Evaluating groundwater infiltration risk in sewer networks under climate change

Groundwater infiltration (GWI) in sewer networks poses significant challenges to infrastructure. However, limited research has assessed the risk of GWI to sewer networks under climate change. This study addresses this gap by developing a numerical model to simulate groundwater flow in the Lower River Otter catchment, United Kingdom. The model was calibrated and verified using monthly data representing an observation period from 2011 to 2023, resulting in a mean error of − 0.12 m, a mean absolute error of 0.48 m, and a root mean square error of 0.64 m after verification. Next, distinct risk zones were delineated based on groundwater depth (GWD) and GWI in sewer networks. This delineation accounted for the observation period with current precipitation levels, and projected increases of 20% and 40% in precipitation (indicative of climate change), across a base period (1961–1990) and future period (2021–2060), under the shared socio-economic pathways SSP245 and SSP585. The model found groundwater flooding affects 13.2% of the region during the observation period, mainly occurring near the river and in areas where the aquifer is sandwiched by aquicludes. Future scenarios indicated that flooding could increase to 15.4% under SSP245 in the future. The area with GWD shallower than 4 m ranges from 17.5% in the base period to 18.1% with a 40% increase in observed precipitation. The model reveals that during the observation period and a 40% increase in precipitation, the area showcases the minimum (26.7%) and maximum (27.6%) proportion of high-risk areas for GWI in sewer networks, respectively. This prioritisation indicates the potential risk of GWI and the need for investigations, such as focused site surveys, to minimise risks of GWI into networks and ensure future sustainability of services.