Distributed Modeling Of Actual Evapotranspiration In Watershed Based On Generalized Complementary Relationship

Evapotranspiration is an important part of maintaining the balance of land surface water and the balance of land surface capacity. The accurate estimation of the actual evapotranspiration can help to improve the utilization of water resources and relieve the tension of the ecological environment. In order to improve the accuracy of estimating the actual evapotranspiration in China, the latest generalized complementary theory is used to estimate the actual evapotranspiration of the basin by meteorological and hydrological data. In this paper, the parameters of the model are calculated by using the actual evapotranspiration of the two basins in china. Then,the distributed simulation results of each component in the model are coupled with the model, and the distributed simulation of the actual evapotranspiration is realized.Based on the distributed simulation, the temporal and spatial characteristics of the actual evapotranspiration were analyzed, and the time trend of the actual evapotranspiration was analyzed. The main achievements were as follows:(1) By analyzing the applicability of the generalized complementary correlation theory model and combining with the actual situation in China, we choose c=2 into the polynomial to calculate the actual evapotranspiration, and get the formula to estimate the actual evapotranspiration. The average absolute error of the 80 watersheds was 11.481 mm and the average relative error was 3%, with the actual evapotranspiration obtained by the water balance equation. Except for the relative errors of some basins in the southwest and northwest part of the basin, especially in the northwest of China, the relative errors of the 10% basins are controlled within 5%.(2) We find the distribution of ? in the spatial distribution: First, the closer to the ocean, the greater the ?, the farther away from the ocean, the smaller the ?.Secondly, the higher the altitude, the greater the effect of the terrain barrier, the corresponding decrease of the water vapor content, so the a increases with the elevation. Finally, ? increases with latitude, but the correlation of ? with latitude is only 0.29, which may be due to the fact that the distance from the ocean has a great effect on a,which may have an effect over latitude changes.(3) It is found that the actual evapotranspiration of China is decreasing from southeast to northwest. From the latitude, the actual evapotranspiration decreases with the increase of the latitude, and the actual evapotranspiration is far from the ocean. Statistical analysis was carried out according to the dry and wet climatic regionalization,two levels of water resources and the provincial administrative divisions.(4) Through the analysis, it is found that the actual evapotranspiration in China has a slight upward trend with the increase of time. The interannual variability of their actual evapotranspiration was analyzed by one-by-two watersheds. It was found that there were 48, accounting for the majority of the basin with the increase of time. Analysis of Person correlation coefficient to obtain the actual evapotranspiration by Spass, found that the decrease of maximum temperature, minimum temperature, average temperature increase, the actual water vapor pressure and diurnal temperature, average wind speed of 2 m pressure is mainly caused by the actual evapotranspiration increased with time. The decrease of sunshine percentage to some extent slows down the rising trend of actual evapotranspiration.