Groundwater and drainage water samples were collected from Al-Mendasah area, North-West of Al-Madinah Al-Munawarrah for irrigation water quality evaluation. The well waters were classified as C4S2 to C4S4 waters i.e., very high salinity and medium sodium to severely saline and very high sodium waters. The drainage waters were classified as C3S2 to C4S3 i.e., high salinity and medium sodium to severely saline and high sodium waters. The groundwater is dominated by Na and Cl ions. The Saturation Indices (SI) showed that the groundwater is unsaturated with respect to anhydrite, halite, gypsum and fluorite; and saturated with respect to calcite and dolomite. The concentration of calcium is much higher than that of Mg. The nitrate contents are much higher than the recommended safe limits of 30 mg L-1 for drinking and other uses. The fluorite (F) concentration in 40% of well waters was higher than the recommended safe limits for drinking water. The strong correlation between SAR vs. adj. SAR and adj. RNa, Na vs. Cl, Mg vs. Cl and Mg vs. SO4 ions indicate the dissolution and precipitation reactions in the rock-water interface that affect groundwater chemistry. The soil infiltration rate will not be affected either by well water or drainage water irrigation. Only, 12% well waters are safe for irrigation directly without serious soil and crop production problems. The use of remaining 78% well waters requires the adoption of certain management practices such as adequate drainage, selection of salt tolerant crops and application of leaching requirements.
Omar A. Al-Harbi, G. Hussain and O. Lafouza, 2009. Irrigation Water Quality Evaluation of Al-Mendasah Groundwater and Drainage Water, Al-Madenah Al-Monawarah Region, Saudi Arabia. International Journal of Soil Science, 4: 123-141.