Current policies often fail to recognise these unintended effects (“externalities”) and to address these trade-offs between water risks (risk-risk trade-offs). Multiple and scattered (“diffuse”) sources of water pollution are challenges in many countries and a multiplying number of water contaminants threaten freshwater quality. The population affected by flood is increasing worldwide and with it the value of assets at risk. The report focuses on OECD countries but also refers to countries outside the OECD area.