Investigation of the hydrochemical quality of surface waters of the Oued Inaouen watershed near the Driss 1er dam (Morocco) using multiv <i>ariate statistical methods and diagram analysis</i>

Abstract

This study, conducted from 2021 to 2023, aimed to determine the physico-chemical quality of the surface waters of the Oued Inaouen watershed near the Idriss 1st dam, and to identify existing pollutants and their origins. The research included spatio-temporal monitoring of 26 surface water stations. Results showed a spatio-temporal differentiation influenced by natural and human factors. The right bank exhibited significant mineralization, while the left bank had soft water due to Middle Atlas liasic limestones and dolomites. Multivariate statistical methods and diagrams (Piper, Schoeller, and Wilcox) were used for hydrochemical classifications and water quality assessment. Over time, surface waters became increasingly enriched with BOD 5 , COD, NO 3- , and NO2-, particularly downstream where more discharges occur. Pollution is linked to untreated household and industrial waste (notably Olive Mill Waste) and agricultural runoff from fertilizers, with greater enrichment during summer and autumn due to low upstream flows.