In this study, the quality of groundwater resources of Farouj plain (northeastern Iran) was evaluated for drinking and industrial usage. For this purpose, 12 groundwater samples were collected to be analyzed. Temperature, pH and electrical conductivity (EC) was measured at the filed. Concentration of major anions (HCO₃^-, SO₄^2-, Cl^-) and cations (Ca²⁺, Na⁺, Mg²⁺, K⁺) was measured at the Ferdowsi University of Mashhad. Compositional types of the water samples were determined as Na-SO₄ and Na-Cl after data plot on the Piper diagram. It is also possible to identify the rock and minerals affecting the chemical composition of water by using the Piper diagram.
Dominant cation of the water samples is Na⁺ and dominant anions is HCO₃^-. Origin of sodium is attributed to dissolution of evaporate and also Na-feldspars of the Paleo-Quaternary volcanic rocks in the region. Origin of bicarbonate ion is attributed to dissolution of carbonate rocks of Tirgan Formation and also dissolution of the plagioclase in volcanic rocks. In terms of total hardness (TH), the samples are relatively hard to very hard. The most important underground water reservoirs in the study area is quaternary deposits, which partly formed by deposition of eroded Neogen red-bed sediments in the area, and affected on water quality due to their relatively high permeability to increase the water hardness.
In order to evaluate the process controlling the water chemistry, physicochemical data such as TDS,   Cl/(Cl+HCO3) and Na/(Na+Ca) were plotted on the Gibbs diagram and accordingly two main process including “Evaporation and “Water rock interaction” were determined for the source of water composition in the studied area. The Schoeller diagram showed that the water has well to inappropriate quality for drinking. Using various indices of Langelier's index, the Ryznar index, Puckorius scaling index and aggressiveness index of corrosion and sedimentation, it was concluded that the studied samples are completely inappropriate for industrial usage as they are almost sediment scaling.