Physical Characteristics: Lake Models

Abstract

The hydrodynamics of water movement is an integral component of a functional lake system. The importance of water movements and associated turbulence either has been underestimated or neglected in a large majority of limnological investigations. Consideration must be given to the effects of Water movements on stratification and on the distribution of temperature, dissolved gases and nutrients, and biota.

The various laboratory exercises outlined below are based on a simple and rather naive model of a lake. Thus you should bear in mind constantly that you are studying only a model and not an actual lake. Furthermore, many of the formulas are simplified accordingly. Some virtues of models are:

• 1. Size is reduced to manageable proportions.

• 2. Complexity is reduced to such an extent that mechanisms and processes may be appreciated readily and intuitively understood.

• 3. Experimentation is facilitated, whereas it may be difficult and/or expensive with a natural system.

On the other hand, unjustifiable extrapolations to natural conditions can be made from the model when the observer is not careful to distinguish between the two. In the experiments outlined here, for example, when the sides and bottom of the aquarium are not insulated, there is more rapid heat exchange between the model “lake” and its surroundings than ever would be the case in nature. Likewise, the amount of energy supplied by the heat lamp in relation to the depth of water is much higher than in natural situations. The reason for the modification is, of course, to accelerate the process. These and similar points should be stressed in your report(s).

These exercises are based on and modified from material prepared by Mortimer (1951) and Vallentyne (1967).