Evapotranspiration Estimates at Yuma, Arizona Using Land Surface Temperatures from ECOSTRESS (Invited Presentation)

Availability of fresh water supplies is critically important for food crop production in Yuma, Arizona, a region that produces ~90% of U.S. supplies of fresh winter vegetables. Sustainability of this irrigated agricultural area is a major concern: climate variability is curtailing Colorado River supplies, while soil salinity levels and demands by urban users are increasing. Measurement and modeling of evapotranspiration (ET) play major roles in addressing this concern. By determining actual ET, one can answer questions of water use efficiencies by crop type and location and help develop different management practices to control salinity. By modeling spatially distributed and Since 2017 we have undertaken ground and spaceborne studies to use ET to revise crop water use baselines and map ET variability across the Yuma region. Key crops are lettuce, spinach, and durum wheat. Water budgets are being monitored using a rotating set of 7 eddy covariance stations, 2 large aperture scintillometers, near-surface soil moisture observations, and in-field water deliveries. Results to date indicate some water use baseline values are too low yet support interpretations for high (>80%) water use efficiencies. Commencing Fall 2018, daily ET maps at 100-m scales will be created using thermal infrared data from ECOSTRESS; these maps will facilitate estimation of ET envelopes for unstressed irrigation practices and help identify regions with anomalously high or low ET. The impact of previously unattainable ~4-day TIR observations from ECOSTRESS upon ET model forecasts will be presented.