20 cm diameter
Opposing black and white quarters
Calibrated line attached, measuring tape reel
Turbidity is a measure of the ability of light to pass through water, essentially the measurement of the water’s murkiness. Measuring murkiness gives an estimate of suspended solids in the water. Turbidity measurements also take into account algae and plankton present in the water. Secchi discs’ ropes are marked at half metre and metre intervals. You measure how far you can lower the disc into the water until you can’t see it anymore. This is known as the secchi depth. If your disc touches the ground, but you can still see it, you can record ‘bottom visible’.