Is it possible for rivers to freeze completely in the winter and stop flowing? Are there known examples of this? If yes, how large can these rivers be and where does the water go?

There are several large Siberian rivers that empty into the Arctic Ocean.

up vote 22 down vote accepted

I am interpreting your question as referring to rivers with flowing water freezing as as opposed to glaciers, which are already frozen.

Under current climatic conditions, small rivers can freeze throughout: from bank to bank, surface to river bed. I'm avoiding using the word solid as some people use that word when a river's surface has frozen from bank to bank.

Large rivers do not freeze "through out" because,

Water, ice, and snow are good insulators and poor conductors of heat. The portions of a lake or river that are exposed to the cold winter air will freeze into ice and this ice insulates the water below from further rapid freezing. Also contributing to the prevention of bodies of water freezing solid is an interesting characteristic of water. Like most other forms of matter, water become denser as it cools, but beginning at about 39°F (4°C) something odd happens - water begins to lose density as it gets colder, becoming least dense when it freezes into ice. This is why ice floats. As water becomes colder it rises to the top, eventually freezing to the layers of ice that are already there. Insulation of the water beneath is increased as the ice thickens so cooling of the water beneath slows.

From The Great Land of Alaska: Why don't lakes and rivers freeze solid?

Also, while water is flowing its potential energy is constantly being converted to heat energy that resists freezing on the molecular level and subsequent crystallization.

For flowing water to freeze, the temperature would have to be exceptionally cold.

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    I totally agree with you – Fred Feb 3 '15 at 13:01
  • Yes, this is what I meant to ask: flowing water that may freeze in the winter. I'd love to see a frozen river, I didn't really expect it to exist. – Glacialis Feb 4 '15 at 1:14

In a way, glaciers are just like frozen rivers. A good start on that topic comes from USGS. Ice (whether in a frozen river or in a glacier) is still a fluid and thus is always moving because of its own weight. A frozen river will still be a river of incredibly slow moving water.

When water is not moving, first the entire volume cools down to 4C (maximum density) as the colder water keeps sinking to the bottom. Then, a thin layer at the surface starts to freeze while floating on the denser water below. By contrast, in moving water, the entire volume has to cool to 0C before freezing starts.

For any river to freeze, heat must be lost at a rate that exceeds the rate of replacement. Because of the high heat capacity of water, fast moving water (e.g., mountain cascades) will be more difficult to freeze because heat loss will be smaller than flow rate. Thus, slow moving small streams tend to freeze quickly.

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    Glaciers aren't frozen rivers. They are accumulations of snow that have failed to melt and over time the unmelted snow compacts to form dense ice. en.wikipedia.org/wiki/Glacier – Fred Feb 3 '15 at 3:41
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    I completely agree with that. My point is that ice (whether in a frozen river or in a glacier) is still a fluid and they keep moving because of their weight. – arkaia Feb 3 '15 at 4:05
  • @Fred Imagine a river made up of an extremely viscous material that flows at incredibly slow rates. – Isopycnal Oscillation Feb 3 '15 at 6:21
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    Which river of flowing water froze to form a glacier? As far as I'm aware, as stated in my previous comment, glaciers formed from an accumulation of unmelted snow which gradually compacted to form dense ice. The ice in glaciers moves/flows down valleys with a velocity profile similar to water in a river, but much slower. The question asked by Glacialis is about rivers that contain flowing water, not glaciers that contain flowing ice. – Fred Feb 3 '15 at 8:04
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    I don't think we are saying that a river of flowing water froze to form a glacier, but rather that both a frozen river and a glacier keep moving. That's all – arkaia Feb 3 '15 at 15:07

On the North Slope of Alaska, I have seen lakes that are frozen all the way to the bottom. It's a fascinating site in the spring when the lakes thaw from the top down because the ice on the bottom of the lake is glued to vegetation and sediments (see picture). Around these lakes are small, narrow rivers called "beaded streams." In the winter/early spring, these streams are either dry or have running water. I don't believe (for all the reasons listed above) that there would be a completely frozen river. Any portion of a river that would be small enough with the potential to freeze completely, would likely dry out before the winter (although the ground all around the river is frozen... permafrost). And any "river" that became standing water, would be classified as a lake, slough, or backwater area.

However, a solution for you may be to check out Alexandra Falls in the Northwest Territories, Canada. The falls are pretty huge and freeze over in the wintertime!

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