Climate Change to Deplete Some US Water Basins Used for Irrigation

By 2050 the Southwest will produce significantly less cotton and forage, researchers report.

A new study by MIT climate scientists, economists, and agriculture experts finds that certain hotspots in the country will experience severe reductions in crop yields by 2050, due to climate change's impact on irrigation.

The most adversely affected region, according to the researchers, will be the Southwest.  Already a water-stressed part of the country, this region is projected to experience reduced precipitation by midcentury.  Less rainfall to the area will mean reduced runoff into water basins that feed irrigated fields.

Production of cotton, the primary irrigated crop in the Southwest and in southern Arizona in particular, will drop to less than 10 percent of the crop yield under optimal irrigation conditions, the study projects.  Similarly, maize grown in Utah, now only yielding 40 percent of the optimal expected yield, will decrease to 10 percent with further climate-driven water deficits.

In the Northwest, water shortages to the Great Basin region will lead to large reductions in irrigated forage, such as hay, grasses, and other crops grown to feed livestock.  In contrast, the researchers predict a decrease in water stress for irrigation in the southern Plains, which will lead to greater yields of irrigated sorghum and soybean.

If efforts are made to reduce greenhouse gases and mitigate climate change, the researchers find that water scarcity and its associated reductions in cotton and forage can be avoided.

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