Estimation of Transient Storage Parameters for Simulation of Pollution Transport in the Gravel Bed Rivers

This research was conducted to test how to exchange mass between the main channel and the stagnant areas of the stream. The transient storage differential equations were selected as the governing equations for simulation of advection- diffusion of pollution in river flow. The experiments were conducted in a gravel bed flume, with length, width and depth of 12, 1.2 and 0.8m, respectively. Three longitudinal slopes of 0.001, 0.004 and 0.007 and three discharges of 7.5, 11.5 and 15.5 (l/s) were selected for the experiments. The numerical model of OTIS-P was used to estimate the four parameters of the transient storage model. Then the observed breakthrough curves were regenerated at the same locations of measured points. Goodness of fit was estimated with the root mean square error (RMSE), Nash and Sutcliffe model efficiency coefficient (NS) and the mean absolute error (MAE). The comparisons revealed that the OTIS-P model (with RMSE between 0.031- 0.118 and Nash- Sutcliffe between 0.48-0.9) could be employed successfully for estimation transient storage parameters. Finally, the reliability of the estimated parameters of the transient storage model was confirmed by the non-dimensional Dam-kohler number.