Run-of-River vs Conventional Storage Hydro
In conventional storage hydro, a dam is placed across a river to create a reservoir with most of the water impounded behind the dam and the flow downstream regulated, which changes the natural variation of flow for the entire downstream river.
Run-of-River hydro projects have a much smaller environmental footprint compared to traditional reservoir storage hydro because they typically have very little water storage capacity thus less land is flooded, reducing potential footprint. With ROR hydro, only a portion of the stream flow is affected, and only a short length of the river experiences reduced flows. The volume of water a ROR project may divert through penstocks to run turbines depends significantly on stream morphology and environmental characteristics, but a typical plant utilizes less than two-thirds of a river’s annual flow. Immediately below ROR Hydro powerhouses, all flows diverted to produce power are returned to the stream and the natural downstream flow patterns are preserved.
Without storage, however, ROR hydro supplies electricity only as natural flow allows. Flow conditions conducive to ROR power generation do not always correspond to times when electricity demand is high. Accordingly, both technologies have advantages and disadvantages and should be viewed as complementary resources.
Run-of-River in BC
Run-of-River hydro projects have been used historically throughout British Columbia to power mines, mills, and towns. As of 2021, there are 68 independent ROR projects supplying electricity to BC Hydro.
In striving to meet environmental assessment standards in BC, the developers, consultants, and suppliers in the ROR hydro industry have become some of the most knowledgeable in the world on minimizing the impacts of hydro power. Some examples include turbine designs and operation measures to ramp up and down in a safe manner to ensure minimal impact on fish and fish habitat as well as energy dissipation chambers to ensure an environmentally sustainable development of local resources.
Although there are countless rivers and streams in the province, not all are suitable for ROR hydro projects. Potential sites must have the right balance between water flow and steepness of terrain; cost-effective transmission access and construction and the ability to operate with minimal impacts on aquatic and terrestrial life. While the potential for ROR hydro in BC is very high, only a small percentage of this potential will be developed because not all sites fulfill these requirements.