Estimation Of Evapotranspiration Based On MODIS Data In Huaihe River Basin

Accurate estimation of evapotranspiration is the Theoretical basis for optimal allocation and utilization of water resources.The application of remote sensing in evapotranspiration remedies the time and energy defects,and can conduct a comprehensive monitoring of the study area,so as to better reflect the regional water cycle and water balance,to provide a basis for the development of scientific irrigation system.Using the 23 periods MODIS data,the meteorological data of 27 stations and DEM data in the Basin,the actual evapotranspiration of the study area was retrieved based on the SEBAL model,and the results were verified by crop coefficient method.The correlation between the evapotranspiration and the influencing factors in the study area was also analyzed.The results of the study are as follows:(1)Using the Penman-Monteith formula,the average evapotranspiration of the Huaihe River Basin during2000?2014 is 865.8mm,showing an increasing trend from east and southwest to northwest.The potential evapotranspiration in the south of Huaihe River is obviously lower than that in the north of the Huaihe River.From the changing trend,the average potential evapotranspiration tendency is-9.93mm/(10a),and the average potential evapotranspiration in the whole area is basically declining,and the decreasing trend of the north of the Huaihe River Basin is obvious.(2)In the study area,The sensitivity of interannual variation to the meteorological factors is:relative humidity>maximum>temperature>average wind speed>sunshine hours>Day minimum temperature;The average sensitivity coefficients of each factor are:-0.89,0.63,0.44,0.38,0.22,0.16.The sensitivity of monthly changes to the meteorological factors is:relative humidity>daily maximum temperature>sunshine hours>average wind speed>daily minimum temperature,The average sensitivity coefficient of each factor is:-1.31,0.38,0.37,0.29,0.22,0,14.(3)Based on the SEBAL model,the evapotranspiration of the Huaihe River Basin was retrieved and the model accuracy was verified by the crop coefficient method.On this basis,the temporal and spatial characteristics of actual evapotranspiration in the Huaihe River Basin in 2014 are analyzed.The actual evapotranspiration in the study area is 353?1078mm in 2014.The evapotranspiration of whole basin is decreasing from south to north,and the difference is significant from south to north.(4)The average temperature,sunshine hours and wind speed of meteorological factors are positively correlated with actual evapotranspiration,The correlation coefficients were 0.42?0.85,0.16?0.63 and 0.21?0.46,respectively.The relative humidity was negatively correlated with the actual evapotranspiration,and the correlation coefficient was-0.71?-0.48.There were positive correlations between NDVI,surface temperature,surface emissivity and actual evapotranspiration,and the correlation coefficients were 0.33?0.89,0.32?0.71 and 0.22?0.83,respectively.The actual evapotranspiration in the study area has a certain correlation with the slope and aspect.When the slope is 5°?16°,the evapotranspiration changes significantly with the slope,and they are positively correlated.The actual evapotranspiration of the south slope is the largest,and the actual evapotranspiration of paddy field is the largest,and the actual evapotranspiration of bare land is the smallest.The remote sensing estimation of the evapotranspiration in the Huaihe River Basin can provide some references for the development of irrigation system,monitoring meteorological disasters and the allocation of river basin water resources.