Study on Actual Evaporation Changes in Area nearby Three Gorges in the Period from 1958 to 2008

This article is based on the daily weather data during the period from January 1st 1958 to December 31st 2008 from 36 weather stations nearby Three Gorges, and gives analysis to change trend and spatial distribution change conditions of yearly average and seasonal actual evaporation in areas nearby Three Gorges before and after water storage in 2003 through MK test methods and rotated empirical orthogonal function (REOF). Study shows that: After water storage in Three Gorges reservoir in 2003, the actual evaporation in summer nearby Three Gorges area was in downward trend, particularly significant in the north part, while the actual evaporation in Spring, Autumn and Winter and annual actual evaporation in south and north parts were in obvious upward trend; Before and after dam construction, the high load sensitive area in Spring moved from north area to south area, and the central lower load value in Summer reduced from -0.35 to -0.55, the actual evaporation declined, and the high and low load values in Autumn were in spatial distribution of positive value reverse change from southwest to northeast part, and the actual evaporation is in obvious reverse change, the low and high load areas before dam construction in Winter were in rather small scope, and the change trends of evaporation in south and north parts were not obvious. The study in this article shows only observation analysis results within 5 years to date from water storage in Three Gorges Reservoir, the change of actual evaporation before and after water storage still requires long time of observation analysis statistics, and the influence on actual evaporation nearby Three Gorges needs verification with more study methods.