Walnut Run drains a highly urbanized 5.8 sq km watershed in State College Borough in central Pennsylvania. The stream is fed by urban stormwater, as well as groundwater springs with relatively high nitrogen concentrations. A floodplain wetland constructed in 2005 diverts a portion of the stream’s flow for treatment, but the performance of this wetland has never been evaluated. Here we present results of field monitoring characterizing hydrological and water quality dynamics; specifically we evaluate nutrient and sediment removal in the wetland, and also quantify the impact on the stream. Initial results indicate that the wetland provides removal of nitrogen during baseflow periods when the stream’s flow is dominated by high-nutrient-containing groundwater contributions and residence times in the wetland are longer. Phosphorus and sediment concentrations and loads are highest during storm events when urban runoff dominates, and the wetland appears to provide limited ability to treat these pollutants given the high flow rates. This research demonstrates the need to understand the sources and dynamics of nutrients and sediment in order to target effective treatment strategies, and will be used to inform future manipulation of inflows to the wetland to attempt to increase overall nutrient and sediment removal rates.

Evaluating Water Quality Performance of a Constructed Floodplain Wetland in an Urban Central Pennsylvania Watershed

Created in 1999, the Environmental & Water Resources Institute (EWRI) is the recognized leader within ASCE for the integration of technical expertise and public policy in the planning, design, construction, and operation of environmentally sound and sustainable infrastructure impacting air, land and water resources.

[Paper Proceedings](https://doi.org/10.1061/9780784483466)