Water Diversion Projects

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Water diversion projects

Water diversion projects include the construction of dams , levees, pumping stations, irrigation canals, or any other manmade structure that modifies the natural flow of a waterway. Diversion projects may be developed for purposes of hydroelectric power generation, farm irrigation, consumer and industrial water supply, and flood control. Throughout human history, communities have altered river systems for their own advantage. There is evidence that large-scale projects dating over 2000 years ago existed in China, the Mediterranean, and the Middle East.

Water diversion globally

In the early twenty-first century, water is one of the commodities deemed most important to the well-being of nations. As of 2002, the world population of 5.6 billion is growing at an annual rate of approximately 90 million, and the global demand for water is expected to rise by 23% annually in the decades to come.

Globally, of the more than 45,000 large dams ([49.2 ft; 15 m] or more in height, according to the International Commission of Large Dams), China has the greatest number with approximately 24,671 large dams, followed by the United States and India with 6,575 and 4,291 respectively. Approximately two-thirds of world's existing large dams are located in developing countries.

Although clean freshwater is a valuable commodity and is short supply in many regions of the world, issues surrounding its diversion and use are often the subject of heated debate. One large-scale dam project that has been hotly debated is the Mekong River project in Southeast Asia. Nations of the region want to control and develop the river basin; environmentalists want to protect it; and caught in the middle is the river itself and the millions who depend on it for their livelihood.

The fields and numerous tributaries that feed into the Mekong River are home to more than 50 million people. Although most of the Mekong basin remains undeveloped, more than 200 dams have been proposed for the Mekong and its many tributaries. In addition to irrigating rice fields in arid regions, the diverted water for the first time offers the opportunity for local inhabitants to produce a variety of crops, thereby fueling economic growth and development.

Yet tens of thousands of families will be forcibly relocated; fisheries will collapse as upstream access to millions of fish is blocked; farmland will be flooded; and development will further restrict the river, leading to potential worsening of floods. Like other major water diversion projects around the world, the Mekong project illustrates some of the profound social, economic, and environmental effects of damming and redirecting the world's rivers.

Water diversion in the United States

Most large-scale water diversion projects in the United States are located along river systems in the western half of the country, where the dry, arid terrain is dependent on water diversion from high capacity riverslike the Colorado, Columbia, Missouri, and Snakefor municipal and irrigation water supplies. The Hoover Dam, Grand Coulee Dam, Columbia River Basin Project, and scores of other dams and diversion projects are built and maintained by the U.S. Bureau of Reclamation (USBR), which was established by the Department of the Interior under the National Reclamation Act of 1902.

Water diversion practices and management in the Western states developed by necessity. Low precipitation levels in the western states meant that pioneer farmers had to find alternate methods of irrigating their crops. The USBR was so named because it was charged with the task of "reclaiming" the dry desert landscape for farming and homesteading through irrigation.

The Bureau's first major diversion project, the Hoover Dam and adjacent reservoir Lake Mead, was authorized in 1928 and completed in 1936. In addition to providing water for agriculture, community, and industrial use, the dam also generates 4 billion kilowatt-hours of hydroelectric power annually for California, Arizona, and Nevada.

As of May 2002, USBR managed 348 reservoirs that hold a capacity of 245 million acre-ft (302.2 billion m3) of water. The Bureau is the largest wholesale water supplier in the United States, supplying irrigation water for 10 million acres of farmland and 31 million people across the West. In addition, USBR generates over 42 billion kilowatt hours of hydroelectric power annually from its 58 power plants . Along with the U.S. Army Corps of Engineers , the Bureau is responsible for the majority of national water projects.

Environmental impact

Although they occupy a smaller area compared to land and oceans, freshwaters are home to a relatively high proportion of species (animals, plants, and microorganisms ), with more per unit area than any other environment (10% more than land, and 15% more than oceans). However, some areas, such as the Amazon, Congo, Nile, and Mekong basins are densely populated with species and are called "hotspots."

In the United States, legislation of water diversion and reclamation programs initially focused on agricultural development, job creation, and power generation. Eventually, the long-term environmental impact of some of these big river projects became apparent as western wetlands disappeared and scores of migratory salmon and other wildlife were designated endangered and threatened under the Endangered Species Act (ESA).

Diversion projects prevent migrating fish from returning to their native upstream spawning grounds. The California Department of Fish and Game estimates that two-thirds of the winter-run chinook salmon that spawn in the Sacramento River do not make it to the Pacific. Water diversion channels can be difficult to navigate, and water diversion pumps that feed the California Water Project kill and maim a large percentage of the migrating population each year. In addition, diversions for irrigation and residential water diversion lowers the water level of the river, slowing the progress of the salmon and increasing river water temperature to inhospitable levels. Despite the integration of fish lifts and fish ladders into modern dams, populations of native fish stocks are still greatly depleted by dam structures.

In addition to the problem of depleted fish stocks, migrating fish such as salmon and trout transport nutrients from oceans to rivers. When this fish population declines, so also does a significant amount of nitrogen and phosphorus , which is typically released into rivers by decomposing carcasses. This nutrient loss affects the ecosystem as well as the fish supply. A renewed interest has been placed on modifying diversion projects to recover river ecosystems and biodiversity .

The impact of water diversion products on habitats in and around rivers, wetlands, and streams can be profound. The U.S. Army Corps of Engineers estimates that there are over 77,000 dams of significant size over 6 ft (1.8 m) in the United States. Levees, dams, shoreline armoring , and other diversion structures change the very geography, geology, and hydrology of the river, influencing flow levels, altering channels, and preventing natural erosion . These structures also block the natural flow of silt and sediments. The natural floodplain is frequently impacted, resulting in a two-fold effect: destroying wetland ecosystems and eliminating a recharging source for the groundwater table. Eventually, structures put in place to prevent flood damage may exacerbate the problem. Dams, levees, and other diversional devices prevent water from heavy rainfalls from naturally dispersing onto floodplains and wetlands.

Water diversion projects also impact the atmosphere . Studies of large reservoirs created behind hydroelectric dams have suggested that decaying vegetation, submerged by flooding , may give off quantities of greenhouse gasessuch as methane gasequivalent to those from other sources of electricity. Thus, hydroelectric facilities that flood large areas of land may be significant contributors to global warming. The water quality of many reservoirs also poses a health hazard due to new forms of bacteria that grow in many of the rivers that have been diverted by dams.

In addition to giving off greenhouse gases , bacteria present in decaying vegetation can also change mercury , present in rocks underlying a reservoir, into a water-soluble form. The mercury accumulates in the bodies of fish and poses a health hazard to both wildlife and humans who depend on these fish as a food source. Methylmercury, the most toxic form of the element, affects the immune system, alters genetic and enzyme systems, and damages the nervous system. Human exposure to methylmercury is almost entirely by eating contaminated fish and wildlife.

A rather surprising global impact of water diversion projects is that the weight of the world's collective reservoirs is speeding up the earth's rate of rotation and is altering the shape of earth's magnetic field, according to NASA geophysicist Dr. Benjamin Fong Chao.

Human impact

Estimates suggest that approximately 4080 million people have been physically displaced by dams worldwide. Millions of people living downstream from dams, particularly those who rely on natural floodplain function and fisheries, have suffered serious damage to their livelihoods, and the future productivity of their resources has been put at risk. Many of the displaced are not recognized as such, and therefore are not resettled or compensated. When compensation is provided, it is often inadequate. When the physically displaced are acknowledged, many are not included in resettlement programs. Moreover, those who are resettled seldom have their livelihoods restored; resettlement programs usually focus on physical relocation rather than the economic and social needs of the displaced.

Indigenous and tribal peoples and vulnerable ethnic minorities have suffered disproportionate levels of displacement and negative impacts on not only their livelihood, but also their cultural and spiritual existence. Large dams have had significant adverse effects on cultural heritage through the loss, submergence, and degradation of plant and animal remains, burial sites, and archaeological monuments. The social, economic, and political status of minority groups often restricts their capacity to assert their interests and rights in land and natural resources , and restricts their role in decision-making that affects them.

In addition, affected indigenous populations living near reservoirs, as well as displaced people and downstream communities, have often faced adverse health conditions from environmental change and social disruption. Gender gaps have widened in these communities, and women have often borne a disproportionate share of the social costs while reaping few of the benefits.

Policies and initiatives

Opposition to diversion projects and their impact on the environment began to pick up momentum in the 1970s. The National Environmental Policy Act of 1970 (NEPA) required thorough study of the environmental impacts of proposed water projects, and inspired greater public scrutiny of the effects of major water projects on the environment. In 1978, President Jimmy Carter announced a new policy of cutting federal funding to new water projects, and developed a "hit list" of dams and irrigation projects.

The financial approach to water management evolved as well. In 1982, the Reclamation Reform Act was signed into law, changing the acreage requirements for irrigation water subsidies in an effort to get large corporate farms to pay a fair market price for their water use. The Water Resources Development Act (WRDA)legislation that is reauthorized by Congress every two years to finance U.S. Army Corps of Engineers' water projectscontained amendments in 1986 that required local interests to share the construction costs of water resource projects built by the Corps.

Environmentalists charge that the USBR and the Army Corps have a history of developing water projects for financial gain regardless of the cost to the environment. At the heart of the debate is the fundamental difference in the way natural water sources are viewedas a fiscal commodity or as a natural resource. As Marc Reisner, author of the critically acclaimed Cadillac Desert, states: "In the East, to 'waste' water is to consume it needlessly or excessively. In the West, to waste water is not to consume itto let it flow unimpeded and undiverted down rivers. ... To easterners, 'conservation' of water usually means protecting rivers from development; in the West, it means building dams." Striking a balance between these two viewpoints to maintain both our riparian ecosystem and our Western communities and businesses, is the challenge facing American government, environmentalists, and other stakeholders.

Because irrigation for farming is a major consumer use of diverted water, improving growing techniques and choosing water-friendly crops may be one solution to minimizing water need. The agricultural industry can also take steps to meet irrigation needs in a environmentally responsible manner by ensuring that adequate fish screens are in place at diversion points and agreeing to lower water delivery rates at crucial spawning times to maintain river flow for migratory fish. Finally, conservation and restoration of agricultural wetlands through government plans such as the Wetlands Reserve Program can help solve long-term flooding problems on farms and restore the habitats of native species.

The WRDA of 1999 enacted an Army Corps of Engineers initiative known as "Challenge 21" focused on replacing dams and other diversionary techniques for flood control with non-structural solutions and environmental restoration programs. Specifically, the initiative calls for less environmentally-invasive programs of preventing flood damage, including federally-funded voluntary buyouts of property on flood plains and restoration of altered flood plain ecosystems.

International agreements and organizations have also established standards for minimizing the negative impact of human activities on biodiversity. Legal coalitions include the World Charter for Nature, the Convention on Biological Diversity, and Agenda 21; international organizations such as the World Bank , the World Business Council on Sustainable Development , and The World Conservation Union (IUCN), have contributed to the development of accepted standards. These standards involve conservation of species and ecosystems, the recovery of degraded ecosystems, the conservation of ecological functions or processes, securing of adequate information for decision-making, and the adherence to high standards for environmental impact assessments.

[Paula Anne Ford-Martin ]



Committee on Missouri River Ecosystem Science; Water, Science, and Technology Board; Division of Earth and Life Studies; National Research Council. The Missouri River Ecosystem: Exploring the Prospects for Recovery. Washington DC: National Academy Press; In press, 2002. Prepublication copy available online at <http://books.nap.edu/books/0309083141/html/R1.html>

MacDonnell, Lawrence. From Reclamation to Sustainability: Water, Agriculture, and the Environment in the American West. Boulder: University Press of Colorado, 1999.

McNully, Patrick. Silenced Rivers: The Ecology and Politics of Large Dams. 2nd edition. London: Zed Books, 2001.

Reisner, Marc. Cadillac Desert: The American West and Its Disappearing Water. 2nd edition. New York: Penguin, 1987.


Bricker, Jennie, and David Filippi. "Endangered Species Act Enforcement and Western Water Law." Environmental Law 30, no.4 (Fall 2000): 735.

Robbins, Elaine. "Damning Dams." emagazine.com (The Environmental Magazine) X, no. 1 (January-February 1999): 16 [cited June 26, 2002]. <http://www.emagazine.com>.


LakeNet. Strategies and Solutions for Managing Water Diversion. May 15, 2002 [cited June 4, 2002]. <http://www.worldlakes.org/Strategies%20and%20Solutions.htm>.

Stein, Jeff, et al. National Wildlife Federation & Taxpayers for Common Sense. Troubled Waters: Congress, the Corps of Engineers, and Wasteful Water Projects Washington, DC: NWF/Taxpayers for Common Sense, 2000. <http://www.nwf.org/greeningcorps/report.html>.


American Rivers, 1025 Vermont Ave., N.W. Suite 720, Washington, DC USA 20005 (202) 347-7550, Fax: (202) 347-9240, Email: [email protected], <http://www.amrivers.org>

International Rivers Network, 1847 Berkeley Way, Berkeley, CA USA 94703 (510) 848-1155, Fax: (510) 848-1008, Email: [email protected], <http://www.irn.org>

U.S. Bureau of Reclamation, Freedom of Information Act (FOIA) Office, PO Box 25007, D-7924, Denver, CO USA 80225-0007 (303) 445-2048, Fax: (303) 445-6575, Toll Free: (800) 822-7646, Email: [email protected], <http://www.usbr.gov>