Water Transparency Protocol

Purpose
To determine the transparency of water with a transparency tube, turbidity tube. Field of appliance: in either still or flowing waters, shallow water sites or in the surface layer of deepwater sites. Method with Secchi disk is also suitable, but it can be used only for still, deep water.

Overview
Students will collect a sample of water in a bucket and then pour water into a transparency tube with a pattern on the bottom, recording the depth of water in the tube just when the bottom cannot be seen anymore. Three measurements in agreement one each other are needed to obtain an average value to report on the Water Quality Data Sheet.

Student Outcomes
Students will learn to:
1.Use a transparency tube in a scientific measurement contest;
2.Examine reasons for changes in the transparency of a water body;
3.Relate the water transparency to the optimal conditions for aquatic life and photosynthetic activity
4.Relate the water transparency with other parameters

Time required for temperature measurement: 10 – 15 minutes
Materials and Tools
1.Transparency tube
Materials to prepare your transparency tube: clear tube of PVC or other plastics, approximately diameter 4,5 cm, length 120 cm, permanent waterproof BLACK marker, meter stick
2.Beaker (or other cup) for pouring water into the tube
3.Bucket equipped with rope tied securely to handle, to collect a representative water sample
4.Distilled water in a wash bottle
5.Latex gloves

Preparation (in lab, before field activity)
Prepare the transparency tube for your class (or group). One is enough for all the students.

Preparing a transparency tube:
1.on the bottom of the inside of the plastic cap, draw a Secchi disk pattern (alternating black and white quadrants) with one black marker
2.put the cap over one end of the tube, so water cannot leak out
3.use the marker and meter stick to draw a scale on the side of the tube. The bottom of the inside of the cap where the Secchi disk pattern is drawn is 0 cm. Mark every cm up from that point, till 120 cm.

Measurement of the water transparency Field procedure
1.Put your latex gloves on.
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.
Stand with your back to the sun so that the transparency tube is shaded. To standardize the data, all measurements are made in the shade.
Pour sample water slowly into the tube using the beaker. Look straight down to the bottom of the tube, with eyes close to the tube opening (without sunglasses!). Stop adding water when you cannot see the pattern at the bottom of the tube.
Rotate the tube slowly to make you sure you cannot see any of the patterns.
Read the value of the depth of water (in cm), helping with the marks on the out part of the tube.
Record the measurement on your Data sheet – under “Observer 1”.