The pelicans you see gathered at the Bow River next to Memorial Drive might not be there much longer.

In the winter, the City of Calgary began construction on weir structures engineered to raise water levels.

This will have both positive and negative effects on the surrounding ecosystem, according to a local expert.

“Effectively (the weir) has created a barrier to upstream fish migration,” said Mac Hickley, manager of the River Valleys Committee for Parks Foundation Calgary.

This has stopped the flow of fish on the river, creating a buildup of river fish making it easy fishing grounds for the pelicans.

“The development itself will have a positive impact on the fisheries,” said Hickley. “It may result in the pelicans dispersing from that area. But the pelicans congregating there was never a natural occurrence.”

The plans for the Bow River are also going to open up the lower part of the river to rafters, canoes and kayakers, upon project completion in 2011.

Until now the weir has been referred to as a “drowning machine,” falling off into the water at the weir leads to an almost certain death.

The increase of human traffic down the river may also have an effect. “From what I’ve gathered rafters do not have a huge effect on the fish except the litter that they leave behind,” Hickley told Metro.

The connection between the two parts of the river far outweighs the temporary environmental effect of construction. Hickley said, “In a couple years (the construction) will be over and nature can take its course.”

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