Since 90% of the water required for various uses in Iran is supplied from groundwater sources, qualitative evaluation of this vital resource is of great importance. The aim of this study was to evaluate the quality of groundwater resources in Razan watershed of Hamedan using MI and PoS indices based on the content of Zn, Pb, Cd, and Cu during spring and summer of 2020. For this purpose, in the middle of spring and summer, 120 groundwater samples were randomly collected from 20 stations and the parameters of pH, EC and temperature were measured in situ. The content of the elements in the samples was read using induction coupled plasma emission spectrometer after the laboratory preparation process. The mean concentrations of Zn, Pb, Cd, and Cu in the samples in spring were 36.3, 7.87, 0.340 and 38.2 μg/l, respectively; In summer it was 38.3, 8.80, 0.430, and 42.4 μg/l, respectively, and in both seasons it was less than the maximum tolerance of WHO and the Department of Environment of Iran for drinking and irrigation of agricultural products. On the other hand, the mean values of MI and PoS indices in spring with 0.920 and 0.360 respectively indicated a clean quality level and minimum pollution and in summer with 1.05 and 0.410 respectively indicated low and mimimum pollution level. Therefore, although at the time of the study, the groundwater resources of the Razan watershed were not exposed to excess pollution to heavy metals, but by the indiscriminate use of agricultural inputs, especially potassium sulfate fertilizers, triple superphosphate, and chemical poisons containing heavy metals by farmers, the possibility of increasing the concentration of heavy metals in the soil and their penetration into groundwater aquifers will not be unexpected in the medium term
