Partial Diversion of the Rupert River

Scheduled to take place in November 2009, the partial diversion of the Rupert river will entail creating a forebay and tailbay (also called diversion bays) and reducing the river's flow.

Impoundment of the Rupert diversion bays

Once impoundment, the Rupert diversion bays will cover a total area of 346 km2. The instream flow release structures at the Lemare, Nemiscau-1 and Nemiscau-2 dams and at Arques and LR-51-52 dikes will allow for the release of 100% of the mean annual flow of the Lemare and Nemiscau rivers into the Rupert River. The main structure, located at Rupert's spillway, will release 29% of the Rupert's mean annual flow back into the river, which will result in a mean annual flow at Waskaganish of 48%. The level of Mesgouez Lake will remain untouched by the rise in water levels in the Rupert diversion bays.

During impoundment of the diversion bays, which will last a few weeks, an environmental monitoring program will be carried out in close cooperation with the Cree tallymen concerned. The program will focus on tracking wildlife in the area and observing the formation and characteristics of the ice cover.

Rupert River ecological instream flow regime

In addition to creating the Rupert forebay and tailbay, the partial diversion involves reducing the river's flow downstream of Rupert dam.

The instream flow release structure at the Rupert spillway will return 29% of the mean annual flow to the river. The ecological instream flow will be 45% at Lake Nemiscau and 48% at Waskaganish, thanks to inflows from the rivers and streams that empty into the Rupert River.

Of the eight hydraulic structures planned downstream of Rupert dam, four are currently under construction at kilometre point (KP) 20, 33, 170, and 223. Work is also being carried out in preparation to build the structures at KP 49, 85, 110 and 290. Once completed, these structures will help maintain water levels in the Rupert over about half its length downstream of the dam.

It is important to note that these mitigation measures will help protect fish habitat, maintain navigation and preserve the landscape of the Rupert River.

Environmental monitoring of the water quality and the condition of the ice cover in terms of snowmobiling safety will be carried out during winter 2009-2010.

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