For any hydrological or hydrogeological system, the arrival of new rains is the input signal to the system. This isotopic signature of precipitation is of major interest in understanding the recharge processes of the aquifer system. On the scale of a given basin, staged stations at different altitudes and spread out in space allow this input signal to be well characterized and to draw the local meteoric water line. In south-eastern Morocco, specifically, in the Errachidia region, several chemical and isotopic studies of the waters of the various aquifers have been carried out. In the absence of a local meteoric water line, these studies were based on the use of the global meteoric water line (GMWL). Thus, the objective of this work is the isotopic characterization and the elaboration of the local meteoric water line of the rainwater of the Ziz watershed. This characterization of the input signal in the study area is based on 41 measurements of stable isotopes (δ18O and δ2H) relating to the precipitations collected during the period from December 2019 to November 2020 in four staged stations at different altitudes and spread over the space from upstream to downstream of the watershed. The linear relationship of δ2H as a function of δ18O describes the local meteoric water line (LMWL) by equation δ2H = 7.5 ± 0.3 δ18O + 4.6 ± 1.7; R2 = 0.93. This equation displays evaporation confirmed by the arrival of continental currents in an arid environment. The variation in precipitation δ18O as a function of the sampling altitudes for the rains highlighted the relationship δ18O = −0.0026 ∗ Z − 1.67, with R2 = 0.93, which means an altitudinal gradient of −0.26‰ per 100 m of altitude. In this regard, the development of the local meteoric water line and the determination of the altitudinal gradient for the first time in this arid to semi-arid region of the watershed will be of great use to researchers and water resource managers; for example, to help determine the groundwater recharge areas, determine the exchanges between surface water and groundwater, and analyze many other hydrological problems.
Karstic aquifers play an important role for drinking and irrigation supply in Morocco. However, in some areas, a deeper understanding is needed in order to improve their sustainable management under global changes. Our study, based on chemical and isotopic investigation of 67 groundwater samples from the karst aquifer in the Rif Mountains, provides crucial information about the principal factors and processes influencing groundwater recharge and residence time. The δ18O and δ2H isotopic values indicate that the recharge is derived from meteoric water at high, intermediate, and low elevations for Lakraa Mountain, North of Lao River, and Haouz and Dersa Mountain aquifers, respectively. All samples show an isotopic signature from Atlantic Ocean except for those from the Lakraa Mountain aquifer, which shows Mediterranean Sea influence. Groundwater age determined by radiocarbon dating using the IAEA model indicates that the ages range from modern to 1460 years. This short residence time is consistent with the detectable tritium values (>2.7 TU) measured in groundwater. These values are similar to those of precipitation at the nearest GNIP stations of Gibraltar and Fez-Saiss, situated around 100 km north and 250 km south of the study area, respectively. This evidence indicates that groundwater in the Rif Mountains contains modern recharge (<60 years), testifying to significant renewability and the vulnerability of the hydrological system to climate variability and human activities. The results also indicate the efficiency of isotopic tracing in mountainous springs and would be helpful to decision makers for water in this karstic zone.
Le bassin de Berrechid situé au Sud de Casablanca, caractérisé par un climat semi-aride, est intensément exploité pour l'alimentation en eau potable et l'irrigation. Les traits géologiques de cette région ont confié à l'aquifère de Berrechid des caractéristiques hydrogéologiques importantes. Afin d'améliorer la compréhension du fonctionnement hydrogéologique de ce bassin, des mesures des concentrations de l'oxygène 18 et du tritium dans 71 échantillons d'eau souterraine et 8 échantillons d'eau de surface ont été réalisées pour étudier l'origine de recharge et l'âge des eaux souterraines de l'aquifère. Les données isotopiques de l'18O ont montré l'existence de deux principales composantes de la recharge de la nappe de Berrechid : une recharge par des eaux non évaporées provenant de l'abouchement latéral à partir du plateau de phosphates et de l'infiltration rapide de la pluie au Nord de la plaine et une recharge par infiltration des eaux de surface fortement évaporées dans le reste de la plaine. L'évaluation des temps de transit de l'eau a été calculée à partir de l'application des modèles d'écoulement exponentiel et de dispersion du programme Boxmodel aux données isotopiques d'entrée et de sortie. Ainsi, l'interprétation des teneurs en tritium et les temps de séjour estimés à l'aide du modèle empirique (moins de 20 ans) ont révélé que les eaux des secteurs Nord et Sud sont récentes, ce qui traduit une recharge récente et continue dans cette zone. Par contre, les eaux anciennes issues d'une recharge locale dans le reste du bassin reflètent la présence d'une lithologie peu perméable.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.