Damage & Damage Control of Large-Scale Dams

Revelstoke is synonymous with large dams; Revelstoke, Hugh Keenleyside, and Mica dams have changed the ecology and biodiversity of the area.

Changing watercourses is nothing new for humanity. The Roman Empire is responsible for building aqueducts throughout Europe thousands of years ago, but the scale of dams and water control has never been as large as it is today.

Locally, dams have become an integral piece of infrastructure in British Columbia. Dams offer inexpensive hydroelectric power, are a significant financial contributor to provincial programs, provide flood protection and areas to recreate.

But it’s not all a good thing.

That massive dams have long reaching environmental impacts is now taken as fact. This story is dedicated to learning about the ecological changes dams cause and the corrective mitigation techniques being utilized locally. It isn’t taking into account the social structures that are irrevocably changed, such as the flooding of existing communities. Environmentally, a known impact has been the disruption of spawning and migration routes for
anadronous (ocean maturing) salmon like the chinook. Damming of the Columbia River has resulted in the loss of 30% of Arrow Lake’s kokanee spawning grounds, as well as spawning grounds of rainbow and bull trout. While the land-locked versions still spawn locally, they are smaller than their ocean faring cousins, who have not swam in the Arrow Lakes for over 75 years, since the construction of the Bonneville Dam on the lower Columbia River. Many are working hard to repatriate salmon to the Columbia. The Canadian Science Advisory Secretariat Science Advisory Report 2009/075 states the decline in chinook, in part from the construction of hydroelectric dams, and part from overfishing, correlates with and is one reason why there is a population reduction of southern resident orcas in the Northern Pacific Ocean. Orcas’ primary food source is chinook. What happens in the interior mountains affects the distant coast.

Fortunately for Revelstoke, the large local reservoirs are set in bedrock foreshores and have glacier fed tributaries, so there is no issue with the siltation of reservoirs and head points (small reservoirs). Regardless of placement, dam and reservoir fragmentation of aquatic and terrestrial ecosystems and can result in loss of species, their diversity and abundance.

So how is damage mitigated?

With the large environmental impacts comes the desire to learn more and do better in the future. Companies are investing in mitigating the impacts of their dams and BC Hydro has spent hundreds of millions of dollars over the past decade learning about and tailoring their reservoir operations to be as least disruptive as possible to the surrounding ecology.

We contacted Giles Shearing, who has an MSc specializing in fisheries and fluvial geomorphology, to ask about what a company like BC Hydro might do to lessen their impact. Shearing is a Revelstoke resident who is passionate about the environment, and is the Principal and Lead Consultant at SEC Consultants. “It’s important to remember that with large dams, rivers are turned into lakes and therefore the ecology changes. There are more than 800,000 small dams worldwide and lots of large dams,” Shearing explains. “Each dam and reservoir have different biotic and abiotic characteristics that requires unique and specific mitigation. My comments are related to dams, not surrounding
infrastructure like roads and right of ways for transmission lines.” Shearing notes that hydroelectric companies use a variety of means to try and lessen their environmental impact. “These can include ramping rates. A ramping rate is how quickly water elevations or flow rates can change,” Shearing explains. “There are also minimum flow requirements, which ensure the river has enough water to maintain productivity.” He adds that target flows help reduce the morality of target species of fish, birds and wildlife. With smaller dams, gravel can be added
downstream of the dam to ensure successful fish spawning and rearing. “There is no doubt that regional ecology is altered,” Shearing says. “Dams have an impact and there are many people working very hard to understand, minimize and or eliminate these impacts.”

For example, reservoirs often struggle with low phytoplankton, an important food for higher trophic levels, a necessity to ensure healthy aquatic systems. According to the Royal BC Museum exhibit Living Landscapes, the Arrow Lakes suffer from a lack of seasonal blooms. The lakes are now being fertilized in an attempt to increase biomass, ensuring healthy fish populations.

Intriguingly, the consequence of dams have entered into the climate change discussions. “The risks of rivers in the world during and after climate change are not well known,” Shearing elaborates. “Some scientists think dams may have the ability to attenuate the warming effect of climate change by using their storage capacity to release flows that match historical discharges and/or ensure enough cold water.”

The fact remains that dams, how they work, how they affect the world around them and, finally, how companies are trying to alleviate these effects, is a huge subject and requires a far larger scope than this post can allow.
For those who are interested, check out the following videos and links to learn more.


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