There is no chemically pure water in the nature. All kinds of water contain more or less chemical components. The chemical quality of water depends on these components.
The following parameters must be determined for the characterization of the river-water:
colour; smell; transparention; temperature; pH; hardness; dissolved oxygen content; biochemical oxygen demand; chemical oxygen demand; suspension content; conductivity; concentration of chloride, sulfate, calcium, magnezium, sodium, potassium, hydrogen carbonate, ammonium, nitrite, nitrate, phosphate, cyanide, nickel, chromate, copper(II) ion, manganese(II) ion, iron, iron(III) ion, phenols, detergents.