Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Earth Systems Science

First Advisor's Name

Leonard J Scinto

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Assefa Melesse

Second Advisor's Committee Title

Co-Committee Chair

Third Advisor's Name

Rene Price

Third Advisor's Committee Title

Commitee Member

Fourth Advisor's Name

Piero Gardinali

Fourth Advisor's Committee Title

Commitee Member

Fifth Advisor's Name

David Fugate

Fifth Advisor's Committee Title

Commitee Member

Keywords

flow regime, water quality, C–Q relationships, echo intensity, high-resolution estimates, phosphorus, canals, sediments, thresholds, management

Date of Defense

3-24-2023

Abstract

Water in the Everglades of central and southern Florida originally flowed from north to south as sheetflow. However, a network of canals, levees, and structures was created to drain the Everglades for agriculture and urban development. These changes altered the natural flow regime, allowing canals to shunt large volumes of water with high phosphorus (P) loads downstream. To remediate this, the Everglades is undergoing a multibillion-dollar hydrologic restoration. One of the restoration goals is to obtain the right water quality and quantity, that is, to provide a more “natural” flow of clean water. This dissertation sought to address this goal by focusing on canals: discharge releases, water quality, and sediment characteristics. The first study characterized and compared the flow regimes of a canal, river, and wetland slough and quantified the effect of flow on water quality constituent behavior using concentration-discharge (C-Q) relationships. The next study developed high-resolution estimates for suspended sediments and P to better assess how rapid changes in canal discharges could impact exports. The final study delineated the dynamics between discharge, water quality, and sediments in canals across the Lower Everglades. The results showed that characteristics of the canal, such as high flow variability and lack of a floodplain, led to an increase in water quality constituent concentrations, especially at high flows. The proximity and discharge volume from a canal inflow structure increased the concentrations of the high-resolution estimates by mobilization and resuspension processes. The suspended sediments closest to the inflow structure had low P contents that increased with increasing distance. Similarly, surficial bed sediments closest to the inflow structure had high bulk density and low P content, while those farther away had the opposite. This indicated that discharges from the structure transported organic P-rich sediments further downstream and left behind heavier P-poor sediments. Thus, canal transport processes are crucial for evaluating restoration goals. I propose that the discharge threshold from C-Q relationships, which segments water quality constituent behavior at low and high flow, be used as a management tool to determine the range of canal discharges that will maximize freshwater delivery and minimize P export.

Identifier

FIDC011056

ORCID

https://orcid.org/0000-0003-2071-2729

Previously Published In

Onwuka, I. S., Scinto, L. J., & Mahdavi Mazdeh, A. (2021). Comparative Use of Hydrologic Indicators to Determine the Effects of Flow Regimes on Water Quality in Three Channels across Southern Florida, USA. Water, 13(16), 2184. https://doi.org/10.3390/w13162184

Onwuka, I.S. ; Scinto, L.J. ; Fugate, D.C. (2023). High-Resolution Estimation of Suspended Solids and Particulate Phosphorus Using Acoustic Devices in a Hydrologically Managed Canal in South Florida, USA. Sensors, 23, 2281. https://doi.org/10.3390/s23042281

Available for download on Monday, April 21, 2025

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