CALL FOR PROPOSALS:

ORGANIZERS

  • Harvey Thorleifson, Chair
    Minnesota Geological Survey
  • Carrie Jennings, Vice Chair
    Minnesota Geological Survey
  • David Bush, Technical Program Chair
    University of West Georgia
  • Jim Miller, Field Trip Chair
    University of Minnesota Duluth
  • Curtis M. Hudak, Sponsorship Chair
    Foth Infrastructure & Environment, LLC

 

Paper No. 38
Presentation Time: 6:15 PM

ASSESSMENT OF DIEL CYCLING IN AGRICULTURAL STREAMS IN SOUTH-CENTRAL MICHIGAN- A FOCUS ON TURBIDITY


WILLIAMS, Abigail M.1, HIDAY, Aaron D.1 and WILCH, Thomas I.2, (1)Geological Sciences, Albion College, Albion, MI 49224, (2)Department of Geological Sciences, Albion College, 611 E Porter St, Albion, MI 49224, amw14@albion.edu

Diel cycling of stream parameters is overlooked in typical water quality assessments. With a focus on turbidity, we analyzed cycling at multiple sites in both agricultural drains and natural tributaries of the upper Kalamazoo River watershed, Michigan. Turbidity and other water quality parameters (DO, water level, temperature, specific conductivity, pH, and total suspended solids (TSS)) were frequently monitored (mostly 10-minute intervals) during summers 2010 and 2011.

Two study sites in Rice Creek, an agricultural drain, show turbidity increases of 10 to 20 NTU at night with broad noisy peaks between 10 pm and 6 am and daytime saddles between 10 am and 7 pm. Downstream turbidity peaks lag upstream peaks by ~2 hours over a distance of 7.7km. Turbidity cycles also vary with depth in the stream. Measurements taken at 10 and 20 cm above the streambed exhibit in-phase diel cycles with the same periodicity and amplitude. Magnitudes are offset by 10 NTU, with higher turbidity closer to the streambed. A strong linear relationship (R2 of 0.89) between turbidity and TSS concentration suggests that turbidity is a good proxy for TSS. Loss-on-ignition of TSS samples indicates that suspended sediment is composed of about 40% organic and 60% mineral material. Measurements in the more natural North and South Branch tributaries of the Kalamazoo River exhibit similar diel turbidity cycles but with lower amplitudes and absolute values than in Rice Creek.

Turbidity cycles are roughly anti-phase with DO and pH, which may indicate a biological control. Simulation experiments of bioturbation result in short-lived and short-traveled pulses of turbidity. Turbidity varies in-phase with groundwater levels and specific conductivity, which may indicate a groundwater sapping effect. Leveloggers measured groundwater levels in four wells in adjacent wetlands. Water table levels, driven by evapotranspiration, varied cyclically with diel amplitudes from 1 to 9cm. We anticipated that stream stage levels would co-vary with groundwater levels but they did not. Stream stage cycles were less regular, out-of-phase, and about 2cm in amplitude relative to groundwater levels. Ongoing work is investigating both biological and physical controls on the diel turbidity cycles.

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