Colorado River Flow Likely to Decline by 10 Percent in Next Few Decades: Study

A new study predicts a 10 percent drop in the annual stream flow of Colorado River over the next few decades, owing to climate change and human population growth.

This might affect the water-sharing agreements between farms and cities across the American southwest.

The new study by Columbia University's Lamont-Doherty Earth Observatory researchers, led by climate scientist Richard Seager, comes just days after a recent comprehensive study by the U.S. Department of Interior and seven Colorado River Basin states projected demand and water supply imbalances throughout the Colorado River Basin and adjacent areas in the next 50 years.

According to the Interior study, the Colorado River is currently supplying water to around 40 million people and the numbers would double to nearly 76.5 million by 2060, as a result of rapid population growth.

The Interior department also projected long and severe droughts by 2060, and a significant 9 percent decline in the flow of the Colorado River.

"The projections are spot on," Bradley Udall, an expert on hydrology and policy of the American West, at the University of Colorado, Boulder, said in a statement. "Everyone wondered what the next generation of models would say. Now we have a study that suggests we better take seriously the drying projections ahead."

The current study was carried in three key regions for water managers - the Colorado River headwaters, the greater California-Nevada region and Texas - as they receive nearly all of its water from within state borders.

Using latest climate models, the research team has projected that all three regions are likely to become arid as a result of warm temperatures and changes in rainfall patterns due to human-caused climate change.

According to the researchers, warmer temperatures might trigger evaporation in areas where there is more seasonal rainfall or snowfall. Climate models project that the temperature would be warmer between 33 and 35 degree Fahrenheit (1 to 2 degrees Celsius) than now, between the years 2021 and 2040.

The river is expected to witness more precipitation on an average, but the annual stream flow of the river is likely to drop by 10 percent and at least by 25 percent during springtime, as warmer temperatures increase evaporation.

California and Nevada will see a 20 percent decline in water flow during spring. There will be 10 percent drop in the annual runoff in Texas. The models predict that precipitation and evaporation rates would go down in spring and summer season in Texas, as there is no moisture to evaporate.

With no alternate water sources available, people in the West have just the choice of cutting back on water use to meet the decline, said the researchers.

The findings of the study are published in the journal Nature Climate Change.