44 Int. J. Water, Vol. 7, Nos. 1/2, 2013 Copyright © 2013 Inderscience Enterprises Ltd. Hydrogeochemistry and groundwater quality assessment of Astaneh-Kouchesfahan Plain, Northern Iran Masoud Saatsaz* Department of Geology, Institute for Advanced Studies in Basic Sciences (IASBS), 45195-1159 IASBS Zanjan, Zanjan, Iran E-mail: saatsaz@iasbs.ac.ir *Corresponding author Wan Nor Azmin Sulaiman Department of Environmental Science, University Putra of Malaysia, 43400 UPM Serdang, Selangor, Malaysia E-mail: wannor@env.upm.edu.my Saeid Eslamian Water Department, Isfahan University of Technology, Isfahan 8415683111, Iran E-mail: saeid@cc.iut.ac.ir Kourosh Mohammadi Department of Irrigation and Drainage Engineering, Tarbiat Modares University, Tehran 14115-111, Iran E-mail: kourosh.mohammadi@gmail.com Abstract: In this study, the hydrochemical characteristics of 230 bore well samples were analysed in Astaneh-Kouchesfahan Plain. Data interpretation shows that alkaline earths (Ca 2+ and Mg 2+ ) exceed the alkalis (Na + and K + ) and weak acids (HCO 3 – ) exceed the strong acids (Cl – and SO 4 2– ) and Ca-HCO 3 type is the dominant hydrochemical facies. The distribution patterns of the abundant parameters show that changes in chemical composition occurred in the middle, southwest and west of the area due to either natural geochemical process and/or anthropogenic activities. The results of factor analysis show that factor 1 of the pre-monsoon and factor 2 of the post-monsoon have high loading in the ions Na + and Cl – . Furthermore, it is indicated that there is an increase in the loadings of Ca 2+ , SO 4 2– , HCO 3 – , Mg 2+ and K + in post-monsoon compared to pre-monsoon due to the effect of precipitation and subsequent dissolution of the calcareous rocks and fertiliser.