This Basin Diagnostic Analysis (BDA) approach summary report seeks to present an overview of the methodology and approach that is being taken as part of a BDA for the 3S sub-basin of Cambodia, Lao PDR, and Viet Nam. The BDA is being developed under the Preparation of a Joint Project in the Sesan, Sekong and Srepok (3S) sub-basin of the Mekong River (3S Joint Project). The preparatory study has been funded by the German Federal Ministry for Economic Cooperation and Development and implemented by the Mekong River Commission (MRC) and GIZ, in cooperation with the International Centre for Environmental Management (ICEM).
The main technical role of the BDA is to identify, quantify, and set priorities for environmental problems that are transboundary in nature. In particular, the BDA aims to
The cross-cutting issues of IWRM, climate change adaptation, ecosystems services, poverty, livelihoods and gender are integrated throughout all four processes. The spatial outputs of the BDA are being integrated into the 3S Basin Atlas and inform the joint priorities and proposed transboundary measures for the Joint Project. This framework approach is presented bellow.
3S Joint Project framework approach, including where the BDA fits in the step process (yellow box)The BDA is intended for use and application by government agencies, river basin planners, provincial development authorities, city planners, civil society organisations and development partners. It is an essential initial foundational assessment in design of the comprehensive 3S Joint Project and to inform other development projects in the sub-basin.
The Joint Project aims to assess the current state of water resources and climate change in the 3S, and opportunities for ecosystem scale interventions for transboundary cooperation on sustainable water resource management and climate change adaptation.
As part of the Joint Project preparatory process, the BDA focuses on the identification of at-risk watersheds, infrastructure, and livelihoods in need of improved resilience and hotspots for ecosystem degradation, flood and drought.
As part of the characterisation and prioritisation process under the 3S sub-basin assessment, five parallel processes are followed (Figure 3):
Data has been collected and analysed on areas such as hydrology, natural resources, biodiversity, land use, flood and drought, climate change projections and socio-economic status and trends. Secondary information has been collected on spatial, sectoral, and provincial plans, as well as existing and planned development projects, relevant to the 3S Joint Project.
A detailed data collection and acquisition plan was developed, which provided an overview of the data requirements, a description and rationale for each dataset and the relevant agency responsible for providing the data. Data requests from the PMU have been distributed to national line agencies via the National Mekong Committees (NMCs), supported by the national consultants. NMCs and line agencies have exchanged all information necessary for the activities, outputs, and effective functioning of the 3S Joint Project under this arrangement.
Important factors shaping the methodological scope for this initial preparatory phase of the 3S Joint Project include:
As a first stage in the BDA, a 3S catchment boundary identification and delineation process has been conducted. It has enabled the aggregation of 48 catchments of an appropriate size and number to conduct the catchment analysis in this study. As a first step, 79 catchments were defined as follows:
Steps to aggregate the catchments for the purposes of the BDA were (i) less than 100 km2 were merged with adjacent catchments, along with 11 catchments under 200 km2, and (ii) the catchments were aggregated according to those delineated by the SWAT hydrological model into 48 catchments, (iii) further consolidated based on the existing MOWRAM Cambodia 3S4P DSS and national river basin planning documents, then (iv) fine-tuned against administrative boundaries (Figure 4).
The 48 catchments provide the foundation units for data gathering and analysis in this study.
The 48 3S catchments defined as the basis for the BDAA review of the existing characteristics and trends across the 3S sub-basin is being undertaken for core technical areas. This analysis is being supported by spatial mapping to show the spatial and temporal distributional changes over time. Technical areas assessed include:
As part of the BDA, a review of relevant policies and institutions (past, present and future) in Cambodia, Lao PDR and Viet Nam, and their relevance for sustainable water resource management and climate change adaption in the 3S sub-basin, is being undertaken including:
Secondary information has been collected on spatial, sectoral and provincial plans, protocols, as well as existing and planned development projects (including on grey, hybrid and green infrastructure), relevant to the Joint Project. The Joint Project builds on past consultations and negotiations among 3S countries and seeks to help implement and maintain the momentum of the resulting plans of action, which have been formally adopted.
A Regional Inception Workshop was held in Hanoi on 17 August 2023, between the three project countries NMC’s and MRC-GIZ. The NMC’s presented an overview of their current work areas and relevant projects in the 3S, which has informed the policy and institutional review.
Governments in the four LMB countries are responding to the challenges of ecosystem restoration, and to flood and drought with increased commitment to integrated water resources management alongside the ongoing development of human engineered (grey) infrastructure at all scales. This action includes mandating and strengthening of river basin-scale planning, investments in ecosystem resilience, climate change adaptation and attention to cross-sectoral and multi-level cooperation. All four governments have made commitments to increase investment in conservation, to halt forest loss and to enhance watershed restoration as part of their participation in the biodiversity and climate change conventions conferences of parties and in response to the UN Decade on Ecosystem Restoration from 2021-2030.
Several significant recent and existing national and bi-lateral projects have been established for the 3S, which are being further aligned and explored, including:
Several existing protocols and plans developed for the 3S basins through MRC consultative mechanisms (Mekong IWRM Project) are being further aligned and explored, including:
The existing national institutional capacity on water resource management and climate change for the three countries of the 3S sub-basin is being assessed, including for the institutional setting, (ii) legal and policy framework and (iii) relevant work by the NMCs. Relevant projects and investments on water resource management and climate change in the 3S sub-basins have been identified. This includes bilateral projects and initiatives. Governance challenges and trends associated with water and natural resources have also been assessed.
Past project challenges and successes (e.g. M-IWRMP – Mekong Integrated Water Resources Management Bilateral Projects (2013-2019) and the 9C-9T Joint Project (2019-2023)) have informed the developing of the proposed 3S Joint Project.
Relevant stakeholders in the 3S countries, basins and provinces have been identified as part of the catchment assessment. This will include both state and non-state actor stakeholder groups, including understanding key national and transboundary stakeholder interactions, challenges and trends on water resource management and climate change adaptation. The types of stakeholders, including how they are affected by and participate in natural resource management, vary from country to country.
Stakeholder groups may include:
Promoting gender equity and social inclusion within project activities and outputs is crucial to IWRM and mitigation activities. Gender and social vulnerability are key considerations of the Joint Project. Vulnerable groups are most likely to be most impacted by, and least resilient to, ecosystem and water degradation, flood and drought and loss of fisheries and other natural resources. Vulnerable groups also include internally displaced persons due to natural and/or human induced disasters.
Relevant global and regional policy frameworks applicable for the 3S Joint Project are being reviewed, including national and MRC policy frameworks and standards in place on gender and vulnerability. A high-level gender sensitive and vulnerability analysis for the 3S sub-basin has been undertaken.
Water resource and climate related challenges have been identified for the 3S sub-basin, based on a review of secondary information, primary data collection and field missions, including:
A comprehensive catchment assessment has been conducted to identify hotspot areas within the 3S sub-basin for ecosystem degradation and flood and drought risk, to inform river basin planning and management, including addressing transboundary issues. Priorities are being identified based on spatial analysis, remote sensing, and ground truthing. The catchment assessment forms a core part of the 3S Joint Project methodology, as highlighted below.
Catchments that are significantly degraded or that contain valuable natural and human assets will be identified by assessing and ranking sub-catchments according to rehabilitation needs.
Seven composite indexes were developed for the catchment hotspot analysis, comprising several parameters, defined as follows:
1. Flood risk | Projected in 2050 (IPSL 4.5) | Average flood depth |
Flood area > 0.5 m | ||
2. Drought risk | Projected in 2050 | Change in number of drought duration |
3. Erosion risk | Potential soil erosion (RUSLE) | |
Erodability index (bedrock) | ||
4. Biodiversity risk | Protected areas | |
Key biodiversity areas | ||
Degree of Naturalness (2020) | ||
Degree of Naturalness loss (2002 - 2020) | ||
5. Forest loss risk | Forest cover (Tree cover > 10%) in 2023 | |
Forest loss (2001 - 2023) | ||
6. Climate risk | Change in precipitation in dry season (2050) | |
Change in precipitation in wet season (2050) | ||
Wettest month precipitation change (2050) | ||
Change in annual temperature (2050) | ||
7. Human pressure | Population density (2020) | |
Agricultural land | ||
Plantations (2020) | ||
Linear infrastructure | ||
Built-up areas |
In addition to the hotspot parameters, six key composite indexes are proposed for the asset analysis, comprising the following parameters:
1. Terrestrial biodiversity | 1.1 Number of threatened species |
1.2 Native species richness | |
2. Aquatic biodiversity | 2.1 Number of threatened species |
2.2 Aquatic species richness | |
3. Fish species (with or without dams) | 3.1 Fish migration |
3.2 Endemic fish species | |
4. Socio-cultural characteristics | 4.1 Ethnic diversity |
4.2 Urban/rural ratio | |
4.3 Population (within 5km of river) | |
4.4 Cultural heritage, tourism and recreational sites | |
5. Strategic infrastructure value | 5.1 Infrastructure density |
5.2 Reservoirs and open water | |
6. Forests | 6.1 Forest landscape integrity |
6.2 Endangered tree species richness |
Connectivity is being assessed by terrestrial and freshwater ecosystems. A 3S sub-basin wide analysis is being undertaken to identify terrestrial corridor opportunities to enhance the connectivity between ecosystems – for example between remaining forest patches and protected areas – and along disrupted drainage corridors – the aim being to enhance ecosystem services and lead to biodiversity net gain.
The 3S basin connectivity is being assessed as part of the BDA, using the following approach:
This analysis will help to identify key areas of concern, or ‘hotspots’, for basin fragmentation, as well as opportunities for increasing connectivity, including the preservation and/or establishment of nodes, stepping stones, corridors and entire landscapes.
To support the development of the indexes, the following spatial data will be explored to provide the GIS layers for these processes. These include (i) biophysical parameters; (ii) strategic infrastructure; and (iii) social parameters.
A key step in the BDA process is to identify the transboundary problems in the 3S sub-basin. Transboundary challenges have been identified based on secondary information, discussions during workshops, NWGs and field missions.
Priority transboundary problems are identified based on the nature and severity of their transboundary impact, including the underlying and root causes, and potential environmental and socioeconomic impacts.