W.A.C. Bennett Dam: British Columbia's Peace River Hydroelectric Giant

**W.A.C. Bennett Dam** on the Peace River in northern British Columbia is one of the largest earth-fill dams in the world and the centerpiece of BC Hydro's Peace River generating system. Completed in **1968**, the **186-meter** dam created **Williston Lake**, the largest artificial lake in British Columbia and one of the largest in the world, stretching 250 kilometers through the Rocky Mountain Trench.

Introduction

Named after the premier of British Columbia who championed the project, the dam's **2,730 MW** G.M. Shrum generating station was the largest in Canada when built and remains one of the most important electricity sources in western Canada. The dam was the first of two major dams on the Peace River, followed by the Peace Canyon Dam downstream and the recently completed Site C Dam.

Engineering & Structure

• Type: Earth-fill dam with gravel-zone core
• Height: 186 meters
• Crest Length: 2,068 meters
• Fill Volume: 57 million m³

W.A.C. Bennett Dam is a zoned earth-fill dam containing 57 million cubic meters of material, making it one of the largest embankment dams in the world. The dam rises 186 meters above the Peace River, with a crest stretching 2,068 meters across the valley. The material for the embankment was sourced from glacial deposits in the surrounding terrain.

The G.M. Shrum generating station at the dam's base houses 10 turbine-generator units with a combined capacity of 2,730 MW. The station is named after Gordon Shrum, the first chairman of BC Hydro. The dam also includes a massive spillway channel capable of releasing flood flows safely around the embankment.

Geographic Setting

• River: Peace River (Mackenzie River tributary)
• Location: Hudson's Hope, British Columbia, Canada
• Coordinates: 56.02°N, 122.20°W
• Williston Lake Length: ~250 km

The Peace River originates in the Rocky Mountains of northeastern BC and flows 1,923 kilometers northeast through Alberta to join the Slave and ultimately the Mackenzie River, which drains into the Arctic Ocean. The dam is located near Hudson's Hope, one of the oldest European settlements in BC, where the river passes through the Rocky Mountain Trench — a vast, straight valley running for 1,600 kilometers along the western edge of the Rockies.

Williston Lake fills three arms of the Rocky Mountain Trench and adjacent valleys, with a surface area of 1,761 square kilometers. The surrounding landscape is northern boreal forest — spruce, pine, aspen, and poplar covering rolling terrain. The reservoir's northern location means it freezes over from November to May, and winter temperatures frequently drop below minus 30°C.

Hydroelectric Power

• Installed Capacity: 2,730 MW
• Annual Output: ~13.5 TWh
• Turbines: 10 units (5 × 261 MW + 5 × 285 MW)
• Grid: BC Hydro system, supplying lower mainland via 500 kV lines

The G.M. Shrum generating station produces approximately 13.5 terawatt-hours per year, roughly one-quarter of BC Hydro's total generation. The electricity is transmitted south to the population centers of Vancouver and Victoria via 500 kV transmission lines spanning over 1,000 kilometers. The dam is the largest single component of BC's electricity system, which is approximately 90 percent hydroelectric.

The Peace River system, including the downstream Peace Canyon Dam (694 MW) and the recently completed Site C Dam (1,100 MW), has a combined capacity exceeding 4,500 MW, making the Peace River one of the most developed hydroelectric rivers in North America.

Environmental & Social Impact

• Area Flooded: 1,761 km² (Williston Lake)
• First Nations Impact: Tsek'ehne (Sekani) and West Moberly peoples displaced
• Downstream: Peace-Athabasca Delta ecosystem altered

Williston Lake flooded approximately 1,761 square kilometers of boreal forest and river valleys, displacing the Tsek'ehne (Sekani) people from their traditional territory in the Rocky Mountain Trench. The flooding destroyed hunting grounds, trap lines, and burial sites that had been used for millennia. The nearby West Moberly First Nations and Prophet River First Nation were also significantly affected.

The dam's regulation of the Peace River has had far-reaching downstream effects, most notably on the Peace-Athabasca Delta in northeastern Alberta — one of the world's largest freshwater deltas. The dam eliminated the Peace River's natural ice-jam floods, which historically pushed water into the delta's perched basins. Without these floods, many of the delta's wetlands have dried out, affecting the ecosystem of Wood Buffalo National Park, a UNESCO World Heritage Site.

Key Facts

• W.A.C. Bennett Dam creates Williston Lake, BC's largest body of water at 1,761 km².
• The 2,730 MW station generates roughly one-quarter of BC Hydro's total output.
• The dam's regulation of the Peace River has dried portions of the Peace-Athabasca Delta.
• Williston Lake floods the Rocky Mountain Trench, one of the longest straight valleys on Earth.
• The dam displaced the Tsek'ehne (Sekani) people from their ancestral territory.

Fun Facts

• The Rocky Mountain Trench, which Williston Lake occupies, is visible from space as a ruler-straight line running 1,600 km along the western edge of the Rocky Mountains.
• During the dam's filling in 1968, the reduction in Peace River flow temporarily increased the size of Lake Athabasca, 1,200 km downstream — demonstrating the interconnectedness of Canada's northern river systems.
• The name "Hudson's Hope" comes from a Hudson's Bay Company trading post established in 1805, long before anyone imagined a mega-dam on the Peace River.

Final Thoughts

W.A.C. Bennett Dam was a defining project in British Columbia's development, providing clean hydroelectric power that has sustained the province's economy for over five decades. Its far-reaching impacts on the Peace-Athabasca Delta and on First Nations communities illustrate how a single dam can reshape ecosystems and cultures across thousands of kilometers.