Paddling While Impaired

Paddling While Impaired

For safety’s sake, I wish people would not mix boats and alcohol, but I’m writing about the other type of impairment that can get in way of having a fun and safe experience on Iowa’s lakes and rivers: water quality.  Every two years, the Iowa Department of Natural Resources takes stock of which lakes and rivers have water quality good enough to fully support recreation, fishing, drinking water supply, and other beneficial uses.  Those that don’t go on the Impaired Waters List.  The draft 2024 Impaired Waters List has been published and you can make public comment through April 12.

Kayaker with impaired waters message

Understanding the numbers

Most of the op-eds and news stories about the impaired waters list focus on the numbers.  There are 572 rivers and streams, 137 lakes, and 12 wetlands on the impaired list.  If you had forgotten that Iowa has water quality problems, here’s your biennial reminder!

This year, there are fewer impaired waters than in the 2022 cycle.  Much will be made of that, and will be much ado about nothing.  The Impaired Waters List is not very useful for evaluating water quality trends, because the number of waters assessed and the methodology used to assess them is always changing.  It’s also worth noting that the assessment period (2020-2022) included long stretches of drought, which means less runoff, so it’s possible that some of the 97 waters removed from the list will go back on the impaired list when we get some wetter weather.

Missing data

Not too long ago, the biggest category in the integrated report was waters not assessed.  This year, it has dropped to 49% of rivers, 44% of lakes, and 21% of wetlands.  We can claim a little bit of credit for this.  Eight stream segments formerly in the not assessed category were tested for E. coli as part of the Story County water monitoring program and are now in a category called Waters in Need of Further Investigation (WINOFI).  There’s a state law that prevents IDNR from using third-party data for regulatory decisions, but I still appreciate that they reached out and included our data in the report!

An example of Waters in Need of Further Investigation (WINOFI)
Seasonal E. coli averages for West Indian Creek, from our local monitoring program.

Finding clean waters

I’m most interested in which waters are impaired and why.  For rivers, the leading cause of impairment is E. coli bacteria, an indicator of fecal contamination and a proxy for other pathogens that could potentially make people sick if they swallow some water while recreating. 

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.  Hopefully this a just a prototype for something even better and more comprehensive.

Interactive map of E. coli in Iowa

Improving Impaired Waters

We don’t want to just avoid the impaired waters, we want to know how to clean them up.  The Impaired Waters List is also a waiting list for a water quality improvement plan, or Total Maximum Daily Load (TMDL).  IDNR has studied swimming beaches at several lakes (including Hickory Grove Lake in Story County), and found that E. coli is highest in the wet sand at the beach, and lower in the lake and tributaries.  For these lakes, that suggests that the biggest sources of contamination are located at the beach, things like geese and diaper malfunctions.  For rivers impaired by E. coli, we don’t know the cause.  Many rivers have been waiting decades for a TMDL in a low priority tier, and a TMDL that was written in 2017 for the Iowa River seemed incomplete.

However, after attending the Raccoon River Watershed Association’s annual conference on March 9, I no longer feel like Iowa has given up on recreational water quality in rivers.  Robin Fortney shared reminiscences of many river trips.  Jon Wenck (IDNR) and Pat Boddy (ICON) talked about Iowa’s growing network of water trails.  It’s clear there are people who care about our rivers and see how they can benefit quality of life and economic development.  Claire Hruby (Drake University) shared some early results from microbial source tracking and microbial risk assessment research in Polk County.   With these approaches, can find out which pathogens are present in the water (not as many as we feared) and whether waste is coming from livestock, wildlife, or humans or a combination!

My contribution to the conference was a nuanced look at exactly how CAFOs (big feedlots) impact water quality.  I hope to share a video of the presentation and a report in our April newsletter.  There are far too many spills and leaking manure storage structures, and manure management plans don’t prevent over-application of nitrogen and phosphorus.  However, the claim that waste from factory farms is responsible for most of Iowa’s impaired waters is just not supported by the data.  Here is one figure from my presentation.  Notice that Iowa has many rivers with extremely high E. coli levels but fairly low livestock densities in the watershed.  To understand E. coli contamination, you have to consider not just the amount of feces produced, but how it likely it is that feces will reach the water before the bacteria die off.

Graph of E. coli vs livestock density in 58 Iowa watersheds

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.

Thumbnail for Clean Water Act Fact 44
Thumbnail for Clean Water Act Fact 45
Green Stuff in the Skunk River

Green Stuff in the Skunk River

On Tuesday, March 12, residents on the north edge of Ames noticed that the South Skunk River was cloudy and had turned an unusual shade of bluish green.  By the time I looked at it on the afternoon of March 13, the color had faded and the water was less cloudy, but it still had a soupy, streaked appearance that I’ve seen before in lakes following a toxic algae bloom.  I’m gonna go out on a limb here and say it’s blue-green algae (cyanobacteria).

Cyanobacteria bloom in the South Skunk River
Cyanobacteria bloom, showing paint-like streaks.
Cyanobacteria bloom in the South Skunk River.

“Algae” is a word that gets lazily applied to any living thing that does photosynthesis but that isn’t a plant: from tiny glittering diatoms in a drop of pond water to giant kelp in the oceans.  The other kind that I noticed in the South Skunk River this week is filamentous green algae, which forms slimy hair-like strands on rocks and globs on the water’s surface.  Color is the least of the differences.

Cyanobacteria are tiny and simple.  There’s strong evidence that the chloroplasts in the cells of plants and green algae are the captured descendants of cyanobacteria. This amazing phenonemon is called endosymbiosis, and it’s happened multiple times in the history of life on earth.  If you’ve never heard of it, I’d recommend this YouTube video, which explains the concept with cartoons.

The practical reason to know if the green stuff in the water is cyanobacteria is because they can produce toxins.  I wasn’t able to get a sample tested for microcystin (and chances are, this algae bloom will have dispersed by the time you read this), but I would recommend keeping your dog out of water that looks like paint or pea soup, to be on the safe side.

Green algae in the South Skunk River (Rick Dietz)
A simple guide for green stuff in the water.

Why is the water so green, so early?  Algae growth is limited by the availability of light, heat, and fertilizer–phosphorus in freshwater, and to a lesser extent nitrogen.  We’re getting unseasonably warm weather before there’s any leaves on the trees to shade the water.  As for the fertilizer, I’m not sure where it came from, or when.  Rick Dietz and I tested nitrate and phosphate with field kits on Wednesday and measured 0 mg/L.  Nitrate and phosphorus levels were also fairly low at this site when we collect grab samples in February.  Maybe something was washed into the river earlier in the week, but it has since been used up by the algae or has washed downstream.  I’ll amend this article if I find out something conclusive.

Inch Your Way to Loving Worms!

Inch Your Way to Loving Worms!

The pretty cecropia moth caterpillar!

 

We won’t be talking about love or flowers this Valentine’s Day, but we will talk about some love-able critters that can eat flowers! They’re squishy, fluffy, or prickly, and sometimes called worms. They can be striped, spotted, or elaborately camouflaged. They are mini bird burritos, have secret appendages, and can trigger gag reflexes. They will become tomorrow’s moths and butterflies. We’re talking about CATERPILLARS!

What exactly is a caterpillar?

These curious creatures are the larval stage of growth in butterflies and moths. The term “caterpillar” is colloquial, and almost exclusively refers to moths and butterflies (although some moth caterpillars are also called “worms” or “inchworms”). Other insects have different terms for their larval stages, such as “maggots” for fly larvae and “grubs” for beetle larvae.

Most people know that the caterpillar/larval stage is one step in the development process called metamorphosis. But did you know that there are two general kinds of metamorphosis: “complete” and “incomplete”? The big difference between the two is that insects using complete metamorphosis go through a pupal stage (a period where they are inactive for a bit). Butterflies and moths go through complete metamorphosis because a caterpillar forms into a pupa when it develops into a chrysalis or rests inside a cocoon. Insects that go through incomplete metamorphosis do not go through a pupal stage (some examples include dragonflies, praying mantids, and crickets).

A black swallowtail caterpillar with beautiful warning stripes that say “don’t eat me”.

Why so squishy?

Back to caterpillars: why would any animal want to be small, slow, and squishy for a period of their life? What is the advantage, considering how tasty caterpillars are to birds, rodents, and many other animals? About 80% of insects (including bees, ants, fireflies, and more!) use complete metamorphosis to grow, which requires this vulnerable phase. Why is this?

Besides the pupal stage, another hallmark of complete metamorphosis is that the larval stage and adult stage have virtually nothing in common. Most scientists agree that this difference is key to the success of complete metamorphosis: young and adult insects don’t have to compete for the same resources. Caterpillars munch on leaves and grow in vegetation while moths and butterflies sip nectar and fly around looking for mates. But what about the fact that most caterpillars are specialists? Why would caterpillars evolve to be picky?

A lucky four-leaf clover.

The brightly colored cloudless sulphur caterpillar!

Luna Moth

A red admiral caterpillar feeds on nettles in Brookside Park!

Why so picky?

To name two examples, monarch caterpillars can only eat milkweed, and red admiral caterpillars will only eat nettles. Wouldn’t it be much more advantageous to be able to eat any kind of plant, or at least a more general group of plants? Not necessarily. Specialist caterpillars seem to have better defenses against predation than generalist caterpillars: monarch caterpillars eat poisonous milkweed plants, and red admiral caterpillars hang out in nettles that sting – most animals will learn to avoid these caterpillars. Scientists also think that specialist caterpillars are better at identifying and choosing plants, and consequently eat more. Because so many caterpillars are specialists, it is imperative to plant as many native plants as possible if you want to help butterflies and moths. It’s surprisingly beneficial to be a picky, squishy caterpillar, but it’s still a dangerous world.

Worm weapons!

Plants can’t supply all necessary defenses – many caterpillars must deploy their own wacky weapons to defend their soft, protein-filled bodies. One tactic is coloration. Caterpillars can be camouflaged to look just like bird poop, or have colorful patterns to warn their predators they are poisonous or bad-tasting. Eastern tiger swallowtail caterpillars look almost exactly like miniature snakes, frightening off birds with their life-like eye spots. These caterpillars also have secret appendages, called osmeteria, that they strike out of their head to mimic a snake’s tongue! Other swallowtail species also have colorful osmeteria they can stick out in conjunction with nasty smells and sometimes irritating secretions (not harmful to humans). Other caterpillars take defense to new lengths: fecal firing.

You read that right. To help hide their smell from parasitic wasps, silver-spotted skipper caterpillars catapult their smelly frass (excrement) 38 body lengths away, a distance equivalent to 228 feet for a six-foot human! Curiouser still, some caterpillars like the walnut sphinx moth can squeak or whistle. The whistle sounds like a bird warning call, causing the hungry bird to drop the caterpillar. But let’s get into some hairier defenses.

A snake-mimicking eastern tiger swallowtail, with its osmeterium acting like a snake’s tongue!

Many caterpillars are hairy enough to make some 1980s bands jealous. Sometimes the fluff just means the caterpillars are cute; other times it means they shouldn’t be touched. Many fuzzy caterpillars can have hairs that break on contact, causing irritation on the finger or mouth that touched them. This doesn’t always affect humans; if you’ve handled woolly bear caterpillars before, you’ve handled these kinds of irritating hairs. Other caterpillars can have more irritating hair, or have specialized hairs that can actually deliver mild venoms. Puss caterpillars get a lot of media attention for the sometimes blistering results they can give to human skin, however there have been no sightings of these caterpillars in Iowa (puss caterpillars grow into a particular species of flannel moth). The buck moth and some slug and saddleback moth caterpillars can cause serious irritation, but sightings and encounters are very rare in central Iowa and symptoms normally do not need medical attention (for specifics on venomous caterpillars, read here). Most fuzzy caterpillars in Iowa are harmless or merely have irritating hairs. Removing hairs with tape, washing the area afterwards, and ice or baking soda paste is the best care for minor rashes from caterpillar hairs.

Pictures: Above, a touch-friendly woolly bear caterpillar. Below, a slug caterpillar that may irritate the skin. While not seen often in Iowa, some slug caterpillars can deliver more of a sting. Besides that, they look SO STRANGE! In nature they look like a spider’s shed exoskeleton, and are well-camoflaged in leaf debris. Read more here!

The last caterpillar defense tactic is one that we hope you aren’t dealing with this Valentine’s Day: manipulation. Some caterpillars can trick animals that are usually predators into being their caretakers! Many gossamer-winged butterflies (a family of butterflies comprised of hairstreaks, blues, coppers, etc.) exude pheromones as larvae that trick ants into thinking the caterpillar is a fellow ant. Some of these dainty blue butterflies use this trick to commit social parasitism! Exactly how they utilize ants varies for each species of this butterfly family; for today we will focus on Edward’s hairstreak, a species of special concern in Iowa. This species of butterfly munches oak leaves as a caterpillar, and utilizes mini shelters created by ants. As a young caterpillar, it stays in the trees. But as it grows older, the Edward’s hairstreak caterpillar eats in trees only during the night; as dawn approaches it drops to the base of the tree to hide in ant-made shelters called byres, which are small piles of thatch created from leaves, sticks, and other forest floor materials. The caterpillars secrete a honeydew as a reward for the shelter and protection the ants provide. This relationship is much more in the spirit of the holiday, giving us a loving mutualism rather than parasitism.

Above, an inchworm on my kale plants this year. Below, a monarch caterpillar that could be harmed by garden pesticides!

From beautiful colors to shooting feces and feeding ants, caterpillars are worthy of love and appreciation! To support this wonderful world of worms, be sure to plant a variety of native plants in your yard, and most importantly do not spray pesticides! Yes, many caterpillars will chew on your garden plant leaves. I suggest allowing a part of your garden to become a “nursery”, a subset of plants that you don’t mind getting eaten by caterpillars. You can “babysit” the caterpillars by moving them off the plants you care about and place them onto the plants in the nursery (using gloves if they are fuzzy). By not spraying pesticides and allowing caterpillars to stay in the garden, you win the fun of watching the caterpillars that ate your dill and carrots turn into black swallowtails! Keeping from spraying pesticides also allows you to enjoy bumble bees visiting your tomato plants and bees sleeping in your flowers. By tolerating the presence of insects and a few munched leaves, you can support an entire little ecosystem with your garden, and witness all the drama the insect world has to offer while pulling weeds and watering plants. Let the backyard garden be your gateway to the curious world of caterpillars!

Visit the following links to dive even deeper into the curious world of caterpillars!

– A list of butterfly/caterpillar host plants: https://henderson.ces.ncsu.edu/2021/05/plants-that-host-butterfly-larvae/

– More information on the importance of caterpillars: https://extension.psu.edu/a-case-for-caterpillars

– A fun read on caterpillars in the US: https://www.newyorker.com/magazine/2023/03/20/the-little-known-world-of-caterpillars

– More on metamorphosis: https://www.scientificamerican.com/article/insect-metamorphosis-evolution/

– More on ant-butterfly relationships: https://sites.tufts.edu/pollinators/2019/07/the-butterflies-who-are-raised-by-ants/

Metrics from the 2023 monitoring season

Metrics from the 2023 monitoring season

Amelia Whitener leads a water monitoring demonstration at a trash cleanup event.

Monitoring a stream once or twice a month is a big commitment, but our locally-led water monitoring program (which started in Story County but has expanded to Hamilton County) has no shortage of committed volunteers!  The following metrics show the continued growth of the program in size and consistency. 

Also, let’s give a shoutout to the people who work behind the scenes to make it happen!  Sara Carmichael of Story County Conservation keeps everyone on track and equipped with supplies.  Heather Wilson of the Izaak Walton League of America helps train volunteers and has been leading up the new Nitrate Watch initiative.  We rely on the IWLA’s  Save Our Streams program for training materials and the Clean Water Hub for data entry.  In addition to volunteer monitoring, Maryann Ryan and her team at the City of Ames Laboratory Services Division process weekly samples from 3 sites and monthly samples from 15 sites.

2022 Season

Volunteers participating

Sites tested at least once

Sites tested at least 20 times

Data sheets entered in the Clean Water Hub

2023 Season

Volunteers participating

Sites tested at least once

Sites tested at least 20 times

Data sheets entered in the Clean Water Hub

In March, Prairie Rivers will release a report detailing the findings.  Here are a few preliminary numbers that give a sense of how 2023 stacks up to the previous year.  

2022 Season

Weeks in Drought

E. coli (geomean) at best site

E. coli (geomean) at worst site

%

"Poor" readings in Clean Water Hub

2023 Season

Weeks in drought

E. coli (geomean) at best site

E. coli (geomean) at worst site

%

"Poor" readings in Clean Water Hub

Drought continues to limit where we have flowing water.  Sometimes, most of the water in a creek is coming from sewage treatment plants, which are able to remove some pollutants but not others.  E. coli bacteria (an indicator of fecal contamination) continues to be high in most waters, likely coming from multiple sources.  Looking at E. coli averages (geometric means) for the 2023 recreation season,  two swimming beaches in the county met the primary contact recreation standard (126 colonies/100mL) but only 1 of 14 streams with enough data to evaluate did, and three exceeded the secondary contact recreation standard (630 colonies/100mL).   Due to restrictive state laws about “credible data”, these sites might appear on a list of “Waters in Need of Further Investigation” but won’t be counted on the 2024 Impaired Waters List.

We continue to work with partners locally and around the state on ways to interpret water quality data and make it more accessible.

Prairie Rivers Wins Grant to Help Pollinators and Farmers

Prairie Rivers Wins Grant to Help Pollinators and Farmers

Prairie Rivers of Iowa has been protecting Iowa’s natural resources for over 20 years. We recently received a grant from the National Fish and Wildlife Foundation to support our work! The grant is awarded through the Monarch Butterfly and Pollinators Conservation Fund. Prairie Rivers of Iowa is one of 18 organizations to receive this grant, including The Nature Conservancy, the Iowa Natural Heritage Foundation, and the Pollinator Partnership.

Helping with Habitat
Prairie Rivers’ project, titled Pollinator Patchwork: Enrolling Private Working Lands into Monarch Butterfly Habitat, focuses on providing technical assistance to farmers and landowners motivated to help pollinators while receiving on-farm benefits as well. Our project, in particular, focuses on women landowners and farm operators, a group that has been historically left out of conversations and under-recruited for beneficial programs for decades. This group is also an un-tapped source for converting low-quality cropland out of production and into beneficial pollinator habitat. To address this issue, Prairie Rivers is creating general and women-specific field days, webinars, and effective outreach materials while partnering with area experts to accomplish these tasks! Our partners include Story County Conservation, Dr. Jean Eells of E Resources Group, area farmer Jim Richardson, Boone and Hamilton County Soil and Water Conservation Districts, and the Story County Water Quality Monitoring Planning Team.

Dr. Jean Eels during a Women Caring for the Land event in 2019.

Dr. Jean Eells is excited to partner with Prairie Rivers of Iowa for this project. Eells received her PhD in Agricultural Education and is highly experienced in effectively creating field days and outreach materials for women:

“This funding will allow us to hold events for landowners that will answer their questions and let them see directly how monarch and pollinator habitats can be created on their acres. I’m especially excited to hold meetings for women landowners where they can get their questions answered in a very friendly forum, whether they are very experienced or just beginning to make space for monarch butterflies.”

Jim Richardson, as a grain farmer and president of the Hamilton County Conservation Board, holds unique insight into farmer attitudes:

“As a farmer, I always like to participate in programs that are a “win-win,” relates Richardson, “I consider Prairie Rivers’ new project to be a “win-win-win.” It’s a win for the landowner who will get maximum revenue off of low-productive ground. It’s a win for the tenant, who will not have to put expensive inputs into marginal land. Lastly, it’s a huge win for our monarchs and all of our pollinators, who will find food sources where they have never been able to before.”

PRI Pollinator Conservation Specialist Jessica Butters

Prairie Rivers of Iowa Pollinator Conservation Specialist Jessica Butters leads this exciting new project. Butters is ready to take action for pollinators and farmers:

“It is exciting to start pollinator-focused projects in rural areas,” Butters states, “Prairie Rivers has started many successful pollinator projects in urban areas. Given that over 85% of Iowa is agricultural land, pollinator conservation on farmland is an enormous piece of the puzzle in supporting monarch butterflies and pollinators. Creating pollinator habitat in agricultural areas will allow us to connect pieces of pollinator habitat together, allowing monarch butterflies and other pollinators to move throughout the state.”

Are you a landowner or farmer interested in adding beneficial pollinator habitat to your land? Don’t hesitate to get in touch with Jessica Butters at jbutters@prrcd.org or call 515-232-0048 for more information!

Can Infrastructure Spending Help Iowa’s Polluted Rivers?

Can Infrastructure Spending Help Iowa’s Polluted Rivers?

The display department for the plans.  If you've read Douglas Adams, you'll appreciate the joke.

“But look, you found the notice didn’t you?”
“Yes,” said Arthur, “yes I did. It was on display in the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying Beware of the Leopard.”

 

– Douglas Adams, The Hitchhiker’s Guide to the Galaxy 

I was reminded of this scene after spending a long day cross-referencing the Raccoon River TMDL (a pollution budget for nitrate and E. coli) with permits and monitoring data for wastewater treatment plants.  In this case, I suspected that polluters were getting away with something, but I’ve had just as much trouble finding information when I wanted to document a success story.

Effluent limits for nitrogen are not strict.  Wastewater treatment plants and meatpacking plants in the Raccoon River watershed routinely discharge treated wastewater with nitrate 4-6x the drinking water standard.  Why is this allowed?  The 2008 Raccoon River TMDL capped pollution from point sources at the existing level, rather than calling for reductions.  Due to limited data, the wasteload allocations were an over-estimate, assuming maximum flow and no removal during treatment. 

Water Treatment

That’s all above board, but someone else at the DNR went a step further.  Wasteload allocations in the TMDL were further inflated by a factor of two or three to arrive at effluent limits in the permits, using a procedure justified in an obscure interdepartmental memo.  The limits are expressed as total Kjeldahl nitrogen, even though the authors of the TMDL made it clear that other forms of nitrogen are readily converted to nitrate during treatment and in the river.   In short, the limits in the permit allow more nitrogen to be discharged than normally comes in with the raw sewage!

For example:

  • The Storm Lake sewage treatment plant has an effluent limit of 2,052 lbs/day total Kjeldahl nitrogen (30-day avg).  Total Kjeldahl nitrogen in the raw sewage is around 1000 lbs/day.
  • The Tyson meatpacking plant in Storm Lake has an effluent limit of 6,194 lbs/day total Kjeldahl nitrogen (30-day avg).  Total Kjeldahl nitrogen in the raw influent is around 4,000 lbs/day.
  • I also checked a permit affected by the (now withdrawn) Cedar River TMDL.  Same story.  The Cedar Falls sewage treatment plant has an effluent limit of 1,303 lbs/day total nitrogen (30-day avg).  Average total nitrogen in the raw sewage is between 1000-1500 lbs/day.
  • Confused about the units?  That may be deliberate.  Total Kjeldahl nitrogen includes ammonia and nitrogen in organic matter.  Nitrogen in raw sewage is mostly in these forms, which need to converted to nitrate or removed with the sludge in order to meet other limits and avoid killing fish.  Nitrogen in treated effluent is mostly in the form of nitrate.  At the Tyson plant, the effluent leaving the plant has around 78 mg/L nitrate, versus 4 mg/L TKN, but figuring that out required several calculations.  At smaller plants, the data to calculate nitrate pollution isn’t even collected.

As part of the Iowa Nutrient Reduction Strategy, large point source polluters are supposed to evaluate the feasibility of reducing nitrate to 10 mg/L, and phosphorus to 1 mg/L.  Tyson did a feasibility study for phosphorus removal, and is now adding new treatment to its Storm Lake plant.  However, it is not required to evaluate or implement further nitrogen reduction, “because it is already subject to a technology-based limit from the ELG.”  This federal Effluent Limitation Guideline was challenged in court by environmental groups this year, and is now being revised by the EPA.  It allows meatpacking plants to discharge a daily maximum of 194 mg/L total nitrogen!

Fortunately, all this creative permitting has little impact on the cost and safety of drinking water in the Des Moines metro.  According to research in the TMDL, point sources only account for about 10% of the nitrogen load, on days when nitrate in the Raccoon River exceeds the drinking water standard.  However, the figure is much higher (30%) for the North Raccoon River.  I started looking at permits and effluent monitoring because I was trying to explain some unusual data from nitrate sensors, brought to my attention by friends with the Raccoon River Watershed Association.  During a fall with very little rain (less than 0.04 inches in November at Storm Lake), nitrate in the North Raccoon River near Sac City remained very high (8 to 11 mg/L).  The two largest point sources upstream of that site can easily account for half the nitrogen load during that period.

Figure from Raccoon River TMDL

I was glad to be able to solve a mystery, and hope that this investigation can lead to some tools and teaching materials to help others identify when and where point sources could be influencing rivers.   The load-duration curves in the 200-page Raccoon River TMDL are very good, but some people might benefit from something simpler, like this table.  In general, the bigger the facility, the smaller the river, and the drier the weather, the more point sources of pollution can influence water quality, and the more wastewater treatment projects can make a difference. 

Spreadsheet for estimating impact of wastewater.

I made this table to estimate how biological nutrient removal in Nevada and Oskaloosa (about 1 MGD each) could improve water quality in the South Skunk River (about 1000 cfs on average near Oskaloosa, but there could be greater benefit in tributaries, or when rivers are lower).

Dan Haug standing by Raccoon River

In this work, I’m supported by partners around the state and a grant from the Water Foundation.  The project (Movement Infrastructure for Clean Water in Iowa) focuses on building connections and shared tools around water monitoring, and will continue through this spring and summer.  The funders’ interest is in helping the environmental movement make the most of the “once-in-generation opportunity” presented by the Inflation Reduction Act and the Bipartisan Infrastructure Law.  This fiscal year, the Bipartisan Infrastructure Law is adding $28 million to Iowa’s Clean Water State Revolving Fund, which provides low-interest loans to communities to replace aging sewer systems and treatment plants.  Can that infrastructure spending help Iowa’s polluted rivers?  We won’t know for sure without better use of water quality data, and greater transparency in state government.