Estimation of Daily Actual Evapotranspiration from ETM+ and MODIS Data of the Headwaters of the West Liaohe Basin in the Semiarid Regions of China

摘要

Evapotranspiration (ET) is an important, but immeasurable, component of the hydrological cycle in semiarid regions. Traditionally, actual ET is computed as residual in water balance equations. It is derived from estimates of potential ET or, indirectly, from field measurements at meteorological stations. Recently, researchers have begun using scintillometers, remote sensing data, and hydrological models to estimate areal actual ET. In this study, the surface energy balance algorithm for land (SEBAL) was used to derive ET maps from moderate resolution imaging spectroradiometer (MODIS) images over the Laohahe basin and Shalamulun River basin. The effect of ground parameters on ET of the study area was quantified using the spatial analysis techniques of ArcGIS. At the end, ET estimated from Landsat 7 enhanced thematic mapper plus (ETM+) was compared with that from MODIS data over the Shalamulun River basin. SEBAL is a suitable algorithm for mapping evaporation over semiarid areas, using MODIS and Landsat images with few or no ground measurements. The ET of the study changes from 0 to 6.57 mm/day. The land use types, elevation, land surface temperature (LST), and terrain all have a direct effect on the spatial distribution of ET. ET simulated from both MODIS and Landsat data give reasonable values; however, results from Landsat ETM+ are better compared to those of MODIS because Landsat data have higher spatial resolutions than MODIS data.