Effects of Streamflow Routing Schemes on Water Quality with SWAT

The TMDL program has been implemented as a watershed management measure for the control of both point and nonpoint pollution sources. An accurate estimation of runoff is essential for the reliable estimation of pollutant loads and thus the development of appropriate pollutant control measures. The objectives of this study were to compare the performance of two different streamflow routing methods (the Muskingum method and the nonlinear storage method) for water quality simulation. SWAT2005 and its modified version SWAT-NSR, which adopt the respective streamflow routing schemes, were compared in terms of their water quantity and quality simulations. From the simulation results, the streamflow routing methods quite affected the peak flows and their attenuation, and subsequently reflected different water quality simulations with respect to sediments and nutrients. Accordingly, the estimated pollutant loads to surface waterbodies were also different depending on the routing scheme used.