Table 2.

Irrigation suitability assessment of groundwater.

Indices	Equation	Objective	Classification	Reference
EC (μS/cm)	-	-	Excellent (<250) Good (250–750) Permissible (750–2000) Doubtful (2000–3000) Unsuitable (>3000)	[67]
TDS (mg/L)	-	-	Good (<450) Permissible (450–2000) Unsuitable (>2000)	[68]
TH (mg/L)	-	-	Soft water (<75.0) Moderate (75.0–150) Hard (150–300) Very hard (>300)	[69]
Sodium adsorption ratio (SAR; meq/L)	$SAR=\frac{{Na}^{+}}{\sqrt{\frac{{(Ca}^{2+}+{Mg}^{2+})}{2}}}$	For measuring the alkali threat in irrigation.	Excellent quality (<10.0)	[70]
			Good quality (10.0–18.0)
			Acceptable quality (18.0–26.0)
			Unacceptable quality (>26.0)
Percent sodium (Na%)	$Na\%=\left(\frac{{Na}^{+}+K^{+}}{{Ca}^{2+}+{Mg}^{+}+{Na}^{+}+K^{+}}\right)\times 100$	For evaluating the effect of Na concentration on soil structure and permeability.	Suitable (<30.0%)	[71]
			Marginal suitable (30.0–60.0%)
			Unsuitable (>60.0%)
Permeability index (PI)	$PI=\left(\frac{{Na}^{+}+\sqrt{{HCO}_3^{-}}}{{Ca}^{2+}+{Mg}^{2+}+{Na}^{+}}\right)\times 100$	For measuring the groundwater suitability for irrigation purposes.	Unsuitable (<25.0)	[72]
			Good (25.0–75.0)
			Suitable (>75.0)
Kelley's ratio (KR; meq/L)	$KR=\frac{{Na}^{+}}{{Ca}^{2+}+{Mg}^{2+}}$	For assessing the Na hazard on water quality.	Unsuitable (>1.00)	[73]
			Suitable (<1.00)
Magnesium hazard ratio (MHR; meq/L)	$MHR=\left(\frac{{Mg}^{2+}\times 100}{{Ca}^{2+}+{Mg}^{2+}}\right)$	For ascertaining the feasible threat from Mg in agriculture.	Suitable (<50.0)	[74]
			Unsuitable (>50.0)
Soluble sodium percentage (SSP)	$SSP=\left(\frac{{Na}^{+}}{{Ca}^{2+}+{Mg}^{2+}+{Na}^{+}}\right)\times 100$	For determining Na solubility proportion relative to other ions.	Good (<50.0) Unsuitable (>50.0)	[75]
Residual sodium carbonate (RSC; meq/L)	$RSC=\left({CO}_3^{2-}+{HCO}_3^{-}\right)-\left({Ca}^{2+}+{Mg}^{2+}\right)$	For evaluating the impact of HCO3− and CO32− on the groundwater quality due to irrigation.	Suitable (<1.25) Marginal (1.25–2.50) Unsuitable (>2.50)	[76]