Determining effective factors controlling chemical parameters of Gamasyab and Ghareh-Sou Rivers (Case study: Kermanshah Province)

In this study, to investigate the water quality of Gamasyab and Ghareh-Sou rivers in Kermanshah province, data from a 5-year statistical period during 2014-2018 was used. To evaluate the water hydrochemical properties, the water type and hydrogeochemical facies of rivers water were first determined using Stiff and Piper diagrams. Next, the controlling factors of the water chemistry of two rivers were determined using Gibbs diagram and Ionic ratios. Also, factor analysis and cluster analysis were used to determine the processes affecting the hydrochemistry of river water. Finally, to predict the possibility of dissolution and precipitation of some minerals, their saturation indices were estimated. The results showed that water type and facies are bicarbonate calcite in both rivers. Also, the main factor in changing the chemical quality of water in both Gamasyab and Ghareh-Sou rivers is water-rock reaction. According to the results of factor and cluster analysis, this factor can be attributed to the dissolution of (1) carbonate and evaporation (2) dolomite formations in the rivers watershed. However, the dissolution of carbonate formations due to their abundances and distributions two watersheds has a more significant effect on the change in water chemistry.This resulted an increase in some chemical parameters such as calcium, magnesium and bicarbonate in the water of these two rivers and also caused positive water saturation index for aragonite, calcite and dolomite minerals. Considering the low contribution of the second factor in changing the chemical parameters, the saturation indices for evaporative minerals of gypsum, halite and anhydrite is negative.