We check for turbidity a lot in places such as bay's, oceans, rivers, and much more. The reason we check for this in the water sources is so we can know how much sediment is in the water. The fish and other creatures in the water breathe, and they cannot have lots of sediment. We test turbidity by placing a disk in the bottom of a turbidity tube. You pour the water and check for visual of the secchi disk, and that is how you know how much sediment is in the water. - Caralyne M