Understanding Lake Residence Time Across Spatial and Temporal Scales: A Modeling Analysis of Lake George, New York USA

• Published in: Water resources research Vol. 60; no. 2
• Main Authors: Auger, Guillaume A. R., Kelly, Michael R., Moriarty, Vincent W., Rose, Kevin C., Kolar, Harry R.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 01.02.2024
• Subjects: Age; Age composition; Algae; Algal blooms; Bays; Eutrophication; Hydrodynamic models; lake; Lake water; Lake water quality; Lakes; Mathematical models; Parameters; Quality management; Residence time; Residence time distribution; Spatial distribution; Spatial variability; Spatial variations; Strong winds; Temporal distribution; Thermocline; Variability; Vertical distribution; water age; Water currents; Water masses; Water quality; Water quality measurements; Water temperature; Wind; Lake George; New York; United States > US
• ISSN: 0043-1397; 1944-7973
• DOI: 10.1029/2022WR034168

Whole lake residence time has been associated with various water quality parameters, including harmful algal blooms. Despite observations of spatial variability in commonly measured lake water quality parameters, little attention is given to the spatial variability of residence time in lakes. In this paper we use water age as a surrogate for residence time and we examine its spatial and temporal distribution in 10 bays of varying size in Lake George, New York (USA). Using a validated hydrodynamic model against observations of water temperature and water currents, and using simulated water age, we show that the average residence time in most of the bays is less than 3 days. Timeseries of bay‐average water age shows that it can sharply decrease within 1 day due to a strong wind event. The average spatial distribution is shown to be non‐uniform, with only a small section of the bottom layer of the bays having a substantially greater age, which may be more than 1 week in certain bays. Snapshots of water age transects indicate that strong wind events substantially change the vertical distribution of water age in some bays, even to the extent of inverting the distribution. The substantial decreases of water age in the bays were associated with the shallowing and deepening of the thermocline. Our results highlight how variations in water residence times within lakes could introduce substantial variation in water quality attributes. Whole lake residence times may serve as a poor proxy to understand the dynamics of water masses, especially in large and morphologically complex waterbodies. Key Points Simulation of water age with a validated hydrodynamic model against temperature and currents Average water age (surrogate to residence time) in bays is smaller than 6 days Spatial distribution of water age within bays is not uniform and strong wind events lead to lower water age within 1 day