Origin of recharge and salinity and their role on management issues of a large alluvial aquifer system in the semi-arid Haouz plain, Morocco

The present study has analyzed the origin of recharge and groundwater salinity in the Haouz alluvial plain, located in Central Morocco. Stable isotopic data (O-18, H-2) indicate that the recharge of the alluvial aquifer is dominated by high-altitude meteoric water originating from the High-Atlas Mountains that border the plain to the south. Tritium globally indicates the presence of recent groundwater, as well as mixing between old and recent groundwater. Alluvial groundwater salinity varies from east to west. This variability is mainly induced by enrichment in chloride and sulfate salt contents. Strontium content reveals that sulfate could be related, respectively, to the influence of the Senonian carbonate deposits containing gypsum. Dissolution of halite is revealed by the plot of O-18 vs Cl, where the most saline samples do not show any changes in O-18. Br/Cl ratio varies in a wide range, probably due to an orographic effect. The nitrate distribution was analyzed using indicator-geostatistical techniques resulting in probability maps. Nitrate contamination is shown to occur particularly in the eastern part of the Haouz plain. In this paper, some aspects of groundwater resources management are addressed. Different management actions are identified with regard to the current water resources status and to the land and water uses. In this framework controlling groundwater abstraction, optimizing irrigation and enhancing mountain-front recharge constitute the major key management actions that should be carried out.