Visibility Disc acc. to Secchi

The Visibility Disc acc. to Secchi is a white lacquered brass disk with a diameter of 200 mm and a weight

of 1.7 kg. It is an easy-to-use instrument for stan- dard monitoring of water transparency in lakes and oceans.

The standard Visibility Disc is equipped with a rope of 3 meters in length. The first 2 meters of rope

above the disc have 10 marks every 20 cm for measurement purpose.

The Visibility Disc is lowered into the water and the immersion depth is read from the marked rope or the

graduation at the tape measure at the moment the disc vanishes from sight. It is lowered another 0.5 m

and then heaved slowly again. The second reading is made when the disc reappears. The arithmetic mean

from both readings equals the visibility depth

ساخت آلمـــان