Date of Graduation

2017

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Omar I Abdul-Aziz

Committee Co-Chair

Kakan Dey

Committee Member

P V Vijay

Abstract

Dynamics of coastal stream water quality and ecosystem health is influenced by a multitude of interacting environmental drivers. A systematic data analytics approach was employed to determine the relative environmental controls on stream dissolved oxygen (DO) dynamics across the Gulf Coast of U.S.A. Pearson's correlation, principal component, and factor analyses were utilized to examine the interrelations among DO, solar radiation, water temperature, atmospheric pressure, flow rate, nutrients, pH, and specific conductance (a surrogate of salinity) in 36 streams. Relative linkages of DO and the environmental drivers were then reliably estimated by resolving multicollinearity with power-law based partial least squares regression (Nash-Sutcliffe efficiency = 0.58-0.94). Based on the dominant controls of DO, streams were grouped into three regions across the U.S. Gulf Coast. In the northern part of Gulf Coast states (Texas, Louisiana, Mississippi, Alabama, and West Florida), water temperatures had the strongest and dictated control on stream DO. However, in the southern part of Texas and Florida coasts, pH showed the most dominant control on stream DO. Further, streams in between these two regions demonstrated notable controls of multiple drivers (water temperature, stream flow, and specific conductance) on DO. Four dynamic process components adequately described the system data variance in all three regions along the Gulf Coast. For example, the 'climate component' (temperature, solar radiation) in the northern part of Gulf Coast showed 2.7, 3.1, and 3.6 times stronger linkages with stream DO than that of the redox (pH, specific conductance), nutrient (total nitrogen, total phosphorus), and hydro-atmospheric (flow rate, atmospheric pressure) components, respectively. In contrast, in the southern part of Gulf Coast region, the redox components showed 1.6, 2.3, and 2.6 times stronger linkages with stream DO than that of the climate, nutrient, and hydro-atmospheric components, respectively. The identified environmental regimes and estimated linkages of stream DO provide important information into the dominant drivers and dynamic process components of water quality in urban/natural streams across the U.S. Gulf Coast. The knowledge and insights would help coastal managers and stakeholders to achieve a good stream water quality and ecosystem health.

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