Instructions

1. Print or draw the secchi disk image to the right

2. Preferably make the disk 20cm in diameter for readings to be comparable to other surveys. Laminate the disk if possible.

3. Punch a hole in the middle of the disk.

4. Tie the metal washer to the end of the string

5. Thread the string through the disk, so that the black & white portions face up from the washer.

6. Choose a time of day that you will take readings from to make your sampling quantitative.
Avoid sampling during rain and up to 3 days after storms to avoid experimental error.

7. Lower the disk into each water sample watch until it disappears.
Now raise the disk until you see it again. Clip the string with the clothes peg at the surface of the water. Record how far you have to lower the disk into the water until you cant see it anymore.
This is your Secchi reading. The lower the reading, the more turbid the water; any sources of error?

8. Make sure you clean the disk between each sample. Do at least 10 samples to get an average.

9. Contact your local water authority or local council environment officer to compare readings.

You will need:

- A printer or a drawing of the secchi disk image

- A local creek, river or bay i.e. still water

- Cardboard, hole punch, metal washer and string

- A laminator would be great to preserve the disk

- Tape measure and clothes peg

- Someone with you who can swim in case of emergency.