Posted on June, 22 2004

A publication to aid informed decision making in dam construction plans and projects
 
The world faces a huge challenge to supply the water and energy needs of a rapidly growing population, as well as reducing poverty. Currently one person in six lives without regular access to safe drinking water; 2 billion people have no access to electricity and 2.4 billion lack adequate sanitation facilities. Efforts are being made to accelerate implementation of the targets in the UN Millennium Development Goals. In this context, dams are emerging as the most popular solution for many decision-makers.

Furthermore, commitments to reduce greenhouse gas emissions under the Kyoto Protocol provide new incentives for developing hydropower dams. However, dams are not the panacea they are made out to be. There are social and environment costs that need to considered. WWF, in association with World Resources Institute, has published this report to help informed decision making by stakeholders and policy-makers involved in dam construction plans and projects.
 
Report Summary

Dams are a blessing...

As they provide water for agriculture and hydroelectricity generation. Half of the world's large dams were built primarily for irrigation. In total, dams are estimated to contribute water to 12-16% of world food production. Hydropower currently provides 19% of the world's total electricity supply, with relatively low greenhouse gas emissions, and as a secure source of water supply, dams also play an important role with 12% of large dams designated for water supply. Many dams have been built for flood control, saving countless lives.

...and a curse too! 

Dams cause serious damage to freshwater ecosystems, affecting both nature and people. Already, in 60% of the world's major rivers flows are interrupted by dams, canals and diversions. Many freshwater habitats and species have been lost, with dams and their associated infrastructure, such as irrigation systems, a major culprit.
 
Environmental Impact of dams
 
* Dams disconnect rivers from their floodplains and wetlands. The damage to freshwater ecosystems can be devastating. They impact on the migratory patterns of fish, and flood riparian habitats, such as waterfalls, rapids, riverbanks and wetlands.
* By slowing the movement of water, dams prevent the natural downstream movement of sediment to deltas, estuaries, flooded forests, wetlands, and inland seas, affecting species composition and productivity.
* Dam operations also influence water quality. Water and sediment retention affect water quality and the waste processing capacity of rivers (the ability to break down organic pollutants). This could lead to production of toxic hydrogen sulphide gas that further degrades water quality.

Social Impacts of dams

* Direct impact: Large scale human population displacement. The World Commission on Dams (WCD) estimated the overall global level of displacement by dams to be between 40 and 80 million people (WCD, 2000).
* Indirect impact: Communities living downstream from dams, particularly those reliant on natural floodplain functions for their livelihoods such as agriculture, herding and fisheries, suffer the most when dams are built upstream.

Interbasin Water Transfer Schemes

* Direct impact: Large scale human population displacement. The World Commission on Dams (WCD) estimated the overall global level of displacement by dams to be between 40 and 80 million people (WCD, 2000). 
* Indirect impact: Communities living downstream from dams, particularly those reliant on natural floodplain functions for their livelihoods such as agriculture, herding and fisheries, suffer the most when dams are built upstream.

River basins under threat
 
The report presents an analysis that examines the present state of dam building in the world's major river basins. It is based on dams currently under construction that are over 60m high, as well as on data on dams that are being planned that are either higher than 60m or will have an installed hydropower capacity of more than 100 MW as of 2003. The analysis includes dams of all types: hydropower, irrigation, water supply, flood prevention as well as multi purpose dams. The analysis demonstrates how vulnerable river basins are, as more and more dams get built within the same basins or even on the same river. Valuable habitats and species are at risk of disappearing from the combined effects of not only one large dam but many.

Best practices
 
Taking best practices from several case studies, the report addresses the key question of how to provide services offered by dams without undue environmental damage and species loss, as well as benefits for all, in particular for those people directly affected by dams.

Key recommendations highlighted in the case studies include:

* Give priority to increasing water and energy efficiency * Undertake a comprehensive options assessment
* Involve stakeholders in project assessments
* Ensure a basin wide understanding of ecosystem functions * Ensure implementation of effective mitigation measures, in particular environmental flows
 
Download full report: Rivers at Risk: Dams and the future of freshwater ecosystems| pdf Format | 4.28 MB | total number of pages: 48
Download summary report: Rivers at Risk: Dams and the future of freshwater ecosystems| pdf Format | 387 KB | total number of pages: 8