Mica Dam: British Columbia's Mighty Columbia River Dam

**Mica Dam** on the Columbia River approximately 150 kilometers north of Revelstoke, British Columbia, is one of the tallest dams in Canada at **243 meters** and one of the tallest earth-fill dams in the world. Completed in **1973**, the dam was a key structure built under the **1964 Columbia River Treaty** between Canada and the United States, which provided for cooperative flood control and hydroelectric development along the Columbia River system.

Introduction

The dam creates **Kinbasket Lake** (also known as McNaughton Lake), a reservoir stretching approximately 216 kilometers through the Rocky Mountain Trench between the Selkirk and Rocky Mountain ranges. With an installed capacity of **2,805 MW** (expanded from the original 1,740 MW), Mica is one of the most powerful hydroelectric stations in western Canada.

Engineering & Structure

• Type: Earth-fill dam with impervious core
• Height: 243 meters
• Crest Length: 792 meters
• Turbines: 6 units (total 2,805 MW after expansion)

Mica Dam is a zoned earth-fill dam rising 243 meters above the Columbia River — making it one of the tallest earth-fill dams in the world. The dam contains approximately 33 million cubic meters of material, with a central impervious core of glacial till flanked by gravel and rock shells. The crest stretches 792 meters across the valley, considerably narrower than most earth-fill dams of comparable height due to the confined mountain setting.

The original Mica Generating Station housed four units totaling 1,740 MW. A two-unit expansion in 2015 added 1,065 MW, bringing the total to 2,805 MW. The dam also provides critical flood storage for the downstream Columbia River system under the Columbia River Treaty, with a flood storage reservation of approximately 7 cubic kilometers that reduces flood risk as far downstream as Portland, Oregon, over 1,000 kilometers away.

Geographic Setting

• River: Columbia River
• Location: Selkirk Mountains, British Columbia, Canada
• Coordinates: 52.08°N, 118.57°E
• Kinbasket Lake Length: ~216 km

The Columbia River at Mica Dam flows through the Rocky Mountain Trench, a massive straight valley that runs for 1,600 kilometers between the Rocky Mountains to the east and the Columbia/Selkirk Mountains to the west. The dam site is flanked by peaks rising over 3,000 meters, covered in dense old-growth cedar, hemlock, and spruce forests. The region receives heavy snowfall — over 2,000 millimeters of snow water equivalent at higher elevations.

Kinbasket Lake stretches 216 kilometers through some of the most spectacular mountain scenery in British Columbia, with arms reaching into both the Rocky Mountains and the Selkirks. The reservoir fluctuates dramatically between full pool and minimum operating level — by up to 43 meters — as water is stored for flood control and power generation. This "drawdown zone" creates a wide, barren band around the reservoir for much of the year.

Hydroelectric Power

• Installed Capacity: 2,805 MW (after 2015 expansion)
• Annual Output: ~7.5 TWh
• Columbia River Treaty: Provides flood storage for downstream US dams
• Grid: BC Hydro integrated system

Mica Dam's 2,805 MW capacity makes it the largest generating station on the Columbia River in Canada and one of the most powerful in western North America. Annual output averages approximately 7.5 terawatt-hours, with generation peaking during the spring freshet when snowmelt fills the reservoir. The electricity is transmitted via 500 kV lines to BC Hydro's grid serving Vancouver and the lower mainland.

Under the Columbia River Treaty, Canada agreed to build Mica and two other storage dams to regulate the Columbia's flow for the benefit of downstream American dams (Grand Coulee, Chief Joseph, Bonneville, etc.). In exchange, Canada receives a share of the additional power generated at US dams due to the improved flow regulation — the "Canadian Entitlement" — which BC Hydro sells. The treaty is one of the most successful international water-sharing agreements in the world, though it is currently under renegotiation.

Environmental & Social Impact

• Columbia River Treaty: Cooperative flood control benefits US Northwest
• Fish Passage: Columbia River salmon blocked far downstream
• Reservoir Fluctuation: 43-meter drawdown creates barren shoreline zones

Mica Dam's environmental impact is primarily related to the reservoir's extreme water level fluctuations. The 43-meter drawdown between full pool and minimum operating level creates a broad barren zone around the lake that inhibits shoreline vegetation growth and reduces aquatic habitat quality. Fish and wildlife in the reservoir area must adapt to these dramatic seasonal changes.

While Mica Dam itself does not directly affect salmon migration (salmon have been blocked far downstream at Grand Coulee Dam since 1942), the dam's regulation of the Columbia's flow affects downstream ecosystems throughout the river's 2,000-kilometer course to the Pacific Ocean. The Columbia River Treaty's renegotiation includes provisions for ecosystem-based function, reflecting growing recognition that the river's ecological health must be considered alongside power generation and flood control.

Key Facts

• Mica Dam is one of the world's tallest earth-fill dams at 243 meters.
• Its 2,805 MW capacity was expanded in 2015 from the original 1,740 MW.
• Kinbasket Lake stretches 216 km through the Rocky Mountain Trench.
• The dam was built under the 1964 Columbia River Treaty with the United States.
• Reservoir fluctuations of up to 43 meters create a dramatic drawdown zone.

Fun Facts

• The Columbia River Treaty is considered one of the most successful international water-sharing agreements in history, having prevented major floods in Portland and the US Pacific Northwest since the 1970s.
• Kinbasket Lake's drawdown zone is so wide in places that it resembles a moonscape — a barren band of exposed silt and gravel between the forest and the waterline.
• The dam's remote location means it is not connected to the highway system year-round; the road north from Revelstoke is closed during winter months.

Final Thoughts

Mica Dam is a cornerstone of both British Columbia's electricity supply and the international cooperation that manages the Columbia River across the US-Canada border. Its towering embankment in the Rocky Mountain Trench demonstrates the scale of infrastructure required to harness one of North America's mightiest rivers, while the ongoing treaty renegotiation reflects evolving priorities around ecological health and indigenous rights.