Courtesy: BC Hydro, County of Northern Lights
July 31, 2024
Re: Site C reservoir filling
We are writing to share an update on our plan to fill the Site C reservoir and commence commissioning of the generating units. As you’re aware, the Site C Clean Energy Project is
located near Fort St John, B.C. on the Peace River. It is the third hydroelectric facility on the river, making efficient use of water stored upstream in Williston Reservoir.
While we recognize drought has impacted many areas in both British Columbia and Alberta, the flows coming out of Site C during reservoir filling will continue to be within our normal operating range, and similar to what we have seen over the past couple of years.
Timeline for filling
We are planning to start reservoir filling the last week of August, subject to potential changes resulting from wildfires, significant rainstorms, or other operational considerations on the system. It will take up to four months to completely fill the Site C reservoir. Filling will proceed at varying rates, with water levels rising between 30 centimetres and three
metres per day. The new reservoir, stretching from Fort St John to Hudson’s Hope, will be 83 kilometres long and widen the Peace River by two to three times, on average. At the dam site, the water will be 52 metres deep.
Filling under drought conditions
The water used to fill the Site C reservoir will come from the upstream Williston Reservoir. The water is managed through BC Hydro’s regular operations where power is generated at WAC Bennett, and then Peace Canyon, before it enters the Site C reservoir. The current drought situation will not impact filling the reservoir. The amount of water required to
fill Site C’s reservoir is many times less than the annual discharge from the upstream Williston Reservoir, even under a drought year. The Site C reservoir will be about five per cent the size of the Williston Reservoir.
Downstream flows
The minimum flow we must always release from Site C is 390 cubic metres per second (m³/s), though there may be times during the reservoir filling period where flows coming out of Site C could be higher. We expect any notable changes to Peace River flows to only occur early on in the reservoir filling process and in the area immediately downstream of the dam, within British Columbia. As the river flows into Alberta, water from tributaries joining the Peace River lessen any changes caused by filling the reservoir.
Commissioning the generating units
During the later stages of reservoir filling, the commissioning process for the generating units will be underway and continuing into 2025. We expect power from the first generating unit will be online and supplying customers this December. When Site C begins operating later this year, water released from the facility will vary between
390 and 2,700 m³/s, depending on electricity demand. This is similar to the range of flows over the past several decades at the Site C location.
These water level changes will have only small effects on Peace River flows downstream of the dam and little impact on Alberta, as they will decrease with distance from the Site C dam site.
Next steps
We continue to be committed to communicating and engaging with a number of stakeholders, along with Indigenous Nations in British Columbia and Alberta, about reservoir filling. We will be announcing the start of reservoir filling and will share progress updates through various means. If you would like more information about reservoir filling, or commissioning of the project, we are happy to connect and engage further.
