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Southwest America: the Colorado River runs dry

Sky view of the Colorado river – NASA/T.Pesquet

From the Rocky Mountains to its delta in Mexico, the Colorado River flows for more than 2,300 km and crosses seven states. It provides drinking water to more than 40 million people and irrigates more than 10,000 km2 of farms dedicated to intensive agriculture (alfalfa, cotton, cattle), including some located in the middle of the desert.

The hydropower plants installed in the river provide an average of 12 billion kWh of electricity a year. And tomorrow?

After 19 consecutive years of drought and increased human pressure, the river is in danger and running dry.

Artificial lakes under pressure

The artificial lakes that have been created to serve as reservoirs for the largest cities of the West are progressively emptying. Lake Mead, created with the Hoover Dam, is the river’s largest reservoir: it provides 90% of Las Vegas’s water requirements. It is now only at 40% of its capacity. On Lake Powell, filled after the construction of the Glen Canyon dam, water use has outstripped the quantity of water entering the reservoir. The level of this lake has fallen by 30 metres in comparison to its highest level at the beginning of the 1980s. What is more, Imperial Valley, a rich farming region of southern California in the middle of the desert, continues to pump water via the All-American Canal, 132 km long. Here, farming withdraws 80% of river water.

A drought that scares

The river run dry no longer reaches its estuary in the sea. Shrubs are planted regularly in the Colorado delta to stabilise the soil but give little respite, since the seawater nonetheless gradually invades this wetland area. Then there is the salinity which worsens the erosion.

Overexploited to supply cities and farming areas, disturbed along its course by mega-dams, the river has suffered the consequences of poor management and climate change, as the ice-melt in the Rocky Mountains does not offset the drought further south. The river is very narrow at certain points. To compensate for this lack of water, farmers and municipalities have dug wells into the aquifers over several years. Between December 2004 and November 2013, the Colorado basin lost about 65 km3 of water, including 50.1 km3 of groundwater. The American West will undergo a water shortage.

The U.S. Bureau of Reclamation, the government agency responsible for managing water, has sounded the alarm of a water shortage in 2020, backed by statistics and models. It has called for the urgent finalisation of plans for the basin to preserve the resource and avoid the restrictions that will have to be imposed.

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