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Article Dans Une Revue Journal of Hydrology Année : 2024

The importance of mountain-block recharge in semiarid basins: An insight from the High-Atlas, Morocco

Résumé

Mountain-block recharge (MBR), consisting of groundwater inflows from the mountain block into adjacent alluvial aquifers, can be an important source of recharge for groundwater in (semi)arid areas. The present study examined Mountain-Block Recharge (MBR) from the Marrakech High-Atlas Mountain to the adjacent Haouz alluvial aquifer in Morocco, using environmental tracers and endmember mixing analysis (EMMA). The influence of the isotopic altitude effect on rainfall (−0.18 ‰ per 100 m for δ18O) in the mountains allows a distinction between groundwater originating from rainfall recharged at different altitudes. Mean δ18O values are heavier at lower altitudes (−5.1 ‰; < 1000 m.a.s.l), compared to medium altitudes (−6.4 ‰; 1000–1500 m.a.s.l), and higher altitudes (−7.6 ‰; >2000 m.a.s.l). Stable isotopes suggest a mountain-aquifer connectivity via two MBR flow pathways: a regional MBR from lower-medium altitudes, and a localised MBR from the foothills. In addition, chloride highlighted a potential origin via regional groundwater flowpath from the lower-medium altitudes where important evaporite deposits are present. Furthermore, samples dominated by lower-medium altitude recharge displayed lower 3H content, suggesting longer residence times typical of MBR, where mountain front recharge prevails. EMMA illustrated MBR contributions ranging from under 1 % to 98 %, varying by proximity to irrigated areas and streams. Eastern areas showed more significant regional MBR influence than the western due to existing faults, acting as hydrogeologic barriers to MBR. These findings are crucial in defining groundwater recharge origins for protection strategies in water-stressed semi-arid regions. Understanding MBR dynamics and connectivity between mountain blocks and aquifers is pivotal for sustainable groundwater resource management.
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Dates et versions

hal-04515578 , version 1 (21-03-2024)

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Citer

Houssne Bouimouass, Sarah Tweed, Vincent Marc, Younes Fakir, Hamza Sahraoui, et al.. The importance of mountain-block recharge in semiarid basins: An insight from the High-Atlas, Morocco. Journal of Hydrology, 2024, 631, pp.130818. ⟨10.1016/j.jhydrol.2024.130818⟩. ⟨hal-04515578⟩
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