Date of Award
Doctor of Philosophy (PhD)
Dr. W. James
Many lakes act as receiving waters for polluted runoff and other effluents. Water quality problems in lakes depend for their management on numerical lake transport models. Lake transport models have recently become quite detailed and realistic. However, a difficulty still facing this field is the determination of the interfacial transports at the boundaries and related model parameters. Numerical modelling of lake physics and bio-chemistry requires special treatment of the boundaries at the air-water interface, sediment-water interface at the bottom of the lake and horizontal densimetric fluxes of active materials across the lake boundaries into and out of the lake. This latter problem is particularly complex when two interconnected lake basins of dissimilar characteristics exchange flow via communicating channel.
In this study, the following important parameters were derived and related to lake and flow conditions: surface drag coefficients, vertical eddy diffusion coefficients and bottom roughness.
At the air-water interface, momentum transfer is studied and the over-water wind stress is determined using the logarithmic wind velocity distribution and Von Karman's integral equation for turbulent flow over a rough movable surface of variable roughness. Thus the wind drag coefficient is determined as a function of wind-and-wave characteristics.
At the lake bottom, shear stress due to a very rough lake bed, with weed growth, is determined as a function of local parameters such as weed length and distribution. The approach is particularly suitable for shallow lakes with considerable roughness. Also, vertical transports at the sediment-water interface and in the water column above the sediments is studied using two natural tracers: temperature and Radon-222 isotope. Vertical eddy diffusivity in the lower layers of a lake is determined as a function of depth and time by using the observed temperature and Radon profiles.
At the lateral boundary, exchange flow between two interconnected stratified bodies of water is investigated. The local exchange is modeled through a proper treatment of stratified flow at the open boundaries at the two ends of the "connecting channel" and proper presentation of the effect of the adjacent basins.
Numerical models are developed to study the above processes and boundary conditions. The computational algorithms are tested for theoretical and computational performance. Numerical models are tested against available field observations at Valens reservoir, Hamilton harbour, Baldeggersee (Switzerland) and Lake Erie.
A three-dimensional hydrodynamical model of lake currents is applied to two, non-stratified and stratified, lakes during summer periods where field observations were carried out: Valens reservoir and Hamilton harbour.
Eid, Bassem M.F., "Investigation into Interfacial Transports and Exchange Flows for Lake Models" (1981). Open Access Dissertations and Theses. Paper 608.