New River Gages Providing Better Flooding Forecasts

By Erin Jordan, Reporter

Kevin Townsend (hat) and Garret Welsh with the USGS monitor water levels on the Iowa River at Merengo. (Dan Sheffer/KCRG-TV9)

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By Richard Pratt

CEDAR RAPIDS, Iowa -- New Eastern Iowa river gages added since 2008 are working well this week, which means the National Weather Service can develop better forecasts as Linn and Johnson counties prepare for major flooding, officials said.

“We’ve actually been very satisfied with the way things are working,” said Jason McVay, a supervisory biologist with the United States Geological Survey (USGS), which maintains about half of the 352 river gages across the state.

“We have a significant number of people out monitoring whether things are functioning,” he said. “We don’t want any of them to go down.”

Iowa’s river gauge network struggled in 2008 as debris disabled the devices or caused false readings. Too few gages meant officials couldn’t tell how much water was being added to the river system by near-constant rain and heavy snow melt.

Federal, state and local agencies worked together since 2008 to add 154 new gages that send real-time updates to the NWS.

“Those flow measurements are vital to our flood forecasts,” said Jeff Zogg, senior hydrologist with the National Weather Service (NWS) in Des Moines. “The collective information allows us to provide more accurate information with more lead time, which can prevent losses.”

Linn County, which had only one river gage before 2008, now has 16. Boone County got 11 new gauges since 2008 and Cerro Gordo, Hardin and Polk counties each got eight.

A new Tama County gage was endangered by a falling tree Thursday, but USGS employees fixed the problem and installed an additional radar gauge for backup readings along the Iowa River, McVay said. They plan to install another radar gage in Marengo next week.

As the U.S. Army Corps of Engineers releases more water from the Coralville Lake, officials will check with USGS employees to make sure downstream gages are accurately reflecting the water flow, he said.

“They make adjustments at the gate level,” McVay said of the Corps. “Our gauges need to verify that.”

Eighty percent, or 127, of the new gauges sending information to the NWS are operated by the Iowa Flood Center, a University of Iowa-based institute established by the Iowa Legislature in 2009. The center has another 25 sensors that are not yet linked to the NWS gage network.

The center developed an inexpensive sensor mounted on a bridge that can measure a river’s height by using ultrasonic waves. Each sensor costs $3,500 to deploy and about $120 a year for a cell phone data plan for transmitting water level readings every 15 minutes.

“We’re very proud of this that we’re complimenting the existing network,” said Witold Krajewski, center director and a UI engineering professor.

USGS gages are more expensive -- between $15,000 to $20,000 to install and $10,000 a year to maintain -- but gather information on water flow, which is vital for forecasts.

The public can see real-time reports from Iowa’s network of river gages at several websites, including: www.rivergages.com, http://ia.water.usgs.gov or http://water.weather.gov/ahps/region.php?state=ia.

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