The Dayet Er-Roumi Lake is one of the main Lakes in Morocco (SIBE), it's the only permanent continental Lake of low altitude. In recent decades, a significant deterioration in water quality generated by various pollutant discharges has been identified. The present study aimed to evaluate the metal contamination, assess the pollution degree and quantify Dayet Er-Roumi's water quality through Spatio-temporal monitoring of several metallic trace elements: Fe, Pb, Zn, Mn, Al, Cr, and Ba during 2019 in four seasons. Seven different sampling points were selected along the study area. The results revealed that the heavy metals concentrations in water varied widely and exhibit fluctuations among different metals during the beginning and end of the present study, the order of abundance of these metals  Al > Fe > Zn > Mn > Ba > Pb > Cr. According to the correlation analysis, highly strong positive correlations were observed among some heavy metals (between Al, Ba, Zn, and Fe), suggesting common sources and identical behavior during their transport. The calculated average of Heavy metal Pollution Index (HPI), based on the critical pollution index (100), denotes that the lake is suffering from serious metal pollution (HPI = 210.665 > 100), the highest level of HPI was recorded during two seasons: spring  (HPI = 651.362) and summer (HPI= 159.945). Overall, the results of HPI show a high degree of contamination indicating serious anthropogenic pollution. The obtained results confirmed that the anthropogenic activities, (agricultural and domestic, etc…) have a considerable impact on the water quality characteristics of the lake.