>0.9

Mg²⁺ rich rocks or seawater mixture

<0.5

Ca²⁺ rich water

Na⁺:K⁺

15 - 25

Natural recharge area

50 - 70

Lower water flow course

>70

Volcanic rocks

<15

Na⁺ depleted water

Ca²⁺ + Mg²⁺:Na⁺:K⁺

>1.0

Upper water flow course of carbonate rocks or precipitation of NaCl from brine or exchange of Na⁺ and K⁺ against Ca²⁺ and/or Mg²⁺

<1.0

Lower water flow course of carbonate rocks

Na⁺:Ca²⁺

>1.0

Base ion exchange

<1.0

Reverse ion exchange

Ca²⁺: ${\text{SO}}_4^{2-}$ + ${\text{HCO}}_3^{-}$

<1.0

Normal hydrological cycle

>1.0

Ca²⁺ − Cl⁻