A report from the Iowa Department of Natural Resources (DNR) shows Iowa had 36 nitrate-related drinking water violations in 2025, which is more than double the number reported in 2024.
Each year, the DNR submits a compliance report to the U.S. Environmental Protection Agency (EPA) detailing violations of federal drinking water standards, from excessive contamination levels to operator certification requirements.
According to the 2025 report, nitrate contaminant levels above the EPA limit was the most common health-based standard violated by public water supply systems. The 36 violations occurred at 13 systems and impacted a total of 2,479 customers, according to the report. Violations of nitrate accounted for 41% of the total 87 violations of health-based standards.
A health-based standard assesses whether the public water supply system produced finished water within the EPA established limits for drinking water contaminants.
The 2024 report showed 14 violations for nitrate contaminant levels at nine public water supply systems, affecting 1,765 customers. This was also the most common violation in 2024 and accounted for nearly 19% of the 74 total violations.
In 2023, Iowa had 38 nitrate contaminant violations at seven public water supply systems. A graph of nitrate violations from 2016 through 2025 from DNR shows 2023 and 2025 had significantly more nitrate violations than the other years.
Slightly more than 90% of Iowa systems pull from groundwater sources. Surface water sources, like a river, and influenced groundwater sources, like a shallow well near a river, account for the other 10% of systems, though these systems serve about 47% of the state population.
Iowa rivers typically have elevated nitrate levels in the spring and summer months as heavy rains flush nutrients off the land and into the rivers. The DNR report said nitrate and nitrite can enter source water from the natural decay of organic matter, commercial fertilizers, contamination from human waste and farm animal waste.
Nitrate concentrations in major rivers like the Des Moines and Raccoon reached near-record high levels during summer 2025, leading to the first-ever lawn watering ban in the Des Moines metropolitan area. Levels remained elevated through the winter, causing Central Iowa Water Works to run its nitrate removal facility for a period in January and issue another lawn watering ban for a short period this summer.
The consumption of water with nitrate concentrations above the EPA limit of 10 milligrams per liter can be fatal for infants under 6 months of age as the contaminant affects the oxygen-carrying capacity of an infant’s blood and can lead to an illness known as methemoglobinemia, or blue-baby syndrome.
Some research also points to adverse health effects with the consumption of nitrate in levels below the EPA maximum and some Iowans believe the nitrate concentrations in the state have contributed to the state’s high cancer rates.
Nitrate concentrations in finished drinking water above the EPA standard are considered an acute violation, meaning it poses an “immediate” health risk, according to the DNR report. A violation occurs when a system records levels above the maximum in a monthly, quarterly or annual compliance period. Compliance is achieved when the system records two consecutive quarters in which the samples are all within the specified limits.
According to the report, more than half of the nitrate violations in 2025 occurred at four public water supply systems. The report said several of the systems with nitrate violations are installing treatment systems or connecting to other systems to address the nitrate violation issue.
The Little Brown Church in Chickasaw County had nine nitrate violations in 2025, Lazy T Campground in Delaware County had four nitrate violations and Lost Beach Resort, also in Delaware County, had four nitrate violations. Early Municipal Water Supply in Sac County, classified as a community water system, had four nitrate violations for the year.
Aside from Early Municipal Water Supply, the systems with the greatest number of violations were classified as transient non-community water systems, a type of public water supply system that serves more than 25 individuals daily, at least 60 days out of the year.
The report also shows “major” reporting and monitoring violations made by public water supply systems. A violation occurs when a system fails to collect, report, analyze or follow the proper sampling guidelines for a given contaminant in any one compliance period, which varies depending on the contaminant.
Approximately 20% of Iowa’s public water supply systems had major reporting and monitoring violations, according to the report. Failure to collect coliform bacteria samples accounted for the majority of reporting and monitoring violations. Iowa had 249 violations for coliform bacteria monitoring at 158 systems.
Nitrate monitoring was one of the contaminants with the highest reporting violations in 2025, with a total of 84 reporting violations across 66 systems.
Reporting and monitoring violations can most often be remedied by performing the necessary monitoring or issuing the necessary public notification. An administrative order can be issued for systems that fail to come into compliance in a timely manner.
Over 3.12 million Iowans — about 95% of the population — are served by public water supply systems, the remaining population is served by private water supplies, like a well on the property.
