Predicting how collection systems will operate in the 2050s in response to changing rainfall patterns

Urban flooding and wet weather pollution are recognized as significant problems across the world, and changes in rainfall patterns due to climate change are likely to exacerbate these problems unless collection systems adapt. This paper shares learning from a ground-breaking project led by CH2M for UK Water Industry Research and approaches used in other CH2M projects around the world. The UK project has made use of very high resolution (1.5km) climate model output to derive change estimates for design rainfall and to develop a perturbation tool that allows time series rainfall data to be adjusted to reflect future rainfall intensities and patterns. Other projects have used different methods to derive new design rainfall statistics and to perturb historic rainfall data; both are commonly used in modelling wet weather collection systems for flooding and pollution investigations. Estimates of rainfall change have been used within collection system models to estimate the flooding and pollution impact of these changes. The methods applied in these projects can be replicated globally.