Fate and transport modelling of microbial water quality: impacts of climate change and socioeconomic development

Anthropogenic activities in a watershed may pose human health risks due to faecal contamination of surface waters. Thus, socioeconomic development is important when predicting future microbial water quality. Moreover, climate change alters meteorological conditions, thereby affecting flow regimes as well as fate and transport of microorganisms. In this study, possible risks due to socioeconomic development and climate change were assessed for the drinking water source Lake Vomb in Sweden by means of water quality modelling. The hydrological model ArcSWAT and the hydrodynamic model MIKE 3 FM were used to simulate fate and transport of two microorganisms, i.e., Cryptosporidium and E. coli, from the watershed to the water intake. The hydrological model and the hydrodynamic model were calibrated and validated using observed data on water flow and water temperature, respectively. The water quality in the watershed and in the lake was simulated for a baseline scenario and for future scenarios in the second half of this century. The future scenarios were formulated based on Representative Concentration Pathways (RCPs) and Shared Socioeconomic Pathways (SSPs). The modelling results illustrated the effects of climate changes and of socioeconomic development. The results were also interpreted in the context of infection risks to drinking water consumers using quantitative microbial risk assessment. This study clearly illustrates that socioeconomic development is important to include when investigating future microbial water quality.