With my 11 colleagues on the World Commission on Dams, we spent two years addressing one of the most contentious issues of economic development. The dams debate contains many elements of the broader issues of growth, technology and equity – to name but a few – which characterize the big debates about how best to help bring about a fairer world for all.

Industry and individuals need electricity. Irrigated crops feed people and earn foreign exchange. Everyone benefits from clean water and by controlling floods.

When 2 billion people lack electricity in a world choking from airborne pollution, hydropower once seemed to offer a clean alternative in countries blessed with rushing rivers. But dams also have a downside. Plagued by cost overruns, they can contribute to unsustainable debt burdens. They cause 4 million people to be displaced each year. Environmental impacts can be devastating. And the sharing of costs and benefits is often inequitable.

The challenge to our Commission was to find a shared set of criteria for deciding when and if a dam is the best option to meet a need and, if it is, to deriving the benefits from dams while minimizing the negatives.

One third of the countries in the world rely on hydropower for more than half of their electricity supply, and large dams generate 19 per cent of electrical power overall. Electricity demand in developing countries continues to rise, and the range of choices to feed this demand is limited.

The Commission set out to review the development effectiveness of large dams and assess the alternatives for water resources and energy development. We undertook eight detailed case studies of large dams and prepared country reviews for India and China, plus a briefing paper on Russia and the newly independent states. A survey of 125 large dams was also developed, along with 17 thematic reviews on social, environmental and economic issues; on alternatives to dams; and on governance and institutional processes.

We learned that large dams built to deliver hydropower had tended to perform close to but still below targets for power generation. They generally met their financial targets, but demonstrated variable economic performance relative to targets.

Ecosystem impacts were generally found to be more negative than positive for dams in general (including those designed for water supply, irrigation and flood control). They have, in many cases, led to significant loss of species and ecosystems. We found that all reservoirs that have been sampled by scientists emit greenhouse gases – as do natural lakes – from rotting vegetation and carbon inflows from the catchment area. The scale of these emissions is highly variable. Data from a hydropower dam in Brazil showed that the gross level is significant compared to emissions from equivalent thermal power plants. However, in other reservoirs (notably those in boreal zones) gross emissions of greenhouse gases are significantly lower than the thermal alternative. Clearly more research is needed to demonstrate the capacity for hydropower to offset climate change.

We concluded that there was a need to look at proposed water and energy development projects in a much wider setting than had been typical in the past. This should reflect full knowledge and understanding of the benefits and impacts of large dam projects and alternative options for all parties. We called for a fundamental change in the way these decisions are made.

In our report and recommendations, five core values emerged as being fundamental to informing the planning of future dams: equity; efficiency; participatory decision-making; sustainability; and accountability.

Armed with these values, we proposed an approach based on recognizing rights and assessing risks – particularly ‘rights at risk’. We considered that this should be the basic tool guiding future planning and decision-making. We felt that this would provide a more effective framework for integrating the economic, social and environmental dimensions for assessing options and for the planning and project cycles associated with large dams.

We then identified five critical decision points when water and energy options are considered. The first two relate to planning:

• Needs for water and energy services must be assessed and validated.

• The full range of options must be reviewed in order to identify the preferred development plan.

When a dam emerges from this process as a preferred development alternative, three further decision points occur:

• During the project preparation phase, it must be verified that all agreements are in place before the construction contract is put out to tender.

• During the project implementation phase, compliance with agreements must be confirmed before the dam is commissioned.

• During the project operation phase, the operating of the dam should adapt to changing external circumstances.

Each of the five decision points represents a commitment to actions that govern the course of future conduct and the allocation of financial and other resources to the project. They are points where ministries and government agencies need to test compliance with preceding processes before giving the green light to the next stage.

Our report offered a new policy framework with fundamental departures from the approach much of the world currently uses. We are gratified by the way the report has been received and pleased that, although our mandate was finite, with a clear two-year time limit, the work of the Commission will be continued through the Dams and Development Project (DDP) under the auspices of UNEP, which will promote and support inclusive and informed multi-stakeholder dialogue on the issues raised by our Commission.