Coquitlam Lake Dam

 
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Did you know that Coquitlam Lake has existed since the last glacier left the region over 10,000 years ago? The building of dams at or around the outlet of the lake only dates back to the late 1800’s. The first was a small crib dam constructed at the outlet of Coquitlam Lake by the City of New Westminster in 1892 to supply water to a growing community.

In 1905, the Vancouver Power Company (a subsidiary of the BC Electric Railway Company and a predecessor to BC Hydro), completed construction of a small 3.3 metre long, log dam below the outlet of Coquitlam Lake (and a tunnel to Buntzen Lake) for hydroelectric purposes, and changed the Coquitlam River watershed forever.

While water continued to be piped to New Westminster and adjacent areas for community purposes, the largest portion of the Coquitlam River flow was diverted out of the watershed through the tunnel to Buntzen Lake and penstocks to an electrical power generating plant at sea level on the Indian Arm of Burrard Inlet.

Because of increasing demand for electricity due to rapid population growth, another larger dam was completed by 1915, and most of the water flowing into the reservoir was licensed in perpetuity to the power company for production of electricity. This dam raised the lake level by an additional 18.3 metres (and increased the surface area of the lake by approximately 30% to 12 km2), but did not provide access for fish passage like the previous two dams.

BC Hydro, the owner of the dam, completed upgrades to this earth and rock fill dam in 1985. In late 2009, a new dam was constructed immediately downstream from the existing dam to address seismic concerns. The present dam has a crest length of approximately 400 metres with base, crest and gravity spillway elevations of 133, 161.4 and 152 metres respectively. The general annual range of reservoir water surface elevations is between 146 and 150 metres above sea level, although these ranges may vary. Fish passage facilities have not been incorporated in any of the design, construction or upgrade work completed to date on the Coquitlam Dam. BC Hydro currently produces approximately 200 gigawatt hours of electricity each year – enough to provide electricity for approximately 18,000 homes.

As a result of construction of the Coquitlam Dams over the last century, fish access to large areas of salmon spawning and rearing habitat above the dam was cut off, the Coquitlam sockeye salmon run was extirpated. Substantially reduced water flows severely impacted salmon spawning and rearing habitat below the dam, contributing to a severe decline in salmon production in the river system.

It is hoped that through implementation of the new Coquitlam-Buntzen Water Use Plan, increased water flow management regimes initiated by BC Hydro in 2010, in combination with the completion of new spawning and rearing habitats and continuing hatchery and stewardship operations, will improve conditions and increase salmon production in the river system downstream from the dam. Efforts are continuing toward re-establishing runs of sockeye and other salmon species in the area above the Coquitlam Dam by establishing continuity between the two watersheds, either by a trap and truck procedure, or preferably by fish ladder.

 
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Our Roundtable Watershed Coordinator can be reached at coordinator@coquitlamriverwatershed.ca

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