The Nile Flows North

"How can a river flow north?" the real estate lady asked me. "I mean, it's impossible." The offending river, within whose watershed I proposed to buy a house, is the Wallkill. It rises in Northern New Jersey – near Sparta – and passes by Middletown, NY, and through Montgomery, Walden, the eponymous town of Wallkill, New Paltz, Rosendale, and finally (with a complication) drains into the Hudson River at Kingston, NY – approximately 100 miles north of its source.

In defense of the American public school system, I add that my realtor was born and educated in Europe.

A colleague of mine (I work at a university) said at least semi-seriously that, except for the Nile, the Wallkill is the only river in the world that flows north.

Now where have I heard that before? I used to live in DeKalb, Illinois. It was common wisdom in those parts (indeed, if memory serves, even stated in the student newspaper), that – except for the Nile – the Kishwaukee River is the only river in the world that flows north.

You've all heard of that, of course: the famous, north-flowing Kishwaukee? The only problem is that only the South Branch (sort of) flows north. The main course, if anything, heads south.

I grew up in Eugene, OR, at the headwaters of the Willamette, which really does flow north. But I don't recall any of my high school chums telling me about the Willamette and the Nile. Maybe they knew me too well. Or perhaps that's because so many other rivers in Oregon flow north: the Deschutes, the John Day, and the Hood. Even the Oregon portion of the Snake flows north.

I do understand that in Cairo the word on the street is that, except for the Willamette, the Nile is the only river in the world that flows north. Odd, since in Sudan for about 200 miles, the Nile River actually flows south.

So what accounts for this urban legend that (fill in the blank) river and the Nile are the only two rivers that flow north? I can think of three reasons.

First, had I pressed her, the reason that my Realtor likely would have given: Rivers flow down, south is down on the map, and therefore rivers must flow south. OK, so that one is silly. My European Realtor should consider the Rhine, Elbe, Neisse, Vistula, and (arguably) the Seine or the Havel.

My colleague, on the other hand, is smarter. He asked for an example of another north-flowing river, and I (pulling his chain) mentioned the St. Lawrence.

"But that doesn't really flow north."

And it is true, it flows only northerly. But that begs the question: how true to the compass does a river actually have to flow before it counts with the Nile? Clearly, if you define "north" narrowly enough, then very few rivers flow north – not even the Nile.

I gave him better examples: The Mackenzie, Churchill, Red (ND), Fox (WI), San Joaquin, Bitterroot, Yellowstone, Madison, Jefferson, Lualaba.

The Lualaba? That, my friend could argue, surely shouldn't be on the list, though it flows nearly due north for almost 1000 miles. After all, it is just a different name for the Congo, upstream from Kisangani Falls. But nobody really knew that: for at least two centuries it was thought that the Lualaba drained into the Nile, surely establishing its northward credential. It was only in 1877 that Henry Morgan Stanley (of "Dr. Livingstone, I presume" fame) took a boat down the Lualaba all the way to its mouth at the Atlantic Ocean.

Lest you think that multi-named rivers exist only in uncharted Africa, think again. Our very own Niagara River flows due north, from Lake Erie to Lake Ontario, and is just an extension of the St. Lawrence.

The Lena, the Ob, and the Don flow north, all of which drain into the Russian arctic.

But that brings us to the third reason for this persistent legend: that it's true. No, I am not wearing a tinfoil hat, but even the most improbable urban legends have a grain of truth. I'll argue this one does, and here is why.

Most of the world's continents are in the northern hemisphere, and conversely, oceans are disproportionately in the southern. Thus, to reach the ocean, rivers must on average flow south.

We are all subject to the Mercator fallacy, and assume that the northern coast is as long as the southern. But it isn't. The northern shores of Russia, Alaska and Canada are much, much shorter than the southern coasts of Asia, Europe and North America. Thus, just by the odds, there have to be many fewer rivers flowing north than flowing south. I do believe this is true.

How could one prove that? I don't know. It would be a lot of work – counting rivers, controlling for south-heading-north-flowing ones, etc., etc. Not worth the candle. So I'll just accept my hypothesis as both reasonable and true.

I'm not willing to give my real estate agent much credit. But my university colleague is not quite as far off the mark as you might have originally thought. North-flowing rivers are, indeed, relatively rare.

The Richelieu, Monongahela, Shenandoah, and the St. Mary's (FL).

I've listed all the ones I can think of. Can you think of more? Creeks, brooks, streams and canals don't count. And neither does the St. Lawrence. But other than that, I'm curious what you'll come up with.

Except for the Nile.

Daniel Jelski is Dean of Science & Engineering State University of New York at New Paltz.