Researchers found that the flow of the Colorado River is slowing due to the impacts of global warming, putting "severe water shortages" at risk for the millions of people who depend on one of America's most famous waterways.
Increasing periods of drought and rising temperatures have reduced the flow of the Colorado in recent years, and scientists have developed a model to better understand how the climate crisis is fundamentally changing the 2,334-kilometer waterway.
Snow loss in the Colorado River basin due to human-induced global warming has caused the river to absorb more energy from the sun, increasing the amount of water lost to evaporation, scientists from the U.S. Geological Survey found.
This is because snow and ice reflect sunlight away from the Earth's surface, a phenomenon known as the albedo effect. The loss of albedo as snow and ice melt is reducing the flow of the Colorado by 9.5% for every 1C of warming, according to research published in Science.
The world has warmed by about 1 ° C since the pre-industrial era and is on track for an increase of more than 3 ° C by the end of the century unless global warming emissions are drastically reduced. For the Colorado, this scenario signifies an “increasing risk of severe water scarcity,” the study indicates, with any increase in precipitation not likely to offset the loss of reflective snow.
According to Brad Udall, a senior scientist at Colorado State University and a Western water supplies expert who was not involved in the research, the extent of Colorado's decline, as described in the Science article, is "staggering."
"This has important implications for water users and administrators," Udall said. “More generally, these results tell us that we need to reduce greenhouse gas emissions as soon as we can. We have wasted almost 30 years arguing about science. The science is crystal clear: we must reduce greenhouse gas emissions immediately ”, he declared.
The Colorado rises in the Rocky Mountains and passes through ranches and canyons, including the Grand Canyon, as it traverses the American West. It previously emptied into the Gulf of California in Mexico, but now ends several miles before this due to the amount of water withdrawn for American agriculture and cities ranging from Denver to Tijuana.
The upper river basin supplies water to some 40 million people and supports 16 million jobs. It feeds the two largest water reserves in the US, Lake Powell and Lake Mead, with the latter supplying Las Vegas with almost all of its water.
Backpacks of snow that last into late spring have historically fed streams that have fed the Colorado River, as well as reducing the likelihood of major fires. As the weather warms, the river evaporates and the risk of wildfires increases.
The climate crisis is exacerbating existing threats to the river, which include intensive pumping of water for agriculture, the use of water in urban areas, and the threat of contamination from uranium mining. Lake Mead, the vast reservoir formed by the Hoover Dam, has fallen to levels not seen since the 1960s.
A 19-year drought that swept through stretches of the river nearly caused the US government to impose mandatory reductions in river water use last year, only for seven western states to agree to voluntary reductions. However, the problems will only become more acute as the weather turns warmer and drier at a time when demand for water from sprawling cities in the western United States increases.