The environmental effects of a hydropower project, particularly one involving a dam and reservoir, are significant and must be taken into account when a project is under consideration. What is going to be submerged when a reservoir is created? What effect will the dam or barrage have on sedimentary flow in the river? What are the greenhouse gas implications? Whose interests are affected? For a run-of-river scheme the level of disruption is likely to be lower but extensive environmental studies will still be required. In both cases all these issues must be addressed. Small hydropower schemes are rarely disruptive on the same scale as large hydropower projects and their impact is usually limited so that decisions can often be made at a local rather than a national level. Large schemes have the potential to affect regions and require much more careful scrutiny at regional or national levels.
This problem is not new. Humankind has been altering waterways for at least two millennia and some of the early structures still exist. Roman dams can be found in use in Spain today. In the past dams have been used to provide water for drinking and irrigation and to help control waterways. Only since the end of the 19th century has electricity generation been added to this list of uses.
While dams will always change the environment, in the past the changes wrought have generally been considered positive, providing an improvement in the living standards and conditions of the people affected. Greater environ- mental awareness coupled with some careless developments led to a change in perceptions toward the end of the 20th century and since then large hydropower schemes have become much more difficult to promote and build. This prompted work by the World Commission on Dams to look at what made a good and what made a bad hydropower project.
The work of the World Commission on Dams resulted in 2000 in the publication of Dams and Development: A New Framework for Decision Making.4 Since then a reappraisal of large hydropower has taken place resulting in greater acceptance of the need to develop waterways. In particular, the link between water projects and the standard of living of people affected has been recognized. This is particularly significant in Africa where hydropower development is far behind other continents and standards of living are often very low too.
So while it is recognized that a hydropower project, particularly a large one, will be disruptive, it is also recognized that it need not necessarily be destructive. Environmental changes will take place, people may be displaced, and habitats destroyed but all these effects can be handled sensitively so that, for example, displaced communities are given a stake in the project and much improved living conditions and inundated habitats are recreated alongside the area destroyed.