This study was conducted to evaluate the quality of the GROUND WATERS and the impact of geological units on these WATERS in Hastijan area. For this purpose, 11 samples of water resources were collected with appropriate dispersal. Physico-chemical parameters of Mn, Ni, Cd, Cu, Zn, As Fe, Cr, and ions K+, Na+, Ca2+, Mg2+, Cl-, So42-, Hco3- as well as indicators TH, TDS, EC, and pH were determined. In order to assess water quality, the Piper diagram, Gibbs diagram, sodium absorption ratio (SAR), chloro alkaline index (CAI), the saturation index (SI), heavy metal pollution index (HPI), and the metal index (MI) were used. Investigating surrounding rocks of the area showed the existence of limestone, dolomite, sandstone, marl, and shale with layers of gypsum have declined the quality of water and have specially increased the salinity and concentration of Na+and Cl- in GROUNDwater resources of the study area. The calculation of saturation index indicated that these WATERS are super-saturated toward the dolomite and calcite minerals, but UNDER-saturated toward sulfate minerals. The iron concentration was higher than the standard limits of 0.2 ppm in about half of the samples that was caused by iron-bearing sandstones of Zaigun and Lalun formations located just upstream of springs.