Depth of view
The depth of view , also called Secchi depth after the inventor of the measuring method Angelo Secchi , describes in limnology the depth at which a Secchi disk just disappears from view. The method, invented in 1865, is still in use and enables long-term comparisons of the depth of view over more than 100 years. For optically very dense bodies of water there is also a measuring device with a sight tube, at the bottom of which an illuminated cross becomes unrecognizable as the level increases.
The depth of view serves u. a. to estimate the depth of the euphotic zone. The euphotic zone is the deep zone where photosynthesis takes place. According to the limnological agreement, 2½ times the secchi depth is calculated as the depth of the euphotic zone and, in a rough estimate, it is assumed that there is only 1% of the light intensity of the surface level.
In fact, the depth of view is not only related to the absorption of light, but also very much to the scattering of turbid substances . During the summer limescale precipitation (milky cloudiness in lakes with hard water) the depth of vision can decrease drastically, although a photometric brightness measurement hardly shows a corresponding loss in depth. Conversely, in clear bog waters, the Secchi disk can still be visible almost to the depth of the Euphotic Zone.
Readings
In the official lake report on the Carinthian lakes of July 5, 2018, the Weißensee is named with particularly high values of up to 12.3 m visibility.
See also
Individual evidence
- ↑ Plankton decline across oceans as waters warm
- ↑ See report: Rain puts waters to orf.at, July 5, 2018, accessed July 5, 2018.