Date of Award

3-27-2019

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Earth Science

First Advisor

Laura Ruhl

Abstract

The Lake Maumelle reservoir is Central Arkansas’s main water supply, primarily servicing the residents of Little Rock, AR. Maintaining a high standard of water quality is important to the over 400,000 residents of this area whom rely on this oligotrophic/mesotrophic waterbody for drinking water. Lake Maumelle is a scenic attraction for recreational boating and bass fishing. The Lake Maumelle watershed is densely forested and mostly within the Ouachita National Forest. Past research has focused primarily on watershed management with land use/land cover modeling and quarterly water sampling of the 13.91mi2 reservoir. Objectives of this investigation were to further understand seasonal and spatial geochemical and planktonic changes within the Lake Maumelle reservoir. Water samples were systematically collected through the water column, throughout the three reservoir zones, and within the littoral zone over a 9-month timespan. We collected depth profiles for water parameters, measured trace element concentrations, and planktonic abundances. Trace element concentrations have been compared with season and location to determine response to environmental change. Additionally, concentrations were compared with samples collected from the lake’s main tributary, the Maumelle River, to calculate enrichment factors. Lake stratification was observed with low dissolved oxygen values at depth during summer months, while mixing of the water column occurred during fall, winter, and spring months. The concentrations of Fe, Mn, Zn, and Sb showed seasonally redox related changes from surface to bottom depths. Elements that are not affected by redox changes (B, Al, Sr, Ba) generally showed little concentration variance between sample locations. Collected plankton samples showed changes in division dominance between bacillariophyta, chlorophyta, and cyanophyta during seasons. Monitoring of cyanobacteria blooms in late winter and spring months is important for aesthetic and lake function as a drinking water source. Lake Maumelle’s nearness to Little Rock, AR, role as a drinking water source, and pristine water quality make it an important resource to understand and protect.

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