Evaluation of Factors Affecting the Chemical Quality of Groundwater of Kahriz Plain Using Statistical and Hydrochemical Methods

Kahriz Plain is located in the West Azarbaijan province, North West of Iran. Groundwater is the only source of water for agricultural and drinking purposes, therefore, its qualitative assessment has a special importance. In order to evaluate Hydrogeochemical variations 18 water samples, uniformly distributed in plain, were collected and analyzed. For assessing factors influencing the chemical quality of groundwater combination of statistical methods such as cluster analysis, factor analysis and hydrochemical methods such as Saturation Index and combined diagrams were used. Based on cluster analysis, groundwater samples fall into three groups. According to the plots of cluster analysis results in Piper diagrams dominant water type for first group is calcic bicarbonate and for groups of two and three is sodium chloride. Stiff diagrams were used to determine the source of groundwater, several sources such as gabbro, limestone, dolomite, shale, salty clays, sea water or a mixture of water sources were found. Based on the factor analysis of the chemical composition of groundwater, Kahriz plain is influenced by four factors. The first factor may be influenced by chemical dissolution processes and saline water intrusion. The second factor can be the result of relationship between aluminum, magnesium and iron ions and alteration of ultramafic rocks. The third factor reflects the impact of domestic wastewater, agricultural activities and highly use of nitrate fertilizers. The fourth factor is the result of chemical weathering of Fluorine and apatite minerals presented in igneous and metamorphic rocks. The calculated mineral saturation indices results show that the water is saturation with respect to the calcite and dolomite and under-saturation to gypsum. Combined diagrams results indicate that processes such as dissolution of halite, alteration of dolomite and ion exchange effect on chemical quality of groundwater.