A Monitor's Guide to Water Quality

Why does it matter?

The availability of light underwater is important because algae and other aquatic plants need light for photosynthesis. Therefore, the productivity of a lake (how much plant and animal life it can support) is in part dependent on the clarity of the water.

Because water clarity is also affected by the amount of algae, Secchi depth can in turn be an indicator of lake productivity, especially if measurements are taken at times of the year when algae are most abundant.

Secchi depth has been measured in lakes and oceans for over a hundred years. While there are other more technologically advanced ways to measure water clarity, Secchi depth is a standard, simple and inexpensive method, and is still in frequent use today.

Related to Secchi depth : turbidity

Secchi depth is influenced by : chlorophyll, total suspended solids (TSS), water colour