干旱区生态环境知识资源中心

The groundwater of Wadi Na’man, located in the western Saudi Arabia, is subject to intense exploitation to accommodate all the water demands of this arid area. The groundwater of its shallow aquifer undergoes significant decline in water level, increasing salinity due to long time of aridity and irregular rainfall. A multivariate statistical technique, factor analysis, was used to identify and understand hydrochemical association and processes leading to the variability of groundwater quality without losing any information of input pattern and avoid limitations that are associated with classical methods. R- and Q-modes of factor analysis were applied to 63 groundwater samples and 21 variables. This analysis revealed that three factors accounted for 55.9% of the total data variability. Factor 1 was dominated by Ca2+, Mg+, Na+, Cl-, and SO42- , as well as trace elements such as phosphorus and boron, suggesting effects from possible water-soil/rock interaction and agricultural activities. Factor 2 represented high aluminum loading as a result of the weathering of aluminum silicate minerals. Factor 3 revealed negative loading of dissolved CO3 and Zn, indicating long-term aridity. Plots of Factor 1 versus Factor 2 and Factor 3 demonstrated that the samples clustered into one group with good separation from outliers. In addition, assessment of the drinking quality suggested that salinity increases with SO42- -Cl--Ca2+.