Study And Application Of Flood Forecast Method On Longwangshan Multi-reservoir

As hydro-junction projects with the flow-regulation function, reservoirs play more and more prominent parts by clipping peak, alternating peak and storing flood water in flood-control of rivers and lakes, which is an effective way to reduce losses of flood disasters. Associated with the scientific research task of LongWangshan Multi-Reservoir Flood Regulation System of the HFDH (Office of Huai'an municipal Flood control and Drought relief Headquarters) in Jiangsu Province, this paper has studied the methods of multi-reservoir flood forecast. The main work and the conclusions of this paper include the followings:The paper summarizes not only the theories of runoff generation and routing generation, but also the watershed hydrologic model, as well as its current situation and progress at home and abroad. What is more, the study introduces the function of IGD (Inverse Gauss Distribution) and linear moment method that can estimate the parameters of the function. Through the comparisons between the IGD (Inverse Gauss Distribution) and standard normal distribution in the function, between the IGD (Inverse Gauss Distribution) and convection-diffusion equation in the expression, it is proved that the IGD (Inverse Gauss Distribution) has the characteristics of excellent capability of statistics, a few parameters, good flexibility, and clear physical meanings, which is fit for the channel flood routing.According to the physical geography condition of the watershed in LongWangshan multi-reservoir, the model of Xin'anjiang three water sources flow is chosen for the runoff generation model of this watershed. The watershed flow concentration is separated into surface part, subsurface part and groundwater part. Considered from the time and space distribution of rainfall in the watershed, the process of the surface routing applies the method of IUH (Instantaneous Unit Hydrograph) of variable rainfall intensity, which is described by the nonlinear reservoir regulating model, while the process of the groundwater routing takes the line reservoir regulating model to calculate.Combined the IGD (Inverse Gauss Distribution) channel routing generation model ofIUH (Instantaneous Unit Hydrograph) with the model of watershed rainfall runoff-forecast, the multi-reservoir flood forecast model is established. The paper illustrates the model structure, set up the object functions of parameters in each child-model; introduces two methods of optimizing model parameters and their steps: the step-accelerated method and the Rosenbrock methodThe researched runoff generation model and routing generation model are applied into the rainfall flood forecast of LongWangshan multi-reservoir. The results show that the determinacy coefficients of runoff generation and routing generation are higher in big or middle floods; besides, the simulated results are satisfactory; while the results of small floods still need to improve further. The reasons for that are as follows: on the one hand, the middle or small-scale water storage projects are obvious to the interception effect on small floods in the watershed; on the other hand, each reservoir is the plain-type reservoir, and backstepping reservoir-inflow according to the water level changes can bring greater deviations, which are unfavorable to the optimization of model parameters.On this basis, using the least squares method calculated from alterable oblivious factor, the paper has done real-time correction of the routing results of forecast model, therefore, the coefficients of efficiency are improved further.