Variation trends of runoffs in the Middle Yellow River basin and its response to climate change

The Yellow River is shortage in water resources,and it's of significance to analyze variation of hydrological variables for sustainable development of water resources.According to the characters of geomorphology and distribution of key hydrometric stations,the middle reaches of the Yellow River is divided into three regions,which are the region from Hekouzhen to Longmen,the region from Longmen to Sanmenxia,and the region from Sanmenxia to Huayuankou.Historical variation trends of runoff in each region are tested with the Mann-Kendall method and the linear regression method.Based on the hypothetical climate scenario and the natural discharge simulation for each region,the responses of runoff to climate change are studied.And results indicate that there are a significant decline trends in the recorded runoff at each key hydrometric stations and the regional runoff.Annual runoff would decrease 3.7%~6.6% if air temperature rise 1℃,while runoff would decrease 17%~22% if precipitation increase by 10%.Thereby,runoff is rmre sensitive to change in precipitation than that to temperature change.