How Clean and Green is Hydroelectricity?

Along with our beavers, other Canadians have been active dam builders. Early dams were quite beaver-like. They needed only to back up enough water to create a “head” – a drop in the water flow that could turn a water wheel to power a saw or a grinding mill; our earliest entry into renewable power sources. In pioneer times, things were pragmatic; there was no room for clean and green thoughts. Both access to water power and the indispensable value of water itself pushed early settlements to build as close as possible to the water – often right on the 25-year flood plain.


Dams have changed and now we hear that hydro-electricity is “clean, green and renewable” and will be a major part of our move away from carbon-based energy and into “decarbonized” renewable energy for our economic future. That may be fine for “in-stream” or “flow of the river” generation where small turbines in the current flow use the natural topographic drop and the seasonal pattern of water flow is not changed.


But for electricity generation that depends on dams, “clean, green and renewable” should be reexamined with reference to other programs that depended on dams. Not only are we building big dams that flood huge areas, as did the W.A.C. Bennett dam in the Peace River valley but also we are changing the geography of large areas. The La Grande and other large geographic rearrangements by Hydro Quebec and the diversion of Manitoba’s Churchill River into the Nelson River and the conversion of Lake Winnipeg into a hydroelectric reservoir exemplify the scale.

The Three Gorges Dam in China illustrates the powerful social impacts of hydroelectric dam projects. This dam flooded 244 square miles and displaced 1.4 million people with another 100,000 still to be displaced. The societal destruction that resulted has been reported to be the greatest current source of social unrest in China. In addition, many reports detail side-effects ranging from landslides to earthquakes, up to magnitude 7.9, and large shifts in ecological processes and major losses of biodiversity.*


Our dam building has similar unwanted effects. It is fundamentally impossible to build dams without changing the seasonal flow patterns of the river. The alternate flooding and re-exposure of large areas of shoreline has several effects. They include increasing the flow of methylated mercury into the food chains.


For surface overflow dams, the water warms on the surface of the impoundment. When released downstream over the surface of the dam that warmed water destroys all cold-water habitats for spawning of trout or salmon and for many other vertebrates and invertebrates that form the food chain.


Surface overflow dams also remove much of the suspended particles from the downstream flow. This reduces downstream particle deposition and changes the balance toward increased erosion. Deposition of particles in dammed impoundments also can reduce “silt-fertilization” of riverine marshes and plains. Normally, small particles laden with nutrient ions are carried by high water and dropped in riverine marshes and interval land as the high water recedes. Such silt fertilization significantly boosts ecological production in those riverine habitats.


Even with expensive “ladders” or bypasses, dams also interrupt the free movement of animals, breaking the populations into isolated genetic and demographic units. Because small populations suffer frequent local extinctions, they must be recolonized by plant or animal movement or the local extinctions will aggregate into regional extinctions. Dams slow or prevent movement vital in recolonization.


These and many other effects should be viewed as costs in the economics of electricity but usually they are not. Instead they commonly are set aside as externalities. In other words as side effects of the business of supplying electricity but they are not counted as real costs. In the business world, costing usually requires stating the values in dollars. Dollar costs for damages to natural processes are difficult to obtain. But they are real and should be entered as significant variables in planning decisions.


Hydroelectricity qualifies as renewable only because the water flow is assumed to continue at the same rates as when the dam was planned. As climate change moves weather patterns geographically, the water supply at particular locations may also vary. Given the increased variance that accompanies climate change and given that some large dams are contributing to climate change, the “renewable” assumption may fail. In 2014 Brazil suffered electricity blackouts when their large dams were hit by the worst drought in 80 years.


Hydro-electricity obtained by damming our rivers and streams is not completely “Clean and Green”. There also are environmental and social costs that should be considered. Decisions about hydro-electricity should always consider two columns – disadvantages as well as advantages. When comparing hydroelectric generation to wind turbines and solar panel farms, the items in those two columns for all types of generation should be truly comparable.


Many old dams in various states of disrepair still occupy narrow spots in many creeks and rivers both in settled Ontario and throughout the boreal forest. Where people have built infrastructures on flood plains around old impoundments, they argue for old dams simply to maintain the water level for their recreational convenience or their profit. In the boreal forest, the continuing ecological effects of old useless dams are ignored. The costs of removal are too inconvenient to consider. In some jurisdictions, such dams without a purpose are being removed to ameliorate their unwanted effects. In the last 25 years nearly 900 such dams have been removed in the U.S. Dams without a purpose have also been removed in Europe. When dams are removed, damages to the biota begin to repair themselves. See, for example:


* As a global example see:


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