River Headwaters and Sources

On January 29, 2008 · 1 Comments

Long is the history of adventurers who explored distant lands and tangled jungles to find the true origin of mighty rivers. But rivers are not simple contiguous lines that trace back easily to a single spot. Rather they are widely spread watersheds that drain to a common outlet. There can be hundreds of liquid tendrils joining and growing in size as they combine into a single entity, an interconnected web originating from many different sources such as lakes, streams, marshes, springs or glaciers.

All sorts of conventions have been created to trace a river back to its source: the farthest point upstream from the mouth; branches with the larger volumes of water; or the highest point of elevation within a watershed might all be examples. Less objective influences such as history, tradition or politics can serve as a deciding factor. No clear-cut definition can be applied consistently but the underlying principal seems to be based on consensus applied case-by-case. The true source, the ultimate headwater of a river is basically whatever people believe it to be.

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National Geographic News recounted their efforts to pinpoint the source of the Amazon River with the assistance of Global Positioning System technology. Their 2000 expedition identified a slope on a remote mountain in southern Peru, Nevado Mismi as the Amazon’s source, defining it by distance.

The person in charge of the instruments that nailed it was geographer Andrew Johnston of the Smithsonian Institution’s National Air and Space Museum in Washington. The source of the river, he says, can be defined as the most distant point in the drainage basin from which water runs year-around, or the furthest point from which water could possibly flow into the ocean.

Thus, very objectively and scientifically, researchers used precise instruments and measurements to proclaim the side of a rock wall on Nevado Mismi as the source of the Amazon River.

Potomac River Watershed

Not every determination throughout time has been this objective, nor did early explorers have sophisticated equipment to assist them as they fanned-out through new lands. The Potomac River of the eastern United States is a case in point. Its upstream path can be tracked back easily until just before Green Spring, West Virginia when the river splits into a northern and a southern branch. Both are significant and both carry about the same volume of water. Logically either could be considered its source, or perhaps equal co-sources.

The South Branch is the longer of the two. It traces back through West Virginia and then just across the border into Virginia, near Hightown in Highland County. Even so the source of the Potomac River is generally identified with the other branch, the North Branch, at the Fairfax Stone. This was an important survey marker placed during colonial times to determine a boundary between Maryland and Virginia in what was then uncharted wilderness. Today it marks the common intersection of Preston, Grant and Tucker Counties in West Virginia. In this instance historical prominence seems to trump  physical distance traveled by water.

Crossing the Mississippi

It’s easy to cross the Mississippi River at its source!

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The Mississippi River presents another oddity. We’ve already established that physical distance isn’t the only way to determine a river’s source so let’s ignore the whole issue of the Missouri River, a tributary that’s as long as the Mississippi River itself. Lake Itasca in northern Minnesota is generally construed to be the Mississippi’s source. A few years ago I walked right across the mighty Mississippi at this location on stepping stones placed conveniently for visitors. It was great fun.

But hold on a minute: take a look at the map above and notice the lake just south of Itasca. That’s Elk Lake and a stream coming from it feeds directly into Lake Itasca. And a couple of streams feed into Elk Lake, and a marshy area feeds those streams. Even though there are plenty of dribbling pools and gurgling springs that are considered the sources of major rivers, in this instance they are dismissed as “too small for the source of the Mississippi.

So once again we’re presented with the conclusion that earning the title of “True Source” depends upon consensus of opinion.

Source of Potomac Watershed map: en.wikipedia.org/wiki/Image:Potomac_watershed.png, under the Creative Commons Attribution ShareAlike 2.5 License.

On January 29, 2008 · 1 Comments

One Response to “River Headwaters and Sources”

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