If you happened to read the Daily Telegraph, back in June 1999, you might have run across this: “The Balkans conflict is at a watershed between a diplomatic settlement and the prospect of a ground war.” If you’re an English speaker from North America, you probably would have wondered, at least for a moment, what on earth they were talking about.
As everybody (in North America) knows, a “watershed” is the geographic area where water from a drainage system (a river, for example) accumulates. It’s not all that unusual to read about something like the “Ohio watershed,” referring to the Ohio river.
Even given that the quote about the Balkans conflict uses “watershed” figuratively, how can what’s essentially a huge basin of water provide a meaningful metaphor in that sentence? The answer, obviously, is that it can’t. And the answer to the next question is “because ‘watershed’ means something different in North America than it means everywhere else.
Visualize a simple garden shed with a peaked roof. When it rains, the roof directs the water to either one side or the other, and the dividing line is right along the peak of the roof. Now imagine a landscape, where rain either flows to one direction or another, depending on the general slope. There’s an imaginary line dividing the flow in one direction from the flow in another. Since the 1700s, that line has been called the “watershed.”
Being “at a watershed” is a figurative use of the “dividing line” sense of the word. That’s what “watershed” means when you read about “a watershed moment.” The phrase is even occasionally used in the US even though our use of “watershed” is usually different.
The different usage of “watershed” didn’t happen immediately; up until around the 1830s, everybody on both sides of the Atlantic agreed that a “watershed” was an imaginary line, not a geological basin. But then R.I. Murchison published Silurian Systems, in which he wrote: “To the south-west of Kington the lower beds of the Old Red Sandstone..have been the sub-aqueous water-shed, down which the coarse detritus has been swept.” Confusion spread. Although, to be sure, at that point the term was technical jargon and not that many people had even heard it.
By 1877, Thomas Huxley tried to start over, redefining the term as neither the line nor the basin, but the slope (either side of the roof of the shed, so to speak): “To avoid all ambiguity it is perhaps best to set aside the original meaning of ‘watershed’, and employ the term to denote the slope along which the water flows, while the expression ‘water-parting’ is employed for the summit of this slope.”
Huxley’s suggestion was taken up by precisely nobody. The original meaning of the term persisted outside North America, and Murchison’s idea — which, for all we know, was a misunderstanding in the first place — presided inside. It was sort of like we reached a linguistic watershed between a line and a basin, and collectively decided on… both! And if you recall the events in the Balkans, pretty much the same thing happened there. The main conflict was resolved by the Kumanovo Agreement in 1999, but skirmishes continued in Albania and Macedonia for two more years.
