Economics & Development

Green water, defined as soil moisture in the root zone and land based evapotranspiration, represents one of the most abundant freshwater sources on Earth, yet remains largely overlooked in transboundary water governance frameworks. This note examines the implications of green water for water security, economic development, and resilience, drawing on recent scientific advances and a review of existing governance and regulatory frameworks. It finds that current transboundary arrangements focus predominantly on blue water (surface and groundwater) and must be expanded to account for green water's critical role in sustaining rainfall patterns, ecosystems, and livelihoods. Low income economies are particularly vulnerable, as they depend heavily on rainfall and therefore bear a disproportionate burden when green water flows are disrupted. The note presents four key recommendations: investing in the protection and restoration of high value ecosystems, especially primary forests; mobilizing existing institutional frameworks such as river basin organizations for intra and cross basin green water governance; leveraging finance and incentive based instruments to support green water management; and advancing knowledge and capacity by integrating green water indicators into water security assessments and water accounting systems. These actions are directed at river basin organizations, national governments, multilateral institutions, civil society, the private sector, and academia.