seiche

Have you ever been at a party where there’s someone on one side of the room holding forth volubly and vapidly, and the crowd around them gradually rarefies while it gets more and more crowded on the other side of the room? You’ve just seen an important fact in fluid dynamics.

You can simulate it. Set a shallow dish of water on the counter. Get low and close to the edge of it and blow. You’ll see that the water makes waves – small, rapid ones, because it’s a small dish – but also that it tends to creep up the other side of the dish while you’re blowing, then, when you stop, it sloshes back to your side for a moment before levelling out with a few back-and-forth waves. Try this several times. (Hold well onto the counter when you stand up after.) You have just demonstrated, in a very small way, a seiche.

A seiche is a standing wave in a bounded body of water: a lake, a reservoir, a swimming pool, your cup of tea. And it’s very much hydrologists’ cup of tea – and some meteorologists’ too. The weather person on Buffalo TV (don’t ask me which station, probably NBC) was talking about seiches last night. There’s a windstorm coming, you see, and the wind is going to be sweeping along the length of Lake Erie. The water will get very wavy, but it will also tend to pile up against the eastern end of the lake. Which is where Buffalo is. A solid windstorm can increase the lake level at Buffalo by up to 5 metres for up to an hour – while at the same time decreasing it at Toledo (the other end) by even more. And don’t forget that Lake Erie drains into the Niagara River at Buffalo. Expect docks along the river to get rather, um, moist. And Niagara Falls to get more… spectacular, I guess.

So the obvious question is, How do you say this word seiche and where does it come from?

The word seiche gained currency after being used by the Swiss hydrologist François-Alphonse Forel in 1890 to describe similar effects in Lake Geneva. Of course, Switzerland has many mountain lakes, and naturally they’re all subject to seiches when the wind picks up. Forel used a term that was apparently in longstanding use in Swiss French to refer to the effect. Since it’s French, you can say it /seɪʃ/ (which is like “say” with a “sh” on the end).

But where did Swiss French get it? That’s uncertain. Probably not from another French word, sèche, that refers to the exposed sea-bottom at low tide; after all, sea bottoms at low tide are not to be seen in Switzerland. The best guess, according to the Oxford English Dictionary and Wiktionary, is that it blew west into the French part of Switzerland from the German Seiche ‘sinking’, repronounced as French without changing the spelling. (The German pronunciation is /zaɪçə/, which… never mind, let’s move on.)

But the thing is, I have a pretty big German dictionary, and it doesn’t have Seiche. It just has seicht, ‘shallow’ (in the same literal and figurative senses as in English). Related, perhaps, but…

But of course I can go online. Wiktionary has Seiche. It tells me it means the following things:

1. (dialectal, vulgar) urine, piss
2. bullshit, nonsense, twaddle

So perhaps Monsieur Forel was at a German cocktail party where someone was holding forth on one side of the room and…

…nah. Couldn’t be.