Abstract: The temporal and spatial distribution characteristics of actual evapotranspiration in Jialing River Basin was investigated using generalized complementary correlation model based on daily observation data of 13 meteorological stations from 1961 to 1979 and annual runoff data in the basin. The correlation between actual evapotranspiration and meteorological factors was examined according to Pearson’s correlation coefficient. Results demonstrated that: 1) the generalized complementary model is applicable to the Jialing River Basin with high accuracy, an average absolute error 6.79 mm and an average relative error merely 1.42 %. 2) In spatial scale, actual evapotranspiration was higher in the north and east of the basin, whereas lower in the south and west with the maximum reaching 649.86 mm found in Diebu County of Gansu Province, and the minimum 188.26 mm in Songpan County of Sichuan Province. A slow downward trend from 1961 to 2000 at a rate of -5.3 mm/10 a was found in the temporal distribution. 3) The correlation coefficient analysis showed that the decline of actual evapotranspiration was closely related to the decreasing supply of sunshine hours and daily range that gave rise to the reduction of radiation-energy item. On the contrary, the increase of daily minimum temperature, daily maximum temperature and actual vapor pressure and the decrease of 2 m wind speed contributing to the aerodynamics item decreasing eased the reduction rate of actual evapotranspiration. The generalized complementary correlation model was applied to the E_Ta of Jialing River Basin for the first time, with favorable estimation accuracy. The research findings offer scientific basis for the evaluation, planning, and sustainable development of water resources.

Key words: generalized complementarity correlation, actual evapotranspiration, temporal and spatial distribution, meteorological factor, coefficient of correlation, Jialing River Basin