Guidance for Dam Design

While implementation of the proposed hydropower schemes on the mainstream Mekong brings potential opportunities for economic development, mainly with improved electricity supply and navigation, the projects will inevitably be accompanied by major risks in the four Member Countries. Some of these may include:

  • The effects on the fisheries resources of the Mekong, especially the barrier effect that dams could have for migratory species, fish biodiversity and the subsequent consequences for people's livelihoods;
  • Effects on sediment and river morphology, with associated risks to the economic life of the mainstream impoundment of water and safe operation, and effects on long-term river bed stability, river bank erosion and channel changes in the downstream reaches; and
  • Potential water quality changes, especially with regard to water pollution and effects on aquatic ecosystem functions and services, as well as wetland systems.

As part of the process of helping Member Countries understand the long-term potential impacts of hydropower (e.g. through the SEA on Mainstream Hydropower Dams), the Mekong River Commission (MRC) is helping to assess the balance between opportunity and risk for these proposed projects to highlight a range of key issues that need to be considered by developers at the project design stage; as well as by MRC bodies, government line-agencies and other stakeholders when any proposed hydropower scheme is submitted for the MRC Prior Consultation process.

This document, Preliminary Design Guidance for Proposed LMB Hydropower Schemes, provides preliminary design guidance in the form of performance targets, design and operating principles for mitigation measures, as well as compliance monitoring and adaptive management for reducing the environmental and social risks posed by hydropower schemes.

The intention of this report is to provide developers of proposed dams on the Lower Mekong mainstream with an overview of the issues that the MRC will be considering during the process of prior consultation under the 1995 Mekong Agreement. Responsibility for ensuring compliance with national standards and provisions of the 1995 Mekong Agreement remains with the project developers. MRC may commission an international expert group to assist in the interpretation of such requirements. Two broader aims are:

  1. To ensure that developers have timely guidance to adopt a consistent approach to the design of individual dams, as well as the proposed mitigation and management measures. This is important, particularly where developments have significant transboundary impacts for people or the environment downstream.
  2. To ensure that the approach of offering performance targets allows developers the flexibility to identify and propose the best solutions.

The guidance is founded on a set of basic Integrated Water Resources Management (IWRM) principles, international best practice and the relevant primary legislation of Member States, namely:

  • Avoidance over mitigation: Emphasis on the avoidance of impacts is preferable to the mitigation of impacts ‐ or compensation for unmitigated impacts; taking care to avoid permanent loss of environmental assets, in particular permanent biodiversity loss.
  • Water as an economic good: Responsibility for mitigation measures and economic compensation for unmitigated impacts is born by the project and users of services it provides. Because it is not always possible to attribute losses to any one particular dam in a cascade, a procedure may be required to ensure that all projects contribute to mitigation measures, particularly for major impacts on the communities that have their livelihoods affected. The extent of such contributions would depend on the scope, extent and valuation of potential impacts.
  • Adaptive management: Given the uncertainty, there will be a need for adaptive management. In the past, potentially significant impacts have often been omitted from concession agreements and power purchase agreements, as operations were dictated predominantly by power dispatch arrangements. Therefore, it will be necessary to include appropriate provisions for adaptive management in both concession agreements and power purchase agreements.
  • Good practice and safe operations: Implementing designs, operation and maintenance regimes, and institutional arrangements according to international good practice and safety standards.

Preliminary guidance provided in the following areas:

  • Guidance on Navigation Lock Design and Operations;
  • Guidance on Fish Passage Design and Operation;
  • Guidance on Sediment Management and River Morphology;
  • Guidance on Water Quality and Aquatic Ecology; and
  • Guidance on Safety of Dams.

Read the Design Guidance Report.