Study On Synergistic Flood Control Operation Of Reservoir Groups Considering Runoff Inconsistency

Water is one of the important natural resources for human survival,and it is also an irreplaceable strategic basic resource for maintaining the healthy and sustainable development of the national economy.Under the combined effects of human activities and climate change,runoff time series exhibit nonlinear,non-stationary,and multi-timescale changes,resulting in difficulties in mining measured data information using traditional "independent and identical distribution" hydrologic model,and the reliability of calculation results is questionable.The Yangtze River is the first largest river in China and the third largest river in the world.However,affected by frequent floods,the high-quality development of the Yangtze River Economic Belt is hindered.As an engineering measure that can directly regulate runoff,reservoirs are an effective way to address the challenges of flood control brought about by changing environments.Carrying out research on synergetic flood control operation of reservoir groups considering the inconsistency of runoff time series has great practical significance for establishing and improving the disaster prevention system and protecting the mother river of the Yangtze River.This paper focused on the new regulation pattern of the Yangtze River composed of Wudongde,Baihetan,Xiluodu,Xiangjiaba(abbreviated as Jinxia Four Reservoirs),and the Three Gorges Reservoir.By comprehensively applying theoretical methods such as statistics,hydrology,applied economics and systems science,this paper deeply studied the application of inconsistency time series in changing,environments,design flood calculation,synergetic flood control operation for reservoir groups and its operation effect evaluation,the main results achieved were as follows:(1)Time series division and evolution analysis.Aiming at the shortcomings of existing methods for identifying consistent changepoints(abbreviated as changepoint)in the application of multi basis mutation analysis intersection to divide the inconsistency runoff time series,a framework and criteria for identifying changepoint that combines the advantages of multiple mutation detection methods and Kolmogorov-Smirnov(K-S)test statistics were proposed.Comparing the accuracy of identifying changepoints of 95 commonly used mother wavelets,the feasibility of optimizing mother wavelet based on wavelet coefficient zero points(changepoints)was explored.The method overcomes the limitations of single mutation analysis,improves computational efficiency.and perfects wavelet transform theory.At the same time.it divides inconsistency time series into sub-series with good consistency.laying a foundation for fully mining measured data information in hydrologic models.(2)Inconsistency time-varying design flood calculation.Aiming at the problem that the annual maximum sampling method focuses on reflecting the distribution of runoff extreme values,and the peaks over threshold method cannot guarantee the uniqueness of sampling results,a lamination peaks over threshold method with high utilization rate of measured data,unique sampling results,and adaptive adjustment of thresholds was proposed by adjusting the sampling direction and threshold selection criteria.Combining with the Poisson model with time-varying parameters.a method for calculating inconsistency time-varying design flood hydrographs was presented.Compared with existing design floods,the design flood proposed in this paper takes into account the measured runoff characteristics such as time dependence,flood peak and volume relationship,and flood area composition,and can independently identify representative hydrograph to generate design value that conform to the interannual variation of runoff.Based on this,an inflow flood identification model was constructed to guide the decision-making of reservoir group operation schemes from the inflow flood magnitude and hydrograph.(3)Study on the synergetic flood control operation with complex hydraulic connections.In view of the phenomenon that the flood control operation scheme in the Yangtze River mostly adopts a short duration flood hydrograph of 1 to 5 days.ignoring the reservoir group storage and discharge conflicts,and the overall results are biased towards ideal,this paper combed the theories of "synchronous storage and discharge" and "asynchronous storage and discharge",defined the downstream flood control protection object demand based on the storage flow and storage and discharge space in one direction,and defined the storage and discharge demand of reservoir groups based on the priority and standby in two directions.Three operation models were constructed,namely,flood regulation routing simulation,storage and discharge sequence simulation,and multi-objective optimization of flood control and power generation.In addition,from the perspective of storage and discharge sequence.storage and discharge timing,and target operating water level,a synergetic flood control operation scheme for reservoir groups covering the entire process of flood storage before,during and at the end of flood season has been developed,to support the integration of the newly added Wudongde-Baihetan cascade reservoirs into the Yangtze River flood control system.(4)Risk-benefit evaluation indicators panel data extraction and mutual feedback response relationship quantification.The evaluation indicators for reservoir operation effectiveness in multi-scenario simulation are usually calculated using the average method,which tends to weaken risks and amplify benefits,and analyze the response relationship of mutual feedback by adjusting optimization objectives or their weights.which can easily lead to spurious regression and conclusions.This paper introduced the Conditional Value at Risk,which has been well applied in the field of economics.to extract daily and ten-day scale evaluation indicators panel data,and introduced a panel vector autoregression model to quantitatively analyze the mutual feedback response relationship between reservoirs and operation functions.Above models provide a feasible way to objectively evaluate the operation effect of reservoir groups,clarify the mutual feedback response of operation functions,predict the development trend of reservoir group interaction,and balance the risk-benefit of each party.