Estimating Actual Evapotranspiration from Satellite and Meteorological Data in Central Bolivia

Abstract

patial estimates of actual evapotranspiration are useful for calculating the water balance of river basins, quantifying hydrological services provided by ecosystems, and assessing the hydrological impacts of land-use practices. To provide this information, the authors estimate actual evapotranspiration in central Bolivia with a remote sensing algorithm [Surface Energy Balance Algorithms for Land (SEBAL)]. SEBAL was adapted for the effects of topography (particularly for elevation, slope, and aspect) and atmospheric properties on incoming solar radiation. Instantaneous fluxes are converted to daily and annual fluxes using reference evapotranspiration. The required input data consist of meteorological data and satellite data. Results show more evapotranspiration for humid regions and less evapotranspiration for dry regions and deforested land. Actual evapotranspiration estimates are compared with annual precipitation measurements from 27 meteorological observations. In case annual actual evapotranspiration is estimated correctly, it must be lower than the precipitation measurements. This is the case for 23 stations. The remaining four stations are all located at higher altitudes (>2700 m). Unfortunately, no actual evapotranspiration measurements are available for additional validation purposes.