THERMAL STRATIFICATION IN MODEL LAKES

Intro to the lab:

This exercise uses ordinary fish aquaria to illustrate the hydrodynamics of water in lakes as it is subject to heating, cooling, and the action of wind.  Specifically, we will examine how light, ice, and wind interact to control thermal distributions in lakes during a complete annual cycle (i.e., from winter ice cover to summer stratification to autumn turnover).  We also will examine the effects of wind energy on water currents.  Of course, it is important to remember that the aquaria are very simplified models of lake systems.  Although these models enable us to control thermal distributions and water currents with ease, we must keep in mind that sloping sides and basin irregularities modify water movements in real lakes.  Furthermore, thermal stratification in real lakes is a much slower and more variable process.

Problem set:

• INTRODUCTION: Write a short introduction to the lab. This should include a background for why we did this lab and why it is important. Length: (no less than 2 paragraphs, no more than 1 page).

• QUESTION TO ANSWER SEPERATELY:

1. 1. What processes determine the thermal patterns with depth during summer?, winter?, fall?
   2. What is the ecological significance of thermal stratification in summer?
   3. What is the ecological significance of fall turnover?

1. 1. Using your understanding of the relationship between water temperature and density with depth, why do some rivers flowing into reservoirs flow down into the hypolimnion whereas others flow across the surface?

1. 1. In your own words, define seiche. What is its limnological significance?

1. 1. What are the benefits to understanding the hydrodynamics of a real dimictic lake by modeling them in lab?  What are the disadvantages?