Impact of Solar Farms on Groundwater Recharge

The decreasing cost of photovoltaic panels has led to a proliferation of solar farms in the upper Midwest where they had previously not been economically viable. However, the hydrologic impacts of these facilities are unknown in humid temperate regions. We hypothesize that shading from photovoltaic panels decreases evapotranspiration and panel geometry redistributes precipitation at driplines creating wetter soil regimes and focused infiltration, respectively. These hydrologic impacts will cascade through other components of the water budget, resulting in particularly strong increases in groundwater recharge — preliminary modeling indicates percent change may exceed 100%. In this project we will quantify changes to hydrologic process that impact groundwater recharge using complementary field and modeling approaches. Our first objective will be to create an ecohydrologic observatory in order to directly measure the changes in soil moisture and groundwater regimes that result at the Kegonsa Solar and Agricultural Research Campus. Our second objective will be to quantify the effects of solar farm installation on groundwater recharge using the water table fluctuation method at our experimental solar farm and an adjacent control site. Our third objective will be to predict the impact of solar farms on hydrologic fluxes across a range of soil and climatic conditions representing the Upper Midwest using numerical simulation of variably saturated groundwater flow. This work will help provide a scientific basis for evaluating the hydrologic co-benefits and/or unintended consequences of solar farm installation. The impact of this work will be enhanced by sharing results through multiple channels including websites and social media, presentations at the Annual Meeting of the Wisconsin Section of the American Water Resources Association, peer-reviewed journal publications, and a workshop with stakeholders from state regulatory agencies, solar farm developers, non-profits working at the food-water-energy-environmental nexus, and other researchers.