Effects of Climate Change on U.S. Irrigation

Abstract

Warming of the global atmosphere by 2°‐5° C, and regional changes in precipitation by mid 21st century as greenhouse gases double, is expected. A composite model predicts the consequences on the geography of U.S. irrigation. Percentages of cultivated area irrigated are projected for each state. Predictions of actual area irrigated, which will depend on economic conditions and availability of new water supplies are not made. In all cases percentages irrigated rise, with the greatest impact of a warmer climate on the agricultural economy in the Western states. In the Western states this will occur because of decreases in total area cultivated due to a loss of rainfall agriculture. In the East, irrigation will increase, accompanied by some decrease in cultivated areas. Improved use of technologies could help meet increasing evapotranspiration needs, but large new surface supplies will generally be required to maintain or increase present levels of irrigation.