Reservoirs

One of the purposes of retaining structures is to store water. Why build reservoirs to store water? Given that electricity consists of countless electrons in motion, it cannot be stored directly. However, storing water for future use allows utilities to meet the demand for electric power... demand that varies considerably according to the time of day and the season. We store wood in a dry place for the same reason: so we can burn logs when we need them.

The ability to turn the tap on and off
In Québec, the demand for electricity is very high on cold winter days and drops significantly during the summer. To ensure a year-round supply of water for its generating units, Hydro-Québec must effectively manage its water resources, which includes analyzing the impact of precipitation and forecasting future requirements.

Hydro-Québec owns 25 large reservoirs. Together, these huge man–made lakes have a maximum storage capacity of 170 billion kWh–the equivalent of Québec's electricity needs for an entire year.

Hydro-Québec's five largest reservoirs

RESERVOIR HYDROELECTRIC COMPLEX VOLUME TO GENERATE ELECTRICITY TOTAL VOLUME RESERVOIR SURFACE AREA
    Billions
of m3
Billions
of m3
Km2
CANIAPISCAU LA GRANDE 39.0 53.8 4,318
MANICOUAGAN MANIC-OUTARDES 35.2 139.8 1,973
LA GRANDE 3 LA GRANDE 25.2 60.0 2,536
ROBERT-BOURASSA LA GRANDE 19.4 61.7 2,815
AUX OUTARDES 4 MANIC-OUTARDES 10.7 24.3 625

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