INVESTIGATION OF THE GROUNDWATER GEOCHEMISTRY OF THE WESTERN ATLAS AND ANTI-ATLAS MOUNTAINS IN MOROCCO USING BORON, STRONTIUM, AND RADIUM ISOTOPES

Morocco is one of the most arid regions of the world and based on several IPCC climate models annual precipitation is expected to decrease over the next few decades. With increasing demand for drinking water and irrigation sources the water crisis in Morocco is expected to become exaggerated. With increased withdrawal of groundwater, salinity levels have risen and become a limiting factor for sustainable management of water resources in Morocco. The degradation in water quality therefore has important implications for future economic development as well as social and political stability in Morocco. Water authorities are already struggling to distribute and provide potable water to the domestic and agricultural sectors in the arid areas of the country.

Here we present the geochemical and isotopic (boron, strontium, and radium) compositions of saline groundwaters from the selected aquifers. The geochemical study aims to evaluate the sources of salinity, mechanisms for salinization, and the occurrence of naturally occurring radioactive nuclides in water resources in three major basins (Souss-Massa, Draa, and Ziz) of Morocco. Identifying the origin of salinity and radioactivity is crucial for predicting future water quality trends, water management, and remediation. Preliminary investigation of geothermal waters shows high levels of naturally occurring radioactivity; 3-4 times higher than the USA-EPA MCL (0.185 Bq L^-1). The geothermal waters also show relatively low ⁸⁷Sr/⁸⁶Sr ratios (0.7076-0.7089), which correspond to the accepted ⁸⁷Sr/⁸⁶Sr ratios in marine facies of the Lower Jurassic and Lower Paleozoic found in the vicinity of the geothermal fields, respectively, and δ¹¹B (normalized to SRM951) values (0 to +12‰) relative to non-geothermal waters in the surrounding basins that are characterized by higher δ¹¹B (+16 to +76 ‰) and ⁸⁷Sr/⁸⁶Sr (0.718-0.721) values. The combined use of radium, strontium, and boron isotopes is shown to be a useful tool to delineate the source of radioactivity and salinity in the investigated water resources.