Natural waters such as mineral water and seawater have often a non-negligible ionic strength due to the presence of dissolved salts which significantly affects their properties.

Surface water: I   =   0.001 – 0.005 M

Potable water, groundwater: I   =   0.001 – 0.02 M

Seawater: I   =   0.7 M

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Note: A solution with a concentration of 1 mol/L is said to be 1 molar, commonly designated as 1 M.

The typical ionic strength of potable water varies depending on the source and treatment process. However, it is generally low, with a typical range of 10-100 mM.

Seawater, on the other hand, has a much higher ionic strength due to the presence of various dissolved salts and minerals. The ionic strength of seawater is typically around 0.7 M, which is about seven times higher than that of potable water.