Irrigation response to drought in the Western United States, 1987-2021

The Western United States (U.S.) relies heavily on scarce water resources for both ecological services and irrigation. However, the response of irrigation water use during drought is not well documented. Irrigation decision-making is complex and influenced by human and environmental factors such as water deliveries, crop yields, equipment, labor, crop prices, and climate variability. While few irrigation districts have plans to curtail water deliveries during droughts, water rights, fallowing patterns, crop rotations, and profit expectations also influence irrigation management at the farm scale. This study uses high-resolution satellite data to examine the response of irrigators to drought by using a novel measure of irrigation management, the Standardized Irrigation Management Index. We assess the state of drought at the field and basin scales in terms of climate and streamflow and analyze the importance of variations in crop price and drought status on decision-making and water use. We show significant variability in field-scale response to drought and that crop type, irrigation type, and federal management explain regional and field-scale differences. The relative influence of climate and prices on crop transitions indicate prices more strongly drive crop planting decisions. The study provides insights into irrigation management during drought, which is crucial for sustainable water supply in the face of the ongoing water supply crisis in the U.S. Southwest.