The world is currently facing many environmental problems related to global warming as a result of increased greenhouse gas emissions associated with the burning of fossil fuels such as coal. Consequently, there is a frantic search for cleaner sources of power to supply the world’s energy demands. Many new energy sources are being explored, including hydroelectric power, which is a renewable source of natural energy that is toted to be both clean and green But is it as environmentally friendly as it’s made out to be?
Effects of Hydroelectric Dams on Rivers
Dams by their very nature block off a waterway, altering the ecology of the river dramatically. Dams restrict the flow of water downstream, and can reduce once fast flowing rivers to just a trickle, or worse still, a dry river bed. This is exacerbated when dams force rivers to alternate between drought and flood in a matter of minutes. Rapid changes in water flow can cause severe erosion, often damaging surrounding riparian ecosystems; sharp temperature variations, which can kill fish and aquatic life; and sudden fluctuations in water levels, which can be fatal for aquatic life, as well as other wildlife, such as birds that may be nesting on riverbanks.
Migratory fish, such as salmon, cannot swim upstream to spawn in the habitat they require for reproduction, and consequently the populations of these fish rapidly decrease. This often has a huge impact on local inhabitants and wildlife that were dependent on this resource for food. Fish moving downstream are put at further risk if they should haplessly swim into the dams turbines, where they will most likely get chopped into sushi – sushi, which unfortunately nobody gets to enjoy.
Dams can also have an adverse economical impact on a region, due to loss of livelihoods from agriculture and fisheries, and from recreational activities including tourism, fishing, kayaking, etc.
Furthermore, as dams restrict water movement, water that accumulates in the reservoir behind the dam wall may experience an increase in nutrients from agricultural runoff. This can fuel algal blooms, which can be fatal to fish and aquatic organisms, and sometimes to wildlife that consume them.
Hydroelectric Dams Contribute to Global Warming
But arguably the most astounding revelation that has recently come to light is that large reservoirs can actually contribute more to global warming than coal power plants. It seems absurd, but read on…
Recent studies have revealed that large reservoirs emit significant amounts of carbon dioxide and methane, both of which are greenhouse gases that contribute heavily to global warming. According to International Rivers, methane is 25 times more potent than carbon dioxide when it comes to heating up our planet, and reservoirs contribute a whopping 23% of total methane emissions from human sources. Methane and carbon accumulate in the reservoir as a result of rotting organic matter that is carried downstream and is trapped behind the dam wall, or from the original riverine forest vegetation that was engulfed by the reservoir, and which slowly decomposes over time. These gases are emitted through natural gaseous exchange at the surface of the lake; when water flows over spills; or as it rushes through turbines.
Is It All Doom And Gloom?
Hydro-electric power is a renewable energy source after all, and if managed responsibly, hydroelectric dams needn’t have such devastating impacts on our rivers. Firstly, some provision would need to be made to allow the free-flow of water and nutrients downstream, and to enable the natural dispersal of aquatic species in order to maintain an ecologically sound river ecosystem. If the dam is managed in a way that mimics natural seasonal flow regimes, this can be achieved. Another option would be to make use of diversion hydropower plants rather than impoundments (dams), where the river doesn’t necessarily need to be damned (pun intended). The diversion type of hydro-plant channels water through a canal outlet, where the energy is harnessed without impeding the flow of water downstream. This seems like a good solution if water does not need to be stored in a reservoir for other purposes (e.g. to supply drinking water).
Conservation groups such as American Rivers and International Rivers are in principal not against hydroelectric dams, however, they are of the opinion that there are far too many, and a fair amount of these are obsolete dams that are equipped with outdated technology, and are therefore not able to operate efficiently or effectively. These organizations are motivating for the removal of obsolete dams in an effort to restore rivers to their natural state. They oppose the construction of new dams, on the grounds that money could be better spent on focussing on harnessing energy more effectively from existing dams that are capable of meeting the nations energy demands.
Yes, there are cleaner and greener alternatives to fossil fuels to supply our energy requirements, but they typically come with a whole new set of environmental problems. Hydroelectric dams are no exception. The financial outlay to get them up and running effectively is huge, and as climate change is expected to affect future rainfall patterns and river flow regimes, one has to question whether the long-term viability of these projects justifies the expense. The cheapest, cleanest, and quickest solution to reduce greenhouse gas emissions is to invest in methods that use energy more efficiently. And while hydropower may indeed play an important role in supplying a clean renewable energy source, this needs to be conducted in a responsible manner, taking the environmental impacts into consideration. As the conservation organization, International Rivers so aptly puts it: ‘healthy rivers are essential for a healthy planet, especially in light of the additional stresses that climate change will have on river-dependent communities and ecosystems.’ They have a slogan that sums up the situation entirely – ‘Don’t sacrifice the planet’s arteries to save her lungs!’