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Isotopic signatures for the assessment of snow water resources in the Moroccan high Atlas mountains: contribution to surface and groundwater recharge

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Abstract

To characterize snow isotopic signatures, monitoring of snowmelt was carried out at two sites (Oukaimden and Ifni) in the Moroccan High Atlas Mountains. For the Oukaimden site, samples of snow were taken by two methods to compare sampling techniques: (1) coring with a polyvinyl chloride (PVC) tube and (2) passive capillary sampling (PCS) installed at the snow/soil interface. The analyses show variable isotope contents, ranging from −14.7 to −2.5 ‰ for oxygen-18 and from −116 to −28.2 ‰ for deuterium. The most depleted values are observed in March 2013 at high elevation (3229 m asl). The majority of snow core samples display fractionation by sublimation, whereas those collected by the PCS sampling method are close to the Global Meteoric Water Line. The isotopic signature is comparable for snow, surface water and groundwater samples, indicating that snowmelt plays an important role in recharging aquifers, lakes, and rivers on the southern and northern sides of the Atlas Mountains. Recharge by snowmelt allows the dilution of salinity in adjacent aquifers. Characterization of the stable isotopic composition of snow obtained from snow cores is limited in comparison with the PCS method, which provides realistic compositions of the melt water contribution to water resources in this semi-arid area.

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