1.0 BACKGROUND

1.1 Changing Context

1. Dam projects are not static but dynamic complexes of technologies, techniques, policies, institutional frameworks, societal values and even visions of development. As the age of already commissioned dams increases, as lessons are learned from the growing experience with dams and as societal values continue to evolve, various stakeholders have begun to re-evaluate the safety, existing operation, monitoring, even utility of these projects all around the world. The balance among the economic, environmental and/or social benefits generated by a dam may vary over time relative to its costs either because of actual shifts in project functioning and/or improved information and knowledge of the impacts of the project. Similarly, the purposes for which a dam was built and its operational objectives may be altered as societies reprioritize their values and broader development goals. Given this changing context, options such as the refurbishment, redesign, modernisation, modification, replanning, reoperation and decommissioning of dam projects will have to be addressed more thoroughly for the sustainable development and management of water and energy resources and services in the future.

2. Refurbishment, redesign, and/or modernisation is generally considered during the phase of operation and monitoring to increase the safety of existing dams (particularly as they age) or to improve the functioning of dams with respect to the various types of benefits originally envisioned. Especially suitable are projects that must be renovated because of faulty design, delapidation, technical breakdown, or sub-optimal functioning due to such factors as siltation or salinisation in the command area. Aside from dam failure as a result of faulty design or natural hazards, the major threat to the productivity and longevity of dams is reservoir sedimentation. Projects that can be improved based on the lessons learned from the practical experience, from better data on key parameters, or from a shift to new technologies and techniques that have become available over time are also likely candidates for renovation during the phase of operation and monitoring.

3. While decisions to refurbish, redesign or modernize are often taken without questioning the original functions for which the dam was built, modification, replanning, and/or reoperation of projects is increasingly being undertaken to satisfy evolving societal needs, values and/or different visions of development. For example, there are numerous cases of dams that have been modified to increase the amount of benefits generated such as raising the height of the dam wall to increase hydropower generation. Another issue that is increasingly under consideration is that of minimum instream flows, and whether operators should provide or increase releases from a project to restore or enhance ecosystem functions.

4. However modification, replanning, and reoperation to satisfy new societal objectives could potentially result in tradeoffs with the original purposes of or extant functioning of a dam project. For example, changes in instream flow requirements can reduce the water available for hydropower, irrigation, and/or other uses. Moreover, decisions on the modification, replanning and/or reoperation of dam projects must be made in the context of broader river basin, sectoral and national systems for water and energy development and management. Often the best options cannot be selected without a focus on these broader systems of which the individual dam project is just one component.

5. The option of decommissioning refers to a range of possible actions, from ceasing operations of a dam project to the full dismantling and removal of all project structures. Dam-safety concerns, the costs of maintenance, the inability to implement necessary upgrades, the high costs of major improvements, unexpected but potentially reversible impacts, as well as social and/or environmental concerns may lead to the choice of decommissioning as opposed to refurbishment, modernization and/or reoperation. While experience with decommissioning is limited, numerous factors clearly must be examined in such cases including the benefits and costs of dam decommissioning in the context of other potential options as well as the technical issues surrounding structure removal, including sediment management and approaches to corridor restoration.

6. This thematic review seeks to clarify the key issues and decision-points that are likely to arise during the life of a dam after it has been commissioned. The focus of this review will thus include the following components:

• assessment of the various factors (faulty design, hydrological changes, sedimentation, salinisation, etc.) that may affect the safety and functioning of a dam after it has been commissioned;

• identification and explication of the types of information required and associated time frames that are necessary for monitoring these factors;

• identification and explication of the policy and institutional frameworks as well as good practices that can increase the likelihood that monitoring of these factors will be transparently and effectively conducted after the commissioning of a dam;

• assessment of when and how decisions related to the refurbishment, modernisation, modification, reoperation and/or decommissioning of dams have been made including how they have taken into account the lessons learned from the growing experience with dams as well as evolving societal values especially with respect to social and environmental impacts;

• identification and explication of the policy and institutional frameworks as well as good practices necessary for decision-making with respect to the options of refurbishment, modernisation, modification, reoperation and decommissioning;

• assessment of the financial and economic aspects of operation, monitoring and decommissioning, including upon whom the financial responsibility of decommissioning falls and potential approaches for the incorporation of decommissioning into the planning, design and appraisal of dams;

• identification and explication of the economic, social and environmental effects of different forms of decommissioning, and the technical issues surrounding dam removal from past and current experience;

• recommendations on criteria and guidelines for the operations, monitoring and decommissioning of dams.

7. Decision-making during the life of a dam after it is commissioned is a central component of the methodology that has been developed for the case studies. Issues such as sedimentation and salinisation during operations have arisen in several of case study and cross-check survey dams. Thus, several questions relevant to operations and monitoring have been included in the cross-check survey. Moreover, refurbishment, mondernization, modification, replanning, reoperation and decommissioning has been considered in many of the focal and non-focal dams located in the river basins being examined by the WCD.

8. There are strong connections between this thematic review and the other options thematic reviews in that the latter will all be evaluating the degree to which improving the function of existing dams is a viable alternative for meeting energy, irrigation, flood management and water supply objectives. This thematic review is also linked to the thematic reviews that touch upon reparations, ecosystem functioning and restoration, global change, economic analysis, planning, environmental and social impact assessment, river basin management, participation and consultation.

9. This thematic review will contribute to all three outputs of the World Commission on Dams. It will add knowledge about the past experience with operation, monitoring and decommissioning to the Global Review and will identify good decision-making practices, policies and institutional frameworks for operation, monitoring and decommissioning to be incorporated into the Framework for Options Assessment. Finally, recommendations to be included in the Criteria, Guidelines and Standards output on operations, monitoring and decommissioning for the future will be derived from this review.