The assessment of water quality has been carried out to determine the concentrations of different ions present in the surface waters. The Seybouse River constitutes a dump of industrial and domestic rejections which contribute to the degradation of water quality. A total of 48 surface water samples were collected from different stations. The first objective of this study is the use of water quality index (WQI) to evaluate the state of the water in this river. The second aim is to calculate the parameters of the quality of water destined for irrigation such as sodium adsorption ratio, sodium percentage, and residual sodium carbonate. A high mineralization and high concentration of major chemical elements and nutrients indicate inevitably a high value of WQI index. The mean value of electrical conductivity is about 945.25 ls/cm in the station 2 (Bouhamdane) and exceeds 1,400 ls/cm in station 12 of Nador. The concentration of sulfates is above 250 mg/l in the stations 8 (Zimba) and 11 (Helia). A concentration of orthophosphate over 2 mg/l was observed in the station 11. The comparison of the obtained and the WHO standards indicates a before using it use in agricultural purposes.