First, you have to define what you mean by "river," and that can be harder than it sounds. The dictionary definition (at least the first one I found) is: "a large natural stream of water flowing in a channel to the sea, a lake, or another such stream." (Oxford)
So you've got "large," which is a judgement call; "natural," which is fuzzy; "stream," which implies flowing, but lots of water flows and some rivers sometimes don't; and "water," which rules out, for example, the L.A. River (most of the time); "flowing," which I say is redundant after "stream;" and "channel," which seems straightforward enough until you consider that some rivers are braided and/or deltaed with multiple channels.
And then you have bodies like the Potomac River, which for much of its lower reaches, all the way up past DC, isn't so much a river as a tidal estuary that happens to be fed by a higher river.
Oh, but that's not all. Dictionary definitions don't cut it here in this blog. I can use them as examples, but they don't resolve arguments.
You know the old saying, "You can't step into the same river twice?" I think it's supposed to be about how things change over time. Water goes in, water flows out, evaporation happens, shores get eroded, sandbars form, megatons of soil get transported, etc. Thing is, rivers (and other streams) don't just change over time; they, like living bodies, are in a constant state of flux ("flux," incidentally, shares a root with "flow" and "fluid").
Consequently, I say you can't step into the same river once. Because between the time your foot touches the surface and the bottom, the river has already changed. Hell, the mere act of stepping into it changes it, however minimally.
So when you're asking a question like the one in the headline, you have to be careful.
Rivers may seem as old as the hills, but they have life cycles just like other natural features do.
Yeah. Like hills.
Some rivers last longer than others, however. So which river is the oldest in the world today?
Remember that a river isn't just its water. Sometimes, it's not even its water, but just its channel, such as the aforementioned L.A. River (which also stretches "natural" to its natural breaking point). Channels change over geological time, though, carved and altered by water flow and other processes such as continental drift.
The winner is older than the dinosaurs: The Finke River in Australia, or Larapinta in the Indigenous Arrernte language, is between 300 million and 400 million years old.
I'm certainly not going to argue about that, though. Australia is a remarkably stable continent (or island or whatever name you slap on the land mass). If I remember right, some of the oldest rocks in the world are also found there, presumably guarded by dangerous wildlife, but don't get me started on how they define how old a rock is.
The arid conditions in the center of the continent mean the river flows only intermittently; most of the year, it exists as a string of isolated water holes.
See?
There's a whole lot of semi-technical geological explanation for how they figured it out at the article. While I have some experience with geology, it was rather secondary to hydrology in my education, so I'm not going to quibble about it. It is interesting, at least to me. But no quotes here.
"Rivers can disappear if a massive influx of sediment overwhelms them (e.g., volcanic eruptions) or if topography changes so dramatically that the flowing water takes a new course across the landscape (e.g., glacial advance and retreat)," Ellen Wohl, a geologist at Colorado State University, told Live Science in an email.
Pretty sure there's more that can change or destroy a river.
In the case of the Finke, Australia has been an unusually stable landscape for a very long time. Resting in the middle of the Australian Plate, the continent has experienced virtually no significant tectonic activity for the past several 100 million years, Baker explained.
Like I said. Only with more detail.
If the Finke ever dries up, the runner up may be the New River, which today is about 300 million years old, Baker said, and runs through Virginia, West Virginia and North Carolina.
And so we get to the final bit in the article, and the main reason I'm sharing this. Australia is on almost the opposite side of the world from me, and I've never been there, but the New River is practically in my backyard, globally speaking. I've known about its ancient age since college, when I took the aforementioned geology and hydrology courses.
Unlike most Virginia rivers, it doesn't flow into the Chesapeake Bay and thence into the Atlantic; instead, it's part of the Mississippi River basin. Which technically flows into the Atlantic, too, but via the Gulf of Mexico.
And unlike the Finke / Larapinta, the New River is always wet. And flowing. They take people whitewater rafting on it. Not me, obviously. But people.
In the interest of full disclosure, I should note this quote, which has cited sources, from the New River article on Wikipedia: "...a claim that the river is the second oldest in the world is disputed by the West Virginia Geological and Economic Survey and the National Park Service." It is, however, still damn old.
The irony, of course, is that it's called the New River, and that's what I find endlessly amusing.
