Recent Changes of Runoff and Their Causes in Upper Yangtze River Basin

The Yangtze River from the source regions to the Yichang station is called as the upper Yangtze River. Firstly, the runoff changes at sixteen main control stations in the upper reaches of Yangtze River Basin were analyzed. The results show that except in the Jinsha River Basin, the runoff in the other basin decreased more or less. Among them, the runoff in the Minjiang River, Hengjiang River, Tuojiang River and Jialing River decreased significantly. The. runoff at the Cuntan station increased before 1968, but decreased significantly after 1993. A large scale distributed monthly water balance model was developed and applied in the upper Yangtze River. The model was used to evaluate the impacts of climate change and human activities on the changes of runoff generation in the upper Yangtze River Basin and to explore the causes of runoff change. The runoff at the Cuntan station of Yangtze River decreased significantly since 1993 and climate change was the main factor that contributed 71. 43% of the runoff change. Meanwhile, it was needed to pay attention that the runoff in the Minjiang River and haling River Basin decreased obviously and the contribution of human activities to runoff change reaches to about 50%. It was related to the intense human activities in those areas. Human activities will most probably play a dominant role in influencing the discharge of the Minjiang River and Jialing River Basin.