Abstract:

Based on annual precipitation observed data of the 79 county and city weather stations of the part correspondence over Poyang Lake basin in Jiangxi Province during 1960~2006,method of linear regression was used to study separately three essential factor change tendencies of annual precipitation,number of rain days and number of heavy rain days and so on in five major basins.Mann method has been carried on the significance test of change tendency.Ratio of departure and meansquare deviation which achieves 15 and 20 is as climatic anomalies test rating.Abnormity inspection to various time series of various basins had been carried out.Using the MannKendall Method to carry on the mutation test to various time series,results are summarized as below：（1）Annual precipitation change tendency of various basins is consistent.The correlation between annual precipitation and annual rainstorm day number is close.In Rao River basin where the precipitation intensity is larger than others there are more heavy precipitation events.Precipitation temporal distribution is relatively even in middle reaches basin of Ganjiang River,where strong precipitation events are fewer.（2）In various basins,time series of annual precipitation and rainstorm day number all display undulation escalation trend.Since 90s exceptionally more probabilities of rainstorm day number have been obvious.（3）Number of annual precipitation day showed undulatory increase before the middle of the 1980s and undulatory decline after the middle of the 1980s.Since 2002 trend of number of rain days has been obviously decreased in all river basins.（4）In various basins,annual precipitation,the precipitation day number and the rainstorm day number have not appeared trendy mutation.（5）Imbalance of annual precipitation temporal distribution is aggravating in Poyang Lake basin in recent 50 years, which leads dry and waterlogged disaster risk increasing.

Key words: five major river systems of Poyang Lake, annual precipitation, number of rain days, number of heavy rain days〖QS〗；change trend