EUTROPHICATION ON TWIN LAKES: APPLYING A PHOSPHORUS BUDGET AND SHORELINE SURVEYS TO ASSESS CURRENT & HISTORICAL LAKE HEALTH
Date of Award
Open Access Master's Thesis
Master of Science in Environmental Engineering (MS)
Administrative Home Department
Department of Civil, Environmental, and Geospatial Engineering
Committee Member 1
Committee Member 2
Committee Member 3
The Twin Lakes system, a series of lakes including Lake Gerald and Lake Roland, was historically categorized as oligotrophic but is now mesotrophic having experienced cultural eutrophication. A mass balance phosphorus budget model was constructed for the Twin Lakes system in Houghton, Co. Michigan for the 2022 stratified season. Additional spatial insights were gleaned through a survey of shoreline water quality, which corroborated the model results. The lakes currently experience substantial depletion of hypolimnetic dissolved oxygen during late summer stratification. A budget reveals approximately 22% (6.6 kg) of the current 29.5 kg total phosphorus inputs to Twin Lakes (during the stratified period) are from sources not clearly attributable to natural processes and are likely attributable to nutrient inputs from the primarily residential shoreline developments. Modeling suggests the lakes were indeed oligotrophic, and that the system would be relatively responsive to loading reductions. Substantial reductions to that “residual load” (in excess of 64%) would be required to return the system to an oligotrophic state. Shoreline surveys support the hypothesis of shoreline development sources nutrient pollution. The performed work brought to question the broad applicability of methods for using optical brightening agents (OBAs) as a tracer of septic leakage. The development of heatmaps as visual tools proved useful for understanding drivers of lake water quality spatially. The lakes show distinct regions of elevated conductivity from the largest contributing tributary, whose watershed bisects a state highway corridor. This suggests road salt contamination to Twin Lakes. This work serves as a case study examination of eutrophication and phosphorus budget for a naturally low productivity system of lakes in series in the Great Lakes region.
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LeMahieu, Tyler K., "EUTROPHICATION ON TWIN LAKES: APPLYING A PHOSPHORUS BUDGET AND SHORELINE SURVEYS TO ASSESS CURRENT & HISTORICAL LAKE HEALTH", Open Access Master's Thesis, Michigan Technological University, 2023.