Understanding and Managing Hydrologic Processes on Solar Farms: Field Investigation in Central Pennsylvania

As solar energy becomes an increasingly cheap source of renewable energy, major utility-scale ground solar panel installations, often called 'solar farms,' are rapidly growing. With these solar farms often covering hundreds of acres, there is potential for impacts on natural hydrologic processes, including runoff generation and erosion. Literature review shows there is still limited research in this area, and that best management practices to address these impacts are variable and not well understood. Thus, our work seeks to fill this gap by providing insights from field investigation on soil moisture, evapotranspiration, and runoff generation. For this purpose, two solar farms were selected in central Pennsylvania for scientific study that are representative of the complex terrain in our region (e.g., high or variable slopes, karst geology). These sites have been instrumented with clusters of soil moisture sensors that allow us to understand how incoming precipitation can be redistributed by solar panels. We are also performing periodic surveys of soil moisture across a wider area and evaluation of multiple soil characteristics. Sensors for runoff detection are located on the slope and around infiltration practices, and we also have pyranometers for monitoring solar radiation under panels. Preliminary data indicates redistribution of water relative to panels, with elevated soil moisture under the panels and at the dripline, but this varies based on soil characteristics and site geometry. There are periods of runoff generation near panel driplines, but runoff has not been detected in an infiltration basin at one site thus far. Thus, existing management practices may be adequate to manage redistribution of water. Ongoing research will continue to elucidate these patterns and implications for best management practices so that we can ensure that solar farms are developed in the most sustainable way possible.