Monitoring ET Over Texas High Plains Using Two-Source Model and High Resolution ASTER Data

Evapotranspiration (ET) has been long been recognized as the most important process that plays an essential role in determining exchanges of energy and mass between the hydrosphere, atmosphere and biosphere. In agriculture, it is a major consumptive use of irrigation water and precipitation. In this study, we applied the Two-Source Model (TSM) to estimate daily ET from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data for the highly advective Texas High Plains where more than 90 percent of the groundwater withdrawals are used for irrigation. Two ASTER images, acquired during the 2007 cropping season (July 11 and September 13), covering a portion of the Texas High Plains including Bushland that houses USDA-ARS Conservation and Production Research Laboratory were used. Atmospheric correction on the ASTER images was done using the MODTRAN, an atmospheric radiative transfer model. Performance of the TSM was evaluated by comparing estimated daily ET with measured data on four large lysimeters in Bushland, TX [35° 11' N, 102° 06' W; 1,170 m elevation MSL] managed by the USDA-ARS-Conservation and Production Research Laboratory. Model performance results indicate that the TSM is suitable for estimating ET over Texas High Plains. However, more evaluation is needed for different agroclimatological conditions in the region.