Light scattering makes it much easier to detect imperfections, variations, and irregularities that are very small. The particles are still large enough to be affected by light and to deflect it, and the scattering will make them more visible indirectly. The optical scatter-detection techniques can be used to calculate the turbidity of a water sample very quickly and accurately.
One of the limitations associated with using turbidity meters is the simple fact that people will need to use them to test water samples only. People cannot place one of these laser beams throughout an entire water source. They will need to make an estimation about the quality of an entire water source based on the samples that they test.
While scientists and water quality monitoring professionals will typically test multiple water samples at a site, they will still only be able to test a limited number of them. From there, they will have to extrapolate. It is true that the turbidity of one sample will tend to be similar to the turbidity of another sample, so the margin for error might be smaller than people think. Still, some water sources can flow according to strange patterns. Technically, nephelometry can only be used to test the turbidity of a water sample.