Determination of weighting factor and storage coefficient for channel routing in a hilly watershed

The weighting factor and storage coefficient were graphically determined for channel flow routing in a hilly sub-watershed of Ramganga river in Uttarakhand. These parameters were used to compute the outflow through the longest stream channel of the watershed using Muskingum method of channel flow routing. The effective rainfall from the isolated storm events in the watershed were transformed into the inflow hydrograph using the time-area-histogram method. The weighting factor and storage coefficient were found to be 0.175 and 2.268 hours, respectively. The simulated outflow hydrograph was compared with the observed outflow hydrograph for prediction purpose by visual inspection and using the statistical indices. The mean values of coefficient of efficiency and absolute relative error in computed peak runoff were found to be 0.939 and 3.878%, respectively.