Environmental Problems, Their Causes, and Sustainability 1

has devastated the area’s fishing industry, which onceprovided work for more than 60,000 people. Fishingvillages and boats once on the sea’s coastline now areabandoned in the middle of a salt desert.Winds pick up the salty dust that encrusts thelake’s now-exposed bed and blow it onto fields as faras 300 kilometers (190 miles) away. As the salt spreads,it pollutes water and kills wildlife, crops, and othervegetation. Aral Sea dust settling on glaciers in theHimalayas is causing them to melt at a faster than normalrate—another example of connections and unintendedconsequences.To raise yields, farmers have increased use of herbicides,insecticides, fertilizers, and irrigation water onsome crops. Many of the chemicals have percolateddownward and accumulated to dangerous levels ingroundwater, from which most of the region’s drinkingwater comes.Shrinkage of the Aral Sea has altered the area’s climate.The once-huge sea acted as a thermal buffer thatmoderated the heat of summer and the extreme cold ofwinter. Now there is less rain, summers are hotter anddrier, winters are colder, and the growing season isshorter. The combination of such climate change andsevere salinization has reduced crop yields by 20–50%on almost a third of the area’s cropland.Finally, there have been increasing health problemsfrom a combination of toxic dust, salt, and contaminatedwater for a growing number of the 58 millionpeople living in the Aral Sea’s watershed.Can the Aral Sea be saved, and can the area’s seriousecological and human health problems be reduced?There is agreement that the sea will neverreturn to its former volume. Efforts have focused primarilyon stopping further shrinkage and undoingsome of the ecological and health damage caused byits shrinkage.Encouraging news. Since 1999, the United Nationsand the World Bank have spent about $600 million topurify drinking water and upgrade irrigation anddrainage systems, which improves irrigation efficiencyand flushes salts from croplands. In addition,some artificial wetlands and lakes have been constructedto help restore aquatic vegetation, wildlife,and fisheries.The five countries surrounding the lake and itstwo feeder rivers have worked to improve irrigationefficiency and to partially replace water-thirsty cropssuch as rice and cotton, with other crops that requireless water. As a result, the total annual volume of waterin the Aral Sea basin has stabilized.In 2004 the United Nations Environment Programmewarned that Lake Balkhash in Kazakhstancould meet a fate like that of the Aral Sea if pollutionand water withdrawals from the river Ili flowing intoit from northwestern China continue increasing.Case Study: The California Water TransferProject—Bringing Water to a DesertThere is controversy over the massive transfer ofwater from water-rich northern California to waterpoorsouthern California.One of the world’s largest water transfer projects is theCalifornia Water Project (Figure 15-13). It uses a maze ofgiant dams, pumps, and aqueducts (cement-lined artificialrivers) to transport water from water-rich northernCalifornia to southern California’s heavily populatedarid and semiarid agricultural regions and cities.For decades, northern and southern Californianshave feuded over how the state’s water should be allocatedunder this project. Southern Californians saythey need more water from the north to grow morecrops and to support Los Angeles, San Diego, and othergrowing urban areas. Agriculture uses three-fourths ofthe water withdrawn in California, much of it used inefficientlyfor growing water-thirsty crops such as alfalfaunder desertlike conditions.Opponents in the north say that sending more watersouth would degrade the Sacramento River,threaten fisheries, and reduce the flushing action thathelps clean San Francisco Bay of pollutants. They alsoargue that much of the water sent south is wasted.They point to studies showing that making irrigationjust 10% more efficient would provide enough waterfor domestic and industrial uses in southern California.Mono Lake, a salt lake in southern California’sdesert just east of Yosemite National Park, is an ecologicalcausality of water transfers from one water basinto another. Diversion of water from rivers feeding thelake has shrunk the lakes volume by one-third. ThisSacramentoRiverNorth BayAqueductSan FranciscoSouth BayAqueductSan Luis Damand ReservoirCalifornia AqueductCALIFORNIAShasta Lake NEVADAOroville Dam andReservoirFeatherRiverSacramentoSan Joaquin ValleyFresnoSanta BarbaraLos AngelesSan DiegoLake TahoeHoover Damand Reservoir(Lake Mead)Los AngelesAqueductColorado RiverAqueductSalton SeaUTAHColoradoRiverARIZONACentral ArizonaProjectPhoenixTucsonMEXICOFigure 15-13 Solutions: California Water Project and theCentral Arizona Project. These projects involve large-scalewater transfers from one watershed to another. Arrows show thegeneral direction of water flow.http://biology.brookscole.com/miller14317