Hydrodynamic modelling of the microbial water quality in a drinking water source as input for risk reduction management

•Major faecal contamination sources around the lake were identified.•Fate and transport of E. coli from these sources to the water intake were simulated.•The spread of contamination was influenced by temperature stratification and wind.•The main inflow to the lake and the on-site sewers contaminated the most.•Based on the results, recommendations for prevention measures were formulated.