Modeling Surface Energy Fluxes Over Texas High Plains Using Two-Source Model.

Evapotranspiration (ET) is an essential component of the water balance and a major consumptive use of irrigation water and precipitation on cropland. In this study, we applied the Two-Source Model (TSM) to estimate hourly and daily ET from the Landsat Thematic Mapper (TM) data for the semi-arid Texas High Plains where more than 90 percent of the ground water withdrawals are used for irrigation. Three Landsat TM images covering a major portion of the Texas High Plains (parts of Texas Panhandle and northeastern New Mexico) were acquired for this purpose during the 2007 cropping season. Atmospheric correction on the TM images was done using the MODTRAN, an atmospheric radiative transfer model. Performance of the TSM was evaluated by comparing estimated hourly and daily ET with measured data on four large lysimeters in Bushland, TX [35⁰ 11' N, 102⁰ 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. Efforts are being made to evaluate the TSM with remote sensing data from 2006 and 2008 cropping season.