Water quality results for 2023 in Story County

Water quality results for 2023 in Story County

Our 2023 Annual Report is now available with results of both volunteer and lab testing of water quality in lakes and streams in Story County.  The 56-page report can be navigating by clicking on headings in the table of contents or by using the “Bookmarks” feature in your PDF reader.  Below are some of the key findings.

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

The volunteer program continues to grow and improve in consistency.

  • 49 volunteers entered 969 data sheets into the Clean Water Hub this season.
  • Many volunteers are monitoring their assigned site biweekly, with 20 sites sampled at least 20 times.
Mayfly larvae (nymph) under magnifying glass

This was a challenging year for fish and aquatic insects.

  • In addition to many creeks drying up, volunteers observed dissolved oxygen drop to low levels at 53% of stream sites. 
  • Biological surveys showed mixed results, with some streams scoring poorly but sensitive insects like mayflies present in others.
Cows with access to creeks are one possible source of E. coli bacteria

E. coli bacteria levels in streams remained high.

  • All thirteen streams with enough data to evaluate this season exceeded the primary contact recreation standard. Three streams exceeded the secondary contact recreation standard: (West Indian Creek, College Creek, and Ballard Creek.
  • However, over the last four years, most sites on the South Skunk River meet the standard when there is enough water to float a canoe.
UV disinfection system at Ames Water Pollution Control Facility

Wastewater treatment plants are not yet capable of removing some of the pollutants we monitor, and can have a large influence during drought when effluent is less diluted.

  • Effluent from the old sewage treatment plant in Nevada was found to be a major source of E. coli bacteria. The new plant, currently under construction, includes a disinfection system that should address the problem.
  • Stream sites downstream of sewage treatment plants tend to have elevated chloride and phosphate.  
Stock photo of cover crops

The encouraging trends we noted in the 2022 report held up with another year of data. Water quality trends are often driven by weather, but we pulled out subsets based on streamflow to remove some of this influence. 

  • E. coli in the South Skunk River below the Ames Water Pollution Control Facility has improved relative to the pre-2014 baseline period, especially during dry conditions when wastewater has the greatest influence.
  • Nitrate in the South Skunk River below the confluence with Ioway Creek improved relative to the pre-2014 baseline period, even after excluding dry periods. This pattern is consistent with improvement from conservation practices.
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.

Think Outside the HUCs

Think Outside the HUCs

“With the Nutrient Reduction Strategy approaching its 10-year anniversary in 2023, Iowans deserve to see water quality results from the nearly $100 million of public money invested since 2013.  Water monitoring is a crucial component to the success of the Nutrient Reduction Strategy and must be designed to assess progress.  A strategy without a way to evaluate progress or outcomes is not a real strategy.”

– from Iowa Environmental Council’s 2022 report:  “Water Quality Monitoring and the Water Quality Initiative

fake text message to introduce blog post

Most water monitoring programs are NOT designed to assess progress.  Often, people don’t begin monitoring in earnest until the grant funding arrives for an improvement project (or on flip side, until an industry with a reputation for pollution sets up shop in the area).  Often, they’re hoping for preliminary results when the grant wraps in 3-5 years.  I’ve been down that road, completed a horrifying statistical analysis, and left this conference poster as a warning to others: “Progress tracking is not a realistic use for typical stream monitoring approaches”.

Our local partners in Story County took this warning to heart and made a plan to sustain water monitoring for at least ten years, while shifting our focus.  We collected lab samples from more sites (less often, and with less hassle) while ramping up the volunteer program, so we could engage the public and get a baseline understanding of water bodies all around the county.  All is well and good.  But now and then I come back to the question “how would you monitor water if you were serious about assessing progress?”.

Preliminary results in 3-5 years might be feasible if you already have baseline data for comparison, and account for any big changes in weather.  The South Skunk River just upstream of Ames was monitored from 2001-2014 by the Iowa DNR, and we resumed monitoring it in 2020.  I have good news and bad news for the newly formed Headwaters of the South Skunk River WMA.

  • Good news: average nitrate concentrations over the last three years have declined 46% compared to the baseline period.  Mission accomplished?
  • Bad news: the trend goes away if you exclude samples collected during a drought when nitrate levels are at their lowest.
nitrate trend in south skunk river above Ames

Study design is key for progress tracking.  In order to be sure that water quality really changed, and to be able to link that change to something that happened in the watershed, scientists approach water monitoring like a medical trial.  To do it right, there should be a treatment group (a watershed that receives conservation funding and attention), a control group (a nearby watershed that doesn’t receive funding), a before period, and an after period.  There should be a full accounting of land management and conservation practices in both watersheds.  If the treatment group improves more than the control group, that’s a good sign the medicine works.  At the time we wrote the Story County Monitoring Plan, doing a paired watershed study of the sort that Michelle Soupir did for Black Hawk Lake didn’t make a lot of sense.

It didn’t make sense to invest in progress tracking, because our WQI-funded watershed project had come to a close, further funding was uncertain, and we couldn’t expect much improvement in water quality based on other metrics to date.  Our watershed coordinators worked really hard, we had enthusiastic partners in local government and agribusiness, and we organized some well-attended field days where we heard from inspiring early adopters of cover crops and bioreactors.  We met some farmers in the watershed who cared enough about soil and water to take a risk and try something new.  Unfortunately, at the end of four years, we had a lot of unspent cost share funds and only enough conservation practices to expect or 1 or 2 percent reduction in nitrogen and phosphorus.  Ioway Creek is a big watershed (147,000 acres).

metrics from wqi project

However, this year I was reviewing our water monitoring data and had one of those moments like when you squint at an optical illusion and suddenly see a rabbit instead of a duck.

“Hey, that looks a lot like an upstream/downstream study for tracking whether projects in the Ioway Creek watershed and the City of Ames have improved water quality!”

  • The medicine: A bunch of conservation practices were installed between 2015 and 2019, some of which address nitrogen and some of which address other pollutants. We could include Jean’s no-till fields in Hamilton County, Jeremy’s cover crops in Boone County, Gerold’s bioreactor in Boone County, the UV disinfection system in Gilbert, the permeable parking lot at Ames City Hall, the stream restoration and saturated buffer at the Tedesco Environmental Learning Corridor, and many others.
  • The treatment group: A downstream site, influenced by all those conservation practices. The South Skunk River at 265th St. has been monitored weekly by the City of Ames since 2003.  At this point the river drains 573 square miles, corresponding to the Ioway Creek watershed plus the Headwaters of the South Skunk River watershed.
  • The control group: An upstream site, not influenced by these practices. At this point, the river drains 316 square miles, corresponding to the Headwaters of the South Skunk River watershed, minus any land within Ames city limits.
  • A before period: Both sites were monitored between 2003 and 2014.
  • An after period: Both sites were monitored between 2020 and 2022.

And then I made a boxplot and squinted a little more and said, “Hey, it looks a lot like nitrate has improved at the downstream site!”  Same thing for E. coli!  Maybe there’s more to this story than just cost-share metrics.

graphs comparing nitrate at upstream and downstream sites

The analysis is described in more detail in our 2022 annual report on water monitoring in Story County.  We’ll also have some opportunities this year to talk with other groups around the state that are doing water quality monitoring and swap some tips and tricks.

Here’s one of mine. To see the “rabbit” in this data, you have to be flexible in how you think about watersheds.  A watershed is just the land area that drains to a common point.  With the right tools, we can delineate a watershed for any point of interest on the river network.  I’ve taught several classes of ninth graders how to do this.  Neither of these sites are in the Ioway Creek watershed, and they aren’t mentioned in the Watershed Plan, but that doesn’t mean they’re not relevant.  The US Geologic Survey’s system for mapping and numbering watersheds is convenient for many purposes.  But if you have access to long-term monitoring data, don’t be afraid to think outside the HUCs!

An Impressive 2022 Stream Monitoring Season

An Impressive 2022 Stream Monitoring Season

Jess Lancial testing water

Jess Lancial testing water quality (photo credit Story County Conservation)

Volunteer Water Monitoring in Story County

A round of applause for all the volunteers and Story County Conservation staff who have diligently been monitoring their assigned stream twice a month in all kinds of weather!   Also, let’s give a shout-out to the people who work behind the scenes.  Sara Carmichael of Story County Conservation keeps everyone on track and equipped with supplies.  Heather Wilson of the Izaak Walton League of America provides training and support to volunteers around the state.  We rely on the IWLA’s  Save Our Streams program for training materials and the Clean Water Hub for data entry.  The three of us will be meeting the volunteers at a training event later this month to kick off another great season.

Three ways to get involved:

  • There’s room for one or two more volunteers to cover a site in Story County, so contact Sara.
  • If you’d like to try water monitoring without committing to a schedule, Prairie Rivers organizes a one-day volunteer event in the Ames area each May, so keep an eye on our events page.
  • If you don’t live in Story County, the Izaak Walton League is launching a new Nitrate Watch program and you can request a bottle of test strips while supplies last.

In March, Prairie Rivers will release a report detailing the findings, but for now let’s admire the scale and consistency of the effort, which has really improved since last year. (Updated 2023-02-18 to include some data sheets that were entered late)

2022 Season

Volunteers participating

Sites tested at least once

Sites tested at least 10 times

Sites tested at least 20 times

Data sheets entered in the Clean Water Hub

2021 Season

Volunteers participating

Sites tested at least once

Sites tested at least 10 times

Sites tested at least 20 times

Data sheets entered in the Clean Water Hub

Story County Water Monitoring & Interpretation Plan, 2021-2030

Prairie Rivers partnered with Story County and 8 other organizations to develop a ten-year Water Monitoring & Interpretation Plan for Story County.  Regular communication between the various groups testing water helps avoid duplication and leads to new opportunities to improve water quality.  Planning for how data can be used over the long term ensures that we get the most value from our time and effort.   Read the plan here

Peeling the Onion

Peeling the Onion

We know that weather influences water quality in Iowa’s rivers.  Last year, there was a drought and nitrate was lower than usual.  This spring, it’s been wetter and nitrate is higher than usual.  If you monitor for 10 years and the first 5 are a little wetter or drier than the last five, you’ll a water quality trend to go with it.  Boring! 

What we really want to know is how people are influencing water quality.  We can get a lot closer to that answer by peeling away the obvious weather-related patterns to reveal underlying trends.

In statistics, it’s called a covariate or an explanatory variable.  If there’s a relationship between your water quality metric and some other thing you’re not really interested in (i.e. streamflow), you can model that relationship to account for part of a water quality trend over time.  What’s left over might be the things you’re really interested in (i.e. how water quality has been affected by changes in crop rotations, conservation practices, sewage treatment, manure management, and drainage).  It’s common enough in the scientific literature (Robert Hirsch’s Weighted Regression on Time, Discharge, and Season is a good example), but should be used more often for progress tracking at the watershed scale. 

To illustrate this general approach, I downloaded daily nitrate data from three stations maintained by the US Geologic Survey.  The sensors at the Turkey River at Garber and the Cedar River near Palo (north of Cedar Rapids) were installed in late 2012; the sensor Raccoon River near Jefferson was installed in 2008.  I wanted a high frequency dataset (to minimize sampling error) that included the episodes of “weather whiplash” in 2013 and 2022.

nitrate trend in the cedar river

“Residuals” are the difference between what we predict and what we measured.  In the first panel, that’s the difference between a measurement and the long-term average.  In the second and third panels, we see how nitrate measurements differ from what we’d expect given flow in the stream today, and flow in the stream last year.  Gray dots – daily measurements.  Red dots- yearly averages.  Blue dotted line – trend.  If I did this right, some of the dots should get closer to the middle.

Nitrate concentrations in rivers increase as the weather gets wetter and streamflow increases… up to a point.  When rivers are running very high, there’s a dilution effect and nitrate concentrations fall.  Based on that relationship, we can explain high nitrate levels in the Cedar River in 2016 (a wet year) and low nitrate levels in 2021 (a dry year).

nitrate vs flow in the Cedar River

Nitrate concentrations tends to be highest on wet spring days following a dry summer and fall, as nitrate that accumulated in the soil during the drought is flushed into drainage systems or washed off the land surface and into rivers.  Here I’ve calculated a moving average of flow over the previous 365 days, and compared that to nitrate concentrations during high flow or low flow conditions.  Based on that relationship, we can explain high nitrate in the Cedar River on wet days in the spring of 2013 and 2022 (following a dry year) and low nitrate on wet days in the spring of 2019 (following a wet year).

relationship between nitrate and last year's flow

After making these adjustments, the downward trend in the Cedar River looks much smaller (0.53 mg/L per year, adjusted to 0.25) and is overtaken by the Turkey River (0.37 mg/L, adjusted to 0.28).  The adjusted trends are statistically significant and could be attributed to conservation efforts in those watersheds.

How did I do this?  For technical details, read here.

nitrate trend in the cedar river

However, there’s still some weather-related patterns we haven’t accounted for.  The Raccoon River near Jefferson also had a steep decline in nitrate since 2013 (1.42 mg/L per year, adjusted to 0.77 mg/L per year) but if you look at the entire record (going back to 2008), it’s part of an up-and-down cycle.  I’ve seen that same pattern in the South Skunk River.  The model explains some of those swings but doesn’t fully explain high nitrate in fall of 2014, spring of 2015 and spring of 2016.  Perhaps the nitrogen that accumulated in the soil during the drought of 2012 took several years to flush out.

In addition to streamflow and last year’s weather (antecedent moisture is the technical term), nitrate can be explained by season, soybean acreage, and baseflow.  If it’s not enough to know that water quality is improving or getting worse, and you’d also like to know why, then let’s peel that onion!