Graduation Year

2024

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Degree Granting Department

Geology

Major Professor

Patricia D. Spellman, Ph.D.

Committee Member

Jason D. Gulley, Ph.D.

Committee Member

Charles I. Breithaupt, Ph.D.

Keywords

freshwater lens, lake water budget, lake-groundwater interactions, The Bahamas

Abstract

Lakes on carbonate islands are known to reduce freshwater lens volumes and alter freshwater lens distribution; however, the magnitude and controlling factors between lake and freshwater lens interactions remain poorly understood. Since freshwater lenses are thin and can be fragmented by lakes in small carbonate islands, it is important to understand the magnitude of exchange between lakes and the freshwater lens to understand potential groundwater depletion. This study utilized high temporal resolution water levels and meteorological data to quantify monthly water budgets for seven lakes on San Salvador Island, The Bahamas. The monthly water budgets accounted for rainfall, potential evaporation, runoff, and residual groundwater. The lakes we investigated cover four different lake basin morphology types, and the relative age of the lake basins is either associated with the Holocene or Marine Isotope Stage 5 (late Pleistocene). Additionally, we delineated the extent of the lakes’ drainage basins with a 50-cm resolution bare earth digital elevation model (DEM) to refine the predicted runoff contributions for lakes where runoff was considered significant. Our results confirm that rainfall and evaporation are the primary controls on lake water level variability, and we show that the magnitude of lake-groundwater interactions may be higher than previously assumed. Furthermore, the net groundwater responses and magnitudes correlate with lake basin morphology type and relative age.

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