Runoff Changes in the Upper Reaches of the Yangtze River

The changes of monthly runoff at the five main control stations in the upper reaches of the Yangtze River were ana- lyzed including Pingshan station of the Jinsha River,Gaochang station of the Minjiang River,Beibei station of the Jialing River, Cuntan station of the upper trunk river and Wulong station of the Wujiang River.It was found that the runoff at Gaochang and Beibei station decreased obviously and the runoff at Cuntan station decreased faintly.And the ratio of runoff from September to November decreased obviously as for the changes of inner distribution.Finally it was concluded that the decrease of the runoff at Cuntan station was caused by the decreases in precipitations in the Minjiang River and the Jialing River basin and the influences of human activities,