2.9 Irrigation indices
It was observed that majority of people in a study area depends on agriculture of their daily income. Consequently, it is necessary to evaluate the suitability of groundwater for irrigation uses (Kumar et al., 2019). Various irrigation indices such as sodium absorption ratio (SAR), residual sodium carbonate (RSC), percentage sodium (%Na), magnesium hazards (MH), permeability index (PI), potential salinity (PS), residual sodium bicarbonate (RBSC), kelly ratio (KR), synthetic harmful coefficient (K), and exchangeable sodium percentage (ESP) are calculated using following formulas,
Sodium Absorption Ratio:
\(SAR=\frac{\text{Na}}{\sqrt{(Ca+Mg)/2}}\) (8)
Residual Sodium Carbonate:
\(RSC=\frac{\text{HCO}3\ +\ CO3}{Ca\ +\ Mg}\) (9)
Percentage Sodium:
\(\%Na=\frac{\ (Na+K)\times 100}{Ca+Mg+Na+K}\) (10)
Magnesium Hazards:
\(MH=\frac{\ Mg\ \times 100}{Ca+Mg}\) (11)
Permeability Index:
\(PI=\frac{\sqrt{\text{HCO}3}\ +\ Na}{\sqrt{(Na+Mg+Ca}}\)