Climate change effect on groundwater characteristics within semi-arid zones from western Morocco

The purpose of this study is to evaluate quantitatively and qualitatively the groundwater from semi-arid environment in the context of climate change by taking the Barremian-Aptian and Hauterivian aquifers of Essaouira basin (Morocco) as an example. For a period of 43 years (1976–2019), the piezometric level shows a continuous decline which reaches 8 m for the Barremian-Aptian aquifer and 5 m for the Hauterivian. Hydrogeochemical analysis shows (i) a remarkable evolution of the facies from the Cl–Na facies to the Cl–Ca–Mg facies, (ii) the groundwater mineralization is governed by the dissolution and bases exchange phenomenon, (iii) the spatial-temporal evolution of the groundwater quality shows a gradual deterioration in time and space. The isotopic technique shows that the groundwater recharge is ensured by precipitation of oceanic origin without notable evaporation. Tritium tracing shows that the recharge of groundwater is post-nuclear, confirming that the recharge of the aquifers within the study area is in close relation to the precipitation. This recharge takes place at altitudes varying between 500 and 700 m asl for the Barremian-Aptian aquifer and between altitudes 350 and 400 m asl for the Hauterivian aquifer. However, the results obtained indicate that the water resource of Essaouira region is very vulnerable to global warming and requires adequate intervention of decision-makers in terms of management, protection and planning. [Display omitted] •Evolution of the chemical facies from Na–Cl type to Ca–Mg–Cl type is probably due to climate change.•Carbonate and evaporate dissolution and Bases exchange process are active in the study area.•Decline in piezometric level.•Degradation of groundwater quality.•Groundwater recharge is indirectly influenced by climate change causing decreased rainfall.