DOI

10.17077/etd.678k07k8

Document Type

Thesis

Date of Degree

Fall 2017

Degree Name

MS (Master of Science)

Degree In

Civil and Environmental Engineering

First Advisor

Weber, Larry J.

Second Advisor

Schilling, Keith

First Committee Member

Mantilla, Ricardo

Second Committee Member

Jones, Chris

Abstract

Conservation practices are needed to reduce nitrate loss across the Midwest. Different riparian wetland designs have been investigated, but the physical, chemical and biological processes controlling nutrient cycling in restored oxbows are not well understood. A restored oxbow’s influence on nutrient cycling was investigated by studying the hydrogeology and water quality at a recently reconstructed oxbow site adjacent to Morgan Creek in Linn County, Iowa. Over a one-year period, the lentic oxbow’s nitrate loading was found to be dominated by flood pulses. Nitrate concentrations in the stream ranged from 7.38 – 12.95 mg l-1, concentrations were consistently low in the oxbow ranging from < 0.10 – 5.35 mg l-1, and the lowest nitrate concentrations were detected in the groundwater ranging from 0.10 to 3.4 mg l-1. Following a spring flood event, an in-situ sensor measured the nitrate concentration in the oxbow. Nitrate retention efficiency was estimated to be 0.30 g N m-2 d-1 or a 74.2% reduction efficiency. The observed nitrate reduction was compared to a first order denitrification model. The observed nitrate reduction measured in the oxbow followed a linear decay rather than an exponential decay suggested by first order kinetics.

Keywords

Floodplain Restoration, Nitrate Reduction, Oxbow, Oxbow Restoration

Pages

ix, pages

Bibliography

Includes bibliographical references (pages 90-98).

Copyright

Copyright © 2017 Bryce Jordan Haines

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