A Complete Water Balance of a Constructed Stormwater Wetland

Constructed wetlands are often overlooked as a stormwater management system in the urban context. In comparison to alternatives (e.g., green roofs, bioretention, bioinfiltration), constructed wetlands have a much larger space requirement, which comes at a cost and can be challenging to allocate. The stormwater management function of constructed wetlands in urban settings has therefore not been extensively studied and understood. Constructed wetlands are well‐understood to provide services to humans and for creating more hospitable habitats to organisms, thus reducing fragmentation of their habitats and aiding in ecological protection and restoration. Ultimately, as hydrological systems, they demonstrate the potential to provide both stormwater and ecosystem services. To assess the stormwater management capabilities of a constructed wetland in Villanova, Pennsylvania, USA, a novel and comprehensive water budget model was developed. The constructed wetland of interest was retrofitted from an existing retention basin with the hypothesis that under a wetland configuration, the system could manage a comparable amount of incoming flow and provide more ecosystem services. The water budget model was aimed at assessing how water flows through the system during both wet (active rainfall) and dry conditions (baseflow between rainfall). Over 10 years of monitoring, the constructed wetland was found to manage 37% of incoming flow through percolation and evapotranspiration from a large receiving area. Additionally, the hydrological signature of the large receiving area mimics that of a less‐developed or less‐impervious area with the constructed wetland in place.