This paper presents new information about the hydrogeochemistry of water resources in the Gharye-Alarab basin (south-eastern Iran) and determines the predominant hydrogeochemical processes in the basin. To study this basin, 31 water samples were sampled, including 11 samples from rivers and 20 samples from groundwater. These samples were analyzed for temperature, total dissolved solids, Eh, pH, electrical conductivity, major ions and 18 trace elements volumes. The most waters were grouped into Ca–Mg–HCO3 type. Reaction of silicate minerals is the main factor of geochemical processes in the study area. Trace elements concentrations are low and Surface waters have lower trace element abundances compared to groundwater. Arsenic compared with other trace elements; shows a rather wide concentration range in the sampled waters, ranging between 0.6 to 502 µg/l and is not dependency with Eh and pH in surface water but are dependent on pH and Eh in groundwater.