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:
\(PI=\frac{\sqrt{\text{HCO}3}\ +\ Na}{\sqrt{(Na+Mg+Ca}}\)