Spatially Explicit Evapotranspiration Mapping for Large Scale Agro-Hydrologic Applications

Evapotranspiration (ET) is one of the major components of the hydrologic cycle. Spatially explicit ET can be used in different applications such as estimating crop consumptive use, drought monitoring, recharged estimation, and understanding basin water balance dynamics. ET can be estimated consistently and reliably using a combination of remote sensed images and weather datasets. The U.S. Geological Survey Earth Resources Observation and Science (EROS) center has created historical (2000-2013) monthly and annual ET grids at 1 km for the conterminous U.S. using the Operational Simplified Surface Energy Balance approach. A validation of the model estimates using lysimeter and eddy covariance flux tower data sets, and basin scale ET shows the reliability of ET in quantifying year-to-year variability of water use, detecting droughts and understanding water balance dynamics of a basin. Model estimates at a field scale showed improved accuracy (up to 90%) at seasonal time scales compared to monthly estimates due to the minimization of random error components with time-aggregation. The increasing availability of global datasets from model-assimilated weather stations and remote sensing creates an unprecedented opportunity to conduct hydrologic investigations around the world at multiple spatial scales.