Rainfall redistribution by agrivoltaic arrays drives soil erosion on karst hillslopes: mitigation through runoff harvesting

The rapid expansion of agrivoltaic systems in karst regions has raised concerns regarding their impacts on soil hydrological processes and erosion dynamics in fragile landscapes. While these systems improve land-use efficiency, their structural configuration alters rainfall redistribution, potentially exacerbating soil erosion on karst hillslopes. However, quantitative understanding of these effects and their implications for soil and water conservation remains limited. This study quantified rainfall redistribution, soil erosion responses, and runoff harvesting potential under agrivoltaic systems in a karst mountainous area. Two field plots (30 m × 3 m) were established beneath photovoltaic (PV) arrays, including one plot equipped with a runoff collection system installed along panel drip lines. A one-year field monitoring experiment under natural rainfall conditions was conducted to assess rainfall redistribution patterns, soil loss, and runoff collection efficiency. Results showed that photovoltaic arrays significantly altered rainfall distribution patterns, with effects strongly dependent on rainfall intensity. During light to moderate rainfall events, 46.79%–66.46% of the total precipitation input during each event was concentrated along panel drip lines. During heavy rainfall to rainstorm events, 49.39%–63.21% of the event precipitation was redistributed to inter-panel areas, whereas less than 10% of the total event precipitation reached beneath panels. This spatial redistribution resulted in significantly higher soil erosion rates at panel edges and inter-panel zones compared to beneath panels ( P < 0.05). Annual soil loss exceeded 5000 t km −2 yr −1 , and bedrock exposure increased from 9.92% to 18.68%, indicating enhanced erosion risk. The runoff collection system effectively intercepted concentrated flow, capturing 69.0%–72.9% of rainfall and reducing localized erosion. These results demonstrate that agrivoltaic-induced rainfall redistribution is a critical driver of soil erosion in karst environments, while targeted runoff harvesting can partially offset these effects. Overall, this study provides field-based evidence of the coupled impacts of agrivoltaic systems on rainfall redistribution and soil erosion, and highlights the importance of integrating hydrological regulation measures to sustain soil resources in karst agroecosystems.