Hydroelectricity is often presented as a green energy source, but how true is this? Hydro has several environmental and aesthetic drawbacks that make it less than ideal compared to the clean power provided by sources such as wind and sun.
The most visible environmental aspect of Hydroelectricity is its impact on the environment, as it requires the damming of rivers. This causes the flooding of low lying land behind the dam and while this is often not desirable, the reality is that it is just an alteration to the environment. If the dam was to remain filled with water all the time, this would have no environmental effect outside the dam area.
Why is it then that Hydroelectric installations are associated with high levels of methane production? When organic matter from plants and animals breaks down without oxygen present, methane is formed. This anaerobic process is very similar to the ones that resulted in the formation of the fossil fuels we use today.
Consider the following chain of events that unfold once the dam has been constructed.
First the land is submerged and the vegetation with it. The vegetation drowns and begins to rot. Since there is very little available oxygen, the plant material breaks down to form, among other things, methane that is absorbed by the water.
This is all normal so far, as this would occur with any permanent flooding. But a Hydroelectricity dam is usually both a power supply and an urban water source and so the water levels in the dam tend to rise and fall a great deal. In dry times the water level will drop to its lowest levels which will expose land around the edges of the water and possibly at the bottom of the dam itself.
This exposed land is ideal for growing plants and so it blooms with new life. As most dams are shallow, the amount of land exposed at the edges as the water drops can be very large. The shallower the dam, the more land is exposed annually.
After a time the rains return and the dam fills up again. The new vegetation is then also covered with water and so rots anaerobically and so more methane enters the water of the dam.
This continues year after year, resulting in a slow but steady increase in the amount of methane absorbed in the water of the dam. This is a problem because methane is not very soluble in water. When the water passes through the dam’s turbines it escapes the water and enters the atmosphere.
Methane is a dangerous greenhouse gas. It is approximately 21 times more effective at trapping heat in the atmosphere than Carbon Dioxide. This means that electricity from a Hydroelectric plant can be up to three times more polluting per energy unit than the same power from a coal or oil fired plant. This figure depends on the climate and geography the Hydro plant is located in, as these factors determining the amount of vegetation added to the dam each year. The Intergovernmental Panel on Climate Change (IPCC) has recognized this issue and now includes methane from Hydroelectricity in national emissions totals. 
Hydroelectricity may be a renewable energy source but it is not an environmentally friendly one. When looking at whether a new Hydro plant is warranted, methane emissions must be taken into account. A cleaner and greener solution is to build solar and wind energy stations as once constructed these have no emissions associated with them at all.
For more information on electricity generation and its issues, visit the Fossil Fuels section of Roger Vanderlely’s website. There you can also find out about getting a good deal on cheap solar panels to become more power independent and do your bit for the environment.
This article is brought to you by George Zalcman. George Zalcman has always had a passion for green technologies, and believes that we should all get on the boat before natural resources become limited. George Zalcman is part of an air to water technology hoping that this will eventually bring an end to the water crisis as well.
