Spatial Arrangement of Stormwater Infiltration Affects Subsurface Storage and Baseflow

Abstract

Urban stormwater management is turning towards use of infiltration facilities, directing water that would have previously flowed overland into subsurface flow paths. Stormwater infiltration alters soil moisture, groundwater, and streamflow regimes, but it has been unclear how the spatial arrangement of infiltration-focused facilities affects catchment-scale water balances. This project used a physically based numerical model to investigate how spatial arrangements of infiltration facilities and subsurface media affects partitioning of water between unsaturated and saturated zones and baseflow duration and timing. More spatially distributed infiltration facilities, as compared to spatially clustered facilities, produced greater unsaturated zone storage, less saturated zone storage, and more total subsurface storage in scenarios where surface ponding was not severe. In silt, widespread surface ponding was observed. In sand, baseflow response to precipitation was delayed with clustered infiltration compared to distributed infiltration. These results can be used to guide decisions about how the spatial arrangement of stormwater infiltration facilities can affect urban catchment management goals, such as increasing plant available water and aquifer recharge or producing desired baseflow timing.