Need to determine how clear the water is? Measure the turbidity or degree of visibility of the water you’re testing with the limnological secchi disc. Results are meaningless if they’re not repeatable and can’t be compared.
The sturdy plastic Secchi disc handily meets industry standards. It is 200 mm in diameter (7-7/8”) and has four quadrants, two white and two black. It is included 20 meters of 1/8” diameter line on a styrofoam form that will float if dropped in the water. Plus instructions that are written at a basic level.
Most scientists use a Secchi disc to determine the index of suspended matter in the water. The smaller the index - say, five feet - the more suspended material there is. The water is, obviously, less transparent, with a lower degree of visibility.
You can also use a Secchi disc to measure the depth of light penetration and can derive a rough estimate of the extent of the littoral zone.
Please note that this unit is designed for occasional student use only and is not meant to replace the professional Secchi discs.