(Don’t) Blame it on the Rain

by Dan Haug | Jul 10, 2025

Gov. Reynolds' interview reminds me of a Milli Vanilli single

Updated on July 31

In an interview with KCCI, Iowa Governor Kim Reynolds blamed the weather for high nitrate levels in the Raccoon and Des Moines rivers that led to an unprecedented outdoor watering ban for the Des Moines metro and dismissed any suggestion that Iowa needs to change its policies. Milli Vanilli’s 1989 hit “Blame it on the Rain” captures the vibe perfectly, so I covered the song and made a silly video with footage from the interview. However, the situation is no laughing matter.

Let me explain the situation as simply and clearly as I can. The high nitrate levels we are seeing this spring are not a fluke, drinking water is not completely safe in many communities across Iowa, and if we stay the course with Iowa’s Nutrient Reduction Strategy we will be waiting a long time for things to get better.

You can’t have it both ways

It’s true, nitrate pollution in rivers is influenced by both rainfall and recent drought. This has been a recurring theme in my analysis of water quality data (most recently here, and most rigorously here). But the Governor and her administration want to have it both ways. When nitrate in the Cedar River dropped due to favorable weather, they took that as a sign that a voluntary approach was working and took the unusual step of trying to withdraw a pollution budget that might have placed limits on new pollution from industry. Just last fall they were arguing that the following rivers should be removed from the Impaired Waters List, based on a 10% rule that makes no sense in the context of drinking water. The table below shows the data that they’re using to make those determinations.

Nitrate data for impaired waters disputed by EPA and DNR

Regardless of whether they meet the technical threshold for impairment, as a practical matter, the Raccoon River and Des Moines River regularly have nitrate levels high enough to cause problems for drinking water supply. The Central Iowa Water Works had to run their nitrate removal facility in 2024, 2022, 2019, 2018, 2017, 2016, 2015, 2014, and 2013. (This was reported recently by KCCI). It’s the largest such facility in the world, and this year it wasn’t enough!

Nitrate levels this spring are higher than average but not a fluke

The graphs below shows how daily nitrate concentrations and discharge (streamflow) in the Raccoon River this year compares to the median for that time of year. It is unusual for wet weather and high nitrate levels to persist through late July, but nitrate does exceed 10 mg/L about half the time in May and June. If you want to understand long-term nitrate trends in the Des Moines River and Raccoon River, read Chapter 5 of the new source water report commissioned by Polk County.

The Raccoon and Des Moines Rivers are not alone in having high nitrate levels this year. Here is 22 years of weekly data from a site on the South Skunk River, just downstream of Ames. This spring, peak nitrate levels (22 mg/L) were the highest we’ve seen since 2014. Average spring nitrate levels (15.5 mg/L) were the highest we’ve seen since 2015. However, it’s only a little above the long-term average (13 mg/L, indicated with a dotted black line) and ranks 7th out of 23 years for which we have data.

Spring nitrate in the South Skunk River, 2003-2025

None of the data I’ve seen rules out a slight improvement in water quality in this or other Iowa rivers, masked by the ups and downs of an 8-10 year cycle. However the data does rule out this year being a fluke and us not having to worry about high nitrate levels in the future!

In Iowa, it’s normal for it to rain a lot in the spring. In watersheds with a lot of tile-drained farmland, it’s normal to see high nitrate levels for several days following a rainstorm. Ames is lucky to have a buried sand-and-gravel aquifer with the right geology and chemistry to remove most of the nitrogen before it reaches wells. If we withdrew water directly from the Skunk River, it would exceed the drinking water standard every year. Many other communities in Iowa are not as fortunate in their geology.

Nitrate in Drinking Water Poses a Widespread Health Risk

The Safe Drinking Water Act was written so that we must draw a hard line between “safe” and “unsafe.” Drinking water utilities must meet a Maximum Contaminant Limit of 10 mg/L nitrate as nitrogen. Most large water systems have been able to say on the “safe” side of the line, although it can be costly to do so. However, the standard hasn’t been updated to reflect research on the link between chronic exposure to nitrate in drinking water and various cancers. And really, it’s better to think of health risks as a continuum from “more safe” to “less safe.” The Environmental Working Group created a map a few years ago showing which communities fall in the “not as safe as they could be” range for nitrate in drinking water. Last year, Iowa Environmental Council recently released a report about the health risks of nitrate in drinking water and is now hosting a series of listening sessions on cancer and the environment.

Conservation efforts have been partially offset by increased fertilizer use

Shouldn’t we expect some improvement in nitrogen levels due to the state’s nutrient reduction strategy and the conservation efforts of farmers? I’ve written another article to dig into this question but the short answer is that we can expect at most a 2% reduction in nitrogen losses over the past decade. That’s for the state as a whole, some watersheds are doing better or worse and we don’t have a good tracking system to evaluate it. Most of the progress that we can expect from cover crops and nitrification inhibitors have been offset by increases in fertilizer application rates, which apparently made economic sense to do.

I can’t really blame farmers for acting in their economic self-interest. I do think it’s fair to blame your elected officials if they can’t take drinking water safety seriously and offer better solutions. Just don’t blame it on the rain.

How to Miss the Point Entirely

by Dan Haug | Jan 9, 2025

This letter is a satire of DNR’s latest response to the EPA’s partial disapproval of Iowa’s 2024 Impaired Waters List. My first impression was that this was a technical dispute with low stakes for water quality and industry. In theory, adding waters to the 303(d) list can result in stricter permit limits on point sources and open up grants for non-point source projects, but in practice there are many loopholes and backlogs that make that unlikely. However, it still matters whether Iowans are getting honest information about the condition of our waters from the agency charged with protecting them. Iowa DNR’s position is ridiculous and indefensible.

To the attention of the US Environmental Protection Agency, Region 7:

Dear Sir,

In your November letter, you stated that Iowa’s 2024 Impaired Waters List should have included six more river segments that are too polluted by nitrate to fully support drinking water uses. The Iowa Department of Natural Resources strongly disagrees and objects to the implication that Iowa’s water is unsafe, or that DNR is not meeting the letter or the spirit of the Clean Water Act.

Just to be clear, we’re not talking about whether the water is safe for fish or swimming. Toxic algae blooms are a separate issue, for which nitrate is at most a contributing factor. Okay, good we’re on the same page. It’s impossible for most waters to end up on the 303(d) list because of nitrogen or phosphorus pollution, because we still haven’t set numeric criteria to protect aquatic life. The 10 mg/L standard for nitrate applies only to the 61 reservoirs and 18 stretches of river that were designated Class C waters, because they are currently or were historically used as a major source of drinking water.

Ultimately, the goal of EPA and DNR is the same: to ensure that Iowa’s drinking water is safe. It is safe! Well… maybe not for adults. We have the second highest cancer rate in the nation and there is growing evidence that one of the risk factors is long-term exposure to moderate levels of nitrate in drinking water. But nobody is seriously proposing we do anything about that! The issue here is whether tap water is safe for babies, whether nitrate-nitrogen is below the Maximum Contaminant Level of 10 mg/L, as required by the Safe Drinking Water Act.

I’m happy to say that water utilities on these six rivers have been able meet that standard by either:

Operating a nitrate-removal facility to clean up polluted river water at a cost of $10,000 a day
Mixing high-nitrate river water with low-nitrate water from wells and reservoirs
Asking customers to cut back on water use during times when the reservoir has a toxic algae bloom
Drilling enough wells so they no longer have to use any river water

What, you don’t think giving up on polluted rivers is consistent with the spirit of the Clean Water Act? Hey, if it works… Oskaloosa switched its water source from surface water to an alluvial aquifer years ago, and those wells usually have low nitrate levels. That means that even though we’re still legally required to assess nitrate in the South Skunk River, we no longer have any practical reason to worry about it! Granted, alluvial aquifers are still susceptible to contamination from the adjacent river. Cedar Rapids recently saw nitrate in their wells rise to 9 mg/L, but we’re crossing our fingers that it doesn’t get worse.

Let’s get back to the main issue under dispute. We’re not talking about water quality in 2024, we’re talking about the assessment that we released in 2024, which uses water quality data from 2020-2022. The silver lining of a multi-year drought is lower nitrate levels in the rivers! We are not talking about whether a single sample of river water exceeds 10 mg/L, we’re talking about whether 10% of the samples exceed 10 mg/L.

Sure, a single sample of finished tap water exceeding the 10 mg/L MCL for nitrate would constitute a Tier I violation of the Safe Drinking Water Act, requiring public notice and corrective action. However, so long as that corrective action is needed less than 36 days each year, we think it’s fair for the burden of removing nitrate from the water to fall entirely on drinking water utilities and their customers rather than polluters.

What, you don’t think this 10% threshold for evaluating the source water makes any sense? Well too bad! We’ve gotten away with doing it this way for decades and calling us on it now would violate the no-take-backsies clause of the Administrative Procedures Act. You’ve made the mistake of focusing on the letter of the law rather than the spirit of the law and we can argue about which pollutants go on which list, which list can be assessed using the 10% binomial statistical exceedance approach, and what hoops you need to jump through to change anything until babies are blue in the face!

Should this arbitrary and capricious abuse of federal authority stand, we might someday have to write a Total Maximum Daily Load (TMDL) explaining why it’s impossible to clean up nitrate in the South Skunk River, Des Moines River, and Iowa River. If you carefully read the TMDLs and permits that we’ve already prepared for the Cedar River and Raccoon River watersheds, you’ll see that would be a waste of our limited staff time and paper.

Nitrate in drinking water is under control. Please stop talking about it. If we must talk about nitrate, we prefer the discussion be framed around Gulf Hypoxia and the Iowa Nutrient Reduction Strategy, because that makes the problem seem far away and less urgent.

Sincerely,

Kayla Lyon, Director

Iowa Department of Natural Resources