Turbidity in river water is affected by the amount of suspended sediment present. By looking at data from New Zealand rivers, researchers found that specific turbidity, which considers the type and size of particles in the water, is a good way to compare sediment levels between different areas. They discovered that specific turbidity is most influenced by the type of rocks in the area, rather than land use or soil. Smaller particles in the water lead to higher specific turbidity, especially in areas with certain types of rocks. This means that the relationship between suspended sediment and turbidity varies across New Zealand, and specific turbidity can help compare sediment levels between different regions.