Snowmelt changes may greatly affect farmers in western U.S.

Farmers in the western U.S. who depend on snowmelt for crop irrigation may be facing major threats from climate change. According to a new study from Ohio State University, snowmelt changes will reduce the water supply when it is needed for seasonal irrigation.

An interdisciplinary team of researchers set out to examine how rising temperatures will impact snowmelt in drainage basins that support irrigation worldwide. 

The experts analyzed monthly water demand combined with snowmelt runoff across basins from 1985 to 2015. Next, the team projected changes in snowmelt after 2 or 4 degrees of climate warming.

The researchers pinpointed the snow-dependent basins that are most at risk of not having water available at the right times for irrigation due to changing snowmelt patterns. The San Joaquin and Colorado river basins ranked as two of the highest-risk basins, which are both located in the western United States. 

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

Projected changes in snowmelt will also adversely affect agriculture across basins in southern Europe, western China, and Central Asia. 

The researchers found that in some basins, rainfall runoff may be able to compensate for declines in snowmelt runoff, depending on the timing and magnitude.

However, in many basins such as the San Joaquin, rainfall will not compensate enough for lost snowmelt to meet irrigation water demands.

The findings indicate that changes in snowmelt will mainly affect crops in the northern hemisphere, including rice and cotton in the summer and  wheat in the spring.

According to Professor Qin, the research could be used to prioritize and inform methods to minimize the impact of changing snowmelt on water supplies for agriculture. In some cases, extra groundwater pumping and reservoir development should be considered.

The study is published in the journal Nature Climate Change.

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By Chrissy Sexton, Earth.com Staff Writer