This work was organized to study the hydrochemistry of groundwater in areas adjacent to Lake Dayet Erroumi to assess their suitability for drinking and irrigation. The physicochemical analysis of groundwater shows that pH, potassium, magnesium and sulfate values are within the permissible limits of the Moroccan standards for water drinking. The nitrate content from three wells exceeds the maximum value allowed by the Moroccan drinking water standards. These high nitrate values may be due to agricultural pollution or local contamination of wells. The values of electrical conductivity, sodium and chloride indicate that the wells on the north shore meet the Moroccan drinking water standards. On the other hand, the other wells recorded very high values surpassing the Moroccan standards for water drinking. The results of the Wilcox and Wilcox log diagrams show that the waters of the wells located north of the lake are suitable for irrigation. In contrast, the waters of the wells on the opposite shore are not suitable for irrigation due to their high salinity. Generally, these waters are suitable for the irrigation of salt-tolerant crops on well-drained soils.