Application of the Irrigation Water Quality Index Model to Assess the Suitability of Groundwater for Irrigation in Wadi Al-Ain, East of Tobruk, Libya

Abstract

Water quality is a fundamental factor in agricultural production, particularly in arid and semi-arid regions, where salinity can adversely affect soil fertility and plant growth. This study aimed to evaluate the quality and irrigation suitability of groundwater from seven wells in Wadi Al-Ain, east of Tobruk, Libya, using physicochemical analyses, irrigation water quality indices, and the Irrigation Water Quality Index (IWQI) model. The analyzed parameters included pH, electrical conductivity (EC), calcium, magnesium, sodium, potassium, chloride, and bicarbonate. In addition, the sodium adsorption ratio (SAR), residual sodium carbonate (RSC), and permeability index (PI) were calculated. The results showed that the groundwater samples were generally suitable for agricultural use under appropriate management conditions. The pH values ranged from 6.9 to 7.6, Na% from 37.3 to 44.4%, SAR from 1.6 to 2.8, and RSC values were less than 1.5 meq/L, while PI values ranged from 55.6 to 66.3%. The IWQI values ranged from 58 to 81, with 71% of the samples classified as moderately suitable for irrigation, 14.5% as low suitability, and 14.5% Suitable for irrigation. These findings indicate that groundwater from the studied wells can be used for irrigation, provided that salt-tolerant crops are selected and water quality is monitored periodically to maintain sustainable agricultural production and soil fertility.