Adaptation is an essential element of human response to climate change. The adverse impacts of climate change on the water sector will be experienced worldwide and are often projected to be most severe in resource-poor countries. Therefore, it is necessary to have access to a diverse array of affordable and appropriate adaptation technologies. This guidebook aims to provide expert information on the technologies most relevant for climate change adaptation in the water sector in developing countries. It is meant to be a practical tool for use by a broad range of stakeholders, including those in governmental agencies, water utilities, community water boards, non-governmental organisations, and private sector companies.