The impact of climate change is likely to have considerable implications for water resource planning, as well as adding to the risks to water infrastructure systems and effecting return on investments. Attention is increasingly being paid to adaptation strategies at the regional and basin level; however, the current paucity of information regarding the potential risk to hydrological systems at this scale presents a substantial challenge for effective water resources planning and investment. This study is intended to help bridge the gap between high-level climate change predictions and the needs of decision-makers—including World Bank Task Team Leaders, government agencies, investors, and national economic development planners—whose programs and investments will be affected by basin- and regional-level impacts of climate change on water resources and related infrastructures.