The value of the EC [mS/cm] is determined by 3 anions: Cl (chloride), HCO3 (bicarbonate) en SO4 (sulphate).

For EC values below roughly 2 mS/cm the relation between EC and chloride is not linear due to the possible presence of bicarbonate and suphate. Above values of roughly 2 mS/cm chloride is dominant and the following relation can be used:

Cl (mg/l) = 360 * EC (mS/cm) – 450

for water of 25 °C. This formula is based on groundwater analysis in the Netherlands and is described in De Louw 2013.

A useful rule of thumb for EC>2 mS/cm is:

Cl (g/l) = EC (mS/cm) / 3

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