Spatio-temporal Variation Of Actual Evapotranspiration In The Wei River

Evapotranspiration is a key link between the atmospheric hydrological cycle and the energy cycle,and is of great significance for understanding climate change and the rational use of water resources.Especially in the case of shortage of water resources,accurate estimation of actual evapotranspiration has important guiding significance for regional agricultural production,ecological environment,and economic development.In this study,the meteorological data of 1970-2018 and the annual runoff data of hydrological stations of 22 ground weather stations in the Weihe River Basin were used to study the temporal and spatial variation of actual evapotranspiration in the Weihe River Basin,and the attribution analysis of the spatial and temporal variation of actual evapotranspiration.Calculate the potential evapotranspiration in the basin by Penman formula,further analyze the relationship between actual evapotranspiration and potential evapotranspiration in the Weihe River Basin,verify the applicability of the Complementary evaporation hypothesis in the Weihe River Basin,and discuss the changes in underlying surface moisture(precipitation)on the actual evapotranspiration in the basin And potential evapotranspiration changes.Based on the above research,this paper draws the following conclusions:(1)In terms of time,the average actual evapotranspiration in the Weihe River Basin has increased over the years.Seasonal changes are more obvious,mainly manifested as the largest summer evapotranspiration value,followed by spring and autumn,and the smallest winter,accounting for 43.25%,31.82%,16.04%,6.65% of the actual evapotranspiration of the year.The largest month of evaporation during the year is July and the smallest month is December.The actual evapotranspiration in the Weihe River Basin fluctuated greatly in the 1980 s,and changed little in other eras.In terms of spatial variation,the multi-year average actual evapotranspiration is basically consistent with the intergenerational spatial distribution.The high-value areas are mainly located in the west of the entire basin and the south side of the main stream of the Weihe River,and the low-value areas are mainly distributed in the middle and northwest of the basin,gradually increasing from northwest to southeast.Increasing trends.The spatial distribution of actual evapotranspiration in spring is consistent with that in winter.The high-value areas are mainly distributed in the Beiluo River in the east of the Weihe River Basin,showing a decreasing trend from west to east.The spatial distribution of actual evapotranspiration in summer and autumn is similar to that of multi-year actual evapotranspiration.It is mainly concentrated in the southern part of the watershed,and low-value areas are mainly distributed in the middle part of the watershed.(2)The attribution analysis of the actual evapotranspiration in the Weihe River Basin shows that over the years the actual evapotranspiration has the strongest sensitivity to solar radiation,followed by wind speed and actual water vapor pressure,and the temperature sensitivity is the least;different meteorological factors have contributed to actual evapotranspiration The contribution is different,the average temperature and wind speed show a positive contribution to the annual average contribution of the basin,the solar radiation and the actual water vapor pressure show a negative contribution,and the saturated water vapor pressure contributes the most;in the annual seasonal distribution,each meteorological factor summer and autumn The sum of contributions is greater than that of spring and winter,and the sum of contributions in the first half of the year is greater than that of the second half.The actual evapotranspiration changes in the basin are mainly affected by the summer and autumn.(3)By comparing the calculation results of actual evapotranspiration and potential evapotranspiration in the basin,it is concluded that the potential evapotranspiration in the Weihe River Basin for many years is much greater than the actual evapotranspiration,and the fluctuation trend of the actual evapotranspiration in each basin is greater than the potential evapotranspiration.The actual evapotranspiration of Jinghe fluctuated the most for many years.The average weighted actual evapotranspiration in the main stream of Weihe,Jinghe,Beiluohe and the whole river basin is basically close to half of the potential evapotranspiration.The potential evapotranspiration of Jinghe is the largest,followed by Luohe,and the main stream of Weihe is the smallest.Based on the analysis of water balance,it is concluded that with the increase of rainfall,the actual evapotranspiration in the Weihe River Basin shows a significant increase trend,while the potential evapotranspiration shows a significant decrease trend.The relationship between the two tends to conform to the theory of complementary evaporation.