Turbidity is a measurement of the clarity of water, which is determined by the amount of suspended solids such as clay, silt, very tiny inorganic and organic matter, algae, and other microscopic organisms. Turbidity is present in every body of water, but significant problems can occur when some activity, whether natural or manmade, disturbs or introduces silt, clay and other matter into a lake, pond, or waterway. Construction, dredging, logging and fires are all human activities that can increase turbidity in nearby bodies of water. Given time and calmer conditions, most larger solids will settle to the bottom - think of the watery silt at the bottom of the local swimming pond or the deadly sediment covering and suffocating the Great Barrier Reef.
Aside from suffocating or outright burying bottom dwelling plants and creatures, highly turbid areas can create dangerous conditions for people and animals. The suspended solids in turbid water can carry contaminants like pesticides or heavy metals from nearby farms or mines. They often shelter biological threats like bacteria, parasites and other microorganisms, including cyanobacteria, which produces deadly red tides. Normally, these pathogens may be present in such tiny amounts that they pose no real risk. However these microorganisms often attach to organic and inorganic sediment, which provides sheltered transportation downstream. High concentrations can result in widespread infection and even death for wildlife or even human populations who use the water. Control of highly turbid waters which permits the sediment to settle out in a controlled location can be key to maintaining the health of human and animal populations, as well as all the associated economic activity they bring.
