On St. Patrick’s Day, I gave a talk for the Izaak Walton League explaining why lakes and rivers turn green and how the assessment process works and why so many waters get stuck on the impaired list. Here is a recording.
Update on nitrate and drinking water
The last time the Iowa DNR submitted a list of impaired waters to the EPA, there was a dispute about six stretches of river that supply drinking water to Des Moines, Cedar Rapids, Iowa City, and Ottumwa, and used to supply water to Oskaloosa. The DNR claimed that the drinking water standard for nitrate should be evaluated using a 10% threshold, but even with this interpretation, two of the rivers failed to meet the standard this time. This chart shows what all the fuss is about.
An Act requiring the Department of Natural Resources to identify specific animal sources of pollutants to a water of the state when determining the water’s inclusion on a list of impaired waters.
Thankfully, the bill did not make it through the second funnel. While it’s useful to know where bacteria is coming from, DNA testing is expensive and should be done after a problem has been identified.
Finding clean waters
I am sometimes asked where to go in Iowa to find clean water for paddling, swimming, floating in an inner tube, or just letting the kids splash and catch crayfish in the creek. A map or list of impaired waters is not very helpful for this, because the waters that aren’t included might be clean, or they might not have been assessed. So I made an interactive map, color-coded to show which lakes and rivers met or exceeded the primary and secondary contact recreation standards, in the last four recreational seasons.
The Fine Print
If you explore the Impaired Waters List and the rest of the assessment database, you will likely run across some things that don’t make sense. I share your frustration! This pair of short videos from our “Clean Water Act: 50 Years, 50 Facts” series contrasts how Section 305(b) and 303(d) of the Clean Water Act should work in theory, and how it can go wrong in practice. However, I continue to see improvements in the assessment database (ADBNet) and water quality database (AQuIA) and want to express my appreciation to IDNR for the data they collect and their efforts to be make it available to the public.
March is Iowa history month and that’s a good opportunity to dust off some material from the archives to share the history of lakes in Iowa, some lost and some found.
Iowa has just 34 natural lakes remaining, most of them located in northern and central Iowa, which was covered by the last advance of ice sheets 12,000 to 14,000 years ago. The examples I will use are from Hamilton County, where naturalist Thomas MacBride had this to say:
“None of the lakes hereabout are very deep. They are all marsh-like, only distinguished from a thousand marshes by the courtesy of the pioneer who called them lakes to suit his fancy, recognizing their greater width and possibly, in some cases their bluffy shores.”
-Thomas H. MacBride, Geology of Hamilton and Wright Counties (1910)
Residents of Hamilton County should recognize one of the lakes on this 1875 map. Little Wall Lake is a popular spot for swimming, fishing, and motor-boating. At 249 acres, it’s plenty big enough to call a lake but only deeper than a marsh because of regular dredging. The lovely cabins for rent from Hamilton County Conservation were built from Iowa-sourced white oak logs as part of a Prairie Rivers of Iowa forestry and economic development project in 2013!
However, the 1,300 acre Lake Cairo and 870 acre Iowa Lake disappeared shortly after A.T. Andreas’s atlas was made. You can still see the shoreline of Lake Cairo on LiDAR, as well as the ditches (Rahto Branch and Ditch 71) built to drain it. Lost Lake Farm, a dairy located on the north “shore”, is named as a nod to that history. They employ rotationally managed grazing practices that build soils and protect water. I got to see this in action as part of Watershed Management Authority field trip in 2018; here’s a photo of the cows making a beeline for the tall grass after the fences are moved!
The scale of the drainage work is impressive, especially given the technology available at the time, and was just one of many such alterations that built up Iowa’s agricultural economy. In this case it made farmable over 1000 acres of Blue Earth muck loams with a corn suitability rating of 63 to 66. However, even at the time, there were disputes about how to balance public and private interests. To learn more about the history of drainage, I recommend a presentation by Joe Otto, recorded on Iowa Learning Farms.
The balance shifted as cropland became abundant and natural areas became scarce. In 1920 (partly at the urging of Thomas MacBride, quoted above) Backbone was dedicated as Iowa’s first state park. The Civilian Conservation Corps built a low dam on the Maquoketa River to form Backbone Lake in the 1930s and since then over 100 other lakes have been created in Iowa for public use by damming streams or by digging quarries and borrow pits.
In 1919, Iowa’s first county park was established in Hamilton County, not far from Lake Cairo, and Briggs’ Woods Lake was created sometime in the late ’60s by damming Terwilliger Creek. There are some more log cabins at this park, also built with the help of my former colleague Mike Brandrup. The porch is a good place to watch the lake and reflect on the complicated history of Iowa’s land and water!
For the past few months, Rick and Dan have been dipping nitrate test strips when we collect water samples for the lab. We have confirmed that the reaction is temperature-sensitive, causing nitrate test strips to under-estimate nitrate concentrations in winter.
Accuracy can be improved by testing a water sample in a warm car, or by allowing an extra 30-60 seconds for the color change, but for best results, follow Heather Wilson’s advice, reprinted below:
“Hach (the manufacturer of the test strips included in your Nitrate Watch kit) says that sampling will be most accurate when the sample temperature is between 20 and 25° C (68 to 77° F). These ideal temperatures are easy to obtain indoors, but much more uncommon outside.
If you are concerned about cold weather impacting your nitrate readings, we recommend collecting your sample in a clean container and allowing the water to come to room temperature before taking your nitrate reading. Make sure to rinse the container three times with water from the water source you are sampling to ensure that no residual water from past samples remains.”
-Heather Wilson, Midwest Save Our Streams Coordinator, Izaak Walton League
The Driftless Water Defenders launched a social media campaign last summer calling for the end of Iowa’s #NoSwimEra. It’s a catchy slogan, and timely. 2025 was an especially bad year for recreational water quality. The Iowa DNR tests for E. coli (an indicator of poop in the water) and microcystin (a toxin produced by algae) at 41 beaches at state parks, every week between Memorial Day and Labor Day. If you had picked a beach and weekend at random for a family outing, there is a 1 in 4 chance you would have encountered a “Swimming Not Recommended” sign when you got there. Over the past 25 years, the number of microcystin advisories has fallen but the number of E. coli advisories and the number of beaches affected has increased.
Iowa’s water quality problems aren’t unique, but they are a lot worse than some of our neighbors. I analyzed 2025 E. coli data from Wisconsin beaches and found that 11% of the water samples had high enough E. coli levels to trigger an advisory (235 CFU/100mL), versus 24% in Iowa. 3% of Wisconsin beaches had average E. coli levels high enough to violate water quality standards (a seasonal geometric mean of at least 126 CFU/100mL), versus 25% of Iowa beaches.
Some of the advisories are posted at lakes where there has already been a lot of public funding invested in lake restoration and in voluntary soil conservation projects in the watershed, so don’t think we can solve this problem with more of the same. At Lake Darling, the work seems to have been undone by an expansion of the hog industry. At the Lake of Three Fires, the work seems to have been undone by conversion of pasture to cropland, motivated by the Renewable Fuel Standard. We need to take a hard look at how state and federal policies allow or even encourage farming practices that foul our lakes.
However, I follow the data where it leads, and it doesn’t always lead to a hog barn. Here is my latest summary of E. coli data collected by the water monitoring program in Story County. Hickory Grove Lake has been well-studied by the DNR, and both DNA markers and transects point to Canada geese on the beach, not livestock in the watershed. College Creek is usually our worst stream on days when it’s flowing, and it has an urban watershed. A large fraction of the bacteria in West Indian Creek came from an old sewage treatment plant that was just replaced this year. DNA testing of water from Ioway Creek showed that human waste is present. We’ll be doing more testing in 2026 to confirm this and narrow down the sources, including a volunteer event in early summer. Donations also help support our monitoring and education efforts!
Some people are afraid to dip a toe in any lake or river in Iowa, and their No Swim Era goes back decades. That’s a shame. Even in a bad year, it’s possible to find clean water for recreation. For example, I took my daughter and her friend swimming and paddleboarding at Peterson Park, a Story County-owned beach where E. coli counts never exceeded the double digits. I joined Iowa Project A.W.A.R.E. to canoe and clean up trash on some scenic stretches of the Upper Cedar and Shell Rock Rivers, which averaged 69 and 45 CFU/100mL for the season–the standard is 126. I’ve updated this interactive map to help you find others.
The new Currents of Change report has some good tips for minimizing your risk of a waterborne illness when recreating in waters of poor or unknown quality. I regularly go in Ioway Creek, which I know to have poor water quality, but pack hand sanitizer and do my best to keep my head above water. I dunked my head in the Winnebago River (which was muddy and hadn’t been tested recently) multiple times during a whitewater kayaking class, but wore nose clips. I stay out of green water but otherwise am comfortable with a certain amount of risk to be able to enjoy the outdoors. But that’s just making the best of a bad situation. No Swim advisories have gotten way too common, and we need to work together to clean up our water and end that era!
When the ball dropped on New Year’s Eve, nitrate in the Raccoon River was once again above the drinking water standard, closing out a bad year for water quality in Iowa. Below, I’ve compared this year’s nitrate levels to long-term averages at sites in Iowa DNR’s Ambient Stream Network with at least 20 years of data to get a sense for where and when nitrate was highest and what was unusual about 2025.
To understand these patterns, it’s important to remember that 2025 was not a uniformly wet year. Heavy rains in July broke or came near to breaking some records and caused flash flooding in many communities. These rains also raised the water table enough to keep drainage tiles flowing into into the fall. However, most of the state received less than average rainfall from January through May and from August through December. In a band from Ames to Charles City, that works out to a much wetter year than normal. In other parts of the state, like Dubuque, Ottumwa, and Red Oak, that works out to a much drier year than normal.
Nitrate was much higher than normal in the Boone River, Skunk River, and many others in northern and central Iowa, especially in July and August. Nitrate was within 1 mg/L of the long-term average for the Nishnabotna and other rivers in southern Iowa and for the Rock and Floyd Rivers in northwest Iowa. In the table below, red indicates nitrate was higher than average, blue is lower than average, and white is close to the long-term average.
There are some unusually high readings (25 mg/L in the South Skunk River in January) and unusually low readings (3.3 mg/L at Beaver Creek In July) that may have been collected during a storm or other event that is not representative. This is a limitation of monthly grab samples and one reason why maintaining Iowa’s network of real-time nitrate sensors is important. The Ioway Creek sensor was removed at the end of 2024, but the pattern I documented here here (a quick flush of low nitrate surface runoff followed by a gradual release of high nitrate drainage water) happened over and over, in many places in 2025. These kinds of leaks can be avoided with changes in cropping systems and land use, reduced with better nutrient management and cover crops, or intercepted and treated with saturated buffers and wetlands, but we’ll need a lot more of them to prevent another bad year like 2025.
It sounds too good to be true, wrote Neil Hamilton in a 2021 opinion piece. Reducing nitrogen fertilizer application rates to the Maximum Return to Nitrogen (MRTN) recommended by Iowa State University promised to save farmers money while keeping nitrate out of the rivers and greenhouse gases out of the atmosphere. In retrospect, it was too good to be true.
Reducing fertilizer rates will cut into profits (for most farmers)
Early this year, ISU researchers published a study in Nature Communications showing that the amount of nitrogen fertilizer required to maximize yield (the agronomic optimum) and maximize profits (the economic optimum) have been steadily increasing, driven partly by corn genetics and partly by weather. The economic optimum is always lower than the agronomic optimum (the revenue from those last few bushels isn’t enough to pay for the fertilizer) but the difference between the two is getting smaller. I wrote about this in July, but since then I’ve had a chance to download and explore the data used in the study. Here are the trends in optimal nitrogen application rates for just the sites in Iowa, compared to actual nitrogen application rates, which I estimated using a combination on IDALS fertilizer sales data and INREC survey data. For more details on the data I used to estimate actual nitrogen application, read this attachment.
The scenarios in the Iowa Nutrient Reduction Strategy were based on data from 2006-2010. At that time, it would have been possible for farmers to reduce nitrogen application rates on corn following soybeans from 151 lbs/acre to 133 lbs/acre while increasing profits, on average. However, those figures were already out of date when the Iowa Nutrient Reduction Strategy was released in 2013, and in the decade since, fertilizer application rates have levelled off while the amount of nitrogen needed to maximize yields or profit has continued to increase. A minority of farmers may still find opportunities to boost profits by reducing nitrogen application, but average rates are now below the economic optimum.
This part of the study looks solid and matches what I’ve seen from other sources. Practical Farmers of Iowa have done their own trials and found that a majority of their participants were able to save money by reducing nitrogen rates in an especially dry year, but in a more typical year only 41% of farmers saw potential for savings.
Reducing fertilizer rates could still have significant water quality benefits
Farmers no longer have an economic incentive to reduce rates (on average) but it’s not hard to imagine policies that could shift the incentives by making it cheaper or less risky to apply at low rates, or more expensive to apply at high rates.
The ISU study includes an “environmental optimum nitrogen rate” that hints at that. The authors used a crop systems model to estimate nitrous oxide emissions and nitrate leaching for different scenarios, assigned a price to the pollution, and calculated the nitrogen application rate that would be economically optimal if those costs were reflected in the marketplace. Instead of evaluating the environmental benefits of reducing rates from current levels, they estimate the impacts of reducing rates (for corn after soybeans) from an economic optimum of 143 lbs/acre to an environmental optimum of 116 lbs/acre. Those are averages for the entire 20 year period and not at all relevant today. Oops! Because of this mistake, they conclude that “a reduction in N fertilizer rate towards improving sustainability will not have the anticipated reduction in environmental N losses because of the nonlinear relationship between N rate and N loss.”
Actually, the non-linear (curved) relationship between nitrogen application rates and nitrate pollution implies that rate reduction will have bigger benefits now than it did when rates were lower. The figures below contrast some outdated assumptions with new reality.
The increase in fertilizer rates has been bad for water quality
In most presentations and interviews about the Iowa Nutrient Reduction Strategy, ISU faculty correctly point out that fertilizer management alone is not enough to meet our water quality goals and emphasize the need for a variety of conservation practices. However, every scenario in the INRS assumed that fertilizer application rates would go down. It may not be possible to meet our goals now that fertilizer rates have gone up.
Based on the increase in fertilizer rates for corn after soybeans (from 151 lbs/acre in 2007 to 173 lbs/acre since 2017), we would expect a 16% increase in nitrate concentration in drainage water. The 3.8 million acres of cover crops reported in recent INREC aren’t enough to undo the damage. Nitrate in streams is also affected by weather, changes in land use, and other practices not modeled here, but fertilizer rates and cover crops do help to explain why nitrate concentrations in many streams peaked between 2013 and 2015 and have fallen since.
What about continuous corn?
Nitrogen application rates for corn after soybeans have gone up, but application rates for continuous corn may actually have gone down. I say “may” because we didn’t have good baseline data. Because corn stover ties up a lot of nitrogen as it decomposes, growing corn after corn requires higher nitrogen application rates to achieve the same yield. The confusing Figure 5 in the Nature Communications paper looks at the yield penalty for reducing nitrogen rates from the economic optimum to the “environmental optimum,” which is what it would make economic sense for farmers to apply if the societal costs of pollution were reflected in the marketplace. The authors concluded that reducing nitrogen application rates past the economic optimum would have unacceptable consequences for grain markets and food security, especially for continuous corn. I looked at the same figure and concluded that growing corn after corn would not be commercially viable in a society that valued clean water, a stable climate, and public health.
Your mileage may vary
My biggest takeaways from both the Iowa State University research and the Practical Farmers of Iowa research are how much the optimum nitrogen rate varies from year to year and place to place. One farmer in the PFI study saved money by reducing rates from 150 to 100 lbs/acre, while another lost money by reducing rates to 246 to 200 lbs/acre.
The ISU study includes nitrogen rate trials for seven sites in Iowa and six years since the Iowa Nutrient Reduction Strategy was released. If you had followed the recommendations from the old nitrogen rate calculator and applied 140 lbs/acre to corn after soybeans, 62% of the trials would been at least 10 lbs/acre below the economic optimum. But even in the most recent year, there were 2 sites where that would have been at least 10 lbs/acre above the economic optimum!
The Iowa Nitrogen Initiative addresses this problem through an expanded program of nitrogen rate trials and a decision support tool that can provide customized recommendations by county given assumptions about rainfall, planting date, and residual soil nitrate. Using the new information, some farmers will find an opportunity to increase profits while reducing nitrogen rates. A larger group of farmers will find opportunities to increase profits by increasing nitrogen rates. Dr. Castellano has made a complicated argument for how the water quality benefits of bringing down the high rates can be greater than the water quality penalties of bringing up the low rates. Great. Please apply that logic to manure.
What about manure?
Since 2017, the INREC survey report has asked farmers what percent of fields receive manure application (about 20%), how much commercial fertilizer is applied to fields that do not (174 lbs/acre for corn in rotation and 199 lbs/acre for continuous corn), and what proportion of cropland is planted to continuous corn (about 12%). Manure expert Dan Anderson recently did some algebra to see what that implies about nitrogen application rates for fields that do receive manure, and came up with 342 lb N/acre on corn-after-soybean and 391 lb N/acre on continuous corn. I used slightly different assumptions and came up with lower numbers, but they’re still much higher than needed to maximize yield. If you’ve read anything by Chris Jones, this won’t come as a surprise.
I’m showing the agronomic optimum rate rather than economic optimum because the economics of manure aren’t the same as commercial fertilizer. Manure has much lower nutrient content and is much more expensive to haul. Manure pits fill up and there’s often a time and labor crunch to get it applied. Manure has highly variable nutrient content, which adds to the uncertainty and makes a supplemental application of commercial fertilizer seem like cheap insurance. If farmers had a strong economic incentive to make the most of manure nitrogen, nobody would be applying it in early fall and we wouldn’t have a cloud of ammonia hanging over the Midwest. There are also some farmers who are doing an exceptional job of conserving soil and water by feeding cover crops, small grains, or forage to livestock, and we should figure out how to level the playing field to make it easier to replicate their model.
Are these changes in nitrogen management good or bad?
It’s a mixed bag. I had to puzzle over this for quite a while!
The increase in the economic optimum nitrogen rate is partly due to good things (improved corn yield response) and partly due to bad things (increasing nitrogen losses to the air and water).
It’s good that nitrogen fertilizer use has gotten more efficient. Farmers can grow more bushels per pound of nitrogen than they used to. It’s bad that manure management plans still allow nitrogen to be applied at a rate of 1.2 lbs per bushel of potential yield.
It’s good that fertilizer rates for corn following soybeans have levelled off recently. It’s bad that nitrogen fertilizer rates went up in the early 2000s.
It’s good that nitrogen application rates for continuous corn have fallen. It’s bad that farmers are planting corn after corn.
It’s good that farmers are now applying less commercial fertilizer (on average) than required to maximize yield. It’s bad that farmers are over-applying manure.
It’s bad that we don’t have a plan to reach the goals of the Iowa Nutrient Reduction Strategy without rate reduction, and it’s bad that the price tag of reducing rates (either to farmers, the public, or both) is higher than we previously assumed. However, it might still be a better deal than other conservation practices. It’s bad than more people aren’t talking about this.
Our third annual Monarch Magic was held at Ada Hayden Heritage Park in Ames on September 6th. 37 families brought their kids to learn about butterflies and nature with hands-on activities. Normally we tag butterflies but didn’t this year because of concern about their numbers. Thanks to Friends of Ada Hayden Heritage Park, Raising Readers in Story County, The Outdoor Alliance of Story County, Trees Forever, Iowa Chapter of the Sierra Club, Story County Conservation, Boone County Conservation, Greater Des Moines Botanical Gardens, Big Bluestem Audubon Society, Pollinator Friendly Ames, Iowa Monarch Consortium, City of Ames (Parks and Rec and Smart Watersheds) for participating!
Our sixth creek cleanup, which we’re now calling PACRAT (Paddle and Cleanup Rivers Around Town) was held on May 3rd. Thirty-three volunteers removed 3,200 pounds of trash from Ioway Creek! Thanks to the City of Ames, Story County Conservation, Outdoor Alliance of Story County, and Skunk River Paddlers for helping make it happen!
Volunteer water monitoring
We continue to experiment with the format for seasonal volunteer monitoring events. In May (as described in another article), we coordinated our event in Story County with Polk County Conservation and created a map showing water quality across central Iowa. On October 11, eight volunteers joined us bright and early so we could test dissolved oxygen at the low point in its daily cycle, for an event we billed as a “water quality breakfast.” All but one of the sites we tested had dissolved oxygen levels of 8 mg/L or higher, which means we weren’t able to narrow down the cause of the problems we’ve seen in past years, but it’s good news for fish and other aquatic life! The lowest reading was College Creek at the ISU Arboretum (6 mg/L), where the water was barely flowing.
Fall is also a good time for biological monitoring. On October 3, an Ames High School environmental science class helped me survey aquatic invertebrates at Brookside Park in Ames. We found enough insects to make it interesting for the students but not a wide enough variety to indicate a healthy aquatic community–the overall score was “fair.” In one picture below, you can see a new cross-vane structure which redirects the creek’s flow to the center and away from eroding banks. It’s one of several interventions the city is making that we hope will reduce erosion and improve aquatic habitat.
Presentations
Dan and Katelyn are always happy to talk about water quality, pollinators, or land stewardship. Our speaking engagements this year included:
A sustainable agriculture class at Iowa State University
4H youth fishing club, by Zoom.
Kirkwood Women in Natural Resources Club
An evening program in Mason City for Iowa Project A.W.A.R.E.
Central Iowa Beekeepers Association winter seminar, by Zoom
A Story County Master Gardeners meeting in Ames
A joint meeting in Stanhope of the Ioway Creek and Headwaters of the South Skunk River Watershed Management Authorities
A panel discussion at a statewide gathering of watershed management authorities in Cedar Rapids
A non-partisan rally organized by the Iowa League of Women Voters
We also hosted a webinar about the importance of native habitat featuring speaker Sarah Nizzi of Xerces Society.
Tabling
Thanks to the following organizations for giving us an opportunity to set up a display and meet members of the community.
EcoVision at the Ames Public Library
STEAM Around the World, organized by the Nevada PTA
We’re looking forward to more opportunities to engage with communities in central Iowa and beyond in what’s left of 2025, and next year!
When the House of Representatives reconvenes in September, they will likely vote on a collection of amendments to the Clean Water Act: H.R. 3898, which they’re calling the PERMIT Act (Promoting Efficient Review for Modern Infrastructure Today). It’s a bad bill and you should urge your representatives to vote against it.
The Clean Water Act no longer works well in Iowa, because our largest remaining source of pollution is agricultural stormwater runoff, which has a special exemption. The Iowa Department of Natural Resources has been reluctant to put waters on the impaired list and write cleanup plans because they can’t enforce them. They have been reluctant to update standards because they think it will result in higher costs for small town sewage treatment plants without making any noticeable difference for water quality in rivers. I have a whole presentation about impaired waters if you’d like more details, but that’s the situation in a nutshell.
HR 3898 makes this worse. It expands exemptions for agricultural stormwater and pesticides without any provisions to encourage conservation. It mixes economic considerations into the process for setting standards and evaluating impairments. If there’s no widely available and cost-effective way to get a pollutant down to the level that science says is needed to protect aquatic life or drinking water, then the DNR would have to set a weaker standard, or delay setting standards. This would leave the public in the dark about the condition of our lakes and rivers.
There has been a long-running controversy over the extent to which the US Army Corps of Engineers and EPA can regulate construction in wetlands and waterways, which hinges on the definition of phrase: “Waters of the United States.” The Supreme Court recently ruled that many kinds of wetlands aren’t covered. This bill would exclude ephemeral streams, which had previously been considered on a case-by-case basis. I would be less worried about the impacts of these decisions if Iowa had state law requiring developers to avoid or mitigate wetland fill, like some of our neighbors do.
HR 3898 goes beyond clarifying a few exceptions to roll back what many people see as federal overreach. It also raises the threshold for general permits, making it easier to fill small wetlands even if they do have an obvious connection to navigable waters. It makes it harder for states to block pipeline projects. Amendments by Democrats to study the impacts of the bill or mitigate them with a no-net-loss policy were rejected and the bill passed out of committee on a party line vote.
The one good thing about the bill is it’s a reminder that Congress does have the ability to fix outdated laws. What we now call the Clean Water Act are the 1972 and 1977 amendments to the 1948 Federal Water Pollution Control Act. Those amendments made a big difference for waters that were once polluted by sewage and industrial waste. This summer, I paddled on a beautiful and relatively clean stretch of the Shell Rock River with a canoe partner who grew up in the area and recalled how foam used to float down the river from meatpacking plants in Minnesota. The law was amended again in 1981, 1987, and 2014. It could use another amendment to cut red tape while better addressing today’s water quality challenges, but this isn’t it!
I’m sharing some vacation photos, taken at the Athabasca Glacier in Alberta, Canada, because it’s a nice window into Iowa’s icy past and its warming future. Earth science concepts like glacial moraines and watersheds and climate change that can be subtle or hidden in Iowa are plain to see in the mountains!
1. Glacial Ice
This is the Athabasca Glacier. It’s a slow moving river of ice 4 miles long and 300-980 feet thick, sliding off the larger Columbia Icefield in the Canadian Rockies. It looks big from a distance, and it feels even bigger when you’re walking across it on crampons and aren’t used to the altitude! The depth of the ice became apparent when we looked into a crevasse.
All of Iowa looked like this at some point during the last 2 million years, except the ice was even thicker. The Des Moines Lobe of the Wisconsinian ice sheet melted from northern and central Iowa just 12,000 years ago, leaving behind flat, marshy land. Other parts of Iowa have been ice-free for longer and had more time for wind and water to shape the hills and valleys.
2. Glacial Till
A sheet of ice hundreds of feet deep is heavy, and pushes against the earth with tremendous force as it slides slowly downhill. This photo shows both the scratches on the bedrock made by the glacier and the glacial till that it leaves behind–an unsorted mix of sand, silt, gravel, and boulders. You don’t have to travel to the Canadian Rockies to see Canadian rocks; during the ice age, the glaciers carried some all the way to Iowa!
Like a bulldozer, glaciers smooth out the ground underneath and leave a big pile of material at the edge when they stop. That’s why there’s a line of hills near Des Moines and a lot of flat land north of there. You can see a flat ground moraine in the foreground of this picture and a steep lateral moraine in the background.
3. Soil Formation
Despite the harsh conditions at the edge of the glacier, a few tiny flowers were blooming! This plant is a Saxifrage, “stone-breaker” in Latin. Plant roots and associated fungi speed up the process of breaking down rock and turning it into soil.
It’s still a slow process! It took thousands of years for prairie roots, microbes, and burrowing animals to turn lifeless glacial till into Iowa’s rich black topsoil, but only 160 years of tillage to lose half of it. Fortunately, there are ways to grow crops without degrading our soil. As Practical Farmers of Iowa puts it, “don’t farm naked!”
4. Continental Divide
The Columbia Icefield sits at the junction of two continental divides. Meltwater from the Athabasca Glacier joins the Saskatchewan River, which ultimately makes its way to Hudson Bay. However, meltwater from the Stutfield Glacier on the other side of the mountain ends up in the Arctic Ocean, and meltwater from the Columbia Glacier goes to the Pacific Ocean.
In the Canadian Rockies, the watershed boundaries are impossible to miss: lines of awe-inspiring mountain peaks on either side of a river valley. You might be driving along the Bow River until you reach it’s headwaters, and then you come to a mountain pass, your ears pop, and… ta da! You’re in a new watershed, following the Mistaya River downhill.
In Iowa, the dividing lines between land that drains to the Mississippi River and the Missouri River (or any other pair of rivers) are hard to find without a topographic map. We’ve put up watershed signs around Story County to make it more obvious.
Why does is matter what watershed you’re in? Well, knowing which land drains to which river can tell you something about the water quality in the river, and who to talk to if you want to improve it.
5. Meltwater
Our guide refilled our water bottles from a stream of glacial meltwater. I felt comfortable drinking it without boiling or filtration because nothing lives on a glacier. Elsewhere in the mountains, there’s a risk that wild animals living in or near the water might have left behind a little present containing a parasite like Giardia. Fecal contamination tends to get worse as you move downstream into areas with a lot of cows or a lot of people, and Alberta has its own set of water quality issues associated with mining and oil extraction. However, there’s a notable difference from Iowa: when natural resource agencies issue a beach advisory because of E. coli, it’s unusual enough to make the news!
The water from the glacier was refreshing but tasted a little… dusty. Like the taste in your mouth when you’re standing on a gravel road and truck passes by. Ames tap water is better!
However, the glacial dust (rock flour) reflects the light, turning mountain lakes a lovely shade of blue, turquoise, or green. In Iowa, green or blue-green colored water is usually a sign of an algae bloom, unpleasant to swim in and possibly toxic!
6. Climate Change
We made sure to include a visit to the glacier in our vacation plans because there may not be many more opportunities to see one. In a stable climate, a glacier would melt a bit in summer and grow back with winter snows. In a warming world, glaciers are melting rapidly.
Driving from the visitor center to the trailhead, we passed a series of ridges (terminal moraines) marked with dates. Since 1844, the ice has been receding and the pace of melting has accelerated in recent years. None of my pictures capture this, so I will screenshot an a pair of images from the Mountain Legacy Project and point you to Amy Snider for more art, maps, and photos about the Athabasca Glacier.
Climate change has been less noticeable in Iowa than in other parts of North America because of the moderating influence of corn sweat (evapotranspiration), but that won’t last. Rising temperatures, more intense spring rains, and greater weather variability are projected to lower yields and undermine what little progress we’ve made in addressing water quality. Alberta’s economy is dependent on fossil fuels, but Iowa has a lot of gain from a transition to green energy, and a lot to lose if we don’t make the switch.
7. Fossils
At the edge of the glacier, we saw a trilobite fossil in a 510-million year old rock, a relic of a time when erosion rates were even higher than they are now because there weren’t any plants yet. The broken shells, sand, and silt that covered the seafloor has since turned to rock and been pushed up to form new mountains.
The trilobites are long gone, wiped out during another episode of global warming and ocean acidification, this one triggered by massive volcanic eruptions 252 million years ago. It was the biggest mass extinction in Earth’s history, but after fifty million years or so, the land, seas and sky were teeming with new species.
If you take a long enough view, arable soil, clean water, and biodiversity are renewable resources. On human timescales, they’re definitely not. Agriculture and civilizations developed during a time of stable climate, and they may not last much longer if we don’t take more aggressive action to limit greenhouse gas emissions. The Earth will go on without us.
You know those United Way posters with a thermometer showing progress toward a fundraising goal? The image above is my attempt at a similarly easy-to-understand progress meter for the Iowa Nutrient Reduction Strategy (INRS). Based on changes to farming practices in the decade since the Iowa Nutrient Reduction Strategy was released, we should have met our goal for phosphorus but have only reduced nitrogen losses by 2%, not enough to undo the increases of the previous decade. These are best-case scenarios which do not account for manure, legacy sediment and nutrients, and interactions between practices.
Iowa State University is responsible for tracking the progress of the INRS, and has created a set of data dashboards covering dollars spent, minds changed, conservation practices on the land, and water quality trends in the rivers. These were updated in May of 2024. There is no top-line summary of where we stand relative to our goals, but wasn’t hard to make one. I just added up the numbers in a pair of tables labelled “change in modeled nitrogen/phosphorus load for practices since the baseline period.”
Baselines, Goals and Timelines
The timeline requires some explanation. The INRS was released in 2013, but the baseline period is 1980-1996. That’s because the Hypoxia Action Task Force was formed in 1997. The task force set a goal of reducing the size of the dead zone in Gulf to 5000 square kilometers (1,930 square miles). The target date for meeting that goal has been pushed back several times. Despite several dry years, the five-year average extent of the dead zone is still twice as big as the target. Last year it measured 6,705 square miles, larger than Connecticut or Hawaii.
To meet the goals for shrinking the dead zone, each state would need to reduce the amount of nitrogen and phosphorus lost down the Mississippi River by 45%. The Iowa Department of Natural Resources determined that mandatory upgrades for 102 municipal wastewater treatment systems and 28 industrial facilities could reduce state’s overall nitrogen load by 4% and phosphorus load by 16%. The remaining 41% reduction in nitrogen load and 29% reduction in phosphorus load would need to come from controlling non-point sources of pollution like agricultural runoff.
Iowa State University was tasked with answering the question: “based on what we know about the performance of various conservation practices, how would it be possible to achieve these goals?” The answer was “only with a combination of practices, and only if every farm uses at least one of them.” This research began in 2010, using data about land use and farming practices from the previous five years (2006-2010), so the load reduction scenarios are relative to that “benchmark” period. The researchers later issued a supplemental report to compare the benchmark period to the baseline. Phosphorus went down due to changes in tillage but nitrogen went up due to an increase in corn and soybean acres and an increase in fertilizer application rates.
Using the information in ISU’s reports and dashboards, I’ve attempted to summarize our progress relative to both the baseline period (before the formation of the Hypoxia Action Task Force) and the benchmark period (before work began on the Iowa Nutrient Reduction Strategy).
Modeling vs. Monitoring
As I said, these are best-case scenarios. While we can certainly expect a big reduction in phosphorus pollution from the growth of no-till and cover crops, ultimately, the only way to be sure that water quality is improving in our rivers is to test it! If there’s a discrepancy between what you expect (a big reduction in phosphorus load) and what you measure (no clear trend in flow-weighted, five-year-moving-average phosphorus loads) that’s a sign that you left something important out of the spreadsheet! The most likely suspects are legacy sediment in the river valleys and livestock manure.
On the other hand, if your water quality data is incomplete or inconclusive or just hard to explain, it’s worth stepping back and asking yourself: “how big a reduction in nitrogen can I reasonably expect, based on the conservation practices installed so far?” If the answer is “1 or 2 percent,” there’s no need to wait for the results of a long-term study to acknowledge that your strategy isn’t working.
I remember doing that kind of reality check in 2019 for the Ioway Creek Watershed Management Authority, at the end of a four-year demonstration project. I did not enjoy being the bearer of bad news then, and I’m not enjoying it now. I remember how much work my colleagues put into those field days, and the ingenuity and vision displayed by the farmers who hosted them. I was there when the woodchips were poured into the first bioreactor in Boone County. So I totally understand the impulse to brag that Iowa now has 300 bioreactors, 3.8 million acres of cover crops, and 10.2 million acres of no-till. Many people worked hard to achieve those numbers! It is real progress! It’s kept nutrients and sediment out the water! It proves that there are many farmers who care about soil and water and are doing something about it! But it doesn’t prove that the Iowa Nutrient Reduction Strategy is working. For nitrogen, it definitely isn’t.
Conservation efforts have been partially offset by increased fertilizer use
I knew that we needed a lot more cover crops, wetlands, and saturated buffers to reach our nitrogen goal. Iowa Environmental Council has made this point with infographics. What I didn’t realize was the extent to which increases in fertilizer application rates have offset the hard-won gains that we’ve achieved so far.
Nutrient rate management was supposed to be the low-hanging fruit the Iowa Nutrient Reduction Strategy. At the time the INRS was written, the Maximum Return to Nitrogen (the point at which the yield bump from an additional pound of fertilizer doesn’t generate enough revenue to cover the costs) was 133 lbs/acre for corn in rotation and 190 lbs/acre for continuous corn. Reducing rates from 150 lbs/acre for corn in rotation and 201 lbs/acre seemed like an easy way to reduce nitrogen in the rivers by 10% while actually saving farmers money. Win-win! Instead, rates for corn in rotation averaged 173 pounds/acre for the past several years, which would raise nitrate levels in tile water by 18%! Rates for continuous corn went down just a tiny bit, to 199 lbs/acre. What happened?
Several of the authors of the INRS science assessment just co-authored a new paper in Nature Communications which provides an answer. 133 lbs/acre was economically optimal under outdated assumptions about corn genetics and yield response, fertilizer and corn prices, and precipitation. Factoring all that in, the optimal rate for corn in rotation actually rose to 187 pounds/acre in 2020, leaving no opportunity for a win-win. Farmers are acting in their rational economic self-interest and applying as much nitrogen as is required to get good crop yields after a heavy spring rain. (Huge caveat: this doesn’t factor in manure). The researchers acknowledged that this is bad for water quality, as measured by a growing gap between the economically optimal rate and an “environmentally optimal rate” with some externalities priced in. Another way to say that: the fraction of agribusiness profits which come at the expense of other industries (i.e. commercial fishing in the Gulf, tourism for communities on polluted lakes) and the public (i.e. utility bills for customers of the Des Moines Waterworks, hospital bills for cancer patients) has been growing.
The companion piece to this paper is a new calculator. N-FACT uses data from on-farm nitrogen rate trials to factor in location, planting date, residual soil nitrogen, fertilizer price, and your best guess about corn prices and rainfall to provide a customized economically optimal nitrogen rate. The research that went into it is very impressive, and gave me a new appreciation all the factors that can influence agronomists’ recommendations and farmers’ decisions. I hope it will lead to reduced nitrogen losses by helping farmers improve their forecasting, but unless you’re doing a split application and soil or corn stalk testing, it seems like there’s still a lot uncertainty. That’s why I’m more excited about Practical Farmers of Iowa N Rate Protection Program, which directly addresses uncertainty and risk.
What we really need is a calculator to answer the following questions about the Iowa Nutrient Reduction Strategy:
How much voluntary conservation will it take to offset future profit-driven changes in the industry?
How soon can we expect to see meaningful reductions in nitrate in our rivers and drinking water?
How many people will get preventable cancers in the meantime?
How long is the public going to put up with this before we demand a change in strategy?
What do I mean by “a change in strategy?” Making policy recommendations isn’t our wheelhouse, but if you’re looking for ideas, you might start with this 2020 op-ed by Matt Liebman, Silvia Secchi, Chris Jones, and Neil Hamilton, or this 2022 report by the Iowa Environmental Council.
