Estimation of spatially distributed evapotranspiration through remote sensing: a case study for irrigated rice in the Philippines
2002
Hafeez, M.M. | Chemin, Y. | Bouman, B.A.M. | van De Giesen, N.
Water for agriculture in Asia is increasingly scarce and ways must be sought to optimize the use and efficiency of irrigation systems, especially in water consuming irrigated rice systems. This requires an understanding of the water balance at different spatial scales of the irrigation system. An important component of the water balance is actual evapotranspiration (ETa). This paper reports on the use of a remote sensing to estimate spatially distributed ETa from irrigated rice in the Upper Pampanga River Integrated Irrigation System (UPRIIS) in Central Luzon, Philippines. The surface energy balance algorithm for land (SEBAL) was used to compute ETa from three Landsat 7 ETM+ images acquired during the second part of the crop growth period in the dry season of 2001. Ground-truth data for the calibration of SEBAL were obtained during satellite overpass. The outputs of the SEBAL computations were georeferenced maps and frequency distributions of daily ETa on the days of satellite overpass. The calculated ETa values were some 6% lower than potential rice evapotranspiration values calculated with the modified Penman Monteith method using weather data from two meteorological stations in the area. It was concluded that SEBAL provides realistic estimates of actual evapotranspiration of irrigated rice over spatially extended areas in the tropics.
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