Quantitative assessment of sewer overflow performance with climate change in northwest England http://researchonline.ljmu.ac.uk/id/eprint/2207/ Article LJMU has developed LJMU Research Online for users to access the research output of the University more effectively. Abdellatif, M, Atherton, W, Alkhaddar, R and Osman, YZ (2015) Quantitative assessment of sewer overflow performance with climate change in northwest England. HYDROLOGICAL SCIENCES JOURNAL, 60 (4). Abstract Changes in rainfall

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... ns associated with climate change can affect the operation of a combined sewer system, with the potential increase in rainfall amount. This could lead to excessive spill frequencies and would also likely introduce hazardous substances into the receiving waters, which in turn, would have an impact on quality of shellfish and bathing waters. This paper quantifies the spilling volume, duration and frequency of 19 Combined Sewer Overflows (CSOs) to receiving waters under two climate change scenarios, the high (A1FI) and the low (B1) scenarios, simulated by three GCMs, for a studied catchment in north-western England. The future rainfall is downscaled, using climatic variables from HadCM3, CSIRO and CGCM2 GCMs, with use of a hybrid Generalised Linear -Artificial Neural Network model. Results from the model simulation for the future in 2080 showed an annual increase of 37% in total spill volume, 32% in total spill duration, and 12% in spill frequency for the Shellfish water limiting requirements, under the high scenario, as projected by the HadCM3 as maximum while the other GCMs projected different changes. Nevertheless the catchment drainage system is projected to cope with the future conditions in 2080 by all three GCMs. The results also indicate that under scenario B1 a significant drop was projected by CSIRO, which could reach up to 50% in spill volume, 39% in spill duration and 25% in spill frequency in the worst case. The results further show that during the bathing season, a substantial drop is expected in the CSO spill drivers as predicted by all GCMs under both scenarios.