Environmental Problems, Their Causes, and Sustainability 1

have been cheaper, less disruptive, and safer to build aseries of smaller dams.15-5 TRANSFERRING WATERFROM ONE PLACE TO ANOTHERCase Study: The Aral Sea Disaster—A Glaring Example of UnintendedConsequencesDiverting water from the Aral Sea and its twofeeder rivers mostly for irrigation has createda major ecological, economic, and healthdisaster.Tunnels, aqueducts, and underground pipes can transferstream runoff collected by dams and reservoirsfrom water-rich areas to water-poor areas. However,they also create environmental problems. Indeed, mostof the world’s dam projects and large-scale watertransfers illustrate the important ecological principlethat you cannot do just one thing. There are almost alwaysa number of unintended environmental consequences(Figure 3-4, p. 38).An example is the shrinking of the Aral Sea (Figure15-12). It is a result of a large-scale water transferproject in an area of the former Soviet Union with thedriest climate in central Asia. Since 1960, enormousamounts of irrigation water have been diverted fromthe inland Aral Sea and its two feeder rivers to createone of the world’s largest irrigated areas, mostly forraising cotton and rice. The irrigation canal, theworld’s longest, stretches over 1,300 kilometers (800miles)—equivalent to one-third the width of the continentalUnited States.This large-scale water diversion project, coupledwith droughts and high evaporation rates in this area’shot and dry climate, has caused a regional ecological,economic, and health disaster. Since 1960 the sea’ssalinity has tripled, its surface area has decreased by58%, and it has lost 83% of its water. In effect it has beentransformed from a single large lake (Figure 15-12, left)into three smaller lakes (Figure 15-12, right). Waterwithdrawal for agriculture has reduced the sea’s twosupply rivers to mere trickles.About 85% of the area’s wetlands have been eliminatedand roughly half the area’s bird and mammalspecies have disappeared. In addition, a huge area offormer lake bottom has been converted to a humanmadedesert covered with glistening white salt. Theincreased salt concentration caused the presumed extinctionof 20 of the area’s 24 native fish species. ThisWorldSat International, Inc. All rights reserved.WorldSat International, Inc. All rights reserved.Figure 15-12 Natural capital degradation: the Aral Sea was once the world’s fourth largest freshwater lake.Since 1960 it has been shrinking and getting saltier because most of the water from the rivers that replenish ithas been diverted to grow cotton and food crops. These satellite photos show the sea in 1976 and in 1997. Asthe lake shrinks, it leaves behind a salty desert, economic ruin, increasing health problems, and severe ecologicaldisruption.316 CHAPTER 15 Water Resources