Operation of the non-linear Muskingum model in the prediction of the pollution breakthrough curves through the river reaches

The Muskingum model in both types of the linear and non-linear is one the most common models in the flood routing through the river reaches. Because of the similarity between the shape of the flood hydrograph and pollution breakthrough curves, it is tried to examine the applicability of the non-linear Muskingum model in the prediction of the contaminant concentration in downstream of the river reaches. The field data series of the MONOCACY and ANTIETAM Creek Rivers which were gathered by USGS have been used. During the tests, Rhodamine were used and the concentration pollute graphs were acquired in the four and eight cross sections of the mentioned rivers, respectively. The triple sets of the model parameters have been extracted in each reach, then the BC curves have been simulated in each position using them. It is observed that this model can rebuild the dimensions of the exit BC curve properly but, it also has some limitations in the modeling of the convection term of the pollution using average flow velocity. For its solution, the extracted BC curves have been transported along the time axis with magnitude of L/u in which L is reach length and u is the average flow velocity. Also, for better understanding of the effects of the model parameters in the simulated concentrations, the sensitivity analysis have been performed and it is found that the parameters of the m, k and x are the most to less effective parameters in the concentration calculation, respectively.