This year, Central Iowa is experiencing unusually high nitrate concentrations in all three primary sources of water used to produce drinking water at the Fleur Drive water treatment plant: the Raccoon River, Des Moines River, and Infiltration Gallery (a perforated pipeline under Water Works Park used to collect and naturally filter water from the Raccoon River). While CIWW and its members have successfully managed elevated nitrate conditions in the past, the current situation is unique because nitrate levels are high across all available sources at the same time.
When nitrate concentrations increase, drinking water treatment plants must reduce production or utilize additional treatment processes to continue meeting all state and federal drinking water standards. As a result, the regional system’s ability to produce drinking water is significantly reduced precisely when summer demand for water is increasing.
Lawn watering is the single largest discretionary use of water during the summer and can account for up to 40% of regional water demand. By temporarily suspending lawn watering, CIWW can dramatically reduce demand and help ensure sufficient drinking water is available for essential uses such as drinking, cooking, bathing, firefighting, and healthcare.
The lawn watering ban is not due to a lack of water in our rivers or reservoirs. Instead, it is necessary because ongoing source water quality challenges are limiting how much water can be treated and delivered while continuing to meet all Safe Drinking Water Act requirements, which is 10mg/L (milligrams per liter).
This year presents a unique challenge for central Iowa’s drinking water system because elevated nitrate concentrations are occurring simultaneously in all three major source waters used for treatment, the Raccoon River, Des Moines River, and Infiltration Gallery, limiting the ability to shift production to lower-nitrate sources. As of June 8, 2026, the Raccoon River has measured nitrate concentrations above 10 mg/L for 136 days, the Des Moines River has registered 117 days over 10mg/L, and the infiltration gallery has registered more than 10 mg/L for 86 days. As a result, the Nitrate Removal Facility has been operating for approximately 95% of the year.
In addition, CIWW has already utilized approximately 50% of the available water stored in Maffitt Reservoir, a critical reserve used to supplement supplies during periods of poor source water quality or drought. Using these reserves this early in the season leaves less flexibility should elevated nitrate concentrations or high water demand continue through the summer.
CIWW and its member agencies continue to safely provide drinking water that meets all state and federal standards and are utilizing all available resources, including the Nitrate Removal Facility, Maffitt Reservoir, Aquifer Storage and Recovery wells, and all available treatment capacity, to maintain reliable service throughout the region.
The challenge is not the amount of water available, it is the reduced treatment capacity caused by exceptionally high nitrate concentrations in our source waters. Reducing lawn watering helps preserve drinking water supplies until source water conditions improve.
Learn more about Central Iowa Water Works at www.ciww.gov or on Facebook or LinkedIn.