Transparency tube (120 cm)
- Fill the tube: Place the transparency tube directly in the stream, facing upstream, and fill it completely with stream water. Avoid disturbing the sediment while collecting your sample, as this can increase turbidity and skew your measurement.
- Find a suitable viewing location: Stand in a shaded area or turn your back to the sun to avoid glare. Remove sunglasses before looking through the tube.
- Look for the Secchi disk: Look straight down through the top of the tube at the black-and-white Secchi disk at the bottom. If you can clearly see the disk: Record 120 cm (1.2 m) as your measurement.
- If you cannot see the disk: Slowly drain water from the bottom of the tube by pressing the pin at the bottom of the tube against your foot or the ground. Continue checking the disk as the water level decreases.
- Record the measurement: Stop draining as soon as the black-and-white pattern on the Secchi disk becomes clearly distinguishable. Read the water level from the centimeter measurement markings on the side of the tube and record the measurement in meters. A higher measurement means clearer water and lower turbidity, while a lower measurement means murkier water and higher turbidity.
- Clean the tube: Pour out the remaining water and rinse the tube with clean water when you return home.