Between 2000 and 2014, the worst 15-year drought on record, the annual flow of the Colorado River was reduced by 19 percent. About one-third of this loss was due to unprecedented temperatures that averaged 0.9°C (33.6°F ) above the 1906-99 average, according to new research from the University of Arizona and Colorado State University.
Hydrology researchers Brad Udall of Colorado State University and Jonathan Overpeck of the University of Arizona say that a shortage of rain and snow during the drought can only account for about two-thirds of the drop in the river’s volume, though, according to CTV News Canada.
Further reading: Lake Mead hits record low as Western drought continues
In a study published in the journal Water Resources Research on February 17, 2017, the researchers concluded the rest of the decline was due to warming temperatures brought on by climate change, which is drawing moisture from the river basin through evaporation from the water, plants, and soil.
The big concern is the problems that will ensue for the 40 million people served by the Colorado River. The 246,000-square-mile river basin spans seven states and Mexico and supports 16,317 square kilometers (6,300 square miles) of farmland.
“Fifteen years into the 21st century, the reality is that climate change is already depleting the Colorado River water supplies at the upper end of the range suggested by previously published projections. Record-setting temperatures are an important and underappreciated component of the flow reductions now being observed,” reads the study.
Further Reading: Next president must act fast on Colorado River water supply cuts
Lake Mead and Lake Powell
The water level at Lake Mead was at 42 percent capacity on Wednesday while Lake Powell recorded 46 percent capacity. Both these reservoirs have been overtaxed and water resources officials are already suggesting that if water levels were to drop any lower, this could trigger cuts in Arizona and Nevada, the first states that would be affected under existing multistate agreements and regulations.
This winter’s snowfall will probably keep any water cuts from happening because the snowpack in the Colorado and Wyoming mountains that provide much of the Colorado River’s water averaged 120 to 216 percent of normal on Thursday.
The research involved using current climate models that led the two scientists to conclude the decline in precipitation should have produced a reduction of about 11.4 percent in the river flow, not the 19.3 percent that occurred. Many climate models can simulate 20th-century conditions well, but the models cannot simulate the 20- to 60-year megadroughts known to have occurred in the past and many of those models did not reproduce the current drought.
Udall and Overpeck found that all the current climate models agree that temperatures in the Colorado River Basin will continue rising if the emission of greenhouse gasses is not curbed.
