Monitoring water clarity and turbidity in rivers

Water clarity and turbidity are commonly used measures of optical water quality. Water clarity (also referred to as visual clarity) is the ability of light to travel through water. Turbidity is a measure of the amount of light scattered by suspended particles (such as clay, silt, algae and other particulate material) and is often referred to as water ‘cloudiness’ or ‘haziness’.

Water clarity may be reduced, and turbidity increased, when there is an increased amount of suspended sediment in the water. Poor water clarity can adversely affect the habitat and food supply of aquatic life, such as fish and aquatic birds, and the growth of aquatic plants; it can also impact aesthetic values and recreational use of rivers and streams.

Measures of optical water quality – water clarity and turbidity – are useful in monitoring programmes for detecting the effect of environmental mitigation actions designed to reduce sediment in waterways.