Water Resources Research Act Program

Details for Project ID AZ-2025_Tronstad

Medium (30-Meter) Resolution Evapotranspiration Modeling of the Quantity of Water Used for Alfalfa and Other Hay in the Lower Colorado River Basin

Institute: Arizona
USGS Grant Number:
Year Established: 2025 Start Date: 2026-08-01 End Date: 2029-07-31
Total Federal Funds: $298,662 Total Non-Federal Funds: $298,662

Principal Investigators: Russell Tronstad

Project Summary: This project aims to accurately quantify and map Lower Colorado River Basin water use of alfalfa and other hay crops at 30-meter resolution and at daily to weekly frequencies, where water shortages are a serious concern. Alfalfa and other hay crops made up 41% of Arizona?s crop portfolio in 2024. Landsat 8 and Sentinel-2 satellite images will be combined to get frequent and detailed estimations of a field?s water consumption or evapotranspiration. The measurements will be matched with ground-level data taken from field research stations near Maricopa and Yuma, Arizona, and Holtville, California, where flux towers measure the actual water lost to evaporation and transpiration. Our ultimate goal is to help farmers, policymakers, and water districts precisely identify where and when large quantities of water are being consumed by agriculture in the Lower Colorado River Basin. Quantifying this ET information will enable better-informed decisions about managing and conserving both ground and surface water resources.