How Iowa's Water Got Here
The story of tile drainage, fertilizer runoff, and a 60-year-old safety standard that's no longer adequate.
In the summer of 2025, something happened in central Iowa that had never happened before: 600,000 people were told to stop watering their lawns.
But it wasn't due to drought. It was the opposite. Spring rains had finally returned after four years of dry conditions, and with them came a surge of nitrate from agricultural fields across the state. The Des Moines and Raccoon Rivers hit concentrations of nitrate as high as 17 milligrams per liter, nearly double the federal safety limit.
Central Iowa Water Works, the regional utility that supplies drinking water to the Des Moines metro, had been running its nitrate removal facility at full capacity for more than 60 straight days. At $16,000 per day. And it still wasn't enough.
The lawn watering ban, the first in the utility's history, was the last tool they had. Without it, the water coming out of your faucet would have exceeded federal limits for the first time.
But this is much more than a story about one bad year. It's a story about how a century of decisions reshaped the way water moves through Iowa, and why the problem is almost certainly going to get worse before it gets better.
Roughly 80% of nitrate in Iowa's rivers originates from agricultural land. (University of Iowa)
THE SOURCE
It Starts in the Field
Plants need nitrogen to grow. In Iowa, that nitrogen comes from three main sources: synthetic fertilizer applied to corn and soybean fields, manure from livestock operations, and naturally occurring nitrogen fixed by legumes like soybeans. According to University of Iowa researchers, roughly 80% of the nitrogen in Iowa's rivers comes from agricultural land.
When it rains, that nitrogen, now in the form of nitrate, dissolves into the water moving through the soil. In a natural system, that water would move slowly through the earth, filtered by wetlands and deep soil layers over weeks, months, or even years before reaching a stream.
But Iowa doesn't have a natural system anymore.
Perforated pipes buried 3-4 feet underground collect excess water and route it directly to streams, bypassing the natural filtration process entirely.
THE DELIVERY SYSTEM
How Tile Drainage Changed Everything
Iowa has always had wet springs. Before the rise of industrial agriculture, the prairie absorbed water like a sponge, with deep root systems and wetlands holding rainfall for months before it slowly moved toward streams. Nitrogen had time to be absorbed, filtered, and processed by soil microbes.
Today, Iowa farmers have installed tile drainage systems on more than 50 million acres in the state, a network of perforated plastic pipes buried 3-4 feet underground across much of the state's farmland. These pipes intercept the water that would have taken weeks or months to reach a stream and deliver it in hours or days.
The result: nitrate has no time to be filtered. It moves directly from freshly fertilized fields to streams, rivers, and eventually to the drinking water supply. Tile drainage essentially turned Iowa's landscape into a nitrate delivery system.
Before Tile: Nitrate Travel Time
Years
After Tile: Nitrate Travel Time
Hours to Days
Acres of Tile Drainage in Iowa
50+ Million
When rain returns after drought, nitrate stored in soil flushes rapidly through tile drainage.
THE TREND
The Problem Isn't Going Away
2025 was a crisis year in Central Iowa, but it wasn't an anomaly. According to Iowa Water Quality Information System researchers, 2025 was actually closer to "normal hydrologic conditions." The years of lower nitrate levels that preceded it were the outliers, caused by an extended drought that kept tile drainage from flowing.
When the rains returned, the system did exactly what it was designed to do: move water off the fields fast. And it took years of accumulated nitrogen with it.
This pattern, drought accumulation followed by wet-year flushing, is expected to intensify as increasingly variable precipitation continues to affect the Midwest. Wetter years push more nitrate through tile drainage. The long-term trend, according to researchers tracking Iowa's rivers, points toward higher and more frequent spikes.
Even the conservation practices that do work face a math problem. One bioreactor, a wood-chip-filled trench that filters nitrate from tile water, treats about 40 acres and costs $15,000 to install. Iowa has 26 million crop acres. At the current pace, The Iowa Environmental Council estimated it would take up to 22,000 years to achieve the state's nutrient reduction goals at the current pace of conservation project installation.
Iowa State University research found that corn and soybean fields with zero fertilizer applied for six consecutive years still leached an average of 8 mg/L of nitrate through tile drainage, just 2 mg/L below the federal limit. The nitrogen is already in the soil. Even if every farmer stopped fertilizing tomorrow, the problem would persist for years.
THE TREATMENT GAP
Your Water Utility Is Fighting a Losing Battle
Central Iowa Water Works is a regional authority that provides drinking water to more than 600,000 people across the Des Moines metro, including Ankeny, West Des Moines, Johnston, Urbandale, Clive, Waukee, and surrounding communities.
Its flagship facility, the Fleur Drive Treatment Plant, has the capacity to pump 75 million gallons of water per day. On a normal summer day, demand can reach 70 to 80 million gallons.
The nitrate removal facility at Fleur Drive, built in the early 1990s and once the largest of its kind in the world, can treat just 10 million gallons per day. That's roughly one-seventh of peak demand.
The nitrate removal facility can treat 10 million gallons per day. Normal summer demand is 70–80 million gallons.
When river nitrate levels spike above 10 mg/L, CIWW uses a blending strategy: water processed through the nitrate removal facility is mixed with conventionally treated water to bring the overall concentration below the federal limit. But when both the Des Moines and Raccoon Rivers are running hot simultaneously, as they did in 2025 with concentrations reaching >17 mg/L, the math stops working.
That's when the lawn watering ban happened. Lawn irrigation accounts for roughly 40% of summer demand. Eliminating it was, in the utility's own words, "the fastest, most efficient way to reduce demand" and the last mechanism available to keep treated water within legal limits before daily life was disrupted due to clean water capacity.
CIWW has plans to expand treatment capacity by 25% over the next decade, adding 34 million gallons per day through new facilities and plant expansions. The estimated cost: $350 million. But even these expansions are designed primarily for population growth, not for escalating nitrate levels. The utility's executive director has been clear: their facilities are "nitrate resilient" but "not built based on nitrate removal."
Iowa has approximately 330,000 private wells. None are subject to federal Safe Drinking Water Act regulations.
THE BLIND SPOT
Private Wells
Roughly 330,000 Iowans get their water from private wells. Under the federal Safe Drinking Water Act, public water systems serving more than 25 people are required to test for nitrates and notify customers of violations. Private wells are exempt. There is no federal agency monitoring them, no required testing schedule, and no notification requirement if levels become unsafe.
The Iowa Department of Natural Resources offers voluntary testing, but participation is low. A 2022 Iowa State University study found that 18% of private wells sampled in high-agricultural-use counties exceeded the 10 mg/L federal limit. In some counties, the rate was higher than 30%.
Unlike public utilities, private well owners have no blending strategy, no emergency bypass, and no utility to call. When their well exceeds safe levels, the water coming out of their tap is the only water they have.
THE SCIENCE
The Data Shows Change Is Needed
The 10 mg/L maximum contaminant level for nitrate in drinking water was set by federal regulators in 1962, primarily to protect infants from methemoglobinemia, or "blue baby syndrome," a condition where nitrate interferes with blood oxygen transport.
That standard has not been updated in over 60 years.
Since then, a substantial body of research has raised concerns about nitrate exposure at levels well below 10 mg/L. A 2019 study published in the International Journal of Epidemiology estimated that drinking water nitrate levels above 5.6 mg/L were associated with elevated colorectal cancer risk. A 2021 National Cancer Institute study found associations between nitrate exposure and increased risk of thyroid cancer, kidney cancer, and non-Hodgkin lymphoma.
The National Toxicology Program completed a systematic review in 2023 concluding that there is "clear evidence" that nitrate in drinking water is associated with colorectal cancer in humans. The EPA has listed nitrate as a potential carcinogen and has acknowledged that the evidence base for revising the 10mg/L standard has grown substantially, but no revision has been proposed.
Some researchers argue the relevant health threshold may be closer to 5 mg/L, meaning treated water at 7–8 mg/L, technically "safe" by current standards, may still carry risk over a lifetime of exposure.
THE SOLUTION
In-Home Protection
There is one technology that reliably removes nitrates at the tap, regardless of what happens upstream, in the treatment plant, or in your well: reverse osmosis.
✓ PROVEN
Reverse osmosis removes 85–95% of nitrates from drinking water. It's the same technology used by hospitals, dialysis centers, and food manufacturers that cannot tolerate nitrate contamination.
✓ PRACTICAL
A point-of-use RO system installs under your kitchen sink and treats the water at the tap you drink from. No whole-house plumbing. No waiting for the city to upgrade its infrastructure.
✓ PERMANENT
Unlike boiling (which concentrates nitrates), pitcher filters (which don't remove nitrates), or hoping your utility's blending math holds, RO works every time — whether nitrate levels are at 5 mg/L or 17 mg/L.
Our system is NSF/ANSI certified for nitrate reduction. Every system is designed to be installed DIY in less than an hour.
5% of all sales go towards Iowa water quality initiatives
Sources
1. Iowa Water Quality Information System (IWQIS) — Iowa State University. Iowa Nitrate Monitoring Network. https://iwqis.iowawis.org
2. Central Iowa Water Works. 2025 Annual Water Quality Report and Nitrate Response Communications. https://www.ciww.gov/news-1/stage-iii-daily-updates
3. Stayner, L.T., et al. (2021). "Atrazine and nitrate in drinking water and the risk of thyroid cancer." International Journal of Cancer.
4. Temkin, A., et al. (2019). "Exposure-based assessment and economic valuation of adverse birth outcomes and cancer risk due to nitrate in United States drinking water." Environmental Research.
5. National Toxicology Program. (2023). NTP Monograph: Nitrate and Nitrite. U.S. Department of Health and Human Services.
6. Weyer, P.J., et al. "Municipal Drinking Water Nitrate Level and Cancer Risk in Older Women." Epidemiology, 2001.
7. Iowa Environmental Council. Iowa Nutrient Reduction Strategy Progress Reports. https://www.iaenvironmentalcouncil.org
8. Iowa State University Extension. "Private Well Water Quality in Iowa." PM 1809.
9. U.S. Environmental Protection Agency. "Nitrates and Nitrites." TEACH Chemical Summary. https://www.epa.gov/sites/default/files/2016-09/documents/nitrates-nitrites_0.pdf
10. Knobeloch, L., et al. "Blue babies and nitrate-contaminated well water." Environmental Health Perspectives, 2000.
5% of every sale supports Iowa water quality initiatives.
