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Eastmain 1-A and Rupert River Diversion Hydropower Project

Maintening Fish Productivity


The aquatic ecosystems in two sections of the project study area will undergo significant changes, namely in the reduced-flow area and the Rupert diversion bay section. Although every section of the study area have been examined within the context of the project impacts review, these sections be subject to specific mitigation and compensation measures, as well as a follow-up program on fish and fish habitat.

Reduced-flow area

The Rupert River stretches out over 560 km from Mistassini Lake to Rupert Bay. There will be a partial flow diversion of the river 314 km from its mouth. An ecological instream flow regime has been planned, in order to protect fish habitats and to maintain fish species downstream from the Rupert dam. This regime will be adjusted according to fish lifecycles such as: spring spawning, summer feeding, fall spawning and winter egg incubation. At the closure point, 71% of the mean annual flow will be diverted, while 29% of the flow will follow its natural course. However, due to lateral water inflow from the tributaries, the flow at the mouth of the Rupert River near Waskaganish will be 48% of the mean annual flow.

Seven weirs and spurs, as well as a rock blanket, will be built at different sites along a 314 km stretch downstream from the closure point. These hydraulic structures will permit the maintaining of 91% of the fish habitat area. Water quality will remain suitable and will permit the maintaining of aquatic ecosystems. By means of instream flow release structures, mean annual flow in the Lemare and Nemiscau rivers will remain the same as in present conditions.

  • Project impacts on fish productivity

In the Rupert River, the fish community is comprised of 22 species. In the reaches influenced by hydraulic structures, flow velocity will be diminished which will accentuate their lentic characteristics. This phenomenon will be favourable to species that prefer lentic habitats, such as lake sturgeon, walleye, lake whitefish, northern pike and fallfish. However, there will be a 10.7% decrease of global production potential (except for Nemiscau Lake, which will not be affected), which will impact upon longnose sucker, burbot, round whitefish, brook trout and spottail shiner. Of the 166 known spawning grounds, only four will be affected by the changes in river flows or by the construction of hydraulic structures.

During summer, the anadromous cisco lake population, to which the Waskaganish Cree community attach great value and which they fish at the Smokey Hill site, feeds in the Rupert Bay and in the Baie-James. At the end of summer and the beginning of fall, it travels back to the lower portion of the Rupert River, up to the kilometric point (KP) 24.5. Notwithstanding the decrease in the streamflow at the mouth of the river, anadromous lake cisco will be able to migrate upstream of the existing spawning ground, which is located between KP 13.5 and KP 24.3. The construction of a rock blanket at KP 20.4 will help to maintain mean and maximum depths as well as aquatic habitat areas upstream from the structures. Moreover, despite changes to hydraulic conditions upstream and downstream of the rock blanket, favourable spawning conditions for this species will be maintained.

  • Conditions to be fulfilled by the proponent

The proponent must submit his fish and fish habitat follow-up program to the Ministère, for approval. He will follow-up on the fish community and on the dynamics of fish populations in the Rupert River. He will also include spring larvae drift to his follow-up program. Moreover, in partnership with the Waskaganish community and the concerned tallymen, he will follow-up on the anadromous lake cisco population structure and migration downstream of KP 25 and will promote voluntary catch registration.

Various compensation and mitigation measures will be implemented in order to limit impacts on fish and fish habitat. Among these measures, 3 spawning grounds will be developed along the first 314 km of the Rupert River to compensate for spawning grounds affected by the changes in the river’s flow or by the hydraulic structures. The physical integrity of the new spawning grounds and their use by spawners are also part of the follow-up program. Should the objectives of these spawning grounds not be reached, the proponent will implement corrective measures.

A follow-up on the use of the eleven lake sturgeon spawning grounds located downstream of the Rupert River dam will be undertaken. A spawning area located at KP 290 will be redesigned, so as to take into account the new flow conditions. A 60 km stretch downstream from Nemiscau Lake will be stocked with juvenile lake sturgeon to restore the population in this sector. Moreover, in partnership with concerned users, the proponent will develop and undertake a program intended to promote lake sturgeon voluntary catch registration downstream from the KP 314 of the Rupert River.

The brook trout population in the first 314 km of the Rupert River is not considered significant. Judging from the inventories, this species seems to prefer the tributaries. Four tributaries of the Rupert River, located at KP 41, 191, 265 and 311, will be developed to increase their potential.

Adaptive management of ecological instream flow, which consists in modifying the flow, should the assessment of its values or periods prove to be faulty, is a part of the project design. This method of instream flow management will apply to anadromous lake cisco, white and longnose suckers, lake sturgeon, walleye and lake whitefish. Different methods will be implemented to analyze the results of each year’s follow-up and, as required by the impact assessment and review procedure, any change in the instream flow regime will have to be authorized by the Ministère.

Rupert Diversion bays section

The Rupert River waters will be diverted to the north, creating two diversions bays linked by a tunnel, the forebay to the south and the tailbay to the north. Design of the hydraulic and retaining structures, such as 4 dams, 8 canals and 75 dikes, was optimized to reduce flooded areas to a minimum.

  • Project impacts on fish productivity

Following the impoundment, which will last about one month, the various lakes and streams in the section will be interconnected to form one body of water. Data from La Grande Complex follow-up programs indicates a thinning of fish populations following impoundment of the reservoirs. This phenomenon will contribute temporarily to a reduction of fishing yield. However, decomposition of flooded organic matter will increase primary productivity, which is beneficial to the fish. Thus, two to six years following the impoundment, fishing yields will gradually increase. Ten to fifteen after impoundment, fish communities in the forebay should resemble those found in natural lakes, such as Mesgouez Lake. The increase in aquatic areas in the Rupert diversion bays will bring about an increase of approximately 500 t in fish biomass, distributed mainly between the dominant species, such as walleye, white sucker, northern pike and lake whitefish.

Lake trout is known as a species which has difficulties adapting to reservoir conditions, due to winter drawdown, which drains spawning grounds. However, less important winter drawdown in the Rupert diversion bays could help maintain fish populations. Moreover, the developing of spawning grounds outside the main reaches, where the drawdown is slight, will allow the species to remain in certain zones.

Hydraulic conditions in the forebay will be beneficial to lake sturgeon feeding. In the long term, downstream migration should bring the lake sturgeon to colonize the tailbay. However, two spawning grounds, located near Mesgouez Lake and in the Misticawissich River, will be flooded during impoundment.

The Rupert genetic line brook trout lives in the Rupert River watershed, from Mistassini Lake to the mouth of the Rupert River, including the Lemare and Misticawissich rivers and some lakes and streams of the diversion bays section. At the time of impoundment, genetic integrity of the genetic line will be protected. Although there will be a decrease in brooktrout abundance in the diversion bay, within the Rupert River watershed, project impacts on the population will be slight and will not endanger its survival.

  • Conditions to be fulfilled by the proponent

As required by the impact assessment and review procedure, the proponent will submit his fish and fish habitat follow-up program to the Ministère, for approval. The developed spawning grounds will be subjected to the same type of follow-up as those in the Rupert River. Fish community and fish population dynamics will also be included in the follow-up program. This will help to ascertain predictions regarding fish biomass and species abundance and, if need be, to adjust the mitigation measures. Moreover, the proponent will implement a communication plan regarding follow-up results. He will also follow-up on brook trout between Mistassini Lake and Mesgouez Lake.

In Des Champs, RP062, RP030 and Cabot lakes, new spawning grounds for lake trout will be developed. The proponent will follow-up on spawners’ use of these developments. Should they prove to be inefficient, other spawning grounds will be developed, in different bodies of water, following authorization by the Ministère, as required by the northern impact assessment and review procedure. The follow-up program will include the monitoring of the physico-chemical conditions in the RP062 and Des Champs lakes.

As for the lake trout, two spawning grounds will be developed for lake sturgeon in the forebay. Moreover, a multispecies spawning ground will be developed to promote lake sturgeon spawning in this section. There will be a follow-up on the physical integrity and spawners’ use of every spawning ground developed in the diversion bays.

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