Iowa's Nitrate Problem: What Des Moines Families Need to Know About Their Drinking Water

March 05, 2026•5 min read

Iowa's Nitrate Problem: What Des Moines Families Need to Know About Their Drinking Water

If you lived in central Iowa during the summer of 2025, you probably remember the lawn watering ban. For the first time in history, 600,000 residents across the Des Moines metro — from Ankeny to Norwalk, Waukee to Pleasant Hill — were told to stop watering their lawns. The reason wasn't drought. It was nitrate.

Nitrate levels in the Raccoon River, one of central Iowa's primary drinking water sources, hit 20.55 mg/L on June 8, 2025 — more than double the EPA's safe drinking water limit of 10 mg/L. The Des Moines River wasn't far behind, regularly testing above 13 mg/L throughout the summer. Central Iowa Water Works (CIWW) had no choice but to implement Stage III water restrictions to keep finished water within legal limits.

Source: Central Iowa Water Works Stage III Daily Updates, June–July 2025 (ciww.gov); Iowa Capital Dispatch, July 25, 2025

What Are Nitrates, and Why Should Iowa Families Care?

Nitrates are a chemical compound that forms when nitrogen from fertilizer and animal manure breaks down in soil. In Iowa — the nation's top corn-producing state, home to more than 53 million hogs and 55 million chickens — there is an enormous amount of nitrogen being applied to farmland every year. When it rains, that nitrogen washes through tile drainage systems and into the rivers that supply our drinking water.

A Polk County–commissioned scientific study, the Central Iowa Source Water Resource Assessment (CISWRA), confirmed that 80% of the nitrogen in central Iowa's rivers comes from agricultural sources. Iowa's waterways carry some of the highest nitrate concentrations in the entire country — in the top 1%, according to the Iowa Environmental Council.

Source: Polk County CISWRA Report, 2025; Iowa Environmental Council, 2024

The Treatment System Is Working Overtime

Des Moines Water Works operates one of the largest nitrate removal facilities in the world at its Fleur Drive Treatment Plant. In 2025, that facility ran for 122 consecutive days at an operating cost of approximately $16,000 per day. Even at full capacity, the treated water leaving the plants averaged around 7–8 mg/L for months on end — technically legal, but well above levels that emerging research links to serious health risks.

As Iowa Public Radio reported, CIWW chemist Lisa Morarend explained the challenge: with raw river water testing at 14–20+ mg/L, the treatment facility has to work constantly to blend and process water down below the 10 mg/L threshold. When all three water sources — the Raccoon River, the Des Moines River, and the infiltration gallery — simultaneously exceeded 10 mg/L in June 2025, the system had nowhere to turn for cleaner source water.

Source: Iowa Public Radio, June 25, 2025; Iowa Capital Dispatch, July 25, 2025; CIWW daily monitoring data

Why "Legal" Doesn't Mean Safe

Here's what most Iowans don't realize: the EPA's 10 mg/L nitrate standard was originally established to prevent a single condition — blue baby syndrome (methemoglobinemia) in infants. It was not designed to account for cancer, thyroid disease, birth defects, or any other chronic health effect. And it has never been updated.

Newer research paints a very different picture. An Axios Des Moines investigation in July 2025 highlighted the Polk County CISWRA report's recommendation that local utilities adopt a 5 mg/L threshold for nitrates — half the current legal limit. Des Moines University professor Jason Semprini, who studied 360,000 Iowa birth records, found that nitrate exposure at just 5 mg/L was associated with low birth weights and preterm births. Iowa State researcher Lu Liu noted that concentrations as low as 3 mg/L can contribute to adverse outcomes.

Meanwhile, from 2006 to 2023, central Iowa's finished drinking water was at or above 5 mg/L roughly 40% of the time.

Source: Axios Des Moines, July 30, 2025; Polk County CISWRA Report, 2025

There Is No Quick Fix

If you're hoping the state will solve this problem in the next few years, the data suggests otherwise. Iowa's Nutrient Reduction Strategy has been in place for over 12 years with no measurable improvement in river nitrate levels. Iowa State University research shows that even corn and soybean fields with zero fertilizer applied for six years still leach 8 mg/L of nitrate through tile drainage. The nitrogen already stored in Iowa's soil and groundwater will take decades to flush through the system.

As University of Iowa researcher David Cwiertny told Iowa Public Radio in August 2025: "It's just going to be a difficult lift to ever see the nitrate [limit] get lower, even with the science that's out there." He specifically recommended that the state support more at-home reverse osmosis systems for Iowans concerned about their water quality.

Source: Iowa Public Radio, August 6, 2025

What Iowa Families Can Do Right Now

Standard carbon filters — the kind found in Brita pitchers, PUR filters, and refrigerator dispensers — do not remove nitrates. Neither does boiling your water (boiling actually concentrates nitrates by evaporating the water). The only proven household technology for nitrate removal is reverse osmosis (RO).

Reverse osmosis is the same technology used at the Saylorville Water Treatment Plant in Des Moines. It works by pushing water through a semi-permeable membrane that filters out 95–99% of nitrates, along with lead, arsenic, PFAS, and dozens of other contaminants. Modern under-sink RO systems install in about 30 minutes with no plumber required.

If you're on a municipal water system in the Des Moines metro, an RO system provides a final line of defense when treatment plants are pushed to their limits. If you're on a private well — where water is

completely unregulated and untested unless you take action yourself — it's even more critical.

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