Modelling the combined impacts of climate change and socio-economic development on waterborne pathogen transport

Protection of our water resources is essential to provide future generations with safe drinking water, recreational opportunities, and reliable ecosystem services. Climate and land use changes exert pressure on the quality of our water resources. Additionally, societal development may generate both positive and negative impacts on future water quality. Thus, decisions made today will impact the water quality of tomorrow. In this paper, we address the issue of future microbial water quality by combining Representative Concentration Pathways and Shared Socio-economic Pathways with projections of societal development, either downscaled to a local level or assessed by local organisations. We use Lake Vomb in Sweden (providing approximately 330 000 persons with drinking water) to illustrate our novel approach of assessing the impact of climate change and societal development on future microbial water quality. The approach includes norovirus, Escherichia coli (as an indicator organism), and Cryptosporidium. Further, we combine hydrological and hydrodynamic fate and transport modelling to simulate future water quality in the tributaries and at the drinking water intake. Future simulations are compared to a baseline scenario representing the current situation. Results show that climate change will reduce future water quality. However, we can also see that societal development significantly impacts microbial water quality, potentially counteracting the increases in microbial concentrations induced by climate change. Therefore, drinking water supply management must adapt to both future climate and societal development.