Water Temperature Protocol

Purpose
: To measure the temperature of water into the riverbed

Overview
Students will use an alcohol-filled thermometer or temperature probe to measure the temperature of water. Three measurements are needed to obtain an average value to report on the Water Quality data sheet.

Student Outcomes with this activity
Students will learn to:
Use a thermometer or a probe for temperature measurements in a scientific measurement contest
Relate the temperature to the optimal conditions for aquatic life
Relate the temperature with other parameters like Dissolved Oxygen
Examine reasons for changes in the Temperature of a water body;

Time required for temperature measurement: 10 – 15 minutes

Materials and Tools
Alcohol-filled thermometer equipped with string to lower the thermometer into the water. The string will end with a rubber band to handle without dropping or loosing the instrument. If possible, choose a thermometer that permits measures at least to 0,5 degrees.
Clock or watch
Distilled water in a wash bottle
Latex gloves

Preparation (in lab, before field activity)
Equip the alcohol-filled thermometer with string and rubber band attached
Check the alcohol column on your thermometer to make sure there are no air bubbles trapped in the liquid.

Measurement of the water temperature. Field procedure
1. Verify at your observation site if you can easily reach the water surface, submerge the thermometer or probe at 10 cm of depth and make the readings in safety conditions without remove the meter from water. These are the best conditions to take the water temperature data: go directly to step 3. If not, go to step 2.

2. Collect a large amount of water with a bucket equipped with a rope. Throw the bucket out to a well-mixed area, a little distance from the shore. If the bucket floats, jostle the rope until some water enters the bucket. You should always take a sample from the top surface water, without the bucket sink to the bottom or stir up bottom sediment. Allow the bucket to fill about 2/3 to ¾. If possible bring the bucket in a shady place and quickly go to the next step.

3. Slip the rubber band around your wrist so that the thermometer is not accidentally lost or dropped into the water. Put the thermometer or the Temperature probe into the water (10 cm under water surface).

4. Leave the thermometer or the probe into the water for two minutes and read the temperature on the meter without removing it from the water.

5. Let the thermometer or probe stay in the water one more minute and read the temperature again. If the temperature has not changed, go to step 6. If not, repeat from step 4 until the temperature stays the same. NOTE: if you are measuring the temperature of water collected into the bucket, be sure that water temperature doesn’t change for the different temperature conditions of the air, and make all the operations as soon as possible. In case of doubt, ask to the teacher.

6. Record the temperature on the Water Quality Sheet. Have two other students repeat the measurements in the same place or catch new water samples and mark the read values under “Observer 2” and “Observer 3”.

7. If the three measurements are within 1,0°C of each other, calculate the average and report the data on the Preliminary data sheet. If the three measurements are not in agree within 1.0°C of each other repeat the observations, taking care leaving the instrument in the water long enough to stabilize and not removing the thermometer from the water so that the temperature doesn’t change before it can be read.

8. At last, rinse the thermometer or the probe with distilled water.

Looking at the data

Water temperature is largely determined by the amount of solar energy absorbed by the water as well as the surrounding soil and air. More solar heating leads to higher water temperatures. Water evaporating from the surface of a water body can lower the temperature of water but only for a very thin layer at the surface.

Water temperature can be sometimes colder and sometimes warmer than the air temperature, because it has a higher specific heat than air, this means it takes water longer to heat up and longer to cool down than air does.
Water temperature can be indicative of where the water originates. Water temperature near the source will be similar to the temperature of the source (e.g., snowmelt will be cool whereas some ground water is warm). Water temperature farther from the source is influenced largely by atmospheric temperature.

Temperature affects the oxygen content of water (oxygen levels become lower as temperature increases). It is also an important factor for life in a water body, because the rates of biological and chemical processes depend on temperature. Warm water can be fatal for sensitive species, such as trout or salmon, which require cold, oxygen rich conditions.

Causes of temperature change include weather, removal of shading stream bank vegetation, impoundment (a body of water confined by a barrier, such as a dam), discharge of cooling water, urban storm water, and groundwater inflows to the stream.