Des Moines metro taps backup water early amid nitrate concerns
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As summer nears, officials from Des Moines Water Works (DMWW) and Central Iowa Water Works (CIWW) are warning residents and businesses that the ability to filter drinking water fast enough remains a concern.
Why it matters: This winter marked only the second time CIWW has activated its nitrate removal facility during these typically slower months, and the pace isn't going down.
State of play: Though nitrate levels are typically at their lowest in the winter, all three of the region's water sources have been exceeding the federal drinking water standard since Jan. 6, according to DMWW CEO Amy Kahler.
- The metro's drinking water relies on the Des Moines River, the Raccoon River, and an alluvial groundwater source.
- DMWW is the contracted operator for CIWW, which supplies water to the Des Moines metro and surrounding rural communities.
How it happened: The Des Moines metro experienced drought from 2020 through 2024, followed by a wetter-than-normal 2025. During prolonged drought, water stops moving through the soil, allowing nitrates to accumulate rather than flush out.
- Once rainfall returns, the stored nitrates get flushed into rivers rapidly and in large volumes. While nitrates occur naturally, commercial agriculture is also a major contributor to the rivers' elevated levels, per a report commissioned by Polk County.
- The last time the nitrate removal facility ran during winter was 2015, under similar conditions.
Zoom in: Officials are still dealing with nitrates in the soil. All winter, CIWW has been drawing from Maffitt Lake, which is typically reserved for summer months when lawn irrigation spikes demand. As a result, the lake now sits 6 feet below its normal level, Kahler says.
- A mild winter and lack of snow melt diluting the nitrates haven't helped, along with an unusual 90-degree day in March that prompted some to start lawn watering.
- "That's just really atypical, and it's concerning, because we are already relying on our backup water supply," Kahler said.
By the numbers: The nitrate removal facility operates at a cost of around $11,000 a day.
- This year so far, CIWW has spent $660,000 on operating and maintaining the removal system. Last year, the cost was $1.6 million, per Tami Madsen, executive director of CIWW.
What they're saying: Officials are asking people to be mindful of lawn watering and irrigation this year. About 40% of all water use during the summer is for lawn watering, Madsen says.
- She recommends people delay watering until May or June.
The bottom line: "We have a deep bench in terms of our backup water sources, our primary water sources. Not a lot of utilities have so many water sources," Kahler says. "But we're using our second string already, and that's concerning going into peak season."