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 In areas called “unsewered communities,” outdated or poorly functioning septic tanks still allow untreated wastewater into our waters.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.
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”.
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.
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!
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.
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.
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.
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.
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.
The Iowa Department of Natural Resources is seeking public comment on the newly released draft impaired waters list. Prairie Rivers of Iowa will be recommending that Squaw Creek and East Indian Creek be added to “Waters in Need of Further Investigation.” We’ll also take this opportunity to try to demystify a topic that can be confusing, using examples from the South Skunk River watershed.
Every two years, the DNR is required to assess the available data to determine whether Iowa’s lakes, rivers, and wetlands are meeting their designated uses. About half the rivers, and a bit more of the lakes have enough data to assess. Since new waters are considered each cycle, the length of the impaired waters list doesn’t really tell us whether water quality is getting worse. Since nutrients aren’t considered for most uses and the data used for the 2018 assessment is from 2014-2016, it doesn’t tell us whether the Iowa Nutrient Reduction Strategy is working. What it tells us is the extent and severity of local water quality problems that have been officially vetted.
A river segment, lake, or reservoir that gets use by paddlers or where children play would be designated A1 (primary contact recreation use) or A3 (children’s recreational use). To determine whether the water quality is good enough to support these uses, the DNR compares E. coli bacteria to the state standard (a geometric mean of 126 organisms per 100mL). If the stream consistently exceeds the standard, that means there could be enough human or animal waste in the water to pose a health risk to anyone that swallowed some–a child splashing in the creek, or a paddler who tipped their canoe might get exposed to a waterborne illness.
Fully supporting: None of the lakes or rivers in our watershed appeared on this list
Not assessed: This includes Squaw Creek, East Indian Creek, McFarland Pond, and many others.
Wait a minute, Squaw Creek and East Indian Creek? Didn’t we work with City of Ames and Story County Conservation to collect three years of monthly E. coli samples, starting during the assessment period? Wasn’t the 2016 geometric mean ten times higher than the standard? Yes, but DNR never approved a quality assurance plan, so under Iowa’s Credible Data Law, they can’t use our data. However, we will write to DNR to recommend that they add those streams to Iowa’s list of waters in need of further investigation (WINOFI). We’re aware that bacteria cleanup plans for large rivers are difficult to do and are a low priority for the department, but we want people to be more aware of the health risks.
Aquatic Life Uses
The South Skunk River is a warm water stream with a smallmouth bass fishery, so is designated B(WW-1). Most of its perennial tributaries don’t have enough water or habitat for gamefish so are designated* B(WW-2) for other aquatic life. Fish kill reports, biological monitoring of fish and invertebrates, and monitoring of dissolved oxygen and some toxic chemicals are used to assess whether water quality is good enough to support these uses.
*Adding to the confusion, smaller creeks are given a presumptive A1 B(WW-1) designation until a Use Attainability Assessment proves otherwise. This change supposedly gives them extra protection, but I don’t see how that would work in practice.
Waters in Need of Further Investigation:Onion Creek, Worrell Creek, and College Creek had some low scores for fish or invertebrates, but DNR hasn’t worked out an appropriate threshold for these headwater creeks. The lower part of Ballard Creek was removed from the impaired waters list and placed in this category when DNR discovered an error in the previous assessment.
Not Assessed: This includes several segments of the South Skunk River, Dye Creek, Clear Creek, Keigley Branch, West Indian Creek and many others.
If a river was added to the impaired waters list, don’t assume it’s gotten dirtier. Maybe it was always polluted and we hadn’t bothered to look. And by the same token, if a river is not on the impaired waters list, don’t assume it’s clean.
This post is part of a series for 2019 Watershed Awareness Month, comparing water quality in a pair of local creeks to learn how land and people influence water.
On May 20, the Skunk River Paddlers launched their canoes and kayaks on Squaw Creek at 100th Street in Hamilton County and paddled down to 140th St in Boone County. The recent rains made it a fast ride!
However, the rain also washed a lot of sediment and quite likely some land-applied manure into the stream. I collected a water sample just before I took this photo and had a lab test it for E. coli bacteria, an indicator of fecal contamination: 2,390 CFU (Colony Forming Units)/100mL. That’s 10 times the primary contact standard for a single sample (235 CFU/100mL) and just shy of the secondary contact standard (2880 CFU/100mL).
Later that day, I collected a sample from Brookside Park in Ames with the help of my son. The lab results came back at 12,800 CFU/100mL, well above the secondary contact standard!
I don’t want to discourage people from recreating in Squaw Creek but I think a safety reminder is necessary:
Squaw Creek has consistent fecal contamination that could pose a risk of acquiring a waterborne illness. The risk is higher after heavy rains when the water is muddy—consider wearing waterproof boots when wading under these conditions. If you come into contact with the water, wash your hands or apply hand sanitizer before eating and take precautions to avoid getting river water in your mouth or on an open cut.
The numbers above are high, but not unprecedented. Over the past three years, City of Ames staff have been tracking E. coli, nitrogen, and phosphorus in Squaw Creek at Lincoln Way and we’ve been sharing the data on our website. 46 out of 48 samples exceeded the primary contact standard for E. coli!
Yes. Yes there is.
The pattern is also not unusual. In our Snapshots, we see that Squaw Creek usually exceeds the standard by the time it reaches Ames and picks up additional fecal contamination by the time it reaches Duff Ave.
The Ames City Council, Public Works Department, and Water & Pollution Control Department are concerned by the data and committed to helping find and address sources of contamination within city limits. The City of Ames spends $3.5 million a year repairing and upgrading its sanitary sewers. However, the data point to multiple sources of E. coli that will make this a difficult problem to solve. In addition to sewer leaks, we probably have some failing septic systems in the upper watershed, cattle in the stream, land-applied manure carried by runoff, pet waste, and wildlife. E. coli can also persist for a while in the sediment, and gets stirred up again after a rain.
In June, I went back to Brookside Park to demonstrate some water quality testing for kids enrolled in the Community Academy summer program. In addition to exploring nature and food systems, the kids have been hard at work improving removing invasive species, planting pollinator gardens, improving trails, and coming up with interpretive signs for Brookside Park. I’m pleased to see that one of the signs is about water quality, including a reminder to wash your hands after entering the creek, and tips on how to reduce pollution. Look for the signs to go up later this summer.
My son Leif shares a draft of a water quality sign at the Community Academy’s open house