Assessment of Irrigation Water Quality in Al-Ajeilat, Libya: Physicochemical Properties, Bacteriological Safety, and Predictive Modeling

Abstract

In arid regions like Al-Ajeilat, Libya, where groundwater is the primary source for irrigation, assessing water quality is essential for agricultural sustainability and public health. This study aimed to evaluate the physicochemical and bacteriological quality of irrigation water from various sources in Al-Ajeilat and to establish a local predictive model between electrical conductivity (EC) and total dissolved solids (TDS). A total of 20 water samples were collected from domestic wells, farm wells, schools, commercial desalination plants, desalination stations, and mosque desalination units. Samples were analyzed for TDS, pH, EC, temperature, dissolved oxygen (DO), and the presence of Escherichia coli using standard methods. Linear regression analysis was performed to model the EC-TDS relationship. TDS ranged from 29 to 845 mg/L, EC from 26.7 to 4780 µS/cm, pH from 6.42 to 7.60, DO from 4.8 to 10.0 mg/L, and temperature from 6.7 to 22.0°C. Farm wells exhibited the highest mean EC (4232 µS/cm), indicating moderate to high salinity hazard for sensitive crops. Desalinated water sources showed very low salinity, making them highly suitable for irrigation. All 20 samples tested negative for E. coli, confirming no detectable fecal contamination. Linear regression demonstrated a strong positive relationship between EC and TDS (R² = 0.991, P < 0.0001), yielding the predictive equation: TDS = 0.157 × EC + 29.12. The derived EC-TDS regression equation provides a rapid, cost-effective tool for salinity assessment in Al-Ajeilat. Desalinated water is recommended for irrigating sensitive crops, while farm wells require salinity management strategies. Regular bacteriological monitoring should be maintained to ensure water safety.