Jordan River Dam

The Jordan River Diversion Dam, known locally simply as Diversion Dam, is a dam on the Jordan River in Jordan River, British Columbia, Canada. Part of a multi-dam hydroelectric system operated by BC Hydro, the facility provides approximately 35% of Vancouver Island's generating capacity. It was the second hydroelectric development on Vancouver Island, succeeding the Goldstream Powerhouse.

Prior to the dam's construction, the Goldstream Powerhouse was the main source of electricity to Victoria. The Jordan River facility dwarfed the previous plant upon its completion.

The Vancouver Island Power Company, a subsidiary of the British Columbia Electric Railway, completed construction of both the smaller Bear Creek Dam and the main Jordan River Diversion Dam in 1911. At 126 feet (38.4 m) from top to bottom, the Diversion Dam was, upon completion, the highest dam in Canada. Water flowed through a 31,600 feet (9.6 km) long flume to a penstock above the power house.

The dam's remote location required the construction of a 3-foot (0.91 m) narrow gauge railway and a cable-railway for the initial ascent from the Jordan River valley. From 1912 to 1931, continual improvements and additional generators increased the capacity of the power house to 26 megawatts.

In 1971, the original flume was replaced by a 7 kilometres (4.3 mi) tunnel, with a penstock feeding a new power house situated across the river from the original. The accompanying service railway was dismantled the same year. A single high-head Francis turbine and generator manufactured by Fuji Electric of Japan replaced the earlier equipment, increasing power output from 26 megawatts to 175–183 megawatts.

The Jordan River hydroelectric system comprises several interconnected components. Water collected at Bear Creek Dam and the Diversion Dam feeds the Jordan River Diversion Reservoir, the largest impoundment in the system, with a surface area of approximately 18 square kilometres (6.9 sq mi) and a licensed full supply storage of about 20.5×10⁶ m³, roughly equivalent to 3.5 days of generation capacity.

From there, the Jack Elliott equalization reservoir (a much smaller headpond of about 1.6 square kilometres (0.62 sq mi) at full pool, holding only a few hours of storage) regulates flow into an 8.8 kilometres (5.5 mi) long tunnel. Water then drops through a steel penstock over the final 330 feet (101 m) of vertical height before reaching the turbine at the generating station near the river mouth.

A 2014 BC Hydro study concluded that the Jordan River dam faced the highest seismic hazard in BC Hydro's system. A magnitude 8–9 Cascadia subduction zone earthquake could potentially cause the dam to collapse, sending a flood wave downstream into the small Jordan River village on the coastal plain.