Turbidity is measured by how scattered incoming light is by floating sediment, solids, and other particles. This can come from natural causes, such as silt and clay pushed downstream by a rainstorm, animal waste, and even algae growth. Increased sediment by urban centers, sewage and farmland runoff are all examples of Human intervention that can increase turbidity.
Runoff from construction sites is a major producer of large floating particles that can cause a lot of erosion and turbidity on it’s own. Pollution both in solids and liquids increases the amount of waste in the water, and even dissolved solids can increase turbidity in a river or lake. Some toxins found in runoff include heavy metals like lead and mercury, which can be devastating to marine and human life alike.