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How does USGS measure river flow? It's not always as easy as it may seem...

Idaho USGS team manually measures river flow by hanging over water on a cable. (KBOI Photo)

The United States Geological Survey measures Boise River levels near the Glenwood Bridge in Garden City.

A device in the water transmits how many cubic feet per second the water is traveling.

However, in order to make sure that gauge is always accurate, crews have to make manual measurements, a task that isn't as easy as it may sound.

As the Boise River roars, USGS hydrographers hang over the water on a cable to make manual measurements of the flows.

"We're out there smiling having fun," said Russ Miller, an Idaho USGS hydrographer.

The numbers Miller and his team collect today are extremely important as the river continues to flood.

"Overnight last night the river was at 9,810 cfs, that's the highest we've seen since the peak measurement, all time ever record for this stream gage since lucky peak dam was constructed," said Tim Merrick, Idaho USGS spokesperson.

That was back in 1983.

The data USGS collects is used to make sure the permanent steam gage is accurate because so many people rely on the numbers it transmits.

"The Army Corps of Engineers, the Bureau of Reclamation are using data from this gage to make decisions about releases from Lucky Peak," Merrick said.

When crews manually measure, the device in the water sends sound waves out to calculate cubic feet per second.

Then they compare those numbers with the permanent stream gage.

If the numbers aren't equal, they have to make changes to the stream gage.

It takes several trips across the river to get the data they need. and crews are making these measurements more often than normal right now.

"In a flood situation like this, we're coming out more frequently, particularly when the releases from lucky peak increase we want to make sure we're collecting date when the river level changes," Merrick said.

The permanent stream gage calculates and transmits real-time flows by blowing gas into the river and measuring the water pressure.

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