The Climate Change Act 2008 requires a series of assessments of the risks of climate for the UK, under both current conditions and over the long term, to 2100. This paper describes the research completed on the impacts of climate change on the UK water sector, involving stakeholder engagement and a mix of literature review, expert elicitation and broad-scale quantitative analysis to develop ten climate change risk metrics. These include measures of the demand for water, impacts on supply, water quality and asset performance using future scenarios based on the UK Climate Projections 2009 and future population projections from the Office for National Statistics. The analysis has resulted in a number of key findings that can help to inform policy in different parts of the UK. Overall the assessment showed that there is likely to be increased pressure on water resources in the UK. These pressures need to be considered in long term plans so that the needs of different users are met without impacting on the environment.