Analysis of the change trend of agriculture irrigation quota in Nujiang dry-arid valley

Based on the monthly climate records of Fugong, Lujiangba, and mengding stations in the period from 1960 to 2000, as well as crop pattern and cultivate data in 2000, Mann-Kendall test and the Rescaled Range Analysis R/S) method was adopted, to research the turning changes trend of dry and wet index and agriculture irrigation quota in Nujiang dry-arid valley in recent 40 years. The result shows that temperature decreases, precipitation increases, ET0 fluctuation change, and more humidity in Nujiang valley. Furthermore, paddy irrigation quota and total agriculture irrigation quota in most area decreases, except paddy irrigation in Lujiangba. The turn point of dry and wet index in Nujiang basin was present to the beginning of 1970’s～1990’s, but evapotranspiration, paddy irrigation quota, and total agriculture irrigation quota does not show the turn point. The farther research discovered the evaporation paradox phenomenon at Fugong and Lujiangba stations. All of those reveal the complicated changes of climatic and agriculture irrigation quota in Nujiang valley, due to geographical and environmental influence in the Longitudinal Range Gorge Region of southwest China.