The present work is the result of a study that was carried out over the period 2010-2012, the objective of which was to determine the state of quality and the development of the synthesis maps of the surface waters of the basin. the Oued Inaouen slope, based mainly on the study of the physicochemical and bacteriological parameters of the surface waters. The analyze were performed on 26 well-distributed sampling points at the Oued Inaouen watershed using standard methods. The results of the analyzes revealed a spatio-temporal differentiation along the Wadi Inaouen watershed, following the intervention of natural and anthropogenic factors. The right bank of the basin is characterized by significant mineralization. On the other hand, the left bank is characterized by fresh water, reflecting the effect of limestone and Liassic dolomites of the Middle Atlas on the chemical composition of the water. This state of pollution is more marked downstream, in the stations that receive more rejects. Added to this are the climatic conditions of the region, which are characterized by very low flows of wadis upstream to dry during the summer season. The origin of this pollution is related to household and industrial discharges (especially waterlogs) dumped without treatment in watercourses, and the leaching of agricultural lands, as a result of the use of fertilizers, with an enrichment of much more important in summer and autumn.