The Zeïda lead mine is located in the center of the upper Moulouya watershed, 26 km north of the city of Midelt. This part of the basin is characterized by a semi-arid to arid climate (300 mm/year) with a scarcity of water resources. This pushes villagers to draw directly from water contaminated by heavy metals and As from the lakes for their domestic needs and crop irrigation, hence the need to preserve these water resources. Mining in Zeïda has set up numerous excavations of several dozen hectares with depths of up to 20 m filled with surface water. The interaction of water with ore remains and with mining waste dams results in an enrichment of lake waters with heavy metals. The study of the comparative dissolution kinetics of galena and cerussite shows that the latter has a higher dissolution rate, which contributes enormously to the alkalinity of the waters.