Estimating Evaportranspiration In Yingtan Agricultural Watershed Using SEBAL And SEBS Model

Land surface water and heat flux is an important part of the energy balance and global water cycle. Monitoring agricultural small watershed surface water and heat flux in timely manner, able to understand the regional context water and energy balance, it has a very important significance to guidance agricultural irrigation and promotion of efficient and rational use about basin water resources.This paper selects a typical hilly agricultural watershed as the research area in Yingtan region, Jiangxi Province. The Landsat8and Pleiades satellite images were used combined with ground measurements and DEM data. The two remote sensing-based models for estimating evapotranspiration (ET) were compared, namely the Surface Energy Balance Algorithm for Land(SEBAL) and the Surface Energy Balance System (SEBS),each energy component of two models are validated with measured data.The results showed that the estimation results by SEBS model in the study area is relatively good.Finaly,According to the analyzed and compared with ultra-high-resolution remote sensing image, it is concluded that the basin of the spatial distribution and change law of crop evapotranspiration,Obtained spatial distribution and variation of various crops evapotranspiration in the agricultural watershed.The main conclusions are as follows:(1) SEBAL model and SEBS model combines Landsat8data can be used to estimate the regional agricultural watershed evapotranspiration better. Comparison with ground truth data shows that the average relative error is of16%and12%. Especially the estimate result which uses the SEBS model is more accurate than that uses the SEBAL model.(2) Digital elevation model(DEM) is successfully coupled in the SEBAL model and SEBS model for the topography correetion(slope,aspect and elevation). Estimate the atmospheric transmittance, surface emissivity, vegetation cover, normalized difference vegetation index, land surface temperatures,solar radiation, atmospheric downward longwave radiation, ground upward radiation, soil heat flux, surface roughness, sensible heat flux, latent heat flux and the kinetic parameters, combined with the Monin-Obukhov Similarity and Bulk Atmospheric Boundary Layer Similarity. The application result of the studied area indicates that the daily evapotranspiration amount estimated by the improved SEBAL model and SEBS model have a smaller error with the measured value, and a higher accuracy. (3) Comparison each energy component results of two models, such as solar radiation, soil heat flux, daily evapotranspiration and kinetic parameters, Found the soil heat flux by SEBAL model is more closer to the ground truth data, and the SEBS model of daily evapotranspiration has a better result.(4) Analysis the evapotranspiration for different land use/land cover(LULC) types. Different evapotranspiration of1land use/land cover(LULC) types are signifieantly different. It is found that evapotranspiration show largest in water areas and least in urban,The general rule is:paddy>tree>rainfed.