Water Consumption Estimation Of Vegetation In Arid Area Based On Mathematical Model

Evapotranspiration,i.e.ecological water consumption is an important part of water cycle.70%of the global land precipitation returns to the atmosphere in the form of evapotranspiration,which can reach 90%of the precipitation in the arid area.As an important part of the energy balance and water balance of the earth's surface,it determines the evolution and formation of the geological environment,and is the basis of the research on water cycle and water balance.Based on this,in order to quantify the evapotranspiration in the study area,know the water consumption in the study area,and make the rational allocation of water resources in the study area,MODIS data,meteorological data and elevation(DEM)data are collected in this study,and the evapotranspiration in the study area in 2008-2017 is inverted through the SEBAL model.The retrieved daily evapotranspiration is verified by the crop coefficient method,and the temporal and spatial distribution rules of evapotranspiration in the study area are analyzed Finally,the SWAT model is constructed to compare the simulation results with the ET of remote sensing monitoring.The specific research results are as follows:(1)According to penman Monteith formula,the potential evapotranspiration of vegetation growth in the study area shows a downward trend,with an average annual potential evapotranspiration of 914.64mm and a downward range of 0.36mm/a.Using Mann Kendall method to determine the evapotranspiration of vegetation growth potential in the season before 1990,the evapotranspiration showed an upward and downward trend,and a linear downward trend since 1990.Combined with wavelet analysis,it is found that there are 27-30 years and 21-23 years oscillation period in the study area,among which the wavelet variance of 28 years is the largest,followed by 22 years.(2)Based on the SEBAL model,the evapotranspiration of the study area in the growth season of 2008-2017 was calculated.In the past 10 years,the evapotranspiration first increased and then decreased.The evapotranspiration in the southeast and northeast of the spatial distribution was significantly different.The evapotranspiration in the southeast was the highest,and the evapotranspiration in the Northeast was the lowest.The trend of monthly average evapotranspiration showed a slight upward trend in 10 years,and the rising range of evapotranspiration was 0.25 mm/a.(3)The evapotranspiration of different land types has obvious differences.The average monthly evapotranspiration is forest land>cultivated land>grassland>Beach>sand land.In 2013 and 2014,the average monthly evapotranspiration was larger than that in other years.In 2010,the average monthly evapotranspiration was smaller.(4)In the early stage of growth,temperature and wind speed have a greater impact on evapotranspiration;in the peak and later stage of growth,surface temperature and elevation have a greater impact on evapotranspiration.(5)The evapotranspiration simulated by SEBAL model is far greater than that simulated by SWAT model,which indicates that the actual water consumption for maintaining the vegetation ecosystem in the study area is far greater than the local precipitation;the maintenance of the local vegetation system requires the supplement of surrounding groundwater;the annual average supplement of groundwater resources in the study area is 290.82mm.