Submitted to: Environmental and Water Resources Institute World Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/1/2009
Publication Date: 5/17/2009
Citation: Chavez, J., Gowda, P., Howell, T.A., Garcia, L., Copeland, K.S. 2009. Mapping ET at high resolution in an advective semi-arid environment with airborne multispectral imagery. Environmental and Water Resources Institute World Congress Proceedings, May 17-21, 2009, Kansas City, Missouri.p.4411-4421.2009 CDROM. Interpretive Summary: Evapotranspiration (ET) maps can be used for monitoring crop water use over a region. They can also be used to assess water use efficiency of irrigation projects. In this study, we evaluated a remote sensing based model for its ability to estimate ET with high resolution data in the Southern High Plains. Results indicate that the model works well when the leaf area index is greater than 2.5 m**2 m**-2. Potential limitation may have been the lack of a representative cold pixel representing a reference crop.
Technical Abstract: Periodic and accurate estimates of spatially distributed evapotranspiration (ET) are essential for managing water in irrigated regions and in hydrologic modeling. In this study, METRIC (Mapping ET at high Resolution with Internalized Calibration), an energy balance algorithm originally developed for application with Landsat imagery at a regional scale, was applied to very high resolution aircraft imagery (0.5-2 m pixels) in the Texas High Plains. ET predictions were evaluated using data from four large precision weighing lysimeters located at the USDA-ARS Conservation and Production Research Laboratory, Bushland, Texas. Statistical results indicated that METRIC worked better for crops with leaf area index greater than 2.5 m**2 m**-2. Potential limitations may have been the areal extent of the imagery, the surface roughness for the momentum transfer sub-model, and the lack of a cold pixel with characteristics similar to the reference crop, i.e. alfalfa.