Agriculture irrigation water requirements change and R/S analysis of Jinshajiang dry-arid valley in recent 40 years

Based on the monthly climate records of Yuanmou,Binchan,Dongchuan,Xiangyun,Chuxiong,and Kunming stations in the period 1960-2000,as well as crop pattern and cultivate data in 2000,the Mann-Kendall trend and the Rescaled Range Analysis(abbr.R/S)method are adopted to research the tendency in aridity-humidity and irrigation water requirements in Jinshajiang dryarid valley in the last 40 years. The results show that the precipitation and the temperature decrease,and sunshine hours increase in the valley. But the temperature increases in the branch upstream of Longchuanjiang,Yupaojiang, Puduhe,etc,thus,results in ET₀ decreases remarkable in Jinshajiang basin. Furthermore,the aridity-humidity index,paddy irrigation quota and total agriculture irrigation quota also decreases. The turn point of climate factors,ET₀,aridity-humidity index,paddy irrigation quota and total agriculture irrigation quota in Jinshajiang valley are focused the late 1970s-1980s and the late 1980s the early 1990s,and Binchuan station which occurs minimum precipitation is most sensitivity to climates change.