Quantifying Water Balance Components at a Permeable Pavement Site Using a Coupled Groundwater–Surface Water Model

Green infrastructure (GI) is being widely implemented in urban areas to capture and remove stormwater from the surface drainage system. Whereas most analyses have focused on diverted surface flow, here the authors demonstrate a method to quantify all components of a hydrologic budget at the site scale. The authors instrumented and applied mathematical modeling to a GI site consisting of a system of tree trenches and permeable pavement in Philadelphia, Pennsylvania. They utilized ParFlow.CLM version 743, a three-dimensional groundwater–surface water–land surface model, to quantify the water budget, including evapotranspiration, infiltration, and recharge to regional groundwater. They compared simulated and observed groundwater levels and analyzed the simulated monthly water balance for the site over 1 year. The authors found that snowmelt was an important source of recharge in the winter months of the 2016 simulation period. During the summer months when evapotranspiration exceeds precipitation, additional water captured by the GI contributing area enhances recharge to groundwater, altering water budget seasonality at the site scale. Simulation results indicate that the GI functioned as intended, converting runoff to recharge, with discharge to regional groundwater throughout the year.