Karkheh River is the third largest river of Iran and has strategic importance for its geographic zone and also has the great impact on the environmental phenomenon. Large part of the river flows in Khouzestan Province and is the main water supply for farming and irrigation of agricultural lands. Therefore, plan and performance of huge agricultural projects of the region is highly depends on the river’s behavior. For this reason water quality for drinking and agriculture consumptions in downstream of the reservoir dam was studied. Duration of statistical evaluation was considered between 2002 to 2011, and qualitative information of Karkheh River was obtained from 11 hydrometric stations that were being in this river’s segment. Annual average values such as EC, SAR, TDS, Chlorine, Sodium and Calcium which are the main quantities of water quality issues related to drinking and agriculture-irrigation water have studied during 10 years period of study. Moreover, international standards such as Schoeller, Wilcox and FAO were considered for the evaluation. The results indicate that in primary segment of the river after the dam, water quality is more suitable for drinking and agricultural consumptions than in middle part and downstream of river especially near to Hour-Al-Azim Pond ;for example, Wilcox Diagram shows that the water quality of the river for irrigation near the stations of Paye-Pol, Abdolkhan and Hamidiyeh are in class C3S1 or acceptable, while downstream stations such as Yazde-No, Pole-Bostan and Pole-Sabeleh and Hoveyzeh are in class C4S2 or inappropriate.