Stormwater Impacts of Solar Installations
Highlight 2 research projects that focus on potential stormwater impacts of large-scale solar installations in Virginia and central Pennsylvania.
Dr. Ryan Stewart presents:
Utility‑scale solar facilities are being constructed throughout Virginia, yet significant uncertainty remains about the volume and timing of stormwater runoff they produce. It is also unclear whether key design parameters for stormwater detention features are being applied appropriately. With support from the Virginia Department of Environmental Quality (VDEQ), we launched a six‑year study in 2023 to measure and evaluate stormwater generation from utility‑scale solar installations across the state. This presentation shares preliminary findings from the first 1–2 years of monitoring, focusing on three representative solar sites in Virginia.
Dr. Lauren McPhillips presents:
With “solar farms” there is potential for impacts on natural hydrologic processes, and a need to understand implications for design of appropriate management practices. We conducted field research on solar farms in central Pennsylvania that represent the complex terrain in our region (e.g., high slopes). Soil moisture data indicates redistribution of water relative to panels, with elevated soil moisture at the dripline, and drier soil under the panel. Soil moisture data indicate periods of saturation and runoff generation near panel driplines, but very limited saturation in the interspace between panel rows, indicating infiltration of runoff. Data from an infiltration basin and trench document the ability to adequately retain and infiltrate runoff. This hydrologic data has been used to calibrate models of solar farm hydrology, which help understand runoff changes from pre- to post-solar farm-development. This research collectively indicates that well-vegetated open space between panel rows plays a critical role in managing runoff. In some cases, structural stormwater management is necessary on solar farms, in order to prevent adverse impacts on runoff. Continued development of best practices will ensure that solar farms are developed with maximum benefit.