Analysis of evapotranspiration characteristics for different land covers over Songnen Plain based on remote sensing

In order to accurate estimation of ET, in this study, the SEBAL model combined with MODIS products and observed weather data were used to estimate regional ET over Songnen Plain during the 2008 growing season (from May to September). When ET measured by eddy covariance system was used to verify the SEBAL model estimation accuracy, it was found that the trends of both ET calculated and observed were highly consistent, ET estimation error of the whole growing season was 18.26%. The results indicated that the ET retrieval method based on remote sending would meet the requirements of regional ET estimation. ET over Songnen in the growing season of 2008 ranged from 183 mm to 1 003 mm and it increased from the southwest part to the east part and northeast part; average ET of each land cover type decreased in the order of: water-body > woodland > wetlands > cropland > built-up > grassland. Finally, ET and precipitation were compared to analyze the water deficit condition; it was found that the average value of water deficit over Songnen Plain was 195.96 mm. In more than 97% of the whole study area, ET was greater than precipitation, it indicated that the ET process rely on groundwater and runoff to compensate for lack of precipitation to a large extent. The higher ET rate and relative lower precipitation in the growing season would do great influence on the ecological environment of Songnen Plain.