Beefed up river gauge network helping with forecasts, planning

More information on river levels is flowing to the public thanks to more than 150 new gauges added to Iowa's rivers and streams since the floods of 2008.

Iowa's river gauge network struggled in 2008 as debris disabled the devices or caused false readings. Too few gauges 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 invested money, time and creative thinking to add 154 new gauges, bringing the statewide total to 352 that send real-time updates to the National Weather Service (NWS).

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

The 2008 flood caused $7 billion damage in Cedar Rapids, ranking at that time as the 5

^th

worst disaster in U.S. history. Flood damage in Iowa City and Coralville topped $1 billion.

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

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 gauge 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.

The United States Geological Survey (USGS) owns 22 of the new gauges. These gauges are more expensive -- between $15,000 to $20,000 to install and $10,000 a year to maintain -- but gather more information.

River flow data collected by the USGS during site visits is necessary for NWS forecasting.

Jason McVay is one of 24 USGS employees who inspects the 186 USGS gauges every six weeks to make sure they are accurately measuring river height based on sea level.

During a recent check, McVay pulls an acoustic Doppler current profiler across the Iowa River along the Benton Street bridge in Iowa City. He records 12 minutes of data to show the river's flow at 4,600 cubic feet per second.

McVay types all the information into a laptop, which is a new tool since 2008. The data is quickly shared with the U.S. Army Corps of Engineers.

“It's amazing how much the river changes,” he said.

The NWS welcomes data collected by the USGS, Flood Center and other agencies that maintain Iowa's gauges, Zogg said. The flood center's measurements of the distance between the bridge and the top of the water can be used to determine river height, which helps the Weather Service track the crest of a swollen river.

The public can see real-time reports from Iowa's network of river gauges on several websites, including:

www.rivergages.com,

http://ia.water.usgs.gov or

http://water.weather.gov/ahps/region.php?state=ia.