Iowa water sensors show 2016 uptick in nitrates

State's sensor network is one of the largest in the nation

Jason McCurdy, a researcher and field technician at the IIHR Hydroscience and Engineering center at the University of Io
Jason McCurdy, a researcher and field technician at the IIHR Hydroscience and Engineering center at the University of Iowa's College of Engineering, installs a water quality sensor used for testing nitrate levels at Miller Creek, west of Gilbertville on Thursday, March 23, 2017. The program has installed the sensors across the state in order to establish a baseline report of various water quality indicators. (Rebecca F. Miller/The Gazette)

LA PORTE CITY — If the doctor says you’ve got to lose weight for your health, you need to step on the scale once in a while, right?

Iowa is among states trying to reduce the amount of nitrates washing from farm fields into streams and rivers, where they can harm human health and are adding to the creation of an oxygen-deprived dead zone near the mouth of the Mississippi River in the Gulf of Mexico.

Iowa has more than 70 sensors deployed this year on streams and rivers across the state that measure nitrate loads and concentration so observers can tell whether water treatment plant upgrades, wetland improvements and agricultural conservation practices are working to reduce pollution.

“Our hope is the policy makers in Des Moines will use that (data) to track progress toward these goals,” said Chris Jones, research engineer with the University of Iowa’s IIHR-Hydroscience & Engineering.

Legislation to help finance more water quality projects made it past a deadline Friday to be further discussed this session. But with daily expenses for legislators expiring April 18 — usually considered to be the end of the session — the clock is quickly ticking on approval of a funding mechanism yet this year.

View a live map of all nitrate sensors in Iowa.

Data released last week by Jones’s lab show 40 percent of the 61 sensors that were in Iowa in 2016 had an average daily concentration of nitrates above the federal drinking water standard of 10 milligrams per liter.


The highest was a groundwater spring at the Manchester fish hatchery, which had an average nitrate concentration of 17.8 mg/L.

Not all these waterways are used for drinking water, but some are.

The Iowa River, which provides drinking water to the UI campus, had an average daily nitrate concentration last year of 7.9 mg/L. The Raccoon River, a drinking water source for half a million people in the Des Moines area, had average daily nitrate concentration in 2016 at 11.5 at Sac City and 10.7 at Jefferson.

Nitrates in drinking water have been linked to cancer, rashes, hair loss, birth defects and other health problems, including infant methemoglobinemia, or blue baby syndrome.

Not just humans are affected.

“Ten mg/L is quite high for a natural water in the context of aquatic life, algae blooms, biodiversity and so forth,” Jones said. “Most of our pre-settlement streams would have had nitrate concentrations below 1 mg/L.”

How sensors work

Iowa’s network of water sensors, deployed by the UI, U.S. Geological Services and the U.S. Department of Agriculture, gather nitrate data on streams and rivers across the state from March through November. Other sensors, often at the same sites, measure water level, sediment pH and dissolved oxygen.

One of the nitrate sensors in the Cedar Rapids watershed is southeast of La Porte City, where farm fields and pastures border Miller Creek.

John McGlothlen / The Gazette

Under a bridge, Jason McCurdy, a UI research assistant, slides a cylindrical water sensor down a PVC tube that juts into the cold stream. Every five minutes, a ray of ultraviolet light scans the water passing the sensor window to take a reading of the nitrate concentration and load.

A nearby control center, powered by a solar panel and a 12-volt battery, sends updates every 15 minutes via cell tower. Tom Stoeffler, another research assistant, powers up his laptop to check the transmission — 4 mg/L, which is within the range of safe for drinking. But a few days later, the nitrate concentration at that site is up to 9 mg/L.

Miller Creek’s average daily nitrate concentration in 2016 was 11.5 mg/L.


Sensor data feed directly into the Iowa Water Quality Information System website, which has an interactive map that lets viewers see the nearly real-time nitrate measurements, as well as weather reports to coincide with the readings.

“It’s pretty neat during a rain event,” Stoeffler said. “There’s an initial dip (in nitrate levels) from the dilution from the rain. Then you start to see a spike as the nitrate starts washing into the creek. Then the peak comes back down.”

Nutrient reduction

The 2008 Gulf Hypoxia Action Plan called for Iowa and other Midwest states to cut nitrogen and phosphorus loads in the Mississippi River by 45 percent. To do that, Iowa developed a Nutrient Reduction Strategy that requires water treatment plants to make improvements and asks farmers to implement voluntary conservation practices.

But there’s no deadline for making the changes — many of which are costly.

Adam Schnieders, the Iowa Department of Natural Resources water quality resource coordinator, said state officials use a variety of metrics to gauge whether water quality improvement programs are working.

“Before we see a reduction of nutrients in the water, we need to see change on the land,” he said.

The strategy requires Iowa municipal wastewater treatment plants processing at least 1 million gallons of wastewater a day to make plans to remove nitrogen and phosphorus from their effluent. In mid-March, 31 municipalities had submitted feasibility studies for plant upgrades, 15 had plans for new facilities and three cities — including Iowa City — already had new facilities online, Schnieders said.

Several companies, including Tyson Fresh Meats, have committed to reducing phosphorus in effluent, and many farmers are participating in voluntary conservation practices, such as growing cover crops or leaving unplanted buffer strips to control erosion, he added.

But the proof is in the water.

“The sensors are a big deal,” Schnieders said. “Iowa has one-third of all sensors deployed in the nation.”


The only other state in the nation with a comparable number of water sensors is California, nearly three times as large as Iowa.

Jones and his team have compiled an annual report on nitrate concentration and load for two years now, with 2016 concentration levels higher than 2015 for nearly all sensors operating both years. But more years of data will show whether increases continue or if there are dips on streams and rivers near where farmers are implementing conservation strategies.

“There’s a lot of uncertainty with the water quality benefits associated with these practices,” Jones said. “A scientific assessment can develop book values for all practices.”

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