Before state wastewater standards went into effect in the 1960s, raw sewage could flow directly to a stream without treatment. Despite the standards, this continues in many areas today. In areas called “unsewered communities,” outdated or poorly functioning septic tanks still allow untreated wastewater into our waters. The Iowa DNR works with these communities to find funding sources and alternative treatment systems and to allow adequate time to upgrade the systems.
The Governor has announced that additional funding through the infrastructure bill that will be available to help unsewered communities upgrade their systems. Could this make a big difference for water quality in Iowa? Statewide, I’m not sure, but I’ve taken a closer look at the Iowa River Basin upstream of Marshalltown, where we know of 11 unsewered communities. Based on my first look at the data, it appears that these communities have little influence on E. coli in the Iowa River itself, but could make a difference for water quality in tributary streams like Beaver Creek in Hardin County.
There are 11 unsewered communities in the upper part of the Iowa River Basin, marked here with yellow circles with an X.
A Water Quality Improvement Plan for E. coli bacteria in the Iowa River Basin was released by Iowa DNR in 2017. As required by the Clean Water Act, these kinds of plans include a Total Maximum Daily Load (TMDL) of pollutants that a water body could handle and still meet water quality standards. Author James Hallmark compares this pollution budget to a family budget: regulated point sources are your fixed bills, non-point sources are your variable expenses, and the margin of safety is your emergency fund. I like this analogy and would add that without some understanding of where your discretionary spending is going, and a realistic strategy to reign it in, you’re probably not going to achieve your goals.
The Water Quality Improvement Plan includes a comprehensive list of E. coli sources but doesn’t single any of them out as being particularly important. It includes a list of potential solutions, but it doesn’t identify which of those would make the most difference. That’s a job for a Watershed Management Plan written with stakeholder input, apparently. However, the document is chock-full of load-duration curves, which I wrote about previously. We can use the information in these charts and tables to take the next step and begin to narrow down where and when the pollution is most serious!
In this article, I won’t pay much attention to “High Flows” and “Low Flows” because there wouldn’t be much recreational use under these conditions. I also don’t look at “mid-range” flows because there’s a bigger mix of sources influencing water quality in these conditions. A closer look at the other two categories is revealing.
If houses are discharging raw sewage directly into a stream, we’d expect to see the highest E. coli concentrations when the stream is running lower than normal, and there’s less dilution. This is indeed what we see in Beaver Creek in Hardin County, which is downstream from the unsewered community of Owasa. Beaver Creek would need a 79% reduction in E. coli load to meet the primary contact recreation standard during “Dry Conditions” and a 38% reduction during “Wet Conditions”.
If not fully treated, sewage could be a major contributor to E. coli in some tributaries of the Iowa River.
Treated sewage also has the biggest influence when streams are lower than usual. The upper reaches of the South Fork receive effluent from the small towns of Williams and Alden, which have waste stabilization lagoons. It’s likely that some bacteria makes it through the treatment process, and this would explain why E. coli is higher during “Dry Conditions” (needing a 73% reduction) than during “Wet Conditions” (needing a 30% reduction). When their permits come up for renewal, Iowa DNR could require a UV disinfection system to ensure that E. coli in effluent is no greater than 126 colonies/100mL.
The blue line is the wasteload allocation–the regulated part of the pollution budget. Even with the best available treatment, wastewater from two towns has a big influence on the South Fork during dry conditions.
In a watershed with few people and many hogs, we’d expect to see the highest E. coli concentrations when the streams are running high and runoff from fields that receive manure application is more likely. This is indeed what we see in Tipton Creek in Hardin County, a watershed containing 47(!) CAFOs, but the levels are not especially high compared to other sites in the Iowa River basin. The recreation standard is met during “Dry Conditions” and would need a 36% reduction during “Wet Conditions.” Handled correctly (applied to flat ground at the right time, and preferably incorporated into the soil), manure and the microbes it contains can be kept out of streams. Preventing loss of the nutrients in manure is a more difficult challenge—nitrate concentrations in Tipton Creek often exceed 20 mg/L!
Despite there being a lot of hogs in the Tipton Creek watershed, E. coli levels are not especially high, relative to downstream locations.
It’s not clear to me whether primary contact recreational use of these streams is a relevant or attainable goal, or whether we should be calibrating our level of concern to the secondary contact recreation criteria. Unless there’s a permit holder affected, IDNR doesn’t investigate whether there’s enough water for kayaking in Tipton Creek, or whether children play in Beaver Creek, so the designated use is presumptive and tells me nothing.
E. coli and recreation on the Iowa River is not as big a concern at Crystal Lake as it is at Steamboat Rock. Photo Credits: Ryan Adams, photojournalist
To protect fishing, paddling, and children’s play on the Iowa River itself, where and when should we focus? The Iowa River at Marshalltown needs a 60% reduction in bacteria load to meet the recreation standard during “Wet Conditions” (10-40% flow exceedance). However, it actually meets the primary contact recreation standard during “Dry Conditions” (60-90% flow exceedance). Focusing on unsewered communities in the watershed would NOT be an effective way to address this impairment.
Beaver Creek (left) has worse E. coli when it’s dry. The Iowa River near Marshalltown (right) has worse E. coli when it’s wet. If the green line is above the red line, that indicates that the E. coli geometric mean for that range of flows exceeds the standard.
Galls Creek in Hancock County has some of the worst E. coli levels measured in the basin, and would have a larger per-acre benefit to the Iowa River if standards could be met. Galls Creek has no unsewered communities but at least 20 farmsteads located along the creek that could have issues with septic systems overflowing under wet weather. The watershed has little woodland and no pasture, so land application of manure from the several CAFOs in the watershed would be most likely animal source of E. coli.
Table by Prairie Rivers of Iowa, using information from the Water Quality Improvement Plan for the Iowa River Basin
This is just a partial review of one of three HUC8s in the Iowa River Basin. There is much more to learn from further discussion with people who know the area well, or from on-site investigation. However, I hope I’ve demonstrated how we might squeeze some more insight out of the data we have, in order to make smart investments in water quality.
Thanks to the 15 volunteers who helped to catch benthic macroinvertebrates (bugs) and test water quality over the weekend!
Volunteers capture benthic macroinvertebrates with a kick net, one of two methods we tried.
Ioway Creek “Snapshots” in May and October are a tradition going back to 2006. Volunteers test water quality at many locations on the same day to get a better picture of what’s going on in the watershed. Since the IOWATER program ended, Prairie Rivers of Iowa has gathered supplies and planned events to keep the tradition going, but this year there was just one little snag: there was barely any water in Ioway Creek or its tributaries!
For most of this fall, our usual gathering place at Brookside Park has looked more like the photo on the left.
Not a problem. The South Skunk River still had flowing water, and this was as good an opportunity as any to survey benthic macroinvertebrates (aquatic bugs), an indicator of water quality and habitat quality in rivers. We were helped in this task by Susan Heathcote, a trainer with the Izaak Walton League’s Save Our Streams program. If you’d like to become certified and missed out on this opportunity to complete the field portion of your training, keep an eye out for more training events with Susan in early spring.
Photo credit: Rick Dietz. Volunteers pick invertebrates off rocks and leaves and sort them in ice cube trays.
In addition to crawfish and dragonflies (always a hit with kids), we found a variety of smaller critters, including sensitive mayflies and stoneflies. Overall, the invertebrate community in the South Skunk River was “good.” In contrast, another stream we surveyed this week (West Indian Creek south of Nevada) had a “poor” score with mostly net-spinning caddisflies. We’ll discuss some possible reasons for this difference at a webinar on November 2nd.
Another option for when streams are dry is to spend some time interpreting the data we have. Following some water quality testing in the Skunk River, I gave a presentation to put those measurements into context. I think the data feels more relevant when you’re at the water’s edge and have just gone through the process of collecting it! If you prefer to do your learning somewhere warm and comfortable, we’ll be covering similar information at a webinar on November 2nd.
This fall, nitrate is zero in most streams that have any water, but over the past 15 years we’ve been able to see which tributaries have the highest and lowest levels.
Another hitch. Thunderstorms were forecast for Sunday! We changed the date to Saturday and are glad we did; the weather was beautiful. This also gave us the opportunity to set up equipment so we could capture water samples from the big rain on Sunday. Three volunteers helped me retrieve a dozen samples on Monday. The samples will be tested for E. coli bacteria and optical brighteners, which may help us find and fix septic and sewer leaks.
Ryan checks a crest stage recorder (a low tech tool for seeing how high the water got) and puts a fresh bottle in a storm sampler.
Many thanks to all who participated. We hope to see you at the next watershed snapshot in May, and hope the water levels will be back to normal!
You may have seen a “Swimming Not Recommended” sign at an Iowa lake this summer. In order to prevent those signs from going up, the first step is often to find the watershed or “beach shed.” That may sound like the place you go to change into your swimming suit or store your boat, but in this case we mean the land area that drains to and influences a given body of water.
For example, while Hickory Grove Lake in Story County is only 100 acres, the phosphorus that stimulates algae blooms could be washing into the lake from over 4000 acres in its watershed. Farmers and homeowners in the watershed have been working since 2008 to install conservation practices and fix up septic systems, with the help of Story Soil and Water Conservation District and other partners. When the rains come and water refills the restored lake, these efforts will ensure that the lake doesn’t refill with algae.
Water quality solutions can get a little smaller and more manageable if we can focus in on a problem area with a smaller watershed. As part of a water quality improvement plan (TMDL) for beaches, the Iowa DNR has done detailed studies of Hickory Grove Lake and five other lakes. They found that in all cases, fecal bacteria (the other cause of beach closures) were higher in the wet sand than in the water, higher at the shoreline than the deeper parts of the swimming area, and lowest outside the swimming area. It means that we can focus on just the 2.8 acres that drain directly to the beach at Hickory Grove (the “beach shed”, as the DNR put it) rather than in the entire lake and its watershed. Solutions for this beach and the other five include regular grooming of the sand, making the shoreline less attractive for geese, and redirecting or treating polluted runoff from parking lots and picnic areas.
But if the water quality problems are big enough (like the dead zone in the Gulf of Mexico) then our solutions need to get bigger. All Iowa is part of the 1,151,000 square mile Mississippi River watershed, so all Iowans can do their part to keep nitrogen and phosphorus from washing downstream.
I got a good look at a cyanobacteria “bloom” over Labor Day weekend, at a lake in Wisconsin. Cyanobacteria can produce toxins, and this proliferation of green gunk had done so earlier in the month, causing a large number of fish to go belly up. Cyanobacteria toxins can also be dangerous for people and dogs.
There were warning signs posted but they were wordy and left some doubt about whether it was okay to go in the water. Some kayakers were ignoring them. This has been an issue in Iowa as well. The Iowa Environmental Council is working with Iowa DNR to make the warning signs simpler and more visible. The Environmental Working Group recommends that midwestern states do more frequent testing for microcystins, the most worrisome class of cyanobacteria toxins. I support these steps, but I also think it’s important to let the public know what to look for, as its not always possible to run tests and post warnings in a timely manner. How about this rule of thumb, illustrated in the graphic above? If it looks like paint, stay out!
Not every cyanobacteria bloom can be so easily identified, and not all cyanobacteria produce toxins, but enough of the toxin-producing species do look like spilled paint or “pea soup,” that it seems like a good starting point.
When I first arrived at the lake, it was streaks of green and brown in the water, like the rinse station for a child’s art project. The next day, more had been blown to our side of the lake and it formed a thick surface scum with bubbles, like latex paint left out for too long, and had a nasty smell. The color was a bright green mixed with brown but cyanobacteria blooms can also be bluish green, blue, brown, or red.
Some of the harmless green things more commonly growing in lakes, streams, and ponds look completely different, as pictured above.
Duckweed looks like confetti scattered on the water surface. There’s a few different species ranging from dots (the 1 cm Spirodela) to specks (the 2 mm Wolffia). They are large enough you see the individual round leaves with the naked eye, and they sometimes have trailing roots. Surprisingly, it’s actually a flowering plant related to peace lillies, with tiny, wind-pollinated flowers. As the name implies, they are an important food source for waterfowl.
Green algae are a huge assortment of plant relatives, some single-celled and microscopic (until there are enough to turn the water green), some joining together into spheres, nets, or filaments. Filamentous green algae look like slimy hair when they grow on rocks, and like drain clogs when they are dislodged and float on the surface or wash up on beaches.
And then there’s a variety of aquatic plants (pondweeds, coontail, and others) that can be found rooted to the bottom. While dense “weeds” can be a nuisance for motor-boaters, a plant-dominated lake is better for fish than an algae-dominated lake, or one with nowhere to hide and nothing to eat.
If the lake looks like paint, stay out! Experts, can I say that? It’s an over-simplification, but not everyone has the patience to read a more complicated message, or the good sense to take it seriously.
For more on harmful algae blooms and how to keep yourself and and your dog safe, the Iowa Public Health Department has some good resources.
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!
