Central Iowa’s drinking water caught between climate change and farming

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The Raccoon River, shown, is one of the two main rivers that feed the Des Moines Water Works. The other is the Des Moines River.

Until the drought, water engineers at the Des Moines Water Works had to make a difficult choice every morning between two rivers that supply the 600,000 people in Iowa’s capital city with clean drinking water.

Would it be the Raccoon River, flowing from the northwest and often laced with levels of nitrates in excess of federal safety standards, or the Des Moines River, flowing from the north and often carrying dangerous concentrations of cyano-bacteria in burgeoning populations of algae? It’s a no-win choice: Extended exposure to nitrates in drinking water has been linked to a range of cancers, the consumption of algae to kidney and liver damage and an array of acute symptoms.

But there’s been a twist to this unappealing choice, some version of which is playing out in cities across the Midwest that lie astride major rivers.

For much of the fall, the drought in Iowa made the decision easy for Ted Corrigan, a water engineer and CEO of the Des Moines Water Works. Less rain meant less nitrogen seeping from the fertilizer applied across the state’s millions of acres of farmland and running off the tiles that undergird many fields into the Raccoon.

Since early September, Des Moines has been drawing from the Raccoon because the concentration of nitrates in it is way down, meaning Corrigan doesn’t have to switch on the city’s multimillion-dollar filtration system, the only way to keep the toxins within a safe range. That’s largely because the Raccoon’s water levels, as of June, were barely 10% of the average for that time of year over the past quarter-century.

Ted Corrigan

In some areas, Corrigan says, the river “was so low you could jump across it.”

In Iowa, drought, devastating to farmers, is intertwined with the flow of nitrogen, devastating to ecosystems and human health. You can monitor the effects of drought by tracking the nitrogen. From 2014 to 2018 the average level in the Raccoon River exceeded the EPA’s limit of 10 milligrams per liter, or 10 parts per million, every year. Then, in July 2020, the drought took hold and the nitrogen levels dropped below 3 ppm every month until October of this year, according to water works records.

In other words, the drought is bad for farmers, but good for those who live downstream from them. For a while.

The drought lifted on Oct. 23, when just one week of intense rains — two inches above the monthly average — catapulted that month into the sixth-wettest in the 148 years that records have been kept in Iowa.

The water started flowing again, and so did the nitrogen. According to Water Works records, nitrogen concentration went from below 2 ppm from April to mid-October, then practically tripled to 5.5 in November after the record-breaking rains.

Corrigan and other water experts in the region now fear what’s on the other side of rainstorms to come: the return of a flood of nitrates to the water.

Drought is one symptom of climate change. Another is disturbance to the moisture balance in the atmosphere, as more rain falls in torrents rather than over a season. In Iowa, the intensity of precipitation increased by more than 15% from 1986 to 2015 when compared to 1901 to 1960, according to the most recent National Climate Assessment. The rain hits harder, which means it reaches deeper into the sub-surface to upend pockets of nitrogen-rich fertilizers that have built up over decades.

Between 2013 and 2015, that’s what happened when a drought was followed by torrential rains, and the nitrogen concentrations in Iowa rivers shot up by as much as 80%.

Corrigan wrote an op-ed in the Des Moines Register in October, warning that the state is in for a repeat of what happened in 2015, when the Water Works had to run its nitrate filtration system for a record 177 days in a row, at a cost to ratepayers of $1.7 million. He fears another year like that is coming as the overflow from Iowa’s chemical-saturated agriculture continues to wreak havoc on Des Moines’ water supply.

The city was compelled to spend $4.1 million back in 1991 to install what is now one of the nation’s largest nitrate filtration systems and spends up to $10,000 a day to run it when the nitrate levels are too high. All of this is paid for by local ratepayers, whose water rates have risen between 4% and 10% almost annually over the past dozen years.

The Environmental Working Group, an advocacy and research organization, found that Iowa is not alone. Despite years of effort by the states bordering the Mississippi River, the EWG found that toxins of many types have invaded America’s water supply, including the pesticide Atrazine; a family of perfluorinated “forever” compounds, including PFAS; Chromium-6; and nitrates. The group identified more than 400 water systems in the United States in which contaminants exceed what many scientists consider safe for drinking. The states showing the most widespread contamination include Iowa, Wisconsin, Nebraska, Illinois, California and Texas — mostly from excess nitrogen in the fields and waste from confined animal feeding operations, or CAFOs.

Des Moines Water Works has one of the nation’s largest ion-exchange nitrate removal systems – the heart of which is eight large tanks that cleanse 10 million gallons of water per day of nitrates. That water is blended back in with the facility’s treatment system, which is rated to treat 75 million gallons of water per day. (Des Moines Water Works)

Contamination has been getting worse since the EWG started measuring in 2005, said Tasha Stoiber, a senior scientist with the group and a co-author of the study. “Decades have been going by,” she said, “without much changing in the regulation of drinking water contaminants.”

The federal safety standards for nitrates date back to 1962. But they have not kept pace with the quantity of toxins in the water or with the science. Health effects are being seen at exposure levels far lower than the accepted federal limit of 10 ppm, according to the Center for Health Effects of Environmental Contamination at the University of Iowa.

David Cwiertny, the center’s director, points to studies that have found nitrates to be a contributing factor to bladder and colorectal cancer and thyroid disease in concentrations at half the federal limit or lower. In 2016, the Environmental Protection Agency declared that nitrate and phosphorous runoff “remains the single greatest challenge to our nation’s water quality and presents a growing threat to public health and local economies.” and kicked off a review of the 10 ppm limit. That review was halted by the Trump administration and has yet to be rekindled by the Biden administration.

Excess nitrates in Iowans’ water — many in private wells in rural communities without the resources to pay for filtration systems like the one in Des Moines — contributes to 10 extra cancers for every 100,000 people according to the EWG. In Iowa, with a population of 3.2 million, that means 320 cancers that would not otherwise develop.  

Nor does the pollution stay in Iowa: The water flowing through Des Moines continues flowing downstream into the Mississippi River. Over the past decade Iowa has maintained its position as the No. 1 or No. 2 contributor to the “dead zone,” the expanding region of the Gulf where all life is smothered by a lack of oxygen caused by the concentration of industrial and agricultural pollutants.

Pads of floating algae in the Des Moines River

In the Des Moines River, which flows through the city’s downtown under a sequence of stately bridges, it’s the bright green pads of floating algae, not nitrates, that present a problem.  The Des Moines exceeded the federal advisory limits for algae in seven of the 12 quarters between 2019 and April 2021, according to the city’s Water Works. To identify the presence of toxic levels of algae in the water is itself a laborious procedure in which water samples must be frozen and thawed three times successively “to break open the cyano-bacteria and get them to spill their guts, so we can see what’s inside them,” Corrigan says.

The EPA sets “health advisory” guidelines of 0.3 parts per billion (ppb) of cyano-bacteria in drinking water that could be consumed by children under 5; for adults the advice is for no more than 1.6 ppb. But the guidelines have no legal teeth. Earlier this year, the EPA included cyano-bacteria on a list of “contaminant candidates” — bureaucratese for currently unregulated substances that are known to end up in water sources and should be considered for further review as possible threats  to public health. 

It is complex: There are 115 substances on the candidate list in addition to cyano-bacteria, providing a disconcerting glimpse into the potential toxins in our water.

In the absence of federal regulation, it’s up to each water district to determine if it wants to follow the EPA’s voluntary guidelines. The Des Moines Water Works has opted to aim for the 0.3 ppb level considered safe for children but is under no legal obligation to do so. In 2020, there was a huge algae spike in the Des Moines River, sending cyano-bacteria levels as high as 7 ppb, or 23 times the amount deemed safe for children. The city relied on the Raccoon River for much of that year, which luckily enough – for the Water Works – had been depleted of nitrogen by the drought that depleted the river.

“But it also raised our blood pressure a little bit,” said Jeff Mitchell, lab supervisor at the Water Works. “We were worried if there was not enough water in the Raccoon and we had to use the Des Moines. There were some tense moments.” It was a tightrope act they don’t want to repeat. The nightmare is that all occur at the same time: excess algae and excess nitrogen overwhelms the filtering system, and drought constricts their options.

The specter of Toledo, Ohio, hangs over every water manager in the Midwest.  In 2014, that city had to shut down its entire water system after toxic algae blooms in Lake Erie flowed into the city’s intake pipes and clogged the filtering system. Nearly 500,000 people were without water for three days.

That scenario prompted Corrigan to set up an emergency-response plan with the Iowa Department of Homeland Security, which included setting aside a cache of enough bottled water for 600,000 people, and an automated alert system that could send texts and emails to everyone in Des Moines. The Iowa officials also have been in touch with the federal Department of Homeland Security, which warns of consequences that seem eerily similar to those being experienced in Des Moines.

“The degradation and depletion of soil, water and biodiversity almost certainly will threaten infrastructure, health, food and security,” reads the department’s most recent Annual Threat Assessment.

Harmful algal bloom at Saylorville Lake Marina in 2020 turns the Saylorville Reservoir green. The reservoir spills into the Des Moines River, one of two river sources for drinking water for 600,000 customers in central Iowa. (Des Moines Water Works)

Meanwhile, the Water Works is assessing the prospects for new funding from the infrastructure bill signed by President Joe Biden last month, which allocates $55 billion for improving the nation’s drinking water quality. At the top of their wish-list are new wells, which would give access to nitrate-free underground water sources, and a new filtration system capable of filtering out the cyano-bacteria from the rapidly expanding algae blooms.

It’s the city’s fate to be located at the point where the Raccoon and the Des Moines rivers converge. That prime location attracted the region’s early white settlers to the plains of central Iowa more than 200 years ago, and before that drew the Ioway, the Otoe and other tribes, which lived in thriving communities along the banks of those rivers for centuries before they were violently uprooted. 

The rivers’ convergence in present-day Des Moines has an entirely different meaning: It’s a bullseye illustrating the connection between climate change and toxins in the water.

“Des Moines,” says Corrigan, “is at this horrible intersection between water quality degradation and drought and ever-increasing demand as the Des Moines area grows. That intersection is a scary place.”

In 2015 the Water Works sued three counties upriver on the Des Moines to try to compel them to pay at least part of the cost for cleansing the city’s water supply. The counties didn’t deny that local farmers contributed to the pollution but won the case on a legal technicality. The judge dismissed the lawsuit on the grounds that responsibility for water quality rests with the legislature, not the courts. The Republican-dominated Iowa Legislature has done little since. In the wake of the lawsuit, it attempted to defund the Water Works, which it considers a threat to industrial agriculture interests in the state, and create a new water authority that reported to the Legislature. That effort failed, and Corrigan has been inviting legislators, both urban and rural, for visits to the facility in an effort to “rebuild the relationship.”

Nor are the Raccoon and the Des Moines the only sources of Iowa’s toxic brew. According to the state Department  of Natural Resources, in 2020 close to two-thirds  of the state’s waterways 61% of rivers and streams, and 67% of lakes and reservoirs — were  “impaired,” meaning too polluted to swim or fish in, which also makes them inaccessible as drinking water sources without significant, and expensive, filtration. That’s up from 58% and 57%, respectively, five years ago.

Where do the toxins come from? It’s not a secret. The Iowa Agriculture Water Alliance, representing Iowa’s three major agricultural interests — soy, corn and pork producers estimates that 92 percent of the nitrogen and 80 percent of the phosphorous in Iowa’s waterways come from farms and CAFOs. Upstream farmers are exempted from monitoring or limits because the Clean Water Act of 1972 is designed to regulate what are known as point sources of pollution— places with fixed addresses, like factories. But farm contaminants flow into rivers from multiple locales; they’re “nonpoint” pollution sources and thus exempt from the law governing toxic releases into the water supply.

Des Moines Water Works Laboratory employees Lisa Morarend, chemist, and Terry Webster, senior chemist, analyze river water to assess levels of nitrate. (Des Moines Water Works)
Getting into the farming business

When it comes to algae, climate change adds the final ingredient to the contaminant cocktail, triggering a cascade of consequences for rivers in Iowa and throughout many intensively farmed areas of the United States.

First, rising water temperatures combined with  phosphorous-rich fertilizer runoff into depleted, slow-moving rivers create highly hospitable conditions for the proliferation of algae. Cwiertny, of the Center for Health Effects of Environmental Contamination, has described these conditions as “a breakfast buffet for micro-bacteria and algae.”

Second, the drought, which has hit Iowa as it has hit much of the Midwest, means there is less water in the rivers, which translates into less filtration to dilute the toxins.

And third, as patterns of rainfall shift from extended rainy seasons to intense downpours, that rain hits fields with built-up stores of excess nitrogen, which spill into the rivers.

“Climate change,” says Anne Weir Schechinger, the EWG’s Midwest director and a co-author of the new drinking-water report, “is not going to make drinking water cleaner for anyone.”

For the Water Works, Corrigan says, there are three options. The first two — legislation and litigation — were tried and thus far been blocked. There is one path left: collaboration. The water works is getting into the farming business.

Earlier this year it took the unprecedented step of engaging with a local farmer cooperative and other municipalities to purchase a $600,000 seed-planting combine. The next step: Lease it to farmers at a discounted rate to encourage the planting of nitrogen-absorbing cover crops in the Raccoon watershed.

Those include rye, oats and mustard, planted between corn and soybean seasons. Corrigan hopes this plan will provide a model for a statewide program to reduce the pollution sources before they hit his Water Works or other water districts facing similar challenges.

“People can’t continue to apply whatever they want upstream assuming that people downstream will remove it,” he says. “We’ve tried all the other paths. And now we’re going to run down this path — and run it hard.” 

Public Health Watch and the Investigative Reporting Workshop are collaborating on stories about threats to clean water and air in communities throughout the country. Mark Schapiro is an award-winning journalist and author of, most recently, “Seeds of Resistance: The Fight to Save our Food Supply” He teaches environment and climate reporting at the University of California, Berkeley.