Evaporation ponds have several uses. Salt evaporation ponds produce salt from seawater. They are also used to dispose of brine from desalination plants. Mines use ponds to separate ore from water. Evaporation ponds at contaminated sites remove the water from hazardous waste, which greatly reduces its weight and volume and allows the waste to be more easily transported, treated and stored. It is important to understand that evaporation is not the same as condensation although evaporation in an enclosed environment can subsequently lead to the condition of condensation as evaporated moisture is "condensed" out of the air and is reverted to a liquid stage.
Evaporation ponds can also be used to evaporate the precipitation that falls on a contaminated site. The contaminants that the water picks up on the ground are left behind after it evaporates. This prevents the contamination from spreading further down the watershed.
Evaporation ponds are used to prevent pesticides, fertilizers and salts from agricultural wastewater from contaminating the water bodies they would flow into. In California, selenium in agricultural wastewater has been especially problematic, causing birth defects in waterfowl.