Controlling Reservoir Operation And Impact Study In Hanjiang Basin

With the fast developments of economy and society,the strategic position of water resources is becoming more and more important.Basin controlling reservoirs,as an important engineering measure of regulating river flow and allocating water resources optimally,play an important role in flood control and drought relief,reservoir regulation and eco-environmental protection.In this study,the rainfall-runoff characteristics and hydro-meteorological prediction availability in the Hanjiang River were analized.The index of Danjiangkou reservoir dynamic control water level during flood season which takes flood control and water supply demands into account;the effect of controlling reservoir operations in Hanjiang River and upstream of Yangtze River on downstream flow regimes were studied.The main research achievements were summarized as following:(1)The physical causes of factors inducing floods in Han River Basin were introduced.The physical causes of flood-causing factors(climate and meteorology),flood area composition,flood season staging,flood encountering laws and reservoir compensation regulation in the middle and lower Han River were studied.Results indicate that there is a change in climatic and meteorological features when rainstorm occurred in Han River.Historical major floods have not occurred after September 15 and the reservoir operation could be turned into refill storage period.(2)The forecast methods and systems for Han River Basin were established and the accuracy of hydro-meteorological forecasts was assessed comprehensively;Results show that hydro-meteorological forecasts of Han River is precise,which can provide technical support for reservoir operation.By utilizing the existing forecast schemes,methods and software systems,the occurrence of floods like "1983.10" can be prevented at earlier times,reducing the mid-and downstream flood hazards.(3)Based on the observed data,the optimal flood-dispatching model was utilized in the reservoir operation simulation of historical typical floods.Classification of reservoir dispatching rules for different periods and flood events was also proposed,whilst the control index of Danjiangkou reservoir water level for different stages was introduced.By optimal flood dispatching,flood control risks of historical floods can be reduced effectively.(4)Dynamic control indices of Danjiangkou reservoir water level during flood season were derived,which can satisfy water demand of the mid-route of South-to-North Water Transfer Project and flood control in the middle and lower Hanjiang River.Then it was further applied in the fall flood scheme of the year 2017.Reservoir water-supply guaranteed rate and hydropower generation benefit can increase about 10%and 5%,respectively.(5)The indicators of hydrologic alteration(IHA),range of variability approach(RVA)methods were used to discuss the effect of controlled reservoirs operation on flow regimes of the middle and lower Hanjiang River.Results show that the Ankang and Dangjiangkou reservoirs have moderate effect on hydrological regimes.A new typical year assessment method was proposed to analyze the effect of control reservoirs’ operations in upper Yangtze River on the hydrological regimes at Yichang station.Results indicate that the hydrologic regimes have been changed moderately after 1999,but nearly severely after 2008 at the Yichang hydrological station.