Turbidity, which measures water clarity, is important for various purposes like checking water safety and studying sediment transport. Optical probes are commonly used to measure turbidity, but they can give false low readings when there is a lot of sediment in the water. This happens because the probes can't handle very high levels of turbidity. In these cases, the probes may show decreasing turbidity values even though the actual turbidity is increasing. To get accurate measurements in high-turbidity conditions, other methods like acoustic measurements or taking sediment samples are needed.