nonlinear muskingum flood routing model with variable parameters

the muskingum method is the most widely used method of hydrologic routing with numerous applications throughout the world in which its popularity is because of its simple conceptual and ease of use. since the relation between the weighted-flow and the storage seems to be nonlinear, a constant exponent parameter is used to account for this nonlinearity. on the other hand, the three constantparameter model cannot address the variations of nonlinearity during routing period. in this paper, the nonlinear muskingum model with variable parameters was recommended and the modified honey bee optimization algorithm was successfully utilized to minimize the sum of squared (ssq) deviations between the observed and routed outflows. the proposed variable-parameter model reduced the ssq value more than 89 % comparing with the best constant-parameter muskingum model in the literature and more than 83 % related to the exponent variable parameter model.