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POSTED: Monday, Nov. 09, 2009

Nooksack River's water flow and river bottom get regular checkups

EVERSON - Jeff Paulat walked slowly along the Nooksack River bridge at the edge of town Friday, Nov. 6, using a green nylon rope to drag a small orange plastic trimaran along the churning surface of the grayish-brown water, from one end of the bridge to the other.

It's a ritual that he and his boss, Darrin Miller, repeat every six to eight weeks here and at about 70 other access points along rivers between Marysville and the Canadian border. They are hydrologic technicians working out of the Sedro-Woolley office of the U.S. Geological Survey, and their little plastic boat is equipped with $40,000 worth of acoustic measuring equipment that enables them to map the ever-shifting bottom of the river.

It's part of the complex technical task of measuring a river's flow in cubic feet of water per second, and relaying flow measurements to the public on the USGS Web site. The measurements on the Nooksack can provide public agencies with warnings of impending floods, and recreationists can use them to judge the safety of river conditions.

Four acoustic beams on the underside of the little boat emit sound waves that are reflected back to provide data that is relayed to Miller's laptop computer via radio waves. The computer screen displays the contours of the river bottom beneath several feet of opaque, silt-laden water.

The USGS maintains a river-level gauge here and at a number of other locations in the Nooksack basin. But Miller said the mere measurement of the water level at a fixed point does not provide precise enough information on the actual amount of water moving downriver.

That's because river channels shift constantly, and that can cause river-level fluctuations unrelated to the actual volume of water.

To get around that problem, Miller and his staff make regular visits to stream gauge sites like the one in Everson, mapping changes in the river bottom that could affect the water-level readings on the gauge. That enables them to adjust their calculations of the volume of water, to make those calculations as accurate as possible.

The river gauge at Everson is equipped with a radio transmitter powered by a solar panel. It transmits river data via satellite to a receiving station on the East Coast for processing. Then it's relayed to the Web site for public use.

"They depend on that data to be almost instantaneous," Miller said. "People need to know that information."

ON THE WEB

U.S. Geological Survey stream flow information for the Nooksack River and other Washington streams is available at waterdata.usgs.gov.