Modeling of a Surface Flow Constructed Wetland Using the HEC-RAS and QUAL2K Models: a Comparative Analysis

To assess the performance and the impact of nutrient discharges of the wetland on the receiving river, the Hydrologic Engineering Centers River Analysis System (HEC-RAS) and the River and Stream Water Quality (QUAL2K) models are examined in this study to evaluate a constructed wetland in the City of Edmonton in Canada. According to the simulation results from the HEC-RAS model and the QUAL2K model, the removal efficiencies of total nitrogen (TN) by the wetland are 25.64% and 13.59%, respectively. For the total phosphorus (TP), the removal efficiencies are similar to the simulation results between the HEC-RAS model and the QUAL2K model, which are 50.00% and 50.91%, respectively. The water quality simulation results from the HEC-RAS model of the wetland and QUAL2K model are both acceptable compared to the on-site field data. With the analysis of the two modeling systems and comparison between their water quality simulation results, the HEC-RAS model gives better performance than the QUAL2K model for this field case. Subsequently, the validated and customized HEC-RAS model is applied for analyzing and predicting the wetland performance, water quality parameter changes and the risks of the wetland effluents on the receiving river water under wetland design scenarios.