Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2012
Publication Date: 5/1/2012
Citation: Chavez, J.L., Gowda, P., Howell, T.A., Garcia, L.A., Copeland, K.S., Neale, C.M. 2012. ET mapping with high-resolution airborne remote sensing data in an advective semiarid environment. Journal of Irrigation and Drainage Engineering. 138(5):416-423. Interpretive Summary: Remote sensing derived evapotranspiration (ET) maps have potential use for crop water management. In this study, an energy balance based ET algorithm 'METRIC' was evaluated with very high resolution remote sensing data. Remote sensing data were acquired over the USDA-ARS Conservation and Production Research Laboratory in Bushland, Texas, during the 2007 summer cropping season. Lysimetric evaluation of the estimated daily ET values indicated that it is possible to apply METRIC with high resolution remote sensing data in a semi-arid environment.
Technical Abstract: Accurate estimates of spatially distributed vegetation evapotranspiration (ET) are essential for managing water in irrigated regions and for hydrologic modeling. The METRIC**TM (Mapping ET at high Resolutions with Internal Calibration) energy balance algorithm was applied to derive ET from six very high resolution aircraft imagery (0.5-2 m pixels). Imageries were acquired over the USDA-ARS Conservation and Production Research Laboratory (CPRL), Bushland, Texas, in the semiarid Southern High Plains. The remote sensing (RS) campaign was occurred during the 2007 summer cropping season. Hourly and daily ET estimations were evaluated using measured ET data from five monolithic weighing lysimeters located in the CPRL. Results indicated that METRIC algorithm estimated ET values well when the surface roughness for momentum transfer considered for heterogeneous surface conditions and when the grass reference ET fraction was used to extrapolate instantaneous estimates of ET. On average, errors in estimating hourly ET were -0.7+/-11.6% and for daily ET error were 2.4+/-9.3%. Results showed that it was possible to apply METRIC with airborne imagery in a semi-arid environment. Although, an appropriate (or combination of) surface roughness length and ET extrapolation methods have to be incorporated into the ET algorithm.