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Lost Creek to Agness is a 30-hour rubber-ducky ride

How long would it take for a leaf (or rubber ducky) to float from the Rogue River's headwaters to the ocean? Also, from Lost Creek Lake to the ocean? I realize it varies based on flow, but any ballpark answer would be appreciated. I wonder this every time I visit the river, and I am not a math wiz.

— Missy E., Medford

Well, Missy, we at Since You Asked Central are all about the rubber ducky vectors and emogis. Also, as far as math goes, if we could actually do math, we wouldn't have to be newspaper reporters.

But even Einstein couldn't compute how long it would take a floating piece of orange, black-sunglassed rubber to get from Boundary Springs into the Pacific surf.

There are way too many variables to ponder as to how long it would take to float down the river's entire 215-mile length, such as the relative volume of water, wind and getting caught in eddies.

Besides, it's actually not even possible to float past impediments such Lost Creek dam, unless by chance the rubber duck sank and got sucked into one of the water-intake ports in the lake and spit downstream as part of Lost Creek Lake's water releases to the upper Rogue River.

But we do have a little math for you, Missy, on how long it takes for a rubber duck if it should get pitched into the outflow at the base of Lost Creek dam, thanks to the hydrologists at the U.S. Army Corps of Engineers and the U.S. Geological Survey.

As part of the Corps' operation of Lost Creek dam for flood control and fisheries enhancement, the Corps needs to know how long its manipulated water flows take to head downstream. Luckily, flows are measured in real time at four gauges on the Rogue — Dodge Bridge at Highway 234, the old Gold Ray Dam site, the Grants Pass water-treatment plant and the riverside burg of Agness 44 river miles east of the ocean.

The Corps has calculated that it takes about four hours for water released from Lost Creek Lake to reach the Dodge Bridge gauge, give or take a few minutes based on low-water or high-water circumstances.

In about two more hours, the rubber duck would be due at the old Gold Ray Dam site (the dam is gone, Missy, but the gauge remains just downstream of where the dam was) and then it would pass under Grants Pass' Cave Man Bridge four hours later.

That's 10 hours from Lost Creek Lake to Grants Pass. Agness is 121 miles farther downstream and full of deep, slow canyons. Depending on volume, it usually takes about 20 more hours to go from Grants Pass to Agness, but it could be as short as 16 hours during near-flood conditions, according to the Corps.

That's all the math we have, Missy, because there are no gauges below Agness.

Reach Mail Tribune reporter Mark Freeman at 541-776-4470 or mfreeman@mailtribune.com. Follow him on Twitter at www.twitter.com/MTwriterFreeman.