Assessment of groundwater quality and its recharge mechanisms using hydrogeochemical and isotopic data in the Tafilalet plain (south-eastern Morocco)

The Tafilalet plain in south-eastern Morocco is characterized by two main economic activities -agriculture and tourism- supported by water from the Quaternary aquifer. This aquifer is under increasing pressure due to low annual rainfall (71.5 mm/year) and intense agricultural activities. Consequently, identifying groundwater recharge mechanisms and assessing their quality is essential for efficient management and sustainable socioeconomic development. This study aims to define the hydrogeochemical and isotopic characteristics and assess groundwater quality and recharge mechanisms in this area. The methodology consists of an investigation coupled with multivariate statistical analysis and combining hydrogeological, hydrogeochemical, and isotopic hydrology data. Results show that the main water types in the study area are sodium chloride and calcium magnesium chloride facies. The groundwater is mainly degraded and highly mineralized. Water shows increasing concentrations of Cl − and Na + due to the evapotranspiration of irrigation water. The isotopic data show average oxygen-18 and deuterium contents of δ 18 O avg = − 6.7‰ and δ 2 H avg = − 48‰, respectively, with tritium activity varying over a wide range, between 3 and 6 TU, indicating recent recharge. The 18 O and 2 H values indicate that the Quaternary aquifer recharge occurred under present climatic conditions. This modern recharge, attested by thermonuclear tritium, is confirmed by radiocarbon ( 14 C = 94.9 to 107.6 cfm). In the study area, the approximate soil and groundwater salinity maintenance in irrigated areas is closely related to the current hydrological conditions and the adopted irrigation mode. Therefore, water management measures such as using modern irrigation methods should be encouraged.