Development and evaluation of numerical hydrodynamic models for small lakes and reservoirs

Abstract

The response of a small lake or reservoir system to wind and streamflow forcing is examined in this paper using a numerical model based on Navier–Stokes equation and a numerical hydraulic model using the segment-node approach. The main mass transport in the lake has been found to be due to wind; the circulation caused by stream inflow and outflow of the lake contributes a relatively small fraction of the total transport. The above-mentioned models have been applied to different wind regimes and constant or variable inflow–outflow conditions of Long Lake (Nova Scotia). Comparisons are made between observed data and model results by both models. The model response has also been studied for generation of seiches and wind setup in the lake; and the response of the lake to these forcing functions has been presented. The comparison of model results with in situ field data establishes model's suitability to make predictions. Drogue and water level measurements were made at a number of locations in the Long Lake to validate the numerical models. The results from the numerical simulation using the two models compare favourably with the observed data. As may be expected, the segment-node modelling scheme was found to be computationally more efficient and relatively easy to run on a personal computer. Key words: numerical model, hydrodynamics, circulation, Long Lake, temperature, dissolved oxygen, stratification, Nova Scotia.