Abstract

Trees planted around rain gardens present an opportunity to remediate stormwater pollutants, diversify habitat, and cool impervious surfaces in municipalities. In semi-arid regions where water resources are scarce however, it is unclear whether stormwater captured in these basins is sufficient to sustain urban trees without supplemental irrigation. This seven-year study examined whether soil moisture could be significantly improved at parking lot curb cuts with rain gardens compared to curb cuts without rain gardens. Hourly volumetric water content (VWC) was measured at 6-inch depth intervals down to 30 inches in a soil profile predominantly composed of clay loam textures. Results indicate that average VWC in rain garden soils was significantly higher at four out of five measured depths and when averaged across the full 30-inch profile compared to sites without rain gardens. Rain gardens also regularly replenished and retained soil moisture above an irrigation threshold across seasons and during periods of drought.

TLDR: Water harvesting techniques like rain gardens and curb cuts are awesome anywhere