: About 98 percent of the world’s water is salt water. Out of the remaining 2% freshwater supply, 87% is frozen, forming the polar ice caps, glaciers, and icebergs. So there remains about 0.2 percent available fresh water contained in springs, rivers, lakes, groundwater, etc. Population growth and industrial development have resulted in increasing demand for water on one hand and pollution of water resources on the other hand. Therefore, to achieve sustainable development it is necessary to have an appropriate management system to protect the existing water resources. In arid regions where the main water source is ground water, the interaction of surface and ground water when the surface water contains considerable amount of pollution becomes an important issue. Gharachai river is located in the central province of Arak, Iran, and is the main receiving water body for discharges form municipal as well as industrial effluents of the region. Since ground water is the main source of water in the region, it was decided to investigate the interaction of this river’s water with ground water from qualitative aspect, especially during the low flow conditions, where the pollution load of the river is at its maximum levels. For assessment of water quality of the river, samples from 10 stations along the river as well as 10 wells in the vicinity of river stations were collected every two months and analyzed for conventional water quality parameters such as BOD, COD, NO 3 , EC, DO, TDS, Cl, PO 4 , T, Coliform and pH. The results were then analyzed using statistical analysis.