Study On Evapotranspiration In ChaKou Small Watershed Based On SEBS Model

Evapotranspiration(ET)refers to the evaporation of surface water and the transpiration of water in plants.It is an important part of maintaining the balance of surface water circulation and surface energy,and it is also an important component of land surface ecological process simulation.The estimates of ET can provide data for the development of precision agriculture,assessment of regional water resources,ecological restoration,drought monitoring,water resources management,and the change of global climate change.The rapid development of Remote Sensing technology in recent years has made it possible to obtain rapid and accurate surface evapotranspiration at regional scale.Topography of the Loess Hilly-gully region is fragmented,and soil and water loss and other ecological environmental problems are very serious.Therefore,in order to understand the land-surface water cycle and surface energy balance in the region,water monitor dynamic based on RS is performed in this area to reasonably and accurately estimate the surface evapotranspiration has an important significance.In this paper,a small watershed in the Loess Hilly-gully region named Cha-Kou was selected as the study area,and Landsat 8 images were used to evaporate the model based on SEBS.The evapotranspiration characteristics in the study area were inverted,and the instantaneous evapotranspiration obtained from the inversion was scaled and calculated.A variety of indirect accuracy verification methods were used to evaluate the accuracy of inversion results,and the spatial distribution of evapotranspiration in the study area was analyzed.In combination with meteorological data,time scale and spatial distribution are used to explore the main factors that affect the temporal variation and spatial pattern of surface evapotranspiration.The main results are:(1)After indirect precision verification of the actual evapotranspiration,the results show that the ET inversion method based on the SEBS model has a high inversion accuracy,and it has certain applicability in the Cha-Kou watershed.(2)The spatial distribution of evapotranspiration in the Cha-Kou watershed is significantly different.The evapotranspiration in the northwestern of the region where there are large areas of forest land and high density grassland is significantly higher than that in the central and southeastern regions.The evapotranspiration of land use types is ranked as follows:Water>Forestland>Grassland.>Cultivated land>Garden>Residential area.It shows that different types of surface cover have a strong guiding effect on the distribution of regional evapotranspiration.Therefore,it is possible to guide the rational use of water according to the type of surface cover.(3)In the time series,the evapotranspiration is the highest in July,and the daily evapotranspiration was positively correlated with temperature and land surface temperature,and the relationship with NDVI was not obvious.On the spatial scale,the spatial distribution of evapotranspiration is:Northwest>Southeast>Central,and the evapotranspiration distribution is negatively correlated with surface temperature,and there is a good positive correlation with NDVI,and the correlation with evapotranspiration parameters is not clear.