Evaluating hydrology and water quality for the Big Black River Watershed in Mississippi was accomplished by using the Better Assessment Science Integrating Point and Nonpoint Source (BASINS 4.5), Loading Simulation Program in C++ (LSPC), and Water Quality Analysis Simulation Program (WASP) models. The watershed model calibration was originally accomplished by using historical data collected from U.S. Geological Survey (USGS). The watershed model was calibrated using data from 2000 through 2018 in order to quantify stream flow and point source discharges under a variety of hydrologic conditions. The model predicted response of hydrology was consistent with the observed data range. The hydrology part of the model was integrated for water quality simulation. Nutrients levels in the river systems were closely examined, without the impacts from point source discharges. The calibrated model could be used as a planning tool to assess the water quality and to calculate total maximum daily load (TMDL) in the nation’s watersheds.