Salinity, Chemistry and Quality of Groundwater in Robat – Khorramabad Plain, West of Iran

Salinization of groundwater in semiarid regions, as a limiting factor of use, has a strategic importance. In this study, the sources of salinity, chemistry and Quality of groundwater in Robat – Khorramabad plain have been identified using geochemical methods. Using data analysis, the concentration of cations and anions are recognized as Ca2+>Na+ >Mg2+>K+ and HCO3-> Cl-> SO42+> NO3-> F-. High concentration of Na+, Cl-, and EC in some places are related to the gypsum and salty Formations. In the study area, the salinization processes have been determined by natural and artificial activities. The mechanisms of salinization are defined by natural dissolution of gypsum and salt from Ghachsaran formation and man-made source (boreholes drilled through Ghachsaran Formation, salt mining, agricultural activity). In addition, high concentration of nitrate is related to agricultural fertilizers and effects of karstification with some possible influence of atmospheric NO3-. HCO3-, Ca2+ and Mg2+ concentration exceeded the standard limit in a few samples; elevated concentration appears to be related to the calcareous formation. Besides, Ca- HCO3 facies is a mainly hydro chemical facies of the groundwater followed by Na-K-HCO3 facies. Finally, according to the hydrogeological properties, chemical analysis, Schoeller, US Salinity Laboratory, piper diagrams and statistical analysis, it is revealed that dissolution of evaporate minerals such as halite and gypsum, increased concentration of total dissolved solids and amount of anoins and cations of groundwater of Robat – Khorramabad plain that caused increase of salinity in the study area.