"It's the best summation of humanity's converging ecological problems and the best roadmap to sovling them, all in one compact package." —David Roberts, Grist on Plan B 4.0: Mobilizing to Save Civilization.
Chapter 3. Emerging Water Shortages: Rivers Running Dry
While falling water tables are largely hidden, rivers that are drained dry before they reach the sea are highly visible. Two rivers where this phenomenon can be seen are the Colorado, the major river in the southwestern United States, and the Yellow, the largest river in northern China. Other large rivers that either run dry or are reduced to a mere trickle during the dry season are the Nile, the lifeline of Egypt; the Indus, which supplies most of Pakistan’s irrigation water; and the Ganges in India’s densely populated Gangetic basin. Many smaller rivers have disappeared entirely. 33
As the world’s demand for water has tripled over the last half-century and as the demand for hydroelectric power has grown even faster, dams and diversions of river water have drained many rivers dry. As water tables have fallen, the springs that feed rivers have gone dry, reducing river flows. 34
Since 1950, the number of large dams, those over 15 meters high, has increased from 5,000 to 45,000. Each dam deprives a river of some of its flow. Engineers like to say that dams built to generate electricity do not take water from the river, only its energy, but this is not entirely true since reservoirs increase evaporation. The annual loss of water from a reservoir in arid or semiarid regions, where evaporation rates are high, is typically equal to 10 percent of its storage capacity. 35
The Colorado River now rarely makes it to the sea. With the states of Colorado, Utah, Arizona, Nevada, and, most important, California depending heavily on the Colorado’s water, the river is simply drained dry before it reaches the Gulf of California. This excessive demand for water is destroying the river’s ecosystem, including its fisheries. 36
A similar situation exists in Central Asia. The Amu Darya—which, along with the Syr Darya, feeds the Aral Sea—is now drained dry by Uzbek and Turkmen cotton farmers upstream. With the flow of the Amu Darya cut off, only the diminished flow of the Syr Darya keeps the Aral Sea from disappearing entirely. 37
China’s Yellow River, which flows some 4,000 kilometers through five provinces before it reaches the Yellow Sea, has been under mounting pressure for several decades. It first ran dry in 1972, and since 1985 it has often failed to reach the sea. 38
The Nile, site of another ancient civilization, now barely makes it to the sea. Water analyst Sandra Postel, in Pillar of Sand, notes that before the Aswan Dam was built, some 32 billion cubic meters of water reached the Mediterranean each year. After the dam was completed, however, increasing irrigation, evaporation, and other demands reduced its discharge to less than 2 billion cubic meters. 39
Pakistan, like Egypt, is essentially a river-based civilization, heavily dependent on the Indus. This river, originating in the Himalayas and flowing westward to the Indian Ocean, not only provides surface water, it also recharges aquifers that supply the irrigation wells dotting the Pakistani countryside. In the face of growing water demand, it too is starting to run dry in its lower reaches. Pakistan, with a population projected to reach 305 million by 2050, is in trouble. 40
In Southeast Asia, the flow of the Mekong is being reduced by the dams being built on its upper reaches by the Chinese. The downstream countries, including Cambodia, Laos, Thailand, and Viet Nam—countries with 168 million people—complain about the reduced flow of the Mekong, but this has done little to curb China’s efforts to exploit the power and the water in the river. 41
The same problem exists with the Tigris and Euphrates Rivers, which originate in Turkey and flow through Syria and Iraq en route to the Persian Gulf. This river system, the site of Sumer and other early civilizations, is being overused. Large dams erected in Turkey and Iraq have reduced water flow to the once “fertile crescent,” helping to destroy more than 90 percent of the formerly vast wetlands that enriched the delta region. 42
In the river systems just mentioned, virtually all the water in the basin is being used. Inevitably, if people upstream get more water, those downstream will get less.
33. Colorado, Ganges, Indus, and Nile rivers from Sandra Postel, Pillar of Sand (New York: W.W. Norton & Company, 1999), pp. 59, 71–73, 94, 261–62; Yellow River from Lester R. Brown and Brian Halweil, “China’s Water Shortages Could Shake World Food Security,” World Watch, July/August 1998, p. 11.
34. Gleick, op. cit. note 3, p. 52.
35. Sandra Postel, Last Oasis (New York: W.W. Norton & Company, 1997), pp. 38–39; World Commission on Dams, Dams and Development: A New Framework for Decision-Making (London: Island Press, 2000), p. 8.
36. Postel, op. cit. note 33, pp. 261–62; Jim Carrier, “The Colorado: A River Drained Dry,” National Geographic, June 1991, pp. 4–32.
37. U.N. Environment Programme (UNEP), Afghanistan: Post-Conflict Environmental Assessment (Geneva: 2003), p. 60.
38. Brown and Halweil, op. cit. note 33.
39. Postel, op. cit. note 33, pp. 71, 146.
40. Ibid., pp. 56–58; population from United Nations, op. cit. note 1.
41. Moench, op. cit. note 29; population from United Nations, op. cit. note 1.
42. UNEP, “‘Garden of Eden’ in Southern Iraq Likely to Disappear Completely in Five Years Unless Urgent Action Taken,” news release (Nairobi: 22 March 2003); Hassan Partow, The Mesopotamian Marshlands: Demise of an Ecosystem, Early Warning and Assessment Technical Report (Nairobi: Division of Early Warning and Assessment, UNEP, 2001).
Copyright © 2006 Earth Policy Institute