Project Background:

The Sekong, Sesan and Srepok rivers, referred to collectively as the 3S river basin, are shared by Cambodia, Lao PDR and Viet Nam and constitute a significant part of the Mekong Basin; one of the most biodiverse regions on the planet, where some 80% of the 65 million people living there depend on the river and its rich natural resources for their livelihoods (Mekong River Commission, 2024). The 3S sub-basin – where all three rivers are transboundary – is one of the most important basins in the Mekong region for flood and drought resilience, sediment dynamics, fisheries, irrigation and aquaculture, natural resource-based livelihoods and biodiversity. Combined, it provides over 20% of mean annual flow of the Mekong and almost 15% of its suspended sediment (Brunner et al., 2019). The sediment in the 3S provides nutrients vital to fisheries in the Tonle Sap and rice production in the Mekong Delta. The 3S sub-basin is the Mekong‘s most important river basin for migratory fish and sustains productive downstream fisheries.

All parts of the sub-basin, and hence the three countries, are bound together in their shared natural and water resource management challenges and solutions. Mitigating ecosystem degradation, a loss of livelihoods, floods and droughts is the overarching objective because of their far-reaching impacts on every aspect of life in the sub-basin, with the threat to become more severe as climate changes take hold. These factors create an urgency for collaborative restoration action and strategic opportunity to intervene, share knowledge between the three project countries and implement appropriate nature-based interventions through a river basin and ecosystem approach.

Project Objective:

The core objective of this preparatory study is to support the design of a comprehensive Joint Project in the 3S sub-basin of the Mekong River, comprising Cambodia, Lao PDR and Viet Nam. The study is providing the information base, decision support tools, needed capacities and an initial framework of actions, which would be picked up for future phases to set out the design of a comprehensive and longer-term Joint Project on sustainable water resource management in the 3S sub-basin.

The Joint Project will be facilitated through cross-border and cross-sectoral engagement, collaboration and validation, supported by GIZ and the Mekong River Commission Secretariat, in coordination with the National Mekong Committees and relevant sectoral agencies in each country. Specifically, this assignment aims to:

• Identify and analyse relevant data and information, prepare situational and trends analyses and undertake a catchment assessment to provide insights on climate change, water and nature resource management, food security and social vulnerability considerations, and present findings via a Basin Diagnostic Analysis;

• Development of basin-wide climate diagnostics to better understand present and future climate pathways and implications, based on the latest CMIP6 global climate models;

• Identify degraded landscapes in each of the three basins which are of high priority for developing projects focused on sustainable water resource management and climate resilience building measures;

• Develop a digitally referenced, online open-source mapping platform for the 3S sub-basin – the 3S Basin Atlas – which includes the integration of relevant spatial data layers and analyses to support decision-making processes, which will be handed over and managed by MRCS;

• Establish transboundary steering mechanisms and implementation agreements for a Regional Steering Committee and three National Working Groups, and facilitate national and regional meetings;

• Design a capacity building programme and provide training to relevant national stakeholders on sustainable water resource management and climate change adaptation; and