Eutrophication in Jordan Lake: Using Specific Conductance During Storm Events to Characterize Nutrient Transport from Varying Landscapes Public Deposited

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  • May 15, 2019
  • Hamilton, William
    • Affiliation: College of Arts and Sciences, Curriculum in Environment and Ecology, Environmental Science
  • As the North Carolina Triangle region experiences rapid growth and development, water quality becomes an increasingly pertinent issue. Increased nutrient loading in the Jordan Lake drinking reservoir causes toxic cyanobacterial blooms that pose public health concerns. The Jordan Lake Nutrient Study seeks to determine how land use within this region affects the transport of nutrients and other contaminants. Over the course of two years, our team collected water level, streamflow, and specific conductance observations at five-minute intervals using automated sensors. Specific conductance indicates the concentration of dissolved ions present in water in µS/cm. Typically, this metric is high in ground water and discharge yet almost absent in rainfall, providing a measurement of contaminants traveling over the landscape that excludes contaminants added by rainfall. We examined changes in contaminant concentrations under changing flow conditions. Storm events are one such change because they cause a sharp increase in flow followed by a gradual recession. Specific conductance exhibits a delayed response to these changing flow conditions that we characterized as dilution (decreased specific conductance) or enrichment (increased specific conductance). We used a hidden Markov model to iteratively filter out storm behavior from intermittent flow conditions. This model, paired with a peak identification function in R, allowed us to distinguish single storm events in large flow datasets. For each storm, we performed hysteresis analyses by plotting flow versus specific conductance and assessing the response of specific conductance. Our preliminary results suggest distinct behaviors of specific conductance between sites. During storms, landscapes with more intense development and flashier (lower duration and higher change in flow) storms often showed dilution, while forested, less developed sites exhibited either enrichment or dilution. These findings support land use as a driving factor of contaminant transport and prompt further investigation into this relationship using a wider range of land uses.
Date of publication
Resource type
  • Funding: Sarah Steele Danhoff Undergraduate Research Fund
  • Riveros-Iregui, Diego
  • Bachelor of Science
Academic concentration
  • Environmental Science
Honors level
  • Honors
Degree granting institution
  • University of North Carolina at Chapel Hill
Graduation year
  • 2019
  • English

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