Watershed Matchup #3: College Creek VS Bluestem Creek
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.
With such a big watershed—147,000 acres—we’ll need the help of a lot of people to improve water quality in Squaw Creek. However, some of the people I talk to assume that water quality is mostly someone else’s problem—it’s the CAFOs fault, or the golf courses, or the residential lawns.
By comparing smaller streams, volunteer monitoring can help us untangle some of the influences and serve as a reality check on the finger pointing. Thanks to the Squaw Creek Watershed Coalition we have some data on a lot of Squaw Creek’s tributaries, some with urban watersheds (College Creek) and some with rural watersheds, some with hog barns (Prairie Creek) and some without (Bluestem Creek). Some streams were even sampled monthly for a few years—not always the same years, but I’ve included some monthly averages to show the seasonal pattern.
|May 2019 Snapshot||Bluestem Creek||College Creek||Prairie Creek||Squaw Creek @Duff Ave|
|Cropland in watershed||90%||19%||82%||81%|
|Nitrate||5 mg/L||2 mg/L||5 mg/L||5 mg/L|
|Phosphorus||0.8 mg/L||0.2 mg/L||0.3 mg/L||0.2 mg/L|
|E. coli||Not sampled||1,220 CFU/100mL||11,700 CFU/100mL||9,600 CFU/100mL|
College Creek is almost entirely within the city of Ames. Urban streams have their own set of water quality challenges. Road salt applied in winter can lead to elevated levels of chloride. E. coli levels used to be very high due to issues with septic systems. Paved surfaces mean more runoff after heavy rains, carrying contaminants and worsening bank erosion. (A 2019 Water Quality Improvement project to install permeable pavement and tree trenches on Welch Ave will help reduce runoff to College Creek).
But despite all the athletic fields and residential lawns in the watershed, College Creek typically has lower nitrate levels than rural tributaries. If you’ve seen your neighbor over-fertilize their lawn and are wondering why that doesn’t have more of an impact, it’s worth remembering that turfgrass is a perennial and, like a good cover crop, is actively growing and taking up nutrients in April and May when most fields are bare.
Bluestem Creek is located in rural Boone County. It is usual in that it has no nearby hog barns, and presumably no hog manure applied in the watershed. It contributes plenty of nitrogen to Squaw Creek but appears to have lower phosphorus levels than Prairie Creek, another rural tributary with at least two hog confinements in its watershed. Hog manure is a good fertilizer (adding nitrogen, phosphorus, and organic matter to the fields where it is applied) but farmers don’t always account for it when applying commercial fertilizer.
Bluestem Creek does have cows, which entered the water for 5 minutes while I was doing water testing this spring. I have a soft spot for cows because their presence on the landscape can make cover crops and more diverse crop rotations financially viable. I’d rather see pasture along the creeks than have it plowed right up to the edge. But it’s true that cows can stir up sediment and poop in the water if they have access to the creek. I’ve heard feedlot owners complain that they have to fill out a lot of paperwork regarding their manure management and receive a lot of scrutiny from their neighbors, while smaller livestock producers are not held to the same standard.
Ultimately, I think stream monitoring data shows that we all have a role to play in improving water quality, whether that’s reducing runoff and erosion in urban streams through rain gardens and permeable pavement, improving soil health with cover crops and no-till, better management of manure and fertilizer, or removing nitrogen from drainage water with bioreactors and saturated buffers.