For the first time, the new regional water utility Central Iowa Water Works implemented a ban on lawn watering on June 12 because nitrate levels of local rivers were in danger of violating federal limits and local treatment plants couldn’t keep up.

The federal limit for nitrates in drinking water is 10 parts per million. Central Iowa’s drinking water supply is currently around 9 parts per million.

At a news conference held Tuesday, Central Iowa Water Works said in the first five days, the ban reduced demand for water by 30%.

Officials from the Great Outdoors Foundation and Polk County said there has been confusion about the reasons behind the ban and why it is needed. During a bus tour of Polk County wetlands hosted by the foundation on Wednesday, a local water expert explained the ban to attendees.

Why nitrate levels are high
The foundation, county and other agencies work together closely to improve water quality in Iowa.

John Swanson, water resources supervisor for Polk County, said several environmental factors, including that Iowa is coming out of a multi-year drought, are contributing to the issue.

“We had very [severe] drought conditions last year, and it’s very common, we see this in our research, water monitoring shows that after a drought, when we get those first rains, usually the first thing we see is a quick, fast flush of all those nitrates that are getting built up in the soil.

“When that rain finally comes, it flushes [nitrates] out and it comes through the system, usually in a short burst. This year, what’s happened is those rains are coming a little bit later in the year, and we haven’t had a lot of rain in the Des Moines area this year, but there has been a lot of rain upstream. There’s been this combination of [factors] that has sustained for several weeks now, this higher nitrate level.

“On one end, [Central Iowa Water Works is] sitting at the bottom of the funnel. All the waters come to them, and they have to get it down to these thresholds.”

Teams working in water conservation, like Swanson’s, are trying to improve water quality to lower the nitrate levels.

“We’re going upstream because we have to fix it at its source. But can we do it fast enough? Are we doing enough? Are we doing it fast enough? That’s the question. How can we do it faster?” he said. “We’ve had some great examples of ramping things up, but the fact that we’re dealing with this right now shows that we have a ton of work to do, and it’s not an easy fix.”

Hannah Inman, CEO of the Great Outdoors Foundation, added that it takes time to treat the water before it is suitable for drinking.

“The Des Moines system can only produce [a certain] amount of cleaned water and then have it blend. They can pump out 10 million gallons a day of clean water, they can maybe blend that up to a certain level. The average usage for Central Iowa Water Works is around 55 million gallons. However, during the summertime, it spikes to around 85 million gallons.”

Inman said the voluntary restrictions, initiated on June 11, aimed to encourage customers to stop irrigating.

“The voluntary ban didn’t really work, because I think most people thought we were talking about water scarcity, not water quality,”she said.

She said the increased demand entering the summer months and warmer weather was another factor in implementing the mandatory ban.

“You have that huge increase in demand when you start to have the warm weather, and that’s what happened this year,”she said. “We had the rush of nitrates that were delayed that would normally be in March or May, and we have the increase of demand at the same time as those late rains, and those two things combined is what led to the mandatory ban.”

She said some also didn’t understand that many metro areas are now part of the regional Central Iowa Water Works utility.

“It’s now combined with Des Moines Water Works, Grimes, West Des Moines and all the partners; it’s now a joint-owned system,”she said. “We have new staff, new protocols, all of that. The first day that they did the mandatory ban, they saw a reduction of around 25 million gallons, of immediate decrease.”

Inman said the situation could prompt future discussions over water usage across the region.

“There’s going to probably be a discussion over the next six months to a year within our community of how important it is to have lawn irrigation? Do we want to pay for water? Do we want to clean that water to use for irrigation? Is there a societal change or cultural shift? Those are conversations that are outside of the Great Outdoors Foundation, but certainly add to why we’re in the situation that we’re in right now.”

The foundation also has an explainer on its website regarding the lawn watering ban.

What’s next

Central Iowa Water Works will send daily updates on nitrate concentrations and water use restrictions. On Wednesday, the utility said in an update that the lawn watering ban remains in place, but member communities are allowed to reopen public splash pads and spray grounds today.

It also shared its longer term plans to increase the water system’s capacity by 25% in the next seven years by expanding the Saylorville Water Treatment Plant’s capacity by 10 million gallons per day, expanding the Grimes Water Treatment Plant and building a new west water treatment plant.

“These facilities will all use the newest available technology to remove nitrate – but they are also being designed to treat for emerging water quality issues,” the update read.

Nitrate concentrations in the rivers are “slowly trending downward,” the update said but it continues to monitor conditions upstream. Drinking water meets all state and federal standards.

The nitrate concentrations as of June 18 are:
Raccoon River: 13.82 mg/L
Des Moines River: 14.89 mg/L
The finished water leaving the Fleur Drive Treatment Plant: 8.05 mg/L.

The ban affects all CIWW member agencies: Ankeny, Clive, Des Moines Water Works, Grimes, Johnston, Norwalk, Polk City, Urbandale Water Utility, Warren Water District, Waukee, West Des Moines Water Works and Xenia Rural Water, as well as communities served by Des Moines Water Works: Alleman, Berwick, Bondurant, Cumming, Pleasant Hill, Runnells, unincorporated Polk County and Windsor Heights.