Distribution Characteristics of Area Rainfall in the Three Gorges Reservoir for Recent 40 Years

Using the daily rainfall data in years of 1980-2016, the area rainfall is calculated by means of site average method, and the following conclusions are obtained. The annual area rainfall in the Three Gorges Reservoir showed great interannual fluctuation with a slow decline trend in the 37 a; The peak of monthly area rainfall appearsed in June in Chongqing to Wanzhou, while in July in Wanzhou to Yichang region; The heavy area rainfall mainly occurred in may to September. The total number of heavy area rainfall in Wanzhou to Yichang was signi ficantly higher than that in Chongqing to Wanzhou region, even in all rainfall levels; The extreme values of area rainfall generally appeared in June to July. The heavy area rainfall below 69.9 mm occurred generally in July, while that above 70 mm was in June. It is exactly the opposite between the 2 subbasins of Wanzhou to Yichang and Chongqing to Wanzhou. The area rainfall of 20 to 29.9 mm occurred 7~9 times, of 30 to 49.9 mm 5~7 times, of 50 to 69.9 mm 1~2 times per year in each subbasin. The area rainfall above 70 mm occured once per 2~5 years. The area rainfall above 50 mm was in low frequency but great infuences, and their synoptic mechanism should be investigated further in the future.