Impacts of Irrigation with Reclaimed Water on Soil and Groundwater: Vegetation- and Season-Dependent Patterns from a Lysimeter Study

Abstract

The use of reclaimed water in agriculture is a potential solution to regional water shortages. A controlled lysimeter study investigated the impact of irrigation with reclaimed water on the soil's water and nutrient balance, and the potential impact on drainage water quality for groundwater recharge. Planted and unplanted lysimeters with defined soil profiles were irrigated with reclaimed or tap water for 12 months (August 2024 to August 2025). The reclaimed water was obtained from a membrane bioreactor. Water balance (precipitation, irrigation and potential evapotranspiration) and drainage water formation were recorded and sampled weekly. The analyses included physico-chemical parameters (pH, electrical conductivity, total bound nitrogen, nitrate, nitrite, and ammonium nitrogen), anions (chloride, fluoride, sulfate), and 21 organic micropollutants. In the planted lysimeters, electrical conductivity increased notably, especially during dry summer periods, suggesting evapotranspiration effects and altered flow paths within the root zone. Conversely, nitrogen concentrations in the drainage water from the planted lysimeters were substantially lower than in the unplanted lysimeters, which is consistent with plant uptake and potentially enhanced microbial conversion in the rhizosphere. In summary, both vegetation and water type markedly affected drainage water quality, with clear differences between reclaimed and tap water as well as strong seasonal effects. The results suggest that when assessing irrigation with reclaimed water, site- and management-specific conditions and vegetation-related differences in drainage water quality and groundwater recharge rates must be considered. © The Author(s) 2026