Head-water area of the Yangtze River is the start site of Yangtze river hydrologic cycle.The water volume,water quality change and human unreasonable activities will influence water environment and spread broad downstream regions.Under the influence of climate change and human activities,the runoff in head-water area didn't happen significant trend changes.According to the monthly runoff,precipitation,temperature and evaporation data in the Yangtze River head-water area from 1956 to 2005,using the principal...