What Influences the Level of the Willamette River in Portland?

What influences the level of the Willamette River in PDX? I get the spring runoff, but in other seasons it seems to rise and fall at random times throughout the week. Why? Does it have anything to do with the rumor that the river flows south to north to keep Portland weird? And does anything reverse its flow? —Rapidly Going Mad

There is a pervasive belief among stupid people that all rivers (or most rivers, or most rivers in the Northern Hemisphere, or most American rivers—it depends on how stupid we’re talking about) flow north to south. A majority of American rivers do flow southward, but that’s just because rivers empty into oceans, and the U.S. has no ocean to its immediate north. (Unless you count Canada, that ocean of goodwill!)

So in this way, the Willamette is unlike other rivers. I suppose there’s a sense in which that makes us weird, but come on: If we can’t find better examples of Portland weirdness than the slightly unusual direction of our river, we should just hang it up and be Irvine. It’s like Mitt Romney telling you he’s a party animal because sometimes, when nobody’s home, he eats breakfast cereal for dinner.

In any case, there are lots of reasons the river rises and falls. The most consequential is precipitation. The connection between long periods of heavy rain in the Portland area and a swelling Willamette is obvious (one hopes) to everyone, but it might not immediately occur to us that some of those “random” increases in flow could be the result of rain or snow farther upstream that never reached the Rose City.

Occasionally the shadowy figures who control the river’s various dams will, for their own inscrutable reasons, release or withhold some extra water. This also affects the river’s level (call it the river’s “stage” if you want to sound like you know what you’re talking about), though not as much as precipitation.

Finally, even though Portland is some 85 miles inland of the Pacific, the tides cause a roughly 2-foot rise and fall in the Willamette’s level every day—though it would be a stretch to call the effect random. And even better for your final question (at which a lesser knowitologist than I might have sneered), when the river is low, this tidal push actually can, briefly, cause the current in the Portland-area Willamette to run gently north to south, making Portland—if only for a moment—normal.

Questions? Send them to dr.know@wweek.com.