As Snowmelt Declines, Farmers in Western U.S. Could Be Among the Hardest Hit

Crops being irrigated in California's Central Valley, part of the San Joaquin Basin.

Crops being irrigated in California's Central Valley, part of the San Joaquin Basin. California Department of Food and Agriculture

As global temperatures continue to rise, farmers in the western United States who rely on snowmelt to water their crops could be one of the most severely affected agricultural communities in the world, according to a new study in the journal Nature Climate Change. Two of the most vulnerable regions to climate change will be the San Joaquin and Colorado river basins, both major producers of crops and livestock.

The study, led by researchers at The Ohio State University, looked at monthly water demand and rainfall and snowmelt in agricultural river basins around the globe from 1985 to 2015. The research also modeled how snowmelt will change as the climate warms, including how much snow will fall and when it will melt.

“In many areas of the world, agriculture depends on snowmelt runoff happening at certain times and at certain magnitudes,” said Yue Qin, an earth systems scientist and lead author of the new study. “But climate change is going to cause less snow and early melting in some basins, which could have profound effects on food production.”

The San Joaquin Basin, located in California, currently gets 33 percent of its water for irrigation from snowmelt. Under a 7-degree Fahrenheit warming scenario, that percentage will drop to just 18 percent. In the Colorado River Basin, the share of irrigation water from snowmelt will decrease from 38 percent to 23 percent. Other extremely vulnerable agricultural regions include river basins in southern Europe, western China, and Central Asia.

In some cases, changes in rainfall patterns may help to make up the difference, Qin and her colleagues said. But they made clear that is not the case in most agricultural zones, which will experience significant water deficits as a result of the declining snowmelt.