Evaluating the suitability of application of hydrological models in a mixed land use watershed

Abstract

This project compared the suitability of two hydrological models for the Flint River watershed (FRW). The Flint River flows into Wheeler Lake, which drains to the Tennessee River, a major source of water in northern Alabama. Two very widely used hydrological models, the Soil and Water Assessment Tool (SWAT) and the Storm Water Management Model (SWMM), were selected for this study. Both models were calibrated and validated for FRW. The calibration parameters were selected based on past research studies which used the same hydrologic models. The calibration parameters for SWMM and SWAT included basin, subbasin, soil, groundwater, channel and land use parameters. During calibration, both models were run at daily and monthly time steps, where simulated streamflows were compared with observed streamflows (years 2004-2013) and various statistical parameters were computed. While comparing simulated and observed monthly streamflows, SWAT showed better performance (r = 0.86-0.97, R2 = 0.73-0.93, bias = 12.2%, RMSE = 5.6 m3/s-8.9 m3/s) than SWMM (r = 0.70, R2 = 0.50, RMSE = 2 m3/s-56 m3/s, bias = 6.2%-8.4%). However, both models showed better performance for monthly streamflows than for daily streamflows. The evaluation determined that SWAT provides a more suitable model than SWMM when applied to a mixed land use watershed like FRW.