Geochemical processes analysis and evaluation of groundwater quality in Hamadan Province, Western Iran

We attempted to identify the geochemical processes responsible for the present status of groundwater chemistry and to assess the suitability of groundwater for drinking and irrigation purposes in Hamadan province, western Iran. Groundwater from 225 regional deep and dug wells was sampled from eight aquifers and analyzed seasonally during 2013–2014. The major ions (K+, Na+, Ca2+, Cl−, SO4 2−, and HCO3 −) were used to recognize the hydrochemical characteristics of the groundwater. Results show that the hydrochemistry of Hamadan province is partly due to the weathering process, dissolution of carbonate formations, the cation exchange processes, and chemical inputs from precipitation. The cation dominance order is Ca2+ > Na+ > Mg2+ > K+, while the anion dominance order is SO4 2− > HCO3 − > Cl−. The groundwater type in Hamadan-Bahar, Kabudrahang, and Ghahavand aquifers (central aquifers) is largely characterized as a chloride water type and in the other aquifers (western, southtern, and northern aquifers), relatively shifted to a HCO3 − water type. Except for a few locations with high values of EC, pH, and other dissolved ions, water quality is suitable for domestic use. Sodium adsorption ratio (SAR), %Na, and permeability index (PI) values suggest suitability of most water samples for irrigation purposes. The majority of water samples belong to C2S1 and C3S1, indicating medium salinity-low sodium and high salinity-low sodium waters, which high SAR, PI, and Na% in a few locations restricts its suitability for agricultural activities.