Reverse Routing of Flood Hydrographs Using Level Pool Routing

In level pool routing, which is the simplest hydrological routing method, the downstream discharge may be expressed explicitly in terms of the inflow and the channel or reservoir characteristics. The level pool routing equation can also be used to estimate the inflow hydrograph given the outflow hydrograph and the water level in the reservoir. Unfortunately, use of the traditional level pool routing method, which is based on the implicit finite difference scheme, for reverse routing has been unsuccessful, despite the simplicity of the problem. If a simple explicit centered differencing scheme is used instead for simulating the inflow hydrograph, the problems associated with traditional schemes, which require the application of filtering techniques, are bypassed. This is demonstrated using a realistic hypothetical example and a case study. The explicit scheme results are comparable in accuracy with results from the implicit scheme without resorting to the use of filtering techniques. The simple explicit scheme produces a direct solution to the problem and should be the preferred method for both level pool and reverse level pool routing.