• Choose a category
• All
• Classic-Fiction

By Root 723 0

and should simply be removed. The United States is at the center of a new movement toward freshwater ecological restoration: In one of the most unsung environmental successes anywhere in the world, over 800 dams have been demolished in recent years and thousands more could follow.23 Rivers can bounce back to health remarkably quickly once concrete impediments are removed: After the destruction of the Edwards Dam on Maine’s Kennebec River, two million alewife fish returned within a year to spawn, and American shad, striped bass, Atlantic salmon, and sturgeon all followed. In September 2011 the tallest dam yet—the 210-foot-high (64-m) Glines Canyon Dam—is slated for removal, aimed at restoring over 70 miles (113 km) of salmon and steelhead habitat. The following month, and with the support of the Yakama Indian Nation, the Condit Dam on the White Salmon River will also be breached.24 Given the massive decline in salmon populations seen recently in the American northwest, the restoration of natural flows to rivers in the region is an urgent priority for fishermen, Native Americans, and conservationists alike.

Where outright removal of dams is not a pragmatic option, there are various technical interventions that can be made to mitigate their ecological impacts. Reservoir intakes can be sited at different levels to allow operators to release the right temperature water from different depths in the lake in different seasons. Water managers can also pay more heed to maintaining “ecological flows,” mimicking a river’s natural flow regime while simultaneously allowing for competing hydroelectric production and irrigation demands—as the U.S. Army Corps of Engineers is now beginning to do in the Missouri. For the Colorado River through the Grand Canyon, experimental human-engineered floods have reestablished habitat and rebuilt sandbanks. Also in the U.S., the Army Corps of Engineers and the Nature Conservancy have embarked on a nationwide partnership to find ways for dam operators to mimic seasonal cycles to restore riverine ecosystems. This Sustainable Rivers Project is currently working on 11 rivers with 26 dams flowing through 13 states.25 Even so, that is still only a tiny proportion of the rivers being affected by dams, and only in one country. Worldwide, we need a revolution in the way that water managers control rivers in order to arrest the decline in freshwater ecosystems by maintaining ecological flows to the furthest extent possible.

In some parts of the world the removal of water from rivers for agriculture has caused such havoc that radical and costly measures will be needed to reverse the damage. Probably the worst water-related catastrophe anywhere in the world afflicts Central Asia, where the Aral Sea—once the world’s fourth largest inland lake—all but disappeared after Soviet managers in the 1960s and 1970s diverted its two main feeder rivers for cotton production. What was once a thriving wetland ecosystem, supporting large-scale commercial fishing as well as numerous waterbirds and other species on river deltas, has been turned into an ecological disaster area. Whole former port towns have been left stranded tens of kilometers from the water line, and two of the remaining three remnant portions of the former Aral Sea are so salty that they support no fish at all. The whole area is raked by toxic dust storms, countless thousands have lost their livelihoods, and the region’s wildlife has been decimated.26

Almost as appalling as the scale of the original damage has been the weakness of the response. Only the small northern part of the basin has been partially protected to restore a semblance of its original water levels, and only at the cost of removing even more water from the south with a dyke. Instead of emptying into the Aral Sea, the southern feeder river, the Amu Darya, now disappears into the desert—all its water is still captured to grow Uzbekistan’s precious cotton, and the situation with the northern Syr Darya river is little better. Even though the Soviet Union has now disappeared, its successor states