Rivers are valuable sources of water supply for various purposes. These sources are seriously exposed to quality degradation due to the entry of various contaminants. Therefore, proper monitoring and quality management of these resources could be very important. In the present study, the quality of the Balikhlou river in Ardabil province, northwest of Iran, was investigated by surveying the trend of changes in river quality parameters, as well as water quality indices. In this study, after collecting the available data, by determining the trend of changes in quality parameters, the suitability of the studied river water quality for drinking and irrigation purposes was determined. The results indicated that there is an inverse relationship between changes in river discharge rate and the concentration of qualitative parameters. Therefore, it was found that salinity-containing pollution sources enter the river upstream of the desired station. Besides, the results of water quality indices showed that the water quality of the studied river is very poor for drinking (WQI>75). In addition, the results of water quality assessment for irrigation use based on SAR, KI, and SSP indices were generally considered inappropriate (SAR>26, KI>1, SSP>50), EC was often permissible (750<EC<2250), and MH was appropriate (MH<50). Our study highlights the importance of river water quality studies over time and thus can lead to better management of these valuable resources.