Deterministic, unsteady, year-round lake water quality and fish habitat simulation models have been developed and are being expanded, validated, and applied. These models simulate daily water temperature and dissolved oxygen distributions in various classes of lakes, including both open water conditions and the ice cover period. The simulations are made for continuous long term periods (e.g., 30 years) in all regions of the contiguous United States. A special effort is directed to quantify the response of water temperatures, dissolved oxygen concentrations, and ice cover characteristics to potential climate change and to further evaluate these effects on fishes in lakes in currently cold regions. Current emphasis is on water quality changes during the cold season and intrusion of warm water organisms into previously cold aquatic systems.
Troy Erickson, Graduate Student Researcher
Xing Fang, Department of Civil Engineering, Lamar University, Beaumont, Texas
Omid Mohseni, Graduate Student Researcher
Gao Shaobai, Graduate Student Researcher
Dragoslav Stefanovic, Graduate Student Researcher
A recently added component of the simulations is convective-diffusive-reactive exchange between littoral (shallow) and profundal (deep) waters of lakes. This requires an extension of the existing one-dimensional (vertical) transport model into another (horizontal) dimension, taking into account the variability of water quality parameters across a lake surface. A model is being developed to simulate lake hydrodynamics in a two-dimensional flow field driven either by forced (wind induced) or natural (buoyancy induced) convection.
Current work on the project includes two-dimensional simulation of flow and water quality in the ice-covered season. The particular challenge is accurate modeling of fluid motion and transport driven by buoyancy forces in a stratified water body. This requires the resolution of a low-Reynolds-number turbulent and pseudo-laminar flow field with damping effects on vertical turbulent transport due to stable thermal stratification.
99/94 |
"Simulated Fish Habitat Changes in U.S. Lakes under Projected Climate Warming Part 1. Cool-Water Fish in the Contiguous U.S.," X. Fang, H.G. Stefan, and S.R. Alam, University of Minnesota Supercomputing Institute Research Report UMSI 99/94, May 1999. |
99/95 |
"Simulated Fish Habitat Changes in U.S. Lakes under Projected Climate Warming Part 2. Cold-Water Fish in the Contiguous U.S.," X. Fang, H.G. Stefan, and S.R. Alam, University of Minnesota Supercomputing Institute Research Report UMSI 99/95, May 1999. |
99/96 |
"Simulated Fish Habitat Changes in U.S. Lakes under Projected Climate Warming Part 3. Warmwater Fish in the Contiguous U.S.," X. Fang, H.G. Stefan, and S.R. Alam, University of Minnesota Supercomputing Institute Research Report UMSI 99/96, May 1999. |
The information on two-dimensional flow is subsequently used in a mass-transport model for various water-quality variables to simulate horizontal and vertical transport from the littoral regions to the profundal portions of a lake. This is important because chemical and biological kinetics in these two regions can be substantially different.
Previously, comprehensive field measurements of water temperature and dissolved oxygen in an ice-covered lake have been conducted in order to support and validate individual model components in the winter season. This extensive set of data is being used for the model calibration and verification on the supercomputing platform.
After extensive verification and calibration, the model is used for studies of transient convective processes, such as the upwelling response of stratified water bodies to surface shear stress, excitation of baroclinic waves by variable wind fields in a lake, horizontal mixing in the epilimnion/metalimnion/hypolimnion, continuous and diurnal cooling/heating of stratified water layers, formation of thermal bars, gravitational circulation in sheltered embayments due to the diurnal heating cycle, density currents, and natural convection in lakes under the ice cover.
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