Dissolved solids are minerals in solution, typically measured in parts per million (ppm) using an electrical conductance meter calibrated to oven-dried samples. In humid regions, dissolved solids are often the dominant form of sediment transport. Solution features such as caverns and sinkholes are common in limestone regions.

Water that contains excessive amounts of dissolved solids is unfit for drinking. Drinking water standards typically allow a maximum of 250 ppm, the threshold for tasting sodium chloride; by comparison, ocean water ranges from 33,000–37,000 ppm. Phosphates and nitrates in solution are the major cause of eutrophication (nutrient enrichment resulting in excessive growth of algae). Dissolved solids buffer acid precipitation; lakes with low levels are especially vulnerable. High levels occur in runoff from newly-disturbed landscapes, such as strip mines and road construction.