Temporal And Spatial Variation Of Evapotranspiration In Genhe River Basin In Recent 40 Years

Based on SWAT model,the annual and monthly variation of evapotranspiration,potential evapotranspiration and soil water content and their spatial distribution pattern in Genhe River Basin during 38 years were studied.The distribution and mutation characteristics of evapotranspiration,potential evapotranspiration and soil water content in Genhe River Basin during different freeze-thaw periods were analyzed.The relationships among meteorological factors,evapotranspiration and soil water content were discussed,and the response relationship between evapotranspiration and soil water content was revealed.The results showed that:(1)the ET and PET of Genhe River Basin showed a fluctuating increasing trend from 1980 to 2017,while the soil water content showed a fluctuating decreasing trend.The annual changes of ET and PET in Genhe River Basin showed a single peak distribution with August as the peak,and the soil water content showed a fluctuating multi peak distribution.(2)The spatial distribution pattern of ET in Genhe river basin is high in the upper reaches and low in the middle and lower reaches;the spatial distribution pattern of PET is southwest >Northeast > southeast;the spatial distribution pattern of soil water content is middle reaches >upper reaches > lower reaches.(3)The ET of the Genhe River Basin increased in growth period,complete freezing period and thawing period,and decreased in the initial freezing period;PET increased in different periods;soil moisture content decreased in different periods.(4)In Genhe River Basin,the ET in different land cover types are: woodland > grassland >cultivated land > construction land > swamp;the order of PET is: cultivated land > construction land > woodland > grassland > swamp;the order of annual mean value of soil water content is:swamp > woodland > grassland > cultivated land > construction land.(5)There was a significant positive correlation between ET and soil water content in Genhe River Basin and various land use types in different periods.In recent 40 years,the correlation between ET and temperature and precipitation is the largest,and precipitation is more significant.Soil water content was positively correlated with precipitation and relative humidity,and negatively correlated with sunshine hours.(6)There are mutation points of ET in different freeze-thaw periods in typical ecosystems.The mutation years are different in each period,and the change degree is different after mutation.Generally,the change in the region is relatively stable.The soil water content of typical ecosystem in different freeze-thaw periods has mutation points,and the change trend is more intense,generally showing a sharp rise at first and then a sharp decline.The research results have important reference significance for the change of evapotranspiration and the effect of freeze-thaw on the local.