Multivariate and seasonal analysis of microbial contamination in the Tamalout Dam water system

Waterborne diseases remain a public health concern, particularly in semi-arid regions where untreated surface waters are widely consumed. In Morocco, microbiological quality is still less investigated than physico-chemical aspects. This study examined bacterial contamination in the Tamalout Dam (Midelt, Morocco) during 2023 through 72 samples from six stations across tributaries and reservoir depths. Results revealed clear seasonal variation: higher temperatures (~16.5 °C) and lower dissolved oxygen (~5.2 mg/L) in the dry season, the turbidity (~88.7 NTU), COD (≈27.5 mg/L), BOD₅ (≈4.3 mg/L), nitrates and ammonium peaked in the wet season. Faecal bacteria exceeded 1,000 CFU/100 mL in tributaries, particularly during rainfall, and Staphylococcus aureus peaked in dry periods. Multivariate analyses identified three distinct pollution profiles linked to season, depth, and source.