You can easily make a sechi disk to measure water turbity -- an indication of water quality in terms of its clarity.
Read more background about this activity in David Schindler's bio...
- 1. a 20cm-diameter, 6mm-thick Plexiglas disk with a hole in the middle (this may be cut from a square sheet of Plexiglas)
- 2. metal disk with a hole in the middle (to weigh down Secchi disk)
- 3. an eyebolt with nuts and washers to fit it
- 4. rope or cord- try to avoid cotton, as it stretches
- 5. waterproof black and white paint
Instructions and materials can be found at the following places: