The primary objective of this systematic review is to identify, assess, and synthesize evidence on the effectiveness of coastal and terrestrial water-sector interventions in achieving desired outcomes at various scales in developing countries. The goal is to facilitate the use of evidence in informing policy and practice decisions within the water sector, particularly climate adaptation and mitigation co-benefits and feed into the future evaluation of the Independent Evaluation Unit of the Green Climate Fund (GCF). In doing so, we address the following review questions:

• What is the effectiveness of selected coastal and terrestrial water-sector interventions at achieving desired outcomes (including mitigation co-benefits) at various scales in developing countries?
• What factors influence the effectiveness of coastal and terrestrial water sector interventions in developing countries?

This protocol presents the overall approach for the systematic review with a particular focus on data collection and analysis.