To characterize the spatial and temporal variability of surface water quality of Oued Tighza in Morocco. Two indices were used. The water quality index was calculated from nine physicochemical parameters (pH, T°, Electrical Conductivity Dissolved O₂ NH₄⁺ NO₃^- SO₄^2- PO₄^3- BOD₅) and the Organic Pollution Index was determined from 3 organic pollution indicator parameters (NH₄⁺ PO₄^3- BOD₅) measured during 12 months on 7 sampling stations. The values that were obtained are between 427.64 as the minimum value at station 7 and 581.717 as the maximum value at station S2 for the WQI and between 1 and 1.33 for the OPI at all stations. The results of both indices corroborate and indicated poor water quality in the different stations sampled. The water quality was critical during the study period due to the effects of the discharge of water from the urban wastewater treatment plant. Based on the results obtained, the values of the water parameters far exceed the values of the surface waters according to Moroccan standards and classify the water quality of the study area as poor to very poor.