Electronic Thesis and Dissertation Repository


Master of Engineering Science


Civil and Environmental Engineering


Yanful,Ernest K.

2nd Supervisor




High nutrient concentrations in surface water have been a serious concern that impacts water quality and ecology. High Phosphorus levels in Medway Creek indicate the presence of a pollution source in the watershed that needs to be identified and quantified. To investigate this issue, the Soil and Water Assessment Tool (SWAT) program has been used in this study with the Geographic Information System (GIS) to model the Medway Creek watershed and assess stream flow and nutrient flux. In this research, the SWAT model has been built, calibrated, and validated using two independent observed data sets to evaluate the SWAT efficiency on monthly and daily simulations. The model has been tested for monthly simulations for the period of 1989 to 1999 and daily for the period 2014 to 2017 to simulate different water resource parameters in the Medway Creek watershed with a focus on stream flow and phosphorus. Discharge and nutrient components are quantified at sub-basin level with monthly and daily time intervals. SWAT-CUP software was incorporated into study by using SUFI-2, an optimization algorithm, to optimize the model parameters and examine the model uncertainty. The model was calibrated over the period of 1989 to 1999 and daily validated for the duration of 2016 to the present. The results show an excellent agreement between the calibrated results and measured data in monthly intervals. and NSE of 0.85 and 0.65 were achieved for the discharge calibration period and the model captured 92% of observed data, Whereas and NSE for TP calibration was 0.67 for both, with 80% observed data captured in the calibration period. For daily simulations, SWAT successfully generated satisfactory results with low performance compared to the monthly simulations .Moreover, the calibrated and a validated model used to estimate the future stream flow and TP in Medway Creek using different climate scenarios .The lack of high-frequency surface water monitoring data was the main obstacle during calibration. During the rapid alteration of the land use in the watershed, the developed model is useful for decision makers to assess future impacts and take actions accordingly.