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

This project tried to evaluate the use of two hydrological models for the Flint River watershed (FRW). FRW is a major tributary of Wheeler Lake watershed (WLW) that drains to Tennessee River, a major source of water supply in northern Alabama. Two very widely used hydrological models namely Soil and Water Assessment Tool (SWAT) and Storm Water Management Model (SWMM) were selected for this study where both models were calibrated and validated for the FRW. The calibration parameters were selected based on past research studies which used same hydrologic models in their study. 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 to 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 =5.6-8.9 cms) as compared to SWMM (r = 0.70, R²=0.50, RMSE= 2 cms to 56 cms, Bias=6.2%-8.4%). However, both models showed better performance for monthly streamflows than daily streamflows. This evaluation resulted in a better suitability of SWAT model as compared to SWMM model when applied to a mixed land use watershed like FRW.