Later this month, we are releasing a report with the findings from Story County’s 2021 water monitoring season.
In some ways, 2021 was an unlucky year to launch a water quality monitoring program. Story County was in drought conditions for much of the year, and smaller streams were frequently dry when we did our monitoring routes.
In some ways, it was an ideal year to launch a monitoring program, because weather always has an influence of water quality and the challenging conditions in 2021 forced us to better account for it.
For the report, this means asking a simple question: “was there enough water to float a canoe on the day you sampled?”
When the South Skunk River is too low for paddling:
Not much water (and not much nitrogen and phosphorus) reaches the Gulf
“Hot spots” for nitrogen and phosphorus are below wastewater treatment plants
When the South Skunk River rises high enough for paddling:
“Hot spots” for nitrogen are in the Headwaters of the South Skunk River Watershed upstream of Ames, as shown in the graph
E. coli levels upstream of Ames (and Ioway Creek) get worse but still meet the standard
E. coli levels downstream of Ames (and Ioway Creek) get better, but still exceed the standard
If I had less curiosity and more sense, I would have written a short report: “great job everyone! We collected a lot of data. Here it is! It’s possible that drought had an influence on water quality.” This was more work, but I hope you get more out of it.
Last month marked the departure of our pollinator and native plant expert David Stein as he heads back to work in his home state, our neighbors to the north, Minnesota. We are missing his passion and work ethic, but our Watersheds and Wildlife program continues as always and efforts are well underway to find his replacement.
David contributed to a large part of Prairie Rivers of Iowa’s continued efforts to impact public awareness and implementation of conservation practices to create native plant, pollinator and wildlife habitat to help improve soil and water quality while protecting the endangered rusty patched bumble bee and other species of greatest conservation need in Iowa. He was instrumental in creating a native seed bank and the development of many acres of habitat.
I recently visited with David as he reflected upon his work here at Prairie Rivers and his hopes for the future state of native habitat and pollinators in Iowa.
What do you feel was your biggest accomplishment while working at PRI? There are a lot! I think both completing the National Fish and Wildlife Foundation grant and setting the stage for PRI’s next series of habitat/conservation projects was probably the biggest accomplishment during my time here. On top of that, raising awareness of pollinator issues and educating interested landowners on how to install habitat was also a major highlight of my work. Re-discovering the rusty patched bumble bee, and mapping out new sightings was definitely a high point for me too.
How do you feel the health of native habitat and pollinators is currently in Iowa? What progress has been made? Where do we need to go from here? We have a long way to go, but I think we’re in a better place than we were a few years ago. Our outreach and education efforts, especially our work with counties, cities and landowners have definitely gotten the ball rolling, but a more hands-on-deck is always better. A coordinated conservation and restoration effort between non-profits, municipalities, farmers, landowners, homeowners, businesses, and interested individuals is really the best and only way forward to reverse pollinator and habitat decline.
What’s next for you? Next, I’ll be working up at the Minnesota Department of Natural Resources in St. Paul. I’ll be able to be involved in habitat projects all throughout the state and be able to meet with a bunch of different stakeholders that are doing some amazing restoration work.
How has working at PRI enriched your professional life? Working here has definitely enriched my professional life. I’ve been able to improve my own knowledge and passion regarding pollinator and wildlife conservation and directly apply it in real-time. I’ve also been able to connect and network with so many amazing stakeholders and partners from a variety of backgrounds. I know that I’ll be able to use these skills and lessons throughout my professional life moving forward.
Water quality in the South Skunk River is still poor but has gotten better in the last five years. One reason for improvement is a new disinfection system at the Ames wastewater treatment plant.
Dr. Chris Jones recently shared a water quality index he developed for Iowa rivers, combining five important water quality metrics. Of the 45 sites in the Iowa DNR’s ambient monitoring network, the South Skunk River near Cambridge scored “poor” and ranked 34th overall. This site also has the 3rd highest phosphorus and the 5th highest E. coli levels.
A follow-up article looked whether the current (2016-2020) water quality index has changed from previous decades. Most rivers have stayed the same or gotten worse, but the South Skunk had a better score. Three of the metrics (total phosphorus, total nitrogen, and E. coli bacteria) improved, while one (turbidity, a measure of sediment in the water) got worse.
Phosphorus and muddy water usually go together, so this odd pattern demanded some explanation. I did my own analysis of the data, curious if the changes were happening under drier conditions (when wastewater has a bigger influence), wetter conditions (when agricultural runoff has a bigger influence) or both.
See last week’s post for an explanation of the flow categories I’m using. I use a lot of boxplots, which show both the central tendency and the spread of the data. The lower end, middle, and upper ends of the box are the 25th, 50th (median) and 75th percentiles. The “whiskers” show the maximum and minimum, unless they’re really far out there, in which case the “outliers” represented by dots. Water quality data never fits a bell curve, so lopsided boxes and outliers are to be expected.
It turns out that the river didn’t get any muddier (it got less muddy) when you compare wet conditions to wet conditions and mid-range conditions to mid-range conditions.
It’s just that the past five years were a little wetter and so a larger share (43% vs 29%) of the samples were collected during wet conditions when the river was moving swiftly and carrying more sediment. A smaller share (25% vs 42%) of the samples were collected during dry and low-flow conditions when the water is usually clear. That made the average sediment concentration increase.
Weather also can explain trends in phosphorus. In the past five years, a smaller share of the samples were collected during dry and low-flow conditions when phosphorus concentrations are especially high. That made the average phosphorus concentration decrease.
Why is phosphorus so high when it’s dry? The monitoring site in question is just below the outfall of Ames Water Pollution Control Facility on 280th St, about 4 miles north of Cambridge. This facility discharges over 6 million gallons a day of treated wastewater. When conditions are dry, the effluent is less diluted, and so phosphorus in the stream approaches phosphorus levels in the effluent (which averages 3.8 mg/L), as shown in the graph below. This year we’ve also monitored West Indian Creek below the Nevada wastewater treatment plant and have seen the same pattern.
Wastewater treatment plants are regulated to minimize the impact on receiving waters and the Ames WPC Facility has one of the best compliance records in the nation. However, while the treatment process is very good at removing ammonia, solids, and oxygen-depleting substances, the process is not that effective for removing nutrients.
The Iowa Nutrient Reduction Strategy is not voluntary for wastewater treatment plants. The Ames Water and Pollution Control Department commissioned a feasibility study as a condition of its permit, which determined that the facility could achieve a 67% reduction in total nitrogen and a 75% reduction in total phosphorus by replacing its trickling filters with an activated sludge treatment system. This new system will be phased in as the filters reach the end of their useful life (starting in 2027) and will cost $39.6 million.
In the last five years we have not seen any reduction in phosphorus during dry and low-flow conditions when wastewater treatment systems have the biggest influence. However, there was a reduction in phosphorus* under mid-range and high flow conditions! This is really interesting–I’ll have to look at some other data sets to see whether it holds up and whether we can link it to conservation practices in the watershed.
For E. coli, we see improvement across all conditions, with the largest improvement during low-flow conditions* when wastewater has the biggest influence.
The effluent discharged to the river has gotten a lot cleaner since the Ames Water Pollution Control Facility built $2 million disinfection system using ultra-violet (UV) light. The system was completed in March of 2015. During the recreational season (March 15-Nov 15), treated effluent passes through two banks of lights that kill microbes. Prior to this, some E. coli and pathogens could make it through the system and end up in the river. Chlorination, a good solution for disinfecting drinking water and swimming pools, is not ideal for wastewater because it can harm fish.
Kris Evans, an environmental engineer for the City of Ames and the project manager, said this about the system:
“By using UV we continue to be “chemical free” for treatment of the wastewater and it’s much safer for staff since they don’t have to chlorinate and dechlorinate. When flow is low at the plant, we are able to lower the intensity of the bulbs to save energy and still meet permit limits; as flow increases so does the UV light intensity. The City started design of the UV system before it was mandated in a permit; we knew it was coming, but wanted to be proactive in the treatment of water, making it safer for those who recreated in the river. It was also the first project the department funded through an State Revolving Fund (SRF) loan.”
We still see high E. coli levels in other streams that receive effluent, but smaller wastewater treatment systems are also making the switch to comply with new permit requirements. In Story County, Gilbert added a UV disinfection system in 2019, the Squaw Valley HOA completed theirs in 2020, and Nevada will build a new wastewater treatment plant in 2022 that includes UV disinfection.
* I’ve written before about the challenges of detecting water quality trends. I’m pleased to report that two of the trends discussed here (a reduction in phosphorus at mid-range flow conditions, and a reduction in E. coli in dry and low-flow conditions) were statistically significant at 90% confidence level, using a test of the difference between medians. The approach employed here (sorting by flow conditions) may be a good way to control for weather and reach more reliable conclusions. It’s exciting to have some good news that holds up to further analysis!
During a long period of dry weather like we’ve been having, some rivers are cleaner than usual, some are just as dirty. It depends on which pollutants we’re talking about, and where they’re coming from. Understanding which is which can help us diagnose problems and prioritize solutions.
The South Skunk River upstream of Ioway Creek is at its cleanest (clear and with low E. coli) when the weather has been been dry. If you’re going to let your kids splash in the water, go here.
Ioway Creek is less muddy but not any cleaner (high E. coli levels) when the weather has been dry and water levels are low. Lots of algae this summer, too.
For example, if a stream has high E. coli levels when water levels are low, that’s probably not because of manure carried in agricultural runoff… because when the soils are this dry, what little rain we get soaks in and doesn’t run off. Under dry conditions, more likely sources are things like cows in the stream or a septic system illegally hooked up to a drainage tile(yes, we’ve seen this happen). We’ll discuss wastewater treatment plants next time.
The figure below, from the cleanup plan (TMDL) for the Iowa River basin, matches E. coli sources to flow conditions. These kind of graphs take some explanation, but it’s a really helpful framework for making sense of water quality data.
The categories on the x-axis are based on percentiles. “High flows” are the top 10% of daily average flows in a given record. Looking at the last 20 years of data from the USGS gage on the W. Riverside Rd. in Ames (Sleepy Hollow Access), that corresponds to at least 5,453 cubic feet per second of water–probably too fast for safe paddling. “Dry conditions” are the 90th to 60th percentile, corresponding to between 10 and 70 cfs of water–definitely not enough water for paddling.
When graphing stream flow or E. coli, we often use a logarithmic scale, where each major tick mark is a ten-fold increase. Since flow can range from 0 to 10,000 cfs in a river like the South Skunk, it’s the only way you can read it.
Boxplots are helpful for seeing summarizing the data. The bottom, middle line, and top of the box represent the 25th, 50th, and 75th percentiles.
In the upper stretch of the South Skunk River, measured at Sleepy Hollow Access, if you take your canoe out during mid-range conditions, it’s more likely than not that E. coli will meet the primary contact recreation standard (the center line on the box, the median, is below the orange line). It’s even cleaner in dry conditions. Paddlers would benefit from attention to E. coli sources that show up under “wet conditions” such as manure carried in agricultural runoff.
In Ioway Creek at Lincoln Way, E. coli is likely to exceed the secondary contact standard under mid-range conditions, and it’s usually exceeds the primary contact standard across all conditions. Kids play in this creek, and they would benefit from some attention to sources of bacteria that show up under “dry conditions”: this could include inspecting septic systems and working with cattle producers to fence cows out of streams.
“If it never rained, we’d have great water quality in Iowa.”
-Jim Richardson
“If it never rained, we’d have great water quality in Iowa,” joked a volunteer at our May 15 water quality snapshot. 15 of us spent the morning testing Ioway Creek and its tributaries in Boone, Hamilton, and Story County and were marveling at the low nitrate levels and crystal clear water at the majority of our sites.
I wish more creeks in central Iowa were like this spot in Boone County. Cows fenced out the creek, a CREP wetland upstream keeping nitrate levels low, orioles and a kingfisher flitting between the trees.
Well, we’ve had some much-needed rain in the week since, and water quality has gone from good to bad. I’ve written before about “weather whiplash” that explains some of the big swings in nitrate over the past decade and here’s an early hint of it. Here’s data from a nitrate sensor in Ioway Creek installed by IIHR-Hydroscience and Engineering. A five-fold increase in nitrate concentrations in just one week! The water has gone back down but the nitrate levels are still above the drinking water standard.
And here’s some water samples I collected on Friday May 21. No, that’s not my coffee thermos, that’s some of the world’s best top soil washing down the Skunk River!
Four samples collected May 21, after a 3/4 inch rain
That’s not to blame the weather. It does rain in Iowa and if your farming practices let a plume of topsoil, manure, or fertilizer wash off the field every time that happens, you’re doing it wrong! Some farmers are doing it right (I saw some cover crops this spring near Nevada and lots driving on I-80) but not enough, especially in the Ioway and South Skunk River watersheds.
Water quality monitoring has been top of mind for Prairie Rivers of Iowa lately and I see an challenge and an opportunity. It’s a challenge to interpret data and track our progress when one good rain can cause water quality to go from clear to coffee-colored overnight! There’s an opportunity to be more strategic about how and where we test, so we notice and communicate more eye-opening moments like this one, and hopefully persuade a few more people to protect soil and water.
Update: June has been abnormally dry and Hamilton, Boone and Story County are experience severe drought. Droughts stress is impacting crops and smaller streams are drying up.
