p. 15. 10 13 40 50 70 75 120 135 170 185 200 2,400 8,000 The energy sector consumes large amounts of water, which is used in all the different steps of energy extraction, production and consumption. Natural gas is the least water intensive fuel, whereas the use of unconventional oil tar sands requires 20 times more water than conventional oil and 100 times more water than natural gas. Biofuels are associated with high water consumption – 3,000 times more water than conventional oil! Table 3 presents the different amounts of virtual water that would be embedded in six types of fuel if they were used to power the same roundtrip New York City-Washington D.C. (requiring an amount of energy equal to 2 million BTUs – British Thermal Units). 14 15 Concept coined by A. Hoekstra and P. Hung. Allan, 2011, p.9. 9 Table 3: Virtual water used in six types of fuels, round trip New York CityWashington D.C. Type of fuel Natural Gas (conventional) Unconventional natural gas (shale) Oil (conventional) Oil tar sands (mining) Biofuel type 1 (irrigated corn) Biofuel type 2 (irrigated soy) Amount of water needed in the extraction/production of 2 Million BTUs of energy 5 gallons 33 gallons 32 gallons 616 gallons 35,616 gallons 100,591 gallons Source: World Policy Institute – EBG Capital analysis based on U.S. Department of Energy 2006, and World Economic Forum and Cambridge Energy Research Associates 2009. Available at: http://www.worldpolicy.org/sites/default/files/policy_papers/THE%20WATER-ENERGY%20NEXUS_0.pdf Water Footprint The concept of water footprint, based on the model of a carbon footprint16, was introduced by Hoekstra and Hung (2002) as an indicator that could map out the impact of all of human consumption on global freshwater resources. The water footprint shows the water use associated with consumption for an individual, institution, or country, including blue, green and gray water. At the individual level, we can add up all the water needed to make food, energy and other products consumed. To calculate your own individual footprint, take the test at the website http://www.gracelinks.org/1408/water-footprint-calculator. The average person on the planet uses 1,056 gallons of water per day – that’s enough to fill up 21 standard bath tubs.17 The average water footprint of an American consumer is 2,220 Gallons per day, which is the equivalent of 44 full bathtubs of water! Having a vegetarian diet or being a meat eater makes the biggest difference in a person’s water footprint, as you can observe by changing the options in the calculator. There is also an important connection between the carbon footprint and the water footprint. Increased use of energy tends to raise both carbon and water footprints (see Box 1). Water footprint of nations can be calculated by taking into account all of the virtual water embedded in all sectors of economic activity, including agriculture, industries, services and domestic use. An important difference between the calculations of the traditional indicator of withdrawal per sector and the concept of water footprint is that the water footprint shows not only freshwater use within the country considered but also freshwater use outside the 16 A carbon footprint measures the amount of carbon emissions associated with a given economic activity. Allan, 2011 p. 4, and http://inhabitat.com/water-footprint-of-humanity-study-shows-average-person-uses1056-gallons-of-water-each-day/. 17 10 country’s borders. It refers to all forms of freshwater use that contribute to the production of goods and services consumed by the inhabitants of a certain country. Figure 8 presents water footprints for a selection of countries. Figure 8: National Water Footprint for selected countries, 1997-2001 3000" 2500" 2000" Agricultural"goods" 1500" Industrial"goods" 1000" Domes8c"water" consump8on" 500" 0" Consumption in cubic meters per person per year Sources: Hoekstra and Hung, 2002, p. 60; also available at http://waterfootprint.org/en/resources/interactivetools/national-water-footprint-explorer/ 11 Box 1: The Water-Energy Nexus The demand for both water and energy is increasing while there are growing limitations on their supply. These two resources are closely connected. Water is itself a source of energy (hydropower) and water is an input to grow the crops used to make biofuels, and is also used in the extraction of fossil fuels (notably fracking gas and tar sands oil). At the same time, energy is necessary to pump and extract water, to clean and recycle it, and to desalinize sea water. Water use in the energy sector primarily occurs in two areas: fuel production and electricity generation. Both of the processes can employ a number of different technologies that have very different water use requirements. Water is used for pressure in drilling oil wells, especially in the nonconventional practices of fracking. Hydraulic fracturing or “fracking” involves pumping large volumes of water, mixing it with sand and chemicals, and sending it to the deep underground at high pressure to fracture the shale rock and release trapped gas. The exact chemical composition of fluids used by oil companies for fracking is unknown and undisclosed for reasons of industrial private intellectual property, which has generated controversy, because of their high toxicity and the risks of contamination of the water used in the process. According to Patrick Sullivan, of the California Center for Biological Biodiversity: “It is water that cannot be put back into the water cycle. It’s water that is by and large gone for good.” This contaminated water poses acute problems of storage to insure that it does not leak back into aquifers from which water is withdrawn for domestic use and for agriculture. Sources: Aida Tabakovic & Elisabeta Poci, 2012, The Water-Energy Nexus, http://www.caee.utexas.edu/prof/mckinney/ce397/Topics/Water-Energy/Water-Energy(2012)_ppt.pdf; http://thinkprogress.org/climate/2015/04/06/3643184/california-70-million-gallons-fracking/ 12 The water footprint per capita of the United States is 2,500 cubic meters per person per year whereas the water withdrawal per capita is 1,500 cubic meters per person per year (Figure 7). The difference between the two figures reflects: 1) the water footprint takes into account all of the green water (primarily rain-fed crops) embedded in all the goods consumed in the US 2) the water footprint includes both an internal component, based on internal water resources, and an external component based on water used for imported products or ingredients. Virtual Water and Trade There is an invisible circulation of water between countries that occurs through trade: water-scarce countries can consume imported products that would have been too water-consuming to produce in their own land. For instance, Saudi Arabian imports of milk and meat from Europe, Argentina or from Australia or New Zealand, allow Saudis living in a desert climate to have access to these goods, which is the equivalent of a water transfer from water-abundant countries to a water-scarce country. But trade does not always follow a logical direction in terms of water transfer. Waterintensive crops such as cotton are often produced in water-stressed or even water-scarce countries for reasons that make little ecological sense. The virtual water embedded in a cotton T-shirt is 2,700 liters. However, cotton is produced in India and other Asian countries which are experiencing water stress/scarcity issues. Figure 9 shows the global picture of the import of cotton to Europe and what this trade implies in terms of water transfers. Figure 9: Virtual Water in Cotton Imports to the European Union (million m3/year), 1997-2001. Source: Hoekstra and Chapagain, 2008, p. 85. 13 The production of cotton for export to Europe creates a water footprint of 5,000 to 7,500 million cubic meters in water-stressed India, and more than 2,000 million cubic meters in water scarce Egypt.18 Figure 10 shows the global picture of the amount of virtual water transferred through global trade, including both agricultural and industrial products. Countries that have a negative balance in virtual water trade (exporting goods that are more water intensive than the goods they import) are colored in green – they are net exporters of virtual water. Countries that have a positive virtual water balance are colored in red – they are net importers of virtual water. Figure 10: Virtual-water balance per country, 1997-2001 (billion cubic meters) Source: Hoekstra and Chapagain, 2008, p. 84-85. If we compare this picture with Figure 3, we observe that many of the Asian countries that are experiencing water stress or near water-stress situations are actually virtual-water exporters. This is the case with India, Pakistan and China. On the other hand, there are countries that are relatively water abundant like Italy or Japan that nevertheless are virtual-water importers. For water-scarce countries it can sometimes be attractive to import virtual water (through import of water-intensive products), thus relieving the pressure on domestic water resources. This happens, for example, in Mediterranean countries, the Middle East and Mexico. But the fact that Northern European countries import a lot of water in virtual form (more than they export) is not driven by water scarcity. In Europe as a whole, 40% of the water footprint lies outside of its borders. 18 Hoekstra and Ashok, 2008, p. 131-135. 14 Water scarcity and conflicts Water scarcity can be a major factor leading to conflicts. For example, the civil war that has been raging in Syria since 2011 is strongly related to water shortage issues. A climatic event, the prolonged 6-year drought, from 2006 to 2011, ruined hundreds of thousands of small scale farmers, and forced them to emigrate to the outskirts of several cities such as Aleppo, Hama, Homs, Damascus and Dara’a, which became centers of political unrest against the Assad regime.19 In one of the most protracted conflicts of our times, between the State of Israel and the Palestinian people, access to the water aquifers underneath the hills of the West Bank constitutes one of the important factors. Although not generally discussed in the media, access to water has been a key factor in the occupation of the West Bank since 1967, including a growing number of controversial Israeli settlements that directly exploit this groundwater resource (See Box 2). Scientists have modeled the impact of climate change on rain patterns in different regions of the world in the decades to come. Their results suggest that the Middle East and North Africa region would be subjected to more frequent and prolonged drought episodes.20 In this already politically volatile region, the growing scarcity of water would likely contribute exacerbating future conflicts. 19 20 The World’s water, volume 8. Peter Gleick, the Syrian conflict and the role of water, p. 147. World Bank Group, Turn down the heat, confronting the New Climate Normal, 2014. p. 125 15 Box 2: Shared water aquifers for two people in conflict: the case of Israel-Palestine As shown in the figure, Israelis and Palestinians rely on the same water aquifers for their needs but the rules that conduct how this common resource is shared are far from being equitable. Source: http://www.mediterraneanaffairs.com/en/events/water-israeli-palestinian-conflict.html A World Bank report indicates that Israelis use four fifth of the West Bank groundwater resources, and the Palestinians only one fifth.21 Israelis use 240 cubic meters of water a person each year, against 75 cubic meters for West Bank Palestinians and 125 for Gazans. However, in Gaza, where Palestinians rely on an aquifer that has become increasingly saline and polluted, the situation is worse. Only 5%-10% of the available water is clean enough to drink. In some areas of the West Bank, Palestinians are surviving on as little as 10 to 15 liters a person each day, which is at or below humanitarian disaster response levels recommended to avoid epidemics. The amount recommended by the World Health Organization is at least 100 liters per day.22 If the Palestinian inhabitants are to develop their country economically and socially in the future, they will have to be able to draw more heavily on this groundwater resource. This explains why this basin has been the most intensely disputed resource in every round of water negotiations between Israel and Palestine. 21 Source:http://www.theguardian.com/world/2009/may/27/israel-palestinian-water-dispute http://siteresources.worldbank.org/INTWESTBANKGAZA/Resources/WaterRestrictionsReport18Apr2009.pdf World Bank Middle East and North Africa Region Sustainable Development, West Bank and Gaza Assessment of Restrictions on Palestinian Water Sector Development – Sector Note – April 2009 22 See B’Tselem http://www.btselem.org/topic/water 16 2. ADDRESSING WATER SHORTAGES To address water shortages, there are technical approaches that can alleviate the pressure on scarce resources by increasing the supply, or by decreasing the demand. There are also institutional approaches, including economic instruments, which can impact demand and keep it from growing beyond the necessary limits. Given the extent of projected water shortages in some regions, a “magic bullet” solution is unlikely. A range of options will be needed. We have a menu of options, but the status quo is not one of them. In the United States, the usual response to water shortages is to divert more water from rivers, build more dams, and drill more groundwater wells. These traditional alternatives are not viable solutions. Other ideas—surreal ones—include towing icebergs from the Arctic, importing water from British Columbia, and seeding clouds. These ideas reflect a misguided hope that there is a new oasis out there, somewhere, that will obviate the need to examine carefully how and for what we use water. More sensible approaches include conservation, desalination, and reuse of treated municipal effluent. Yet even communities that have embraced these measures still face ominous water futures.23 Increasing Water Supply: Aquifers, Dams, and Desalination Past water management policies have generally focused on ways to increase the supply of water. In regions where freshwater supplies are insufficient to meet demand, additional water has often been obtained by extracting groundwater from aquifers. While underground aquifers are normally recharged by water seepage, in most cases withdrawal rates greatly exceed the rates of recharge. Countries such as Saudi Arabia and Libya rely on “fossil” groundwater from ancient aquifers in desert areas, which have practically no recharge and are likely to be depleted over the next forty to sixty years. In the western United States, the Ogallala Aquifer is also severely depleted, and as a result irrigated area has started to shrink. Similar problems affect aquifers in North China and in India. (For more on the exploitation of aquifers around the world, see Box 3.) Another way to increase water supplies is to construct dams. Dams can capture seasonal floodwater that would otherwise be unavailable for human use and use stored water to provide hydroelectric power. Worldwide close to 48,000 large dams are in operation, about half of them in China.24 These dams provide 19 percent of the world’s electricity. More dams are still being built, mainly in China, Japan, Turkey, and Iran, but the best sites are already in use. Existing dams are often affected by problems of siltation, and new large dam proposals have been criticized for the environmental and social damage resulting from the flooding of large areas.25 For example the Three Gorges Dam in China, the largest hydroelectric dam in the world, displaced 1.3 million people and disrupted the habitat of dozens of endangered species. 23 Gleick, 2011, p. xi-xii. Large dams are defined as those over 15 meters in height. http://wwf.panda.org/what_we_do/footprint/water/dams_initiative/quick_facts/. 25 See World Commission on Dams, 2000. 24 17