CLIMATE CHANGE AND MUTATION ANALYSIS IN WEIHE RIVER BASIN IN THE LAST 50 YEARS

Meteorological data from 1958—2008 in Weihe River were used to analyze time series trend of precipitation and temperature in Weihe River basin,by the Mann-Kendall and R/S method,Point mutations were then calculated.It was found that the average annual precipitation on Weihe River showed a rising trend from upstream to downstream.The annual precipitation decreased during the last 50 years,but with no statistical significance.The decreasing trend of precipitation was significant in spring and autumn;but a significant increase was seen in winter.Hurst index was found to be 0.49,showing a weak variation,future precipitation variation being insignificant.It was also found that the average annual temperature in the middle reaches were maximal in the Weihe basin.A marked upward trend was found by time series method,significant in spring,autumn,winter,but not significantly in summer.Viewed from the Hurst exponent,future annual average temperature was likely to continue to rise.Analysis of temperature and precipitation mutation revealed complex changes in precipitation,every 50 years showed a different degree of mutation,this being particularly significant for the 60's and 90's.Compared with complex precipitation change,temperature for each site mutation occurred only once in the 90s,and it was significantly warmer after temperature mutation.