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STORMWATER TREATMENT: WET/DRY PONDS VS. CONSTRUCTED WETLANDS
Citation:
Nietch**, C., M Borst*, AND M O'Shea*. STORMWATER TREATMENT: WET/DRY PONDS VS. CONSTRUCTED WETLANDS. Presented at ASCE Urban Water Resources Res Council/Engineering Found Conf, Snowmass, CO, 8/19-24/2001.
Description:
The presence of aquatic macrophytes in structural stormwater BMPs complicates the mechanistic interaction between biogeochemistry and hydraulic efficiency that dictates the performance of these management strategies. This project relies on extant data and controlled experiments to quantify the relative effectiveness for stressor reduction in retention/detention-type structures. Based on their popularity and availabiolity of existing data, we focus on a constructed wtland-type design compared with a wet/dry pond-type design. Effectiveness is assessed by the relative retention of sediment, nitrogen, and phosphorus during controlled experiments in BMP mesocosms under different physical design scenarios and simulated rain events. The goal is to develop a comprehensive mechanistic model of sediment and nutrient dynamics in these small-scale (1-20 acre runoff area) event-based treatment structures. Data from larger-scale treatment wetlands coupled with macrophyte production and decomposition studies suggest that the presence of wetland vegetation can enhance hydraulic efficiency, which increases sedimentation and nutrient retention, but, also, may result in episodic nutrient mobilization, the effect of which is species-specific. Mesocosm experiments are designed to correlate hydraulic efficiency with sediment and nutrient dynamics to test the hypothesis that reed-based, vegetated systems would be most effective at stressor reduction in stormwater treatment structures.