Evaluation of groundwater quality in Al-Qassim area , Saudi Arabia, using cluster and factor analyses

Groundwater quality is controlled by many factors, the most important of which are aquifer geology, interaction between groundwater and the aquifer material, and influence of land use activities on the area. Since many variables interact in the chemistry of groundwater, evaluation of groundwater quality can be carried out with the help of multivariate statistical techniques. This paper deals with the application of cluster analysis and factors analysis to groundwater quality data in Al- Qassim area in central Saudi Arabia. The study area lies between latitudes 26° -27° N, and longitudes.43° 45 - 44° 03 E. The samples were grouped into three clusters. The first cluster included all samples belonging to the sandstone members of the Qassim Formation. The samples of the second cluster were attributed to the productive zones within the Khuff Formation while third cluster included all the samples from the Saq Aquifer. Three main factors were observed in the data. The first factor accounts for about 51.7% of the total variance. It reflects high landings for SO2-4, Na+, CI-, EC, TDS, Ca2+ and B in their order of importance, respectively. The second factor extracted from the variables accounts for about 10.1% of the total variance. It reflects moderate to high loadings for HCO-3, SiO2 and Fe. The presence of bicarbonate in this factor highlights the presence of recharge water. The third factor represents only 8.4% of the total variance. It shows moderate loading of nitrate ion concentration. The analyses revealed five main processes affecting groundwater quality in Al-Qassim area. These are dissolution, evaporation, limited recharge, return water irrigation and wastes