The Mystery Of Niagara Falls

There is a real mystery concerning the ceaseless flow of water over Niagara Falls. I have written quite a bit about my new findings in the natural history of the Niagara area. The mystery which we will explore today is not about the nature of the falls themselves or the area, but is about why the falls exist at all.

Just stop and think about it. A tremendous amount of water keeps pouring over these falls. Where does this water come from and why does it's flow never stop? These are questions about the falls that never seem to be asked. So much of what I write online is not the answering of questions that no one else can answer, but the asking of questions that no one else has asked.

The water that goes over Niagara Falls comes, of course, from the upper Great Lakes. The Niagara River brings water from Lake Erie, which is connected to Lake Huron, Lake Michigan and, Lake Superior. This is certainly no mystery.

But for water to keep pouring over the falls while the water levels of the upper lakes remains constant can only mean that there is excess water coming from somewhere. Many tons of water evaporate from the Great Lakes every second. Most of that water falls within the lakes' watershed and goes right back into the lakes.

Since the Great Lakes are essentially a closed water system, how can there be the excess water which goes over Niagara Falls?

First, we need to examine the winds around the Great Lakes. The world has bands of prevailing winds by latitude. The earth rotates eastward so that the prevailing winds around the equator are from the east.

North and south of that zone, further away from the equator, the prevailing winds counter the equatorial direction so that they are from the west. Going further north and south, the prevailing winds are once again around the poles the winds tend to be from the east, the Polar Easterlies.

On a map showing Hudson Bay in northern Canada, we can see that there are many more rivers flowing into the bay from the west, than the east. This is because the prevailing winds at that latitude are from the east and they pick up water from the bay and drop it to the west, where it flows back in.

The fact that the prevailing wind is from the west, rather than the east, is very important to the Great Lakes, and to Niagara Falls. The beginnings of the Mississippi River are not far east of the largest of the Great Lakes, Lake Superior. The way I see it, if the prevailing wind were from the east it would pick up a lot of water from the lakes and drop it into the Mississippi River watershed. This would greatly diminish the volume of water in the lakes and there would be no excess water to go over Niagara Falls.

Fortunately for Niagara, most of the water that is removed from the upper Great Lakes by the west wind ends up back in the lakes' watershed when it falls as precipitation and eventually goes over the falls.

There are exceptions to this. One example is the water which evaporates from the upper lakes and falls into the watershed of Lake Ontario, the one "lower" lake downstream from the falls. Water which follows this route circumvents the falls. This includes water which enters Lake Ontario by rivers other than the Niagara. The Genesee River collects rainwater and snowmelt and empties into Lake Ontario at Rochester. On the Canadian side, the Humber River at Toronto and the Trent River further east, also represent water from the upper lakes which has gotten into Lake Ontario without going over the falls.

Incidentally, the reason that the gorge of the Niagara River gets narrower north of the whirlpool is because the Trent River system once drained the upper Great Lakes across Ontario and during this time, it was only Lake Erie which was draining through the Niagara River. The flow was less and thus this section of the gorge is narrower. I have not discovered this, it is already known.

Where I live, I notice that a south wind very rarely brings precipitation. This means that a wind from the south will be warm and dry and will thus pick up quite a bit of moisture from the lakes. We can see on a map that if we go a considerable distance north of the Great Lakes, the rivers flow northward, toward Hudson Bay. The lakes certainly do lose some water in this direction in the summer.

There is one other major route of water out of the Great Lakes. This is the Ohio River. It is easy to find this river on a map because it starts at Pittsburgh, with the joining of two smaller rivers, and forms the western border of West Virginia and the northern border of Kentucky.

Notice how the Ohio River almost always froms an approximate midpoint between the Great Lakes and the Appalaichan Mountains. This river drains into the Mississippi River and is a counduit for water that has evaporated from the Great Lakes and has fallen as precipitation south of the line from which it would have flowed back into the lakes.

So, water leaves the upper Great Lakes via the Ohio River, when it evaporates and falls outside the lakes' watershed to the south. It ends up in the watershed of Lake Ontario, without going over the falls, when it evaporates from the upper lakes and falls far enough to the west. More water is lost from the lakes when the warm, dry south wind of summer carries evaporated lake water far enough north to fall in the watershed of Hudson Bay.

But still, there is enough excess water coming into the upper lakes to create the flow over Niagara Falls. Where does this water come from?

An east wind bringing a lot of water with it from the Atlantic Ocean would be mostly blocked by the Appalaichan Mountains. The south winds in the Great Lakes region are mostly dry. The prevailing wind in the area is from the west, but the American west is also known for it's dryness.

As it turns out, both Niagara Falls and the Great Lakes are dependent on what goes on in a region to which few people give much thought.

In the north of Canada, direcly north of the Great Lakes in fact, is the wide expanse of Hudson Bay. Sorrounding Hudson Bay is low and swampy ground that is just about as vast as the bay itself. Few people live around Hudson Bay and really not many people have ever seen it, but tourists to Niagara Falls and residents of the entire Great Lakes region might want to give it a brief thought of appreciation because it is absolutely vital to the lakes.

Not only is Hudson Bay and the sorrounding swamp a source of water to the Great Lakes by way of evaporation, there are an fantastic number of small lakes, carved by glaciers, in the provinces of Ontario and Manitoba to the west. A really amazing fact is that about half of the surface area of both of these two vast provinces is either lake or swamp. And both lakes and swamps contribute water into the air by evaporation.

We can see by the river systems in the far north of Ontario that most of the water which evaporates from Hudson Bay and falls as precipitation ends up back in the bay, because it falls within it's watershed. But if any of this water gets far enough south before falling, it will fall into the Great Lakes watershed. Hudson Bay tends to freeze over during the winter, so this evaporation must take place during the warmer months.

So, not only is there no mystery about why there is the excess of water in the Great Lakes which flows over Niagara Falls, it can actually be broken down into a fairly simple and accurate formula.

A = B - (C + D + E)

Where A is the flow of water over the falls, as well as that which is diverted for the generation of electricity.

B is the water which evaporates from Hudson Bay, the sorrounding swamp land and, the lakes in Ontario and Manitoba to the north and northwest of the Great Lakes, and which falls as precipitation within the Great Lakes watershed.

C is the water which evaporates from the Great Lakes and it's watershed and is carried northward so that it falls in the Hudson Bay watershed.

D is the water which evaporates from the upper Great Lakes and falls as precipitation in the watershed of Lake Ontario. D is approximately equal to the flow of water in the St. Lawrence River minus that in the Niagara River.

E is the water which evaporates from the Great Lakes and it's watershed and falls as precipitation in the watershed of the Ohio River to the south.

Thus we can say that the Great Lakes, the largest system of fresh water in the world, is a product of both Hudson Bay to the north and the Appalaichan Mountains to the east and south.

To have a look at the falls and sorrounding cities go to http://www.multimap.com/