Seite - 215 - in Book of Full Papers - Symposium Hydro Engineering

between the main stream of the Yangtze River. The meteorological stations near the reservoir area (Wushan and Badong) are the representative stations near the reservoir area, and the meteorological stations far away from the reservoir area (Wuxi, Xingshan, Enshi and Jianshi) are the representative stations. The temperature monitoring number in the near and far reservoir areas is selected and compared with the difference between them. Through the analysis we can see that, The annual variation trend of annual average temperature in the near and far reservoir area is consistent, The annual mean temperature difference between the near and far reservoir areas increased after 2003. the difference is 0.8℃, the average annual temperature difference than 1976-2008 (0.5℃) increased by 0.3℃,It shows that the temperature near the reservoir area is slightly increased after water storage. time interval content Winter temperature difference Summer temperature difference After storage Temperature difference(Near and far reservoir area) 0.9℃ 0.4℃ Pre storage 0.5℃ 0.5℃ change Increase0.4℃ reduce0.1℃ Table 1: Comparison of temperature difference between the near and far reservoir area Further analysis showed that the summer warming in the near reservoir area was smaller than that in the far reservoir area after the impoundment, resulting in a decrease of the average temperature difference between the 0.1℃ in summer, indicating that the reservoir had a cooling effect on the waters near the area. In winter, near reservoir area is affected by reservoir, and the increasing range is slightly larger than that in far reservoir area. The average temperature difference between them increases by 0.4℃, indicating that the reservoir has "warming effect" near the water area. As the temperature difference has ruled out the impact of the climate background on the entire reservoir area, we can think that the change of mean temperature difference in near and far reservoir area is caused by local climate effect of reservoir, increasing temperature in winter and cooling in summer. 3.3. THE CHANGE OF PRECIPITATION NEAR THE RESERVOIR AREA IS NOT OBVIOUS COMPARED WITH THE FAR RESERVOIR AREA The comparison method of precipitation ratio in two regions( near and far reservoir area) is used. the effects of the removal of large scale changes and to a relatively stable ratio change, found near reservoir area and far reservoir precipitation ratio change trend is not obvious,The fluctuation of precipitation ratio in the years after 215