Pollution, Not Drought, Prompts Lawn-Watering Ban in Des Moines

Right before a sweltering weekend in Iowa, the water authority for the Des Moines metro area banned its 600,000 customers from watering their lawns. 

Though that’s a water conservation practice familiar to residents of drought-stricken states, the Iowa ban isn’t about water scarcity. Instead, it’s due to near-record levels of pollution in the area’s waterways from nitrate leaching from fertilized farm fields.

“Our plants are having a difficult time treating the high nitrate concentrations in the river,” Tami Madsen, executive director of Central Iowa Water Works, announced at a press conference last week. “If we continue at this rate, we will violate the nitrate standard set by the EPA.”

For decades, municipal water works chemists have observed a steady increase of levels of nitrate in the Racoon and Des Moines rivers, the primary sources of drinking water for residents of the state’s largest city. 

A key part of the nitrogen cycle, nitrate is naturally occurring and essential for plant growth. But in Iowa, it gets liberally added as fertilizer in the form of synthetic products and manure.

“Seventy percent of our state’s land is in corn or soybean production. We’ve known for decades, probably close to 50 years now, that we lose a lot of nutrients from that production system,” said Chris Jones, a former lab supervisor at Des Moines Water Works and retired hydraulic research engineer for the University of Iowa.

This month, nitrate in the Racoon River hit levels not seen since 2013, with readings as high as 19 milligrams per liter, nearly double the U.S. Environmental Protection Agency’s maximum allowable concentration for drinking water. 

Nitrate contamination over 10 milligrams per liter poses serious health threats, the EPA says. It can hinder red cells’ ability to transport oxygen through the body, causing poor birth outcomes for pregnant women and putting infants’ lives at risk.

Children under 6 months can develop “blue baby syndrome” from excess nitrate, a rare but serious illness that can be fatal.

On top of those risks, nitrate can form compounds in the body that are known to cause cancer in animals and may do the same in humans. A 2019 report by the Environmental Working Group suggested that nitrate water pollution in the U.S. might be causing about 12,000 cancer cases a year.

Utilities can treat water to reduce nitrate levels. But while Central Iowa Water Works (CIWW) said it continues to produce drinking water that meets the EPA nitrate standard, the water authority may be on the cusp of a public health challenge. Officials hope that reducing water use by banning lawn watering will make all the difference.

“This is a call for help,” said Juliann Van Liew, director of the Polk County Health Department, at last week’s press conference. “We know there are concerns for nitrate’s ability to impact chronic conditions across the life course, but right now what we’re worried about is that acute toxicity.”

If at any point CIWW fails to keep nitrate levels below the EPA limit, it will be required to notify users that the water is unsafe for pregnant women and children. CIWW would then be in violation of the Safe Drinking Water Act and could face enforcement action by the EPA.

The battle with nitrate in the Des Moines area watershed is decades-long. 

In agricultural Iowa, nitrate leaches out of soil and into water in particularly high volumes. A 2007 study by the U.S. Geological Survey identified Iowa as one of nine states collectively responsible for over 75 percent of nitrate and phosphorus in the Gulf of Mexico. One ripple effect of that runoff is a low-oxygen “dead zone” in the gulf every summer.

“We know that farmers apply too much nitrogen fertilizer to their corn,” said Jones, the retired engineer. “What the corn can’t use is the surplus, and that doesn’t go off into the Milky Way. It ends up in our rivers and our lakes.” 

Iowa leads the nation in corn production, according to the U.S. Department of Agriculture, the majority of which is used to produce ethanol.

Tile drainage systems used by farmers to shed excess moisture from fields feed directly into the Racoon and Des Moines rivers and their tributaries, says John Swanson, water resources supervisor for Polk County, which includes Des Moines and many of its suburbs.

“Whether it’s naturally occurring or whether it’s from farming operations, we know that nitrates come out of those tile systems,” said Swanson. His team works directly with farmers throughout the watershed to implement practices that keep nutrients in the soil and out of the water, such as nitrate-capturing bioreactors and buffers that filter tile-drained water through nitrate-thirsty plants. 

Since the introduction of Iowa’s nutrient reduction strategy in 2013, farmers in the state have been encouraged to opt in to financial and technical assistance programs designed to help them minimize field nutrient loss. But the demand for those voluntary programs is greater than the supply, said Aaron Lehman, president of the Iowa Farmers Union. 

“We’re relying on an incentive-based, voluntary program,” Lehman said. “And I’d argue that we have not done enough to make that work.” 

Given the Trump administration’s proposed cuts to the USDA’s Natural Resources Conservation Service, Lehman fears that even fewer assistance programs will be available to farmers hoping to reduce their impact. 

The Fight to Keep Drinking Water Clean

The lawn-watering ban in Des Moines is “eye-opening,” said Polk County’s Swanson. “We’ve got a long way to go. Because the water is not getting better by itself.”

In fact, the water might be getting worse. A fact sheet produced by the Des Moines Water Works Nitrate Removal Facility, overseen by CIWW, says nitrate concentrations in the Racoon and Des Moines rivers have steadily increased over the past 25 years.

In 1989, nitrate levels in the Racoon River first surpassed the EPA’s drinking water threshold of 10 milligrams per liter. The city of Des Moines constructed its $4.1 million nitrate-removal facility after the state’s Department of Health and Human Services mandated action that same year. 

When nitrate levels are dangerous, river water is diverted to the facility, which can purify up to 10 million gallons of water each day. A second, smaller treatment facility was constructed north of the city in 2011 to serve an expanding suburban population.

In 2013, Des Moines relied heavily on the treatment facilities as nitrate levels in the Racoon River surged to a whopping 24 milligrams per liter, worsened by a flood that followed drought conditions. 

CIWW was able to continue producing EPA-compliant water without issuing a mandatory watering ban. But following the 2013 crisis, the city of Des Moines sued drainage districts in three upstream counties in federal court, seeking damages for the pollution and the costs of treatment. The lawsuit was dismissed on the grounds that the drainage districts lacked legal authority or responsibility to address the pollution issues.

Now, the facility is once more being stretched to its limits, said Madsen, the executive director of CIWW. The public demand for clean water is greater than the authority can produce as it attempts to limit the amount of river water that is used in the treatment process.

The region doesn’t lack water, it lacks clean water, Jones emphasized. “This is what’s referred to as a pollution-induced scarcity,” he said. “The amount of water in the rivers is plentiful even now, but we can’t use it the way we’d like to.”

CIWW has not predicted when it might lift the watering ban.

“It’s not a quick fix,” Swanson said of the watershed’s nitrate problem. “Polk County is a microcosm of all the issues Iowa faces.”