Abstract:

 In recent years， there is an increasing temporal and spatial distribution change of  water  in most river basins due mainly to human activities and climate change These changes have resulted in a series of physical and chemical effects Therefore， runoff variation under the influence of climate change and human activities has become a hot topic at home and abroad As the biggest and most important reservoir in the upper Hanjiang Rivier， Ankang Reservoir is the water source of the Middle Route of the SouthtoNorth Water Diversion ProjectThe study on the runoff variation under the effect of its impoundment will have a great meaning for protecting water resources in the Hangjiang River In this paper，based on the hydrological data from 1970 to 2010， the multitemporal scale variation （interannual and annual changes） in runoff of the downstream of Ankang Reservoir was analyzed Mannkendall trend analysis was adopted to identify the trend of runoff and abrupt change Then the impoundment time of Ankang Reservoir was used for the boundary of analysis In order to explore the influence degree of the operation of Ankang Reservoir on its runoff of downstream， double mass curve for annual rainfall stream flow was used to eliminate the influence of precipitation and a part of human disturbance from upstream Under application of this method， results would provide an important theoretical and quantitative reference in understanding the influence of the instruction of hydraulic engineering and the sustainable use of regional water resources The research showed that the annual runoff of the Ankang station was mainly contributed by those occurring from July to October with a proportion of 6126%And in general speaking， the streamflow had a decreasing trend during the last 4 decades According to the MannKendall trend test，sudden changes from high flow to low water in annual runoff of the Ankang station was found in 1990 which was exactly the year of the impoundment of Ankang Reservoir Contrasting the runoff data before and after the operation of Ankang Reservoir，we could see that the fluctuation of its interannual and annual changes both became smaller However， the results of double mass analysis showed that the runoff decrease in Ankang station could mainly be attributed to the impoundment and operation of Ankang Reservoir，and its contribution was as high as 838%Although in this paper，we did not take the effects of human economic activities and the evaporation into account， the result could still state the fact that the water conservancy project would bring a great impact on the runoff of downstream，and should not to be ignored