How is this year different than previous years?

Q. Nitrate concentrations look the same as years prior and we have never had a ban, what is different?

A. The provided graphics illustrate the three primary sources of raw water that our Fleur Drive Water Treatment Plant utilizes, with an additional line indicating the maximum contaminant level (MCL) of 10 mg/L. These three sources are the Racoon River, the Des Moines River, and the infiltration gallery. The infiltration gallery is a system of underground pipes located near the Raccoon River in Water Works Park used to collect water for the Fleur Drive Treatment Plant.

Nitrate concentrations in the source water were at near historic levels, with only 2013 being higher in recent history. When all three sources are above 10 mg/L treatment becomes incredibly challenging. We have several tools at our disposal to meet this challenge, including aquifer storage and recovery wells, low nitrate reservoirs, multiple water treatment facilities, the nitrate removal facility, and our water shortage plan. Our water treatment professionals utilized each of these tools to their fullest before turning to the public through the water shortage plan. 

In each of the phases we messaged even odd watering and other tools to reduce water consumption, but use continued to increase until we were at over 108% of our total treatment capacity with a projection of exceeding 114% of our available treatment capacity. This puts our system at risk of violating the nitrate standard of 10 mg/L, which would expose our most vulnerable populations to serious health risks.

Last year, and in years past, voluntary water conservation measures were issued but there were a few differences this year – two of the biggest being that the rise in nitrate concentrations and the rise in irrigation happened at the same time and all three water sources are consistently above 10mg/L. Last year, as you can see from the charts below, the nitrate concentrations in the three sources were much different during peak lawn watering, making the demand more manageable with voluntary lawn watering messaging and even/odd watering.

2013 - the Infiltration Gallery remained close to 10mg/l throughout the period. This allowed for a voluntary water restriction to be effective in managing demand and meeting the nitrate standard.

2024 - the Infiltration Gallery nitrate concentration rose after the Des Moines River concentrations significantly decreased below 10 mg/L. Voluntary water restrictions were issued and were effective in reducing demand to assist in meeting the nitrate standard of 10 mg/L.

2025 - all three sources of water have remained persistently above 10mg/L during our period of peak demand. We began messaging requests for a voluntary 25% reduction to lawn watering on May 30. For thirteen days we continued to see an increase in usage rather than decrease. On June 11 we increased the voluntary reduction to 50% (on this day, all three of our available sources were higher than the MCL), and on June 12th we moved to a full ban.

There are some years where the nitrate levels in one, two, or even three of the water sources we treat remain below 10mg/L, which means the nitrate removal equipment does not turn on at all. 2023 was one of those years.

The great news is that we’re seeing the rebound happen in smaller amounts after each rain event and we expect to continue to see that happen in the coming days. The CIWW Technical Committee, composed of all twelve member agencies, has been working collaboratively throughout this process to monitor the nitrate levels. We all look forward to ending the Stage III lawn watering restrictions and returning to normal operations.