Indices

Formula

Reference

Percentage Sodium

$\%\text{Na}=\frac{{\text{Na}}^{+}+{\text{K}}^{+}}{{\text{Na}}^{+}+{\text{K}}^{+}+{\text{Ca}}^{2+}+{\text{Mg}}^{2+}}\times 100$

(Wilcox, 1955)

Kelly Ratio

$\text{KR}=\frac{{\text{Na}}^{+}}{{\text{Ca}}^{2+}+{\text{Mg}}^{2+}}$

(Kelley, 1940)

Magnesium Absorption Ratio

$\text{MAR}=\left(\frac{{\text{Mg}}^{2+}}{{\text{Mg}}^{2+}+{\text{Ca}}^{2+}}\right)\times 100$

(Szaboles & Darab, 1964)

Total Hardness

TH (CaCO₃) mg/L = 2.5 Ca²⁺ + 4.1 Mg²⁺

(Todd, 1980)

Residual Sodium Carbonate

$\text{RSC}=\left({\text{CO}}_3+{\text{HCO}}_3-\left(\text{Ca}+\text{Mg}\right)\right)$

(Eaton, 1950), (Raghunath, 1987)

Sodium Absorption Ratio

$\text{SAR}=\frac{\text{Na}}{\sqrt{\frac{\text{Ca}+\text{Mg}}{2}}}$

(Richard, 1954)

Permeability Index

$\text{PI}=\frac{\left(\left(\text{Na}+\text{K}\right)+\sqrt{{\text{HCO}}_3}\right)\ast 100}{\text{Ca}+\text{Mg}+\text{Na}+\text{K}}$

(Doneen, 1962)

Water Quality Index

$\text{WQI}={\displaystyle \sum _n^{i=1}{W}_i{q}_i}{\left[{\displaystyle \sum _{i=1}^n{W}_i}\right]}^{-1}$

(Sisodia & Moundiotiya, 2006)