A Framework to Model the Hydrology of Solar Farms Using EPA SWMM

As the demand for renewable energy increases, solar energy is becoming an increasingly important power source. Implementing solar energy on a large scale requires solar farm installations on land covering hundreds of acres of area. Solar farms alter the existing land use and may affect the catchment’s hydrological response. However, the impact of solar farms on catchment hydrology is not well understood, partly due to the lack of established modeling methods tailored to their unique land cover. The areas over which solar panels are installed are impervious on the panel and pervious underneath it, making it challenging to model. This study proposes a framework to model the hydrological response of a solar farm using the United States Environmental Protection Agency (US EPA) Storm Water Management Model (SWMM). The framework divides each row of the solar farm into four sections, the impervious solar panel, a wet section at the dripline that captures the majority of runoff from the panel, a spacer section that encompasses the space between the solar panel rows, and an under-panel section which represents the space under the solar panel. The runoff from one section is routed to the next section in the order of natural water flow. All four sections together represent one row of the solar farm, so runoff from each row is then routed to the next row until the outlet. With this general setup, many variables, such as land cover, the slope of the land and solar panel, panel width, and rainfall events can be easily modified to understand the effect on hydrology for specific scenarios. This relatively simple framework can improve our ability to represent the hydrological response of a catchment before and after the installation of solar farms and can serve as a preliminary tool for the planning and design of solar farms, and identification of stormwater management needs.