Abstract:

Based on the daily precipitation data of eight representative stations in the east of Sichuan Basin during 1961-2010,this paper analyzed the variation tendency of the annual and seasonal precipitation by using linear analysis and precipitation trend coefficient method.And this paper defined regional flooddrought indices with Zindex and studied the periodic rules on multitime scale by applying Mexican Hat wavelet transform method.The results indicated that annual precipitation had been lentamente declined in the area,but at the same time,the trends of seasonal precipitation was very different.The autumn precipitation was decreasing significantly,while there was an increasing trend in summer and winter.The flooddrought of four seasons had different annual and decadal time scale periodic variation characteristics,and different time scales had alternated on different cyclic rules.Approximate 6 years and 10 years periods in spring and autumn were found,and recently 6 years period was obvious.The summer had entered a waterlogging period on approximately 20 years scale period and the precipitation was not stable.Thus,high grade and serious flood disaster was easy to occur.And recently,autumn is in a approximately 10 years scale drought period and will turn to a partial flood period in the future