Why does Niagara falls not run out of water?


It goes down no?

In: Earth Science


Because rain flows in to lake Erie keeping it full. It flows down the falls in to lake Ontario, then eventually in to the ocean. That’s why other rivers also don’t run out of water.

Simply put, the water cycle. Water evaporates, is condensed into clouds and falls as rain. Fortunately for the falls the jetstream air current flows over the Great Lakes picking up all that evaporated water and bringing it up towards the areas that feed the rivers that feed the falls. This area is known as a watershed and it is hundreds of thousands of square kilometers big. All the tons of rain that falls in that watershed all eventually flows over the falls.

The rivers are also constantly fed by groundwater. All the rain that got absorbed into the soil sinks down and flows underground. Sometimes it reaches a point where the weight of the earth pushed it back up through the earth creating a spring. That spring will feed a wetland or stream that will flow to the falls. In the end it is still just every drop of rain that ever falls in that watershed eventually making it over the falls.

A waterfall is not much different than the rest of the river. Rivers run horizontally, and a waterfall is a vertical section of that river. Niagara Falls is a 0.051 km vertical section of the 54 km long Niagara River. So, the question is less about why the Falls keeping falling, but why the River keeps run, since the rest of the river has much more water.

The answer to that is the water cycle. Niagara falls is fed by Lake Erie, which is fed by lake Huron, which is fed by lakes Michigan and Superior. So, it has a fairly large water supply. Those lakes stay full because of rain. Water from various places evaporate, and then fall in the lakes. If the water does not fall directly in the lakes, it falls in areas where the water will drain into the lakes. Also, a bunch of snow falls on the ground during the winter. When this snow melts in the spring and summer, it drains into the lake as well.

It will eventually run out, as the Great Lakes’ watershed is only like 1% renewed annually… but the Great Lakes (Superior, Huron, Michigan and Erie) that feed the Niagara River are absolutely massive. I believe they hold close to a quarter of the entire planet’s freshwater.

If flow rates over the falls stay the same (which they do control, monitor and limit very closely now to ensure diversion to power generation/utility consumption is fair and not drying it up), part of the falls could disappear in 2,000years. Even if these falls have a never ending source of water, the other thing is that the falls’ location is eroding further upstream over time. Although man made intervention could slow this down, the forces of erosion are pretty constant and it will eventually run it all the way back to Lake Erie (in ~50,000years) to turn it into more of a series of rapids versus the massive falls that exist today.

Found most of this info here: