Assessing the combined effects of urbanisation and climate change on the river water quality in an integrated urban wastewater system in the UK

Climate change and urbanisation are key factors affecting the future of water quality and quantity in urbanised catchments and are associated with significant uncertainty. The work reported in this paper is an evaluation of the combined and relative impacts of climate change and urbanisation on the receiving water quality in the context of an Integrated Urban Wastewater System (IUWS) in the UK. The impacts of intervening system operational control parameters are also investigated. Impact is determined by a detailed modelling study using both local and global sensitivity analysis methods together with correlation analysis. The results obtained from the case-study analysed clearly demonstrate that climate change combined with increasing urbanisation is likely to lead to worsening river water quality in terms of both frequency and magnitude of breaching threshold dissolved oxygen and ammonium concentrations. The results obtained also reveal the key climate change and urbanisation parameters that have the largest negative impact as well as the most responsive IUWS operational control parameters including major dependencies between all these parameters. This information can be further utilised to adapt future IUWS operation and/or design which, in turn, should make these systems more resilient to future climate and urbanisation changes.

► Combined impact of urbanisation & climate change on river water quality was studied.
► The combined impacts were investigated in the context of IUWS operational control.
► Operational control parameters affect the water quality by controlling the CSOs.
► Climate change parameter RD has more impact on river water quality than RI.
► PCW is the most significant urbanisation parameter affecting the water quality.