The turbidity test is used to see how clear or cloudy the water is. The turbidity of the water is determined by the type of river bottom, the pollutants, or the plant and animal life in the river. The Root River has a silt bottom therefore the river will be more turbid than bodies of water with a rock or sand bottom. The turbidity of the river increases with the increased runoff after rainfall. Turbidity range from 10 to 200 NTU units. The lower the NTU number the cleaner the water.