RESERVOIR DRAWDOWN IMPACTS ON SEDIMENT RESUSPENSION AND EUTROPHICATION DOWNSTREAM (LAKE SINCLAIR, GEORGIA, USA)**

Authors

Michelle Crumley*, Georgia College & State University, Milledgeville, GA 31061Follow
Anya Mukundan, Georgia College & State University, Milledgeville, GA 31061Follow
Samuel Mutiti, Georgia College & State University, Milledgeville, GA 31061Follow
Christine Mutiti, Georgia College & State University, Milledgeville, GA 31061Follow
Kalina Manoylov, Georgia College & State University, Milledgeville, GA 31061Follow

Abstract

Reservoir drawdowns are widely used for dam maintenance, hydropower operations, and shoreline management, yet they strongly influence water quality through the exposure and mobilization of littoral sediments. These resuspended sediments release nutrients into the water column and alter downstream environments. Lake Sinclair, Georgia, undergoes winter drawdowns every five years that expose shorelines and modify flow regimes; however, reflooding may contribute to turbidity spikes and nutrient pulses, potentially amplifying algal growth in the Oconee River downstream. Given Lake Sinclair’s importance as a municipal water source, recreation area, and diverse habitat, this study aims to evaluate the ecological consequences of these drawdowns to improve understanding of their effects on water quality and reservoir management. We investigated the physical, chemical, and biological characteristics, including nutrient, turbidity, and algal levels, of Lake Sinclair and the Oconee River prior to, during, and after the 2025 winter drawdown. Preliminary results indicate that Lake Sinclair displays signs of disturbance, including persistent high turbidity (17.39 to 16.85 FNU), diatom dominance emergence (+93.4%), and cyanobacteria collapse. In comparison, the control lake that did not experience drawdown, Lake Oconee, showed predictable seasonal changes consistent with cooling temperatures, including a 33% turbidity decrease and a moderate increase of diatoms by 33.6%. Further, the Oconee River has early signs of downstream disturbance propagation including dramatic increases in nitrate (+69.3%) and turbidity (82%). Future monitoring will evaluate turbidity spikes, nutrient release, and sediment-driven chemical changes throughout reflooding. Early results demonstrate the extensive effects on sediment chemistry, nutrient transport, and algal dynamics, emphasizing the need to consider water quality and ecological impacts in future reservoir management.

Acknowledgements

GCSU Aquatic Sciences Center(Funding and Equipment), GCSU Department of Biological and Environmental Sciences (Equipment), Georgia Power (Site Access)

Recommended Citation

Crumley*, Michelle; Mukundan, Anya; Mutiti, Samuel; Mutiti, Christine; and Manoylov, Kalina (2026) "RESERVOIR DRAWDOWN IMPACTS ON SEDIMENT RESUSPENSION AND EUTROPHICATION DOWNSTREAM (LAKE SINCLAIR, GEORGIA, USA)**," Georgia Journal of Science, Vol. 84, No. 1, Article 191.
Available at: https://digitalcommons.gaacademy.org/gjs/vol84/iss1/191