Abstract:

Actual evapotranspiration of watershed is an important part of hydrological circle and water balance,and it is significant to analyze the actual evapotranspiration of Poyang Lake watershed to research its water resources.In this paper,complementary relationship evapotranspiration model was selected to estimate the actual evapotranspiration of 9 meteorological stations from 1955 to 2001.For studying the seasonal variation of the watershed evapotranspiration,statistical method was adopted.The results show that the annual actual evapotranspiration presents singlepeaked pattern and its peak value occurs in July;the evapotranspiration in summer is larger than that in spring and autumn,and it is the smallest in winter.For analyzing the longterm trend of 9 stations Db3 function of wavelet method was selected,and the results indicate that the evapotranspiration in the area declines during the studying period. It turns to descend at about 1998,and the rate becomes very slow thereafter.After comparison among precipitation,potential evapotranspiration and meteorological elements (net solar radiation,temperature,vapor pressure difference and wind velocity) in Poyang Lake watershed during the same period,it is inferred that the change of actual evapotranspiration is a result of multiple factors,among which the net solar radiation and wind velocity are the main factors.

Key words: actual evapotranspiration/complementary relationship evapotranspiration model/trend/wavelet analysis/ Poyang Lake watershed