Heat Budgets of Stormwater Ponds and Use of the Stowaway Temperature Logger

Introduction A variety of factors affect the heat budget (change of heat content) of a body of water. Many of these factors vary substantially over a day-night period. Your assignment is to calculate a heat budget for a stormwater detention pond for one 24 h period and examine the dominant factors in the heat budget.

Procedure You will work in groups of 4 or 5, primarily for logistics reasons. Groups need not plan on working together for more than this exercise, and each of you will write his/her own lab report. Choose among yourselves a pond that is convenient to sample and work on. Be sure everyone in the group knows where the pond is, how to reach it, where to park, etc. Select a 24 period over which to deploy one of the Stowaway loggers. We will select suitable days to meet our respective schedules. Each group must have one or more representatives present to "launch" the Stowaway using the laptop and to download their data the next day. Choose who will be there and arrange a definite time for each operation. The use of the Stowaway, laptop and software will be demonstrated to each group. Initially your instructor will do the actual computer work, but eventually at least some of you can do this for yourselves. When your group has received its launched Stowaway, carry it to your pond and deploy it as you are shown. The aim is to have the logger barely float at some distance from shore. Use the monofilament line, weights, and small stakes as you are shown. Try to give your logger as much of a full 24 hour period to log temperatures as you can, then retrieve it, noting the time when you take it out of the water. During either your deployment or retrieval, measure the approximate area of your pond by pacing along its length and width and measuring your pace length in meters. A small sketch will help you determine area. Note also cloudiness, wind, etc. Return the logger and materials to the lab for your meeting with the instructor, who will download your data, print out a plot of your temperature data, and make copies of the plot and pond sketch for each group member. Calculate a total heat budget for your pond using the minimum and maximum temperatures recorded. Given that one calorie is the amount of heat to raise one gram of water by 1 degree C, and that 1 gram of water equals one cubic centimeter, you can calculate the total heat budget for your pond, assuming a 1 m depth, as:

(max temp - min temp) x depth (=100 cm) x area (in cm!)

The result should be a large number of calories. View your temperature log printout. When are temperatures highest and lowest? What are major portions of the heat budget you see operating in your data set?

Take a look at results from Stowaway Temperature logger deployments.

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