Adapting irrigated agriculture in the Middle Rio Grande to a warm-dry future

Study region: Middle Section of the Rio Grande Basin (MRG), U.S.Study focus: Long-term tradeoffs of technologically possible land and water management in-terventions were analyzed to adapt irrigated agriculture to growing water scarcity in a desert environment under a projected warm-dry future. Nineteen different intervention scenarios were investigated to evaluate potential watershed-scale agricultural water savings and associated water budget impacts in the MRG. The interventions are based on (i) management innovations of growers in implementing deficit irrigation and changing cropping patterns using existing crops, (ii) changing cropping patterns by introducing new alternative drought-and salt-tolerant crops, and (iii) limitations of the soil and water assessment tool (SWAT) model to perform scenario simulations.New hydrological insights for the region: (1) status quo irrigation management cannot sustain the current crop mix in the face of dwindling river water and likely fresh groundwater depletion within the 21st century; (2) existing cropping and irrigation interventions create limited water savings; and (3) deficit irrigation of alfalfa or removing it from the crop mix allows moderate water savings to sustain high-value perennial pecan crops but the region will remain vulnerable to intensive, prolonged droughts. Strategies for future agricultural water sustainability in the study area could include transitioning to relatively drought-and salt-tolerant crops, desalinating brackish groundwater for irrigation, and developing water markets to increase flexibility in water use.