Evapotranspiration estimation based on the SEBAL model in the Nansi Lake Wetland of China

Abstract

As a major component of the water budget of a wetland, evaporation has proven difficult to measure evapotranspiration accurately. This paper developed a scheme to assess actual evapotranspiration (ETa) across a range of land uses in Nansi Lake Wetland, China, using a remote sensing technique and the Surface Energy Balance Algorithm for Land (SEBAL) model. The estimation of pixel-scaled ETa was conducted via SEBAL using Landsat-7 ETM+ images, DEM and meteorological data. Compared with the recorded pan evaporation, the estimated evapotranspiration calculated by SEBAL agreed well with the results derived from pan observations. Then, the spatial distribution characteristic of daily evapotranspiration was analyzed by referencing the land-use map of 2000. It was found that the open water body and creed swamp were at a high evapotranspiration rate, while the crop land, grassland and rural residential land took the second place, and the overflow land, town constructed land and bare soil were at the lowest evapotranspiration rate, which accorded with the evapotranspiration theory. The research demonstrates the considerable potential of SEBAL model for estimation of spatial ETa with little ground-based weather data over large areas such as wetlands.