Driven by the mighty waters of Kootenay Lake’s West Arm and the Kootenay River, Nelson Hydro generates power for its 11,000 customers at the 16MW Bonnington Dam power plant and the city’s community solar array, then distributes power from the dam, solar array and FortisBC’s supply system, to a network of seven substations and 320 kms of transmission and distribution lines.

How Generation Works

Nelson Hydro owns and operates a run-of-the-river 16 MW hydroelectric generation facility that harnesses the power of moving water to generate renewable electricity located at Bonnington Falls on the Kootenay River 16 km southwest of Nelson. The current water license allows a year-round output of 9.1 MW, which represents about 50% of our annual energy requirements and generates the most electricity during freshet, or, the time between mid-May to mid-July when the headwaters of the Kootenay River are at their peak from melting snow from the surrounding mountains.

Watch the video below to learn how a run-of-the-river hydroelectric generating station works.

Steps to Generating Power

1. Dam. There is potential energy stored in the water reservoir (forebay) impounded by the dam. It is converted to kinetic energy when the water starts flowing down the penstock from the dam and through the turbine.
2. Generator: The falling water strikes a series of blades in the turbine that are attached to a shaft which converts kinetic energy to mechanical energy which rotates the turbine. The shaft is attached to a generator so that when the turbine turns, the generator turns. The generator converts the turbine's mechanical energy into electric energy.
3. Step-up Transformer: Nelson Hydro generators produce electricity at 12kV. In order for the transmission lines to carry the electricity efficiently over long distances, it is increased to 63kV (transmission voltage) by a step-up transformer.
4. Terminal Station: Terminal stations receive the flow of power from the Step-Up Transformer and then they reduce the voltage to 12kv-25kv (distribution voltage) levels.
5. Transmission Lines: Transmission lines supply power from terminal stations to distribution substations.
6. Distribution Substation: A distribution substation is a system of transformers, meters, and control and protective devices. At a distribution substation, the transmission voltage is reduced to distribution levels and supplied to individual feeder circuits.
7. Distribution System: The distribution system is comprised of lines, poles, transformers and meters distributing the power from the distribution substation to individual homes. The distribution level voltages are transformed to customer level voltages by means of a distribution transformer on the utility poles for overhead power and also on pad-mount transformers for underground power.

Water Rights and Purchased Power 

With our big beautiful lake full to the brim and Nelson Hydro’s Kootenay River turbines turning full tilt each Spring, our customers sometimes inquire as to why the City-owned power company has to buy electricity from elsewhere throughout the year. Approximately 50 percent of the annual energy requirements are obtained via wholesale power purchase from FortisBC. 

Fact is, while it may look like the river provides a limitless amount of water, flows are accounted for year-round, by the provincial government’s Controller of Water Rights. The Nelson Hydro power plant gets only a small percentage of the Kootenay River’s water. Very specific totals are earmarked for generating stations downstream. 

The exception is during the spring freshet. (A freshet is a flood of water that occurs due to heavy rain, or in the case of our Kootenay springtimes, melting mountain snow.) During freshet, there is extra water available, and most dams in BC, like the Upper Bonnington, spill water during freshet. 

Water that comes down the Kootenay River is 100% allocated to by the Controller of Water Rights within the government of BC. Nelson Hydro has been granted 2,963cfs of the 46,023cfs of the hydrogeneration output of the Kootenay River. 

For comparison’s sake, here’s a look at who gets what, when it comes to water: Nelson Hydro, owned of course by the City of Nelson, captures 2,963 cubic feet per second (cfs) — or the maximum output of its 16 megawatt (MW)  power plant during freshet. One megawatt would supply power to about 750 homes at a time. Just across the river, Fortis BC’s Upper Bonnington generating facility gets 13,060 cfs, or 65 megawatts. Further down, the Kootenay Canal, owned by BC Hydro gets 30,000 cfs, enough to produce 580 megawatts. 

What is not generated, the remainder is purchased. Nelson Hydro connects to the FortisBC electric system at three points; Fortis' Coffee Creek, Nelson Hydro's Generating Station, and Nelson Hydro's Granite Substation. These interconnections are required so that the 88,569,058 kWh (2022) of purchased energy can seamlessly integrate into the Nelson Hydro grid to supply the needs of our customers.

Nelson Hydro, founded in 1892, today one of Western Canada’s few municipal-owned hydro generating systems, is just a piece of the province’s power puzzle.