Minimizing environmental impacts of solar farms: a review of current science on landscape hydrology and guidance on stormwater management

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 the potential for impacts on natural hydrologic processes, including runoff generation and erosion. Here we review the current state of scientific research on the hydrology and water quality impacts of solar farms, as well as management recommendations for minimizing any impacts. The limited field measurements indicate the redistribution of soil moisture around solar farms, but the net impacts on runoff and erosion are less clear. Research focused on coupling solar farms with agriculture as ‘agrivoltaics’ demonstrates reduced evaporative water losses and associated crop stress, particularly in more arid regions. With regards to land and the stormwater management associated with solar farms, most US states currently do not have solar farm-specific recommendations and instead defer to standard stormwater management permits and guidance. In states with solar farm-specific guidance, typical recommendations include minimizing construction-related compaction, ensuring a high cover of perennial vegetation with minimal maintenance, and designing with pervious space between solar panel rows to promote infiltration of any runoff; in some cases, structural stormwater management like infiltration basins may be required. In general, solar farms can be designed to minimize the impact on landscape ecohydrological processes, but more research is needed to determine whether current recommendations are adequate. In particular, there is a need for more field research on less ideal sites such as those with higher slopes.