Turbidity measurements can be used to estimate suspended solids in water from a single watershed. The accuracy of the estimate can be improved by removing the sand and measuring it gravimetrically. Sediment yield is strongly influenced by geology of the drainage area. Mineralogy of the suspended material is also influenced by geology but to a lesser extent. Mineralogical measurements can be used to trace the sources of sediment where differences in geology exist within a watershed. They work best on smaller watersheds where the number of tributaries is small and distances short. They are probably best used in conjunction with other measurements such as suspended load and stream flow. X-ray diffraction patterns can be used to determine whether the major source of suspended clay in a stream is sheet erosion of weathered surface soil or erosion of unweathered subsoil and geologic materials.