Suitability Assessment of Surface Water Quality for Irrigation: A Case Study of Modjo River, Ethiopia

Table 9

Classification of IWQI parameters for surface water samples.

Hazard group	Weight	Parameter	Range	Rating	Suitability	Sample (%)	Gi
Salinity	5	EC (dS/cm)	<0.65	3	High	Nil	8.335
			0.65 ≤ EC ≤ 2.9	2	Medium	66.7
			>2.9	1	Low	33.3
Infiltration and permeability	4	EC (µS/cm) with SAR	See Table 6	3	High	16.7	8.668
				2	Medium	83.3
				1	Low	Nil
Specific ion toxicity	3	SAR	<10	3	High	Nil	6.667
			10 ≤ SAR ≤18	2	Medium	66.7
			>18	1	Low	33.3
		Chloride (mg/L)	Cl^− < 140	3	High	100
			140 ≤ Cl^− ≤ 350	2	Medium	Nil
			Cl^− > 350	1	Low	Nil
		Boron (mg/L)	B < 0.7	3	High	16.7
			0.7 ≤ B ≤ 3.0	2	Medium	66.7
			B > 3.0	1	Low	16.7
Trace element toxicity	2	Chromium (mg/L)	Cr < 0.1	3	High	33.3	4.666
			0.1 ≤ Cr ≤ 1.0	2	Medium	66.7
			Cr > 1.0	1	Low	Nil
Miscellaneous effects	1	Nitrate nitrogen (mg/L)	NO3 < 5	3	High	100	1.722
			5 ≤ NO3 ≤ 30	2	Medium	Nil
			NO3 > 30	1	Low	Nil
		Bicarbonate (mg/L)	HCO3 < 90	3	High	Nil
			90 ≤ HCO3 ≤ 500	2	Medium	16.7
			HCO3 > 500	1	Low	83.3
		pH	7.0 ≤ pH ≤ 8.0	3	High	Nil
			6.5 ≤ pH < 7.0 and 8.0 < pH £ 8.5	2	Medium	Nil
			pH < 6.5 or pH > 8.5	1	Low	100