Estimation And Heterogeneity Analysis Of Manas River Basin Evapotranspiration Based On SEBAL Model

Surface evaporation is the key link in hydrological cycle,and it is also the basis of energy exchange of terrestrial gas system and hydrothermal exchange of underlying surface.The accurate estimation of evapotranspiration intensity in the basin is of great value for water resources evaluation and surface energy balance research.Based on the Manas basin as a typical study area,this paper uses remote sensing interpretation and SEBAL model calculation to retrieve the evapotranspiration in the study area.The results show that:1.From the overall point of view,different underlying surface types in the basin have large differences in surface hydrothermal flux distribution.The net radiation flux is high when the surface vegetation cover is high and the surface temperature is low.The sensible heat flux is similar to the soil heat flux.2.The FAO Penman-Monteith formula was used to verify the accuracy of the evapotranspiration estimation results of the SEBAL model,and the errors were all within 20%,indicating that the SEBAL model has good applicability to the evapotranspiration estimation of the Manas River Basin.3.The daily evapotranspiration in summer was ranked as water > cultivated land > woodland > grassland > alpine meadow > unused land > desert > permanent glacial snow.The total amount of evapotranspiration in sunny days of the whole region is in the increasing trend,and the total amount of evapotranspiration in oasis zone has been kept the largest in the whole region,and the total amount of evapotranspiration in each district is consistent with the change trend of the total amount of evapotranspiration in its main land.The total amount of daily evapotranspiration in the year is summer > spring > autumn > winter,the oasis zone contributes the most to the whole region in spring and summer,and the desert zone contributes the most to the whole region in autumn and winter.4.The evapotranspiration was positively correlated with temperature,wind speed and NDVI.The correlation was NDVI? temperature and wind speed from big to small.Spatial variation of evapotranspiration is influenced by land-use type,NDVI and groundwater level in pre-mountain plain area;interannual evapotranspiration in oasis and Gobi belt is influenced by land-use evolution and NDVI,while desert and mountain areas are mainly controlled by climate;evapotranspiration in vegetation area is influenced by land-use type,NDVI and groundwater level depth,and non-vegetation area is controlled by climate change,among which temperature is the most significant.5.The daily ecological water demand of the typical vegetation in the watershed increases year by year,and the daily ecological water demand of the oasis belt increases the most;the daily ecological water demand of each quarter of the year is summer> spring> autumn> winter,and the daily ecological water demand of each sub-area is oasis belt> Gobi Belt> Mountain> Desert Belt.In view of the large increase in daily ecological water demand in the oasis belt,the oasis area should scientifically reclaim on the premise of maintaining crop output,adjust the original crop planting structure,improve irrigation technology,and ensure the long-term healthy development of water resources and ecological environment in the basin.