How do hydro-electric dams still generate power if the rivers freeze?
When it comes to dam maintenance, a lot of owners are curious how their dam will operate in winter. And here is an answer:
Rivers only freeze on the surface, below the surface they still flow, unless they are really shallow. Ask any fish.
Intakes for the dams are underwater, not at the surface, so hydroelectric dams still work quite well.
The most common hydroelectric situation involves a deep reservoir created upstream of a dam, and these do not freeze due to the water depth. (Bear in mind, that even on a still lake, the ice depth rarely exceeds one metre.) Another type, called “run of the river” which are commonly smaller, can be subject to freezing, depending on the river depth and flow rate.
The “run of the river’ type are used in situations in which the surrounding area is to be preserved. Frequently, these exist in urban situations which had a seasonally operated gristmill or sawmill that was evolved to become a hydroelectric generator. It would be unfeasible to tear out most of the town around that to create a reservoir.
-Loring Chien, Engineer