5.9 Environmental impact of hydroelectricity
We might usefully start by briefly summarizing the environmental benefits of hydroelectricity compared with other types of power plant:
- in operation it releases no CO2, and negligible quantities of the oxides of sulfur and nitrogen that lead to acid rain
- it produces no particulates or chemical compounds such as dioxins that are directly harmful to human health
- it emits no radioactivity
- dams may collapse, but they will not cause major fires
- hydroelectric plant is often associated with positive environmental effects such as flood control or irrigation, and in some cases, its development leads to a valued amenity.
However, during the twentieth century, the construction of large dams has led to the displacement of many millions of people from their homes, and dam failures have killed many thousands. We’ll consider these and other deleterious effects under three headings:
- hydrological effects
- other physical effects
- social effects.
These three categories are not of course independent. Any hydrological change will certainly affect the ecology and thus the local community.