Date of Award

6-21-2023

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Eric Peterson

Abstract

Suspended sediment and phosphorus are among the major pollutants of stream ecosystems. Suspended sediment has been documented as vector for nutrient transport, specifically phosphorus, in streams. Sources of suspended sediments include agricultural fields, channel sediments, and streambanks. Suspended sediments within the stream channel could fill up reservoirs over time thus, reducing reservoir storage capacity. Suspended sediments can cover breeding and nesting areas of aquatic habitats, leading to their displacements. Sources of phosphorus include point sources such as wastewater treatment plants and industrial effluent, and nonpoint sources such as agricultural fields and urban runoff. Phosphorus is a limiting nutrient in freshwater and elevated concentrations have led to eutrophication and hypoxic conditions. Controls of suspended sediments and phosphorus transport within a watershed include basin slope, soil texture, runoff, and agriculture fields. The overall goal of this study is to quantify the export of total suspended sediment (TSS) and total phosphorous (TP) during storms in an agricultural-dominated watershed from April 2018-December 2019 study period. Analysis of discharge, TSS, and TP data showed that discharge and presence of bare soils controls the export of TSS and TP in the Money Creek sub-watershed. Spring had the highest TSS and TP loads due to the spring having the highest discharge volumes. Loads of TSS and TP in winter were less than in spring, but the winter still had more TSS and TP loads than the summer and fall combined. Because of the lowest discharges, summer experienced the least amount of TSS and TP loads. Both TSS and TP loads, and flow-weighted TSS concentration and flow-weighted TP concentrations exhibited a positive relationship within the study period and across the seasons. There is a general increase in flow-weighted concentration of TSS and TP as discharge increases suggesting that discharge is not the only control of TSS and TP loads and concentrations. The seasonal relationship indicates that the winter and spring had more TSS and TP loads and flow-weighted concentrations than in fall due to the presence of bare soils. Bare soils serve as a source that allows for the mobilization of large amount sediments during high discharge volumes. The highest TSS and TP loads were transported in winter and spring when the soil was bare. The lowest TSS and TP loads were transported in the summer due to the presence of vegetation cover which limits the transport of TSS and TP loads and flow-weighted concentrations. The link between TSS and TP suggests that solutions to decreasing TSS transport and loads will reduce TP transport and loads. Growing cover crops is a mitigation strategy for nutrient management that also serves as a soil conservation practice. The use of cover crops as a mitigation strategy could potentially reduce soil erosion, improve soil health, enhance agricultural productivity.

Comments

Imported from Efobo_ilstu_0092N_12406.pdf

DOI

https://doi.org/10.30707/ETD2023.20231004061828269197.999980

Page Count

70

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