Which water source usually has the highest concentration of dissolved solids?

Groundwater typically has the highest concentration of dissolved solids compared to the other sources listed. This is primarily due to its prolonged interaction with various minerals in the soil and rock formations underground. As rainwater seeps through the ground, it dissolves minerals and other substances, leading to a buildup of dissolved solids over time. Groundwater can also accumulate salts and other minerals, especially in arid regions where evaporation rates are high, concentrating these substances.

In contrast, surface water, like rivers and lakes, generally has lower concentrations of dissolved solids because it is more exposed to physical and biological processes that can dilute these substances. Rainwater has notably low concentrations of dissolved solids when it falls, as it is initially the most pure form of water collected from atmospheric condensation. Distilled water, on the other hand, undergoes a process that removes nearly all dissolved solids, resulting in very low concentrations.