Impact of climate forecasts on the microbial quality of a drinking water source in Norway using hydrodynamic modelling

Abstract. This study develops hydrodynamic and water quality models for long-term prediction of E. coli concentrations at the raw water intake point of lake Brusdalsvatnet in Norway. The study is based on previously observed concentrations of E. coli in the tributaries of the lake and local projections of precipitation and air temperature in the region. The results indicate a gradual rise in the temperature of water at the intake point from the base year (2017) through to year 2075. Shorter spring circulation and longer autumn circulation periods are expected in the lake in future. Concentrations of E. coli at the intake point of the lake are expected to marginally increase in future. By the year 2075, the models predict a 3 fold and 2 fold increase in E. coli concentrations respectively for the spring and autumn seasons compared to current levels. The results is expected to provide the water supply system managers of Ålesund with the information necessary for long term planning and decisions in the protection of the drinking water source. The method used here can also be applied to similar water supply systems for developing effective risk management strategies for recent and future scenarios.