The Use of SWMM for Wetland Hydrological Analysis

Dequan Zhou, Charles Gyening and Rahul Narula, Hatch Ltd., ON, Canada


There is a need for hydrological analysis for riverine wetlands. As the name implies, a wetland is located on the floodplain area of a river which is periodically flooded when extreme storms occur in the watershed. After floods, the wetland retains a permanent water level or keeps saturated conditions over a period of time. The wetland may be dry during periods of extreme drought. The hydrological conditions of wetlands have significant impacts to the biological and ecological systems in the wetland. Hence, any disturbance to the natural hydrological conditions could lead to unrecoverable consequences.

When modeling the hydrological conditions of a wetland, it is important to simulate both the baseflows and peak flows. An EPA SWMM model was developed for a wetland considered in this study. The baseflow component was modeled by the groundwater module of EPA SWMM. Calibration of the groundwater component of the model is the key step in correctly simulating the baseflow behavior of the river flow processes. The baseflow pattern in the river determines the groundwater boundary conditions of the wetland and hence has significant impacts to the water table variations in the wetland area. Baseflow pattern in the river also plays a key role in analyzing the frequency and duration of the flood flows within the wetland area.

This paper focuses on the following aspects: 1) identification of key parameters governing the performance of baseflow pattern; 2) the sensitivity of these key parameters; 3) evaluation of simulation results.

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