- 1Swiss Federal Institute of Aquatic Science and Technology (Kastanienbaum, Switzerland), Department Surface Waters - Research and Management, Switzerland (jemima.rama@eawag.ch)
- 2Faculty of Geoscience and Environment, Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, Switzerland
- 3Tahoe Environmental Research Center, University of California, Davis, Davis, California, USA
- 4Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, Pennsylvania, USA
Topographic constraints, such as sills or constrictions, play a critical role in regulating water exchange between different basins, often creating complex circulation patterns that influence the transport and distribution of sediments, nutrients, and oxygen. Although extensively studied in oceanography, these topographic features are also present in multi-basin Swiss lakes (e.g., Lake Lucerne, Lake Zug, Lake Lugano) but have received less attention. This study examines the inter- basin exchange in Lake Zug, where two basins, a shallow northern basin (100 m deep) and a deeper southern basin (180 m deep), are connected by a lateral constriction. Lake Zug is meromictic, remaining stratified throughout the year, with anoxic conditions prevailing below approximately 120 m. Consequently, the shallow northern basin remains well-oxygenated, while the bottom 60 m of the southern basin is characterised by anoxic water. Past fine-scale measurements have revealed the presence of oxygen intrusions at depth, suggesting episodic oxygen supply to the anoxic zones of the southern basin.
We hypothesise that the constriction between the basins influences lateral inter-basin exchange, thereby controlling the oxygen supply from the oxic northern basin to the deep anoxic zones of the southern basin. The primary aim of this study is to identify the dynamics within each basin and determine the nature of the hydraulic control exerted by the constriction. By identifying the physical mechanisms that drive inter-basin exchange, this study seeks to clarify the factors influencing oxygen supply in the southern basin and its impact on the vertical zonation of redox processes. A combination of field measurements, including temperature, oxygen, turbidity, and velocity, and a 3D numerical model are employed to investigate both lateral and vertical transport in the lake. Preliminary findings on the dynamics of Lake Zug, with a focus on the physical processes at the constriction, will be presented. An understanding of the hydraulic control in Lake Zug could enhance our knowledge of exchange flows and their impact on oxygen distribution in multi-basin lakes.
How to cite: Rama, J., Doda, T., Sepúlveda Steiner, O., N. Ulloa, H., Janssen, D., and Bouffard, D.: The role of a lateral constriction in controling water exchange and oxygen distribution in a two-basin lake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14922, https://doi.org/10.5194/egusphere-egu25-14922, 2025.
