Bash a hole, scoop it out. It may also be possible to get food from lakes and rivers too, via ice fishing. Wells will still work too, as the freezing line won't penetrate too far into the ground unless you're actually in the arctic permafrost. If it is big enough and frozen enough, sure. At river-freezing temperatures you may find that the snowpack is sufficient for sledging over pretty much anywhere, though rivers do have the advantage of being nice and flat and so make for good roads.

Note that it is possible for rivers and lakes to freeze without being traversable, though you'd hope that people who lived near such places and used them as means of transport would understand these things. A frozen surface on a plunge pool under a non- or partially-frozen waterfall is probably not a good place to walk over, for example. The real important factors are the dimensions of your river, how slowly it freezes, how fast the water is moving, and how far your drop is.

Waterfalls do not just suddenly freeze in place, instead the surface of the river freezes creating a surface for the liquid water underneath to cling to as it flows under it and itself subsequently freezes.

A wider, faster moving waterfall is harder to freeze because you must first freeze the entire top edge of the waterfall in a fashion that creates an ice bridge to build on. This makes narrower waterfalls more ideal. If you have a wider river, you will want many rocky outcroppings at the waterfall's edge so that you have several shorter ice bridges instead of one longer one. Otherwise your river will have more time to freeze depriving you of the needed flow before you can start building your actual icy waterfall.

Once you have a solid icebridge over flowing water, you get icicles that slowly form. The slower your water freezes the better because once the river freezes through you will eventually stop having flowing water to continue to build the ice up. A slower starting water flow is also better because if the water is flowing too quickly with too much volume, then it will melt the ice faster than the cold air can build it up.

As the icicles grow they will also become heavier increasing their odds of breaking and falling off under their own weight, ideally the temperature will continue to slowly drop as the icicles form strengthening the ice at the top so it does not snap will allowing enough water to keep flowing to continue to build the ice up. In short, yes but it is much harder if your waterfall is not shaped right or if it is moving too fast.

In the examples below, the first waterfall has a lot more shelves and narrow areas to bridge making it easier to freeze. The second one would probably not freeze except under extraordinary conditions. Speaking of extraordinary conditions, Starfish Prime's Niagara falls example demonstrates, several really good points about this process that I think deserves a little bit of extra attention.

If you look at section A below you will see where an ice bridge formed and the waterfall is just stepped enough to get the multiple layers of icicles. Section B shows another mechanic by which larger faster flowing waterfalls can freeze where by the water at the bottom freezes and builds up.

It is more structurally sound than hanging ice but typically requires lower temperatures because you need to contend with the depth of the water at the waterfall's base. It also tends to look more like piled up clumps of snow and ice and less like a "frozen waterfall"; so, it probably does not answer your question as well, but I suppose it can help compensate for a bigger more overhanging waterfall if it builds up high enough.

The main river does not need to be completely frozen for this to happen, but there will at the very least be patches of ice, probably along the shores and shallows. The middle, deeper parts of the river will take longer to freeze, but if you want the icefall to be around for awhile, it will need to stay cold enough that the river will eventually fully freeze. In the event of a long term, full freeze, they can just melt ice and snow for water.

Should not be a big deal. If the ice is thick enough, yes you could use sledges to traverse it, but it has to get and stay pretty cold for a long time for the ice to get thick enough for this to be a good idea. The icefall would probably need to form at the beginning of a freeze, and they would need to wait days or weeks for the river to harden enough to support traffic.

It is possible, indeed. After that, small shards of ice will start forming in the top of the waterfall where the water starts falling , building and growing over time, until its height makes the waterfall seem to be frozen.

A waterfall can start freezing without the river being completely frozen, but if enough time passes, the entire waterfall will be solid frozen, and the river as well. About the water issue, as LiJun stated, they can melt the ice by using fire, or they can break the ice in the river to get the water below remember that only the superficial layer of rivers will freeze. That had Ginny from Marine on St.

Croix wondering: How does a waterfall freeze? Good Question. Monday afternoon, many families stopped by Minnehaha Falls in Minneapolis to soak in the view. Some people got dangerously close, enough to not only get soaked, but be in range of falling ice. The combination of flowing and frozen water is a risky situation to walk on.

But two years ago, the Polar Vortex had all the right elements to stop this waterfall cold, according to National Weather Service Meteorologist Paige Marten. WCCO asked several kids near the falls what it would take to make a waterfall freeze. Unlike a lake or pond, a waterfall and its source — rivers and streams — are constantly moving and mixing the water.

But if the temperature stays below freezing for an extended period of time, the water will supercool. During that process, frazil ice forms. She says the particles are about a millimeter in size. Frazil ice usually appears in turbulent water. Under the right weather conditions, those water droplets are liable to freeze as they accumulate on the trees, boulders and railings that surround the falls.

Also, there are days when a thin layer of frozen spray and mist hardens over the falls. Right beneath this icy blanket, however, you'll still find plenty of liquid water flowing on its usual downward path.

Bottom line: Niagara Falls isn't going to freeze all the way through anytime soon. But that's just one landmark. Let's talk about some other waterfalls. On a cold morning in January , physics professor Michael J. Ruiz and independent researcher Charles Cranford filmed a foot meter waterfall in North Carolina that had mostly frozen.

Trickling over some of the ice was a stream of supercooled water. Supercooled water is water that remains liquid below the normal freezing temperature of H2O: 32 degrees Fahrenheit or 0 degrees Celsius.

It was significantly colder outside when Ruiz and Crawford recorded their video; the local temperature was just 5 degrees F degrees C. Under those conditions, even the supercooled water couldn't stay liquified for long. In this amazing footage captured by the duo, you can actually watch flowing, supercooled H2O at the Carolina waterfall freezing into ice in real time.

And not just any ice. The water was hardening into a clumping collection of tiny, needle-shaped crystals. Meteorologists call that frazil ice. Often associated with turbulent , supercooled water, frazil ice can also develop when mist droplets freeze. The ice is a common sight around certain waterfalls — like the ones at California's Yosemite National Park — in below-freezing weather.

When frazil ice clings to a rocky surface, it can become a platform for even more ice to build up.