Wells Run Dry - Article 21 When the World’s Wells Run Dry...

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Unformatted text preview: Article 21 When the World’s Wells Run Dry . It may seem to defy the logic of a closed planetary system, but the supply of water available for irrigation is indeed diminishing—at an alarming rate by Sandra Postel n 1970, farmers in rural Deaf Smith County in the Texas panhandle encountered a small but definite sign that local agriculture was seriously out of bal- ance. An irrigation well that had been drilled in 1936 went dry. After more than 30 years of heavy pump- ing, the water table had dropped 24 meters. Soon other wells began to dry up too. Water tables were falling across a wide area of the Texas High Plains, and when energy prices shot up in the 19705, farmers were forced to close down thousands of wells because they could not longer afford to pump from such depths. During the last three decades, the depletion of under- ground water reserves, known as aquifers, has spread from isolated pockets of the agricultural landscape to large portions of the world's irrigated land. Many farmers are now pumping groundwater faster than nature is replenish- ing it, causing a steady drop in water tables. Just as a bank account dwindles if withdrawals routinely exceed deposits, so will an underground water reserve decline if pumping exceeds recharge. Groundwater overdrafting is now widespread in the crop-producing regions of central and northern China, northwest and southern India, parts of Pakistan,- much of the western United States, North Af- rica, the Middle East, and the Arabian Peninsula. Many cities are overexploiting groundwater as well. Portions of Bangkok and Mexico City are actually sinking as geologic formations compact after the water is re- moved. Albuquerque, Phoenix, and Tucson are among the larger U.S. cities that are overdrafting their aquifers. Globally, however, it is in agriculture where the greatest social risks lie. Irrigated land is disproportionately impor- tant to world food production. Some 40 percent of the global harvest comes from the 17 percent of cropland that is irrigated. Because of limited opportunities for expanding rainfed production, we are betting on that share to increase markedly in the decades ahead, in order to feed the world’s growing population. As irrigation goes deeper and deeper into hydrologic debt, the possibilities for serious disruption grow ever greater. Should energy prices rise again, for ex- ample, farrners in many parts of the world could find it too expensive to irrigate. Groundwater overpumping may now be the single biggest threat to food production. Our irrigation base is remarkably young: 60 percent of it is less than 50 years old. Yet a number of threats to its continued productivity are already apparent. Along with groundwater depletion, there is the buildup of salts in the soil, the silting up of reservoirs and canals, mounting com- petition for water between cities and farms and between countries sharing rivers, rapid population growth in re- gions that are already water-stressed—and on top of all that, the uncertainties of climate change. Any one of these threats could seriously compromise agriculture’s produc- tivity. But these stresses are evolving simultaneously— making it increasingly likely that cracks will appear in our agricultural foundation. Few governments are taking adequate steps to address any of these threats and, hidden below the surface, groundwater depletion often gets the least attention of all. Yet this hydrologic equivalent of deficit financing cannot continue indefinitely. Groundwater withdrawals will even. tually come back into balance with replenishment—the only question is whether they do so in a planned and coordinated way that maintains food supplies, or in a cha- otic and unexpected way that reduces food production, worsens poverty, and disrupts regional economies. It is true that there are enormous inefficiencies else- where in the agricultural sector—and tackling these could 162 From World Watch, September/October 1999, pp. 30-38. 0 1999 by the Worldwatch Institute. Reprinted by permission. take some of the pressure off aquifers. A shift in diets, for example, could conserve large amounts of irrigation water. The typical U.S. diet, with its high share of animal prod- ucts, requires twice as much water to produce as the nu- tritious but less meat-intensive diets common in some Asian and European nations. If U.S. consumers moved down the food chain, the same volume of water could produce enough food for two people instead of one, leaving more water in rivers and aquifers. But given the rates of groundwater depletion, there is no longer any reasonable alternative to tackling the problem di- rectly. Aquifer management will be an essential part of any strategy for living within the limits imposed by a finite supply of fresh water. The Groundwater Revolution During the first century of the modern irrigation age— roughly from 1850 to 1950—efforts to develop water sup- plies focused mainly on rivers. Government agencies and Ancient Romans made this water-carrying pipe with cement and crushed rock. Courtesy George E. Bartuska, Winter Park, Florida. 21. When the World’s Wells Run Dry private investors constructed dams to capture river water and canals to deliver that water to cities and farms. By the middle of this century, engineers had built impressive irrigation schemes in China, India, Pakistan, and the United States, and these nations became the world’s top ‘ four irrigators. The Indus River system in South Asia, the Yellow and Yangtze Rivers in China, and the Colorado and Sacramento-San Joaquin river systems of the western United States were each irrigating sizable areas by 1950. The global irrigation base then stood at 100 million hec- tares, up from 40 million in 1900. Between 1950 and 1995, world irrigated area in- creased to more than 250 million hectares. Even as the construction of large dams for hydroelectric power, water supply, and flood control picked up pace, a quiet revolution in water use unfolded during this period. Ru- ral electrification, the spread of diesel pumps, and new well-drilling technologies allowed farmers to sink mil- lions of wells into the aquifers beneath their land. For the first time in human history, farmers began to tap groundwater on a large scale. . Aquifers are in many ways an ideal source of water. Farmers Can pump groundwater whenever they need it, and that kind of availability typi- cally pays off in higher crop yields. Compare this with the standard scenario for irrigating with river water: river flow is erratic, so a reservoir is usually required to store flood water for use in the dry season. And reservoirs—especially arid-land reservoirs such as Lake Nasser behind Egypt’s High Aswan Dam—can lose 10 percent or more of their water to evaporation. In addi- tion, the large canal networks that move water out of reservoirs are often unreliable—they may not deliver enough water when farmers actually need it. Aquifers, on the other hand, have a fairly slow and steady flow that is usually available year-round and they don’t lose water to evapo- ration. Finally, groundwater is generally less ex- pensive to develop than river water. Data from 191 irrigation projects funded by the World Bank show that groundwater schemes cost a third less on average than surface schemes. Not surprisingly, huge numbers of farmers and investors turned to groundwater as soon as they acquired the means to tap into it. In China, the number of irrigation wells shot up from 110,000 in 1961 to nearly 2.4 million by the mid-19805. In India, government canal building nearly dou- bled the area under surface irrigation between 1950 and 1985, but the most impressive growth was in groundwater development: the area irri- gated by tubewells ballooned from 100,000 hec- tares in 1961 to 11.3 million hectares in 1985—a 113-fold rise, most of it privately funded. (A tubewell is a narrow well that is drilled into an aquifer, as opposed to a larger- 163 v i 1 “a .I ,' I' ,. .1 . l l;‘ .I I. r W... A .w- m .4“ .‘A M .‘ inn; .3: .L- .‘ -uan. ..’.«r.,. J: ;:<_‘,~:.t‘.:"...-.. "\:7- v -. -"-l as...» - ,-,‘g_~;=..~— u m 2:"? 5 4° RESOURCES: Water diameter well that is excavated, either by hand or with ma- chinery.) In neighboring Pakistan, groundwater was the fast- est-growing form of irrigation from the mid-19605 through the 19805. A public program of tubewell development failed miserably, but private groundwater investments climbed steeply. The total number of tubewells in that country rose from some 25,000 in 1964 to nearly 360,000 in 1993. After World War II, the United States experienced a groundwater boom as well. Farmers in California stepped up their pumping of groundwater beneath the rich soils of the Central Valley, which was well on its way to be- coming the nation’s fruit and vegetable basket. But the greatest aquifer development was in the U5. Great Plains, a region that straddles the 100th meridian, the nation’s transition zone from rain-fed to irrigated agriculture. In a striking bit of good fortune, the drier western portion of the plains is underlain by a vast underground pool called the Ogallala. One of the planet's greatest aquifers, it spans portions of eight states, from South Dakota in the north to Texas in the south. The Ogallala extends for 453,000 square kilometers, and—prior to exploitation—held 3,700 cubic kilometers of water, a volume equal to the annual flow of more than 200 Colorado Rivers. In the years after World War II, a new generation of powerful centrifugal pumps allowed farmers to tap into this water on a large scale, first in northwest Texas and western Kansas, and then gradually farther north into Ne~ braska. Today, the Ogallala alone wa- ters one-fifth of US. irrigated land. The Ogallala Aquifer Area enlarged below. When Major Stephen long sthck out west, up the South Platte River in 1820, he named the "desolate j" waste” he encountered west of ’r the 100“1 meridian the Great ' American Desert. Attempts to cultivate this arid land led to disasters such as the Dust Bowl. Taking Stock Like any renewable resource, groundwater can be tapped indefi- nitely as long as the rate of extraction does not exceed the rate of replen- ishment. In many regions, however, aquifers get so little natural recharge that they are essentially nonrenew— able. These "fossil aquifers” are the But in the 19505, new pumps opened up the Ogallala aquifer, one of the world’s largest underground reservoirs. Changing the desert into a breadbasket, the aquifer now waters one- filth of US. irrigated land. But averpumping is draining the Ogallala much more quickly than it is recharged. Falling water tables and higher pumping costs have forced many farmers to abandon irrigation: while more than 5.2 million hectares were irrigated by the Ogallala in 1978, a decade later that number had dropped 20 percent, to 4.2 million. Without significant changes, the Ogallala oasis may turn out to be little more than a mirage. remnants of ancient climates that were much wetter than current local conditions. Pumping from fossil aqui~ fers depletes the supply, just as pump- ing from an oil reserve does. Even where aquifers do get replenished by rainfall, few governments have estab- lished rules and regulations to ensure that they are exploited at a sustain- able rate. In most places, any farmer who can afford to sink a well and pump water can do so unrestrained. Ownership of land typically implies the right to the water below. The up- shot is a classic "tragedy of the come mons,” in which individuals acting out of self-interest deplete a common resource. In India, for example, the situation has become so severe that in Septem- ber I996 the Supreme Court directed one of the country’s premier research centers to examine it. The National Environmental Engineering Research Institute, based in Nagpur, found that "overexploitation of ground water re- sources is widespread across the country." Water tables in critical ag— ricultural areas are sinking "at an _ _ _ . __,_._2--.____. .— alarming rate,” due to rapid proliferation of irrigation wells, which now number at least 6 million, and the fail- ure to regulate pumping adequately. Nine Indian states are now running major water deficits, which in the ag- gregate total just over 100 billion cubic meters (bcm) a year—and those deficits are growing (see table, "Water Deficits in Key Countries and Regions, Mid-1990’s"). The situation is particularly serious in the northern states of Punjab and Haryana, India’s principal breadbas- kets. Village surveys found that water tables are dropping 0.6 to 0.7 meters per year in parts of Haryana and half a meter per year across large areas of. Punjab. In the state of Gujarat, on the northwest coast, 87 out of 96 observa- tion wells showed declining groundwater levels during the 19805, and aquifers in the Mehsana district are now re- portedly depleted. Overpumping in Gujarat has also al- lowed salt water to invade the aquifers, contaminating drinking water supplies. In the state of Tamil Nadu, in the extreme south, water tables have dropped by as much as 30 meters since the 19705, and aquifers in the Coimbatore district are now dry. Farmers usually run into problems before the water dis- appears entirely. At some point, the pumping costs get out of hand or the well yields drop too low, and they are forced to choose among several options. They can take irrigated land out of production, eliminate a harvest or two, switch to less water-intensive crops, or adopt more- efficient irrigation practices. Apart from shifting out of thirsty nonstaple crops like sugarcane or cotton, improving efficiency is the only option that can sustain food produc- tion while lowering water use. Yet in India, investments in efficiency are minuscule relative to the challenge at hand. David Seckler, Director General of the lntemational Water Management Institute in Sri Lanka, estimates that a quarter of India’s grain harvest could be in jeopardy from groundwater depletion. Besides threatening food production, groundwater over- pumping is widening the income gap between rich and poor in some areas. As water tables drop, farmers must drill deeper wells and buy more powerful pumps. In parts of Punjab and Haryana, for example, wealthier farmers have installed more expensive, deeper tubewells costing about 125,000 rupees ($2,890). But the poor cannot afford such equipment. So as the shallower wells dry up, some of the small-scale farmers end up renting their land to the wealthier farmers and be- coming laborers on the larger farms. Other countries are facing similar problems. In Paki- stan’s province of Punjab—the country’s leading agricul- tural region, which is just across the border from the Indian state of the same name—groundwater is being pumped at a rate that exceeds recharge by an estimated 27 percent. In Bangladesh, groundwater use is about half the rate of natural replenishment on an annual basis. But during the dry season, when irrigation is most needed, heavy pumping causes many wells to go dry. On about a third of Bangladesh’s irrigated area, water tables routinely drop below the suction level of shallow tubewells during 21. When the World’s Wells Run Dry the dry months. Although monsoon rains recharge these aquifers and water tables rise again later in the year, farm- ers run out of water when they need it most. Again, the greatest hardships befall poor farmers, who cannot afford to deepen their wells or buy bigger pumps. In China, which is roughly tied with India for the most irrigated land, groundwater conditions are equally unset- tling. N0rthern China is running a chronic water deficit, with groundwater overpumping amounting to some 30 bcm a year. Of the three major river basins in the region, the Hai is always in deficit, the Yellow is almost always in deficit, and the Huai is occasionally. This northern and central plain produces roughly 40 percent of China’s grain. Across a wide area, the water table has been dropping 1 to 1.5 meters a year, even as water demands continue to increase. Modeling work by Dennis Engi of Sandia National Laboratories in New Mexico suggests that the water deficit in the Hai basin could grow by more than half between 1995 and 2025, even assuming that China completes at least part of a controversial plan to divert some Yangtze River water northward. Engi projects a 190 percent deficit increase for the Yellow River basin. Over the time frame of Engi’s study, the combined deficit in these two basins could more than double, from 27 bcm to 55 bcm. As in India, the unsustainable use of groundwater is creating a false sense of the nation's food production po- tential. The worsening groundwater deficits will eventually force Chinese farmers to either take land out of irrigation, switch to less thirsty crops, or irrigate more efficiently. How they respond will make a big difference to China’s grain outlook: that projected 2025 deficit for the Hai and Yellow River basins is roughly equal to the volume of water needed to grow 55 million tons of grain—14 percent of the nation’s current annual grain consumption and about a fourth of current global grain exports. In the United States, farmers are overpumping aquifers in several important crop-producing regions. California is overdrafting groundwater at a rate of 1.6 bcm a year, equal to 15 percent of the state’s annual groundwater use. Two- thirds of this depletion occurs in the Central Valley, which supplies about half of the nation’s fruits and vegetables. By far the most serious case of depletion, however, is in the region watered by the Ogallala aquifer. Particularly in its southern reaches, the Ogallala gets very little replen- ishment from rainfall, so almost any pumping diminishes it. Currently the aquifer is being depleted at a rate of some 12 bcm a year. Total depletion to date amounts to some 325 bcm, a volume equal to the annual flow of 18 Colo- rado Rivers. More than two-thirds of this depletion has occurred in the Texas High Plains. Driven by falling water tables, higher pumping costs, and historically low crop prices, many farmers who de- pend on the Ogallala have already abandoned irrigated agriculture. At its peak in 1978, the total area irrigated by the Ogallala in Colorado, Kansas, Nebraska, New Mexico, 165 5 '3‘ RESOURCES: Water Oklahoma, and Texas reached 5.2 million hectares. Less than a decade later, this area had fallen by nearly 20 percent, to 4.2 million hectares. A long-range study of the region, done in the mid-19805, suggested that more than 40 percent of the peak irrigated area would come out of irrigation by 2020; if this happens, another 1.2 million hectares will either revert to dryland farming or be aban- doned over the next two decades. Desert Fantasies In North Africa and the Arabian Peninsula, where it rarely rains, a number of countries depend on fossil aqui- fers. Saudi Arabia, for instance, sits atop several deep aqui- fers containing some 1,919 cubic kilometers of water—just oVer half as much as the Ogallala. The Saudis started pumping water on a grand scale after the OPEC oil em- bargo of the 19705. Fear of a retaliatory grain embargo prompted the government to launch a major initiative to make the nation self-sufficient in grain by encouraging large-scale wheat production in the desert. The govern- ment heavily subsidized land, equipment, and irrigation water. it also bought the wheat at several times the world market price. From a few thousand tons in the mid-19705, the annual grain harvest grew to a peak of 5 million tons in 1994. Saudi water demand at this time totaled nearly 20 bcm a year, and 85 percent of it was met by mining nonrenewable groundwater. Saudi Arabia not only achieved self-sufficiency in wheat; for a time, it was among the world’s wheat exporters. _ But this self-sufficiency would not last. Crop produc- tion soon crashed when King Fahd’s government was forced to rein in expenditures as the nation’s revenues declined. Within two years, Saudi grain output fell by 60 percent, to 1.9 million tons in 1996. Today Saudi Arabia is harvesting slightly more grain than in 1984, the year it first became self-sufficient, but because its population has grown from 12 million to more than 20 166 million since then, the nation has again joined the ranks of the grain importers. Moreover, the Saudis’ massive two-decade experiment with desert agriculture has left the nation much poorer in water. In its peak years of grain production, the nation ran a water deficit of 17 bcm a year, consuming more than 3,000 tons of water for each ton of grain produced in the hot, windy desert. (The standard ratio is 1,000 tons of water per ton‘ of grain.) At that rate, groundwater reserves would have run out by 2040, and possibly sooner. In re- cent years, the annual depletion rate has dropped closer to the level of the mid-19805, but the Saudis are still rack- ing up a water deficit on the order of 6 bcm a year. Africa's northern tier of countries—from Egypt to M0- rocco—also relies heavily on fossil aquifers, with esti- mated depletion running at 10 bcm a year. Nearly 40 percent of this depletion occurs in Libya, which is now pursuing a massive water scheme rivaled in size and com- ' plexity only by China’s diversion of the Yangtze River. Known as the Great Man-Made River Project, the $25 billion scheme pumps water from desert aquifers in the south and transfers it 1,500 kilometers north through some 4,000 kilometers of concrete pipe. The brainchild of Libyan leader Muammar Qaddafi, the artificial river was christened with great pomp andceremony in late August 1991. As of early 1998, it was delivering 146 million cubic meters a year to the cities of Tripoli and Beng- hazi. if all stages are completed, the scheme will eventually transfer up to 2.2 bcm a year, with 80 percent of it destined for agriculture. As in Saudi Arabia, however, the greening of the desert will be short-lived: some water engineers say the wells may dry up in 40 to 60 years. Some water experts have called the scheme “madness” and a "national fantasy.” Foreign engineers involved in the project have even questioned Qaddafi’s real motives. Some have pointed out that the pipelines are 4 meters in diameter, big enough to accommodate trucks or troops. Every 85 kilometers or so, engineers are building huge underground storage areas that apparently are more elabo- rate than needed for holding water. The master pipeline runs through a mountain where Qaddafi is reported to be building a biological and chemical weapons plant. But other engineers have scoffed at the possibility of any mili- tary motive, notingfor example, that the pipelines have no air vents. From the fields of North Africa to those of northern China, the story is essentially the same: many of the world’s most important grainlands are consuming ground- water at unsustainable rates. Collectively, annual water de- pletion in.lndia, China, the United States, North Africa, and the Arabian Peninsula adds up to some 160 bcm a year—equal to the annual flow of two Nile Rivers. (See, table, "Water deficits in Key Countries and Regions, Mid- 1990’5.) Factoring in Australia, Pakistan, and other areas for which this author did not have comparable data would likely raise this figure by an additional 10 to 25 percent. ..,._.-._,,.,,... . M .. "Nana- .._... 4.. l The vast majority of this overplumped groundwater is used to irrigate grain, the staple of the human diet. Since it takes about 1,000 tons of water to produce one ton of grain (and a cubic meter of water weighs one metric ton), some 180 million tons of grain—roughly 10 percent of the global harvest—is being produced by depleting water supplies. This simple math raises a very unsettling ques- tion: If so much of irrigated agriculture is operating under water deficits now, where are farmers going to find the additional water that will be needed to feed the more than 2 billion people projected to join humanity’s ranks by 2030? Texas Ingenuity The only way to sustain crop production in the face of dwindling water supplies is to use those supplies more efficiently—to get more crop per drop. Few farmers have a better combination of incentive to conserve and oppor- tunity to innovate than those in nortwest Texas. As the Ogallala shrinks, water efficiency is increasingly the ticket to staying in business. And the response of these Texan farmers is grounds for hope: better irrigation technologies and practices can substantially delay the day of reckon- ing—buying valuable time to make an orderly transition to a more sustainable water economy. During the 19805, the steady drop in underground water levels prompted local water officials and researchers to put together a package of technologies and management options that has boosted the region’s water productivity. Spearheaded by the High Plains Underground Water Conservation District in Lubbock, which overseas water management in 15 coun- ties of northwest Texas, the effort has involved a major up- grade of the region's irrigation systems. Many conventional gravity systems, in which water simply flows down parallel furrows, are less than 60 per- cent efficient: more than 40 percent of the water runs off the field or seeps through the soil without benefiting the crap. Farmers in the High Plains have been equipping their systems with surge valves that raise efficiency to about 80 percent. Just as the name implies, surge irrigation involves sending water down the furrows of a field in a series of pulses rather than in a continuous stream. The initial pulse somewhat seals the soil, letting subsequent surges flow more quickly and uniformly down the field. This evens out the distribution of water, allowing farmers to apply less at the head of their fields while still ensuring that enough water reaches crops at the tail-end. A time- controlled valve alternates the flow of water between rows, and its cycle and flow rates can be adjusted for different soils, furrow lengths, and other conditions. When combined with soil moisture monitoring and proper scheduling of irrigations, surge systems can cut water use by 10 to 40 percent compared with conventional furrow irrigation. Savings in the Texas High Plains have averaged about 25 percent. High Plains farmers have 21. When the World’s Wells Run Dry typically recouped their investment in surge equipment— which ranges from $30 to $120 per hectare depending on whether piping is already in place—within two years. Many farmers in the region are also using more efficient sprinklers. Conventional sprinklers are more efficient than furrow irrigation in most contexts, because they apply water more uniformly. But in dry, windy areas like the US. Great Plains, spraying water high into the air can cause large losses from evaporation and wind drift. The High Plains District is encouraging the use of two varieties of low-pressure sprinklers. One type delivers a light spray from nozzles about a meter above the soil surface, and typically registers efficiencies of 80 percent, about the same as surge irrigation (see table, "Efficiencies of Selected irrigation Methods, Texas High Plains"). A second variety, however, does substantially better. Low-energy precision application (LEPA) sprinklers deliver water in small doses through nozzles positioned just above the soil surface. They nearly eliminate evaporation and wind'drift, and can raise efficiency to 95 percent—often cutting water use by 15 to 40 percent over other methods. In the High Plains District, LEPA has also increased corn yields about 10 percent and cotton yields about 15 per- cent. The water savings plus the yield increases add up to substantial gains in water productivity. Farmers convert- ing to LEPA typically recoup their investment in two to seven years, depending on whether they are upgrading an existing sprinkler or purchasing a new one. Virtually all the sprinklers in the High Plains District are now either the low-pressure spray or LEPA. ’ More recently, the district has begun experimenting with drip irrigation of cotton. Using a network of perfo- rated plastic tubing installed on or below the surface, drip systems deliver water directly to the roots of plants. Drip irrigation has cut water use by 30 to 70 percent in coun- tries as diverse as lndia, Israel, Jordan, Spain, and the United States. And because plants grow better with opti- mal moisture, drip systems often boost yields by 20 to 50 percent. Since drip systems cost on the order of $2,500 per hectare, they have typically been used just for high value crops like fruits and vegetables. But as water itself grows more expensive and as new, lower-cost systems hit developing-country markets, the technology will become more useful. Because cotton is such a thirsty and widely planted crop, using drip systems to irrigate it could save large quantities of water in Texas and elsewhere. Working with local farmers, the district is giving drip a tough test by comparing its performance to that of LEPA—the most water-efficient sprinkler design now on the market. After the first year of trials, drip produced 19 percent more cot- ‘ ton per hectare than the LEPA-irrigated fields. The Texas High Plains program has also included sub- stantial extension work to help farmers adopt water-saving practices. (Extension programs are outreach efforts by gov- ernment agricultural agencies and some universities.) For example, extension agents spread the word about furrow diking—one of the most readily accessible water-saving 167 _ -;_ .. . r- .. s1; 5.31. zen-£4".- " ‘—.-§t]m ‘ ......-.|..-.—.,-..‘,.-_ ~.-- __7. . :u .. - .« ._- «"3 nos“. ._.._ .5“. rte—me 2:: . 5 .r— .f ‘-'=._- -'_r1 5 '3’ RESOURCES: Water ‘ measures. Furrow dikes are small earthen ridges built across furrows at regular intervals down the field. They form small basins that trap both rain and irrigation water, thereby reducing runoff and increasing soil absorption. Furrow dikes are key to obtaining the highest possible irrigation efficiency with LEPA, for example, and to storing as much pre-season rainfall in the soil as possible. Constructing furrow dikes costs about $10 per hectare. James Jonish,'an economist at Texas Tech University, points out that if furrow dikes capture an extra five centimeters of rainfall in the soil, they can boost cotton yields by up to 225 kilograms of lint per hectare, a potential economic gain of $400 per hectare, depending on cotton prices. In contrast, getting those higher yields bypumping an additional five centimeters of groundwater would cost $15 to $22 per hec- tare and would of course hasten the aquifer’s depletion. Overall, the High Plains District program has allowed grow- ers to boost the water productivity of cotton, which accounts for about half the cropland area, by 75 percent over the last two decades. Full irrigation of cotton used to require a well capable of producing at least 10 gallons a minute per acre (four-tenths of a hectare), but the district now considers 2 to 3 gallons 3 minute sufficient. Despite these successes, High Plains farmers face an uphill battle. Drought conditions in 1998 forced them to pump more groundwater than usual. Water tables dropped an average of 0.64 meters between early 1998 and early 1999, twice the average annual drop over the last decade. The first half of 1999 was wetter than usual but given the general trend, further improvement is essential. The district is now ramping up a program in which computer systems use real-time weather data and more precise information on crop water needs to adjust irrigation regimes. This ap- proach will, for example, allow a two-and-a-half-day cycle of LEPA irrigation, rather than the usual five- to seven-day cycle. Shorter cycles should make it possible to maintain 168 a nearly ideal moisture environment with even less water than the standard LEPA approach, since the very small volumes of water released can be carefully calibrated to match the crop’s immediate demand. Preliminary results with corn and cotton show promising yield increases. Water district assistant manager Ken Carver expects the program to go into widespread use soon after its introduc- tion this year. The potential of this approach is enormbus: it offers a way to irrigate corn, wheat and other grains nearly as efficiently as drip systems irrigate fruits, vegeta- bles, and cotton. In areas where groundwater is diminish- ing, these methods hold out hope that production declines can at least be delayed—and in some areas, perhaps, avoided altogether. Setting New Rules No government has made a concerted effort to solve the problem of groundwater overpumping. Indeed, most contrib- ute to the problem by subsidizing groundwater use. Many farmers in India, for example, pay only a flat fee for elec- tricity, which makes the marginal cost of pumping ground- water close to zero. Why invest in more-efficient irrigation technologies if it costs nearly the same to pump 10,000 cubic meters of groundwater as it does to pump 5,000? Likewise, Texas irrigators get a break on their federal income taxes for depleting the Ogallala aquifer: they re- ceive a "depletion allowance” much as oil companies do for depleting oil reserves. Each year, they measure how much their water table has dropped, calculate the value of that depleted water, and then claim an adjustment on their income tax. This subsidy may partially explain why some farmers use the water saved through efficiency im- provements to grow thirstier crops rather than leaving it in the ground. From a social standpoint, it is far more sensible to tax groundwater depletion in order to make current users pay more of the real costs of their activities. Such a tax would allow products made with the depleted water—whether beef steaks or cotton shirts—to better re- flect their true ecological costs. Governments have also failed to tackle the task of regu- lating access to groundwater. To prevent a tragedy of the commons, it’s necessary to limit the number of users of the common resource, to reduce the quantity of the re- source that each user can take, or to pursue some com- bination of these two options. This regulating function can be performed by a self-governing communal group—in which rights and responsibilities are determined by the farmers themselves—or by a public agency with authority to impose rules for the social good on private individuals. In reality, however, groundwater conditions are rarely even monitored, much less regulated. Only recently has the groundwater issue begun to ap- pear on national agendas—and still only in a few coun- tries. Officials in India circulated a "model groundwater bill” in 1992, but none of the Indian states has passed legislation along those lines. Some have made efforts to regulate groundwater use through licensing, credit, or electricity restrictions, or by setting minimum well-spacing requirements. But no serious efforts have been made to control the volume of water extracted. V. Narain, a re- searcher at the New Delhi-based Tata Energy Research Institute, puts it simply: "groundwater is viewed essentially as a chattel attached to land," and there is "no limit on how much water a landowner may draw.” Indian researchers and policymakers broadly agree that rights to land and water need to be separated. Some have argued for turning de facto private groundwater rights into legal common property rights conferred upon communi- ties in a watershed. But instituting such a reform can be a political high-wire act. Wealthy farmers, who have the ear of politicians, do not want to lose their ability to pump groundwater on their property in any quantity they desire. The United States has no official national groundwater policy either. As in India, it is up to the states to manage their own aquifers. So far, only Arizona has passed a com- prehensive groundwater law that explicitly calls for bal- ancing withdrawal with recharge. Arizona's strategy for meeting this goal by 2025 would take some of the strain off its overpumped groundwater by substituting Colorado River water imported through an expensive, federally-sub- sidized canal project. But few regions can rely on such an option, which in any case merely replaces one type of excessive water use with another. An important first step in developing a realistic ground water policy is for governments to commission credible and unbiased assessments of the long-term rate of recharge for every groundwater basin or aquifer. This would estab- lish the limit of sustainable use. The second step is for all concerned parties—including scientists, farmer and com- munity groups, and government agencies—to devise a plan for balancing pumping with recharge. If current pump- 21. When the World's Wells Run Dry ing exceeds the sustainable limit, achieving this goal will involve some mix of pumping reductions and artificial re- charge—the process of channeling rainfall or surplus river water into the underground aquifer, where this is possible. Arriving at an equitable way of allocating groundwater rights such that total pumping remains within sustainable levels will not be easy. Legislatures or courts might need to invoke a legal principle that elevates the public interest over private rights. One possibility, for example, is the public trust doctrine, which asserts that governments hold certain rights in trust for the public and can take action to protect those rights from private interests. Some scholars have recommended use of the public trust doctrine to deal with India’s groundwater problem. Recent rulings in the United States show that this legal instrument is potentially very powerful. The California Su- preme Court ordered Los Angeles to cut back its rightful diversions of water from tributaries that feed Mono Lake, declaring that the state holds the lake in trust for the peo- ple and is obligated to protect it. The applicability of the public trust or similar doctrines may vary somewhat from one legal system to the next, but where a broad interpre- tation is feasible, there could be sweeping effects since even existing rights can be revoked in order to prevent violation of the public trust. Once a legal basis for limiting groundwater use is es- tablished, the next step is to devise a practical plan for actually making groundwater use sustainable. Mexico is one of the few countries that seem to be tackling this task head on. After enacting a new water law in 1992, Mexico created River Basic Councils, which are intended to be water authorities open to a high degree of public partici- pation. For example, the council for the Lerma—Chapala River basin, an area that contains 12 percent of Mexico’s irrigated land, is in the process of setting specific regula- tions for each aquifer in the region. Technical committees are responsible for devising plans to reduce overpumping. Because these committees are composed of a broad mix of players, including the groundwater users themselves, they lend legitimacy to both the process and the outcome. Although the details of a workable plan will vary from place to place, it is now possible to draw a rough blueprint for sustainable groundwater use. But nearly everywhere, the first big hurdle is overcoming the out-of-sight, out-of- mind syndrome. When looking at, say, a field of golden wheat, it can be difficult to imagine why harvests like that can’t just go on forever. But the future of that crop—and of humanity itself—will depend on how well we manage the water below. Sandra Postel is director of the Global Water Policy Project in Amherst, Massachusetts, and a senior fellow at the Worldwatch Institute. She is the author of Pillar of Sand: Can the Irrigation Miracle Last? (W. W. Norton & Com- pany, 1999), from which this article is adapted. 169 ...
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Wells Run Dry - Article 21 When the World’s Wells Run Dry...

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