The quantification of natural recharge rate is a prerequisite for efficient and sustainable groundwater resources management. Since groundwater is the only source of water supply in the West Bank, it is of utmost importance to estimate the rate of replenishment of the aquifers. The chloride mass-balance method was used to estimate recharge rates at different sites representing the three groundwater basins of the Mountain Aquifer in the West Bank. The recharge rate for the Eastern Basin was calculated as between 130.8 and 269.7 mm/year, with a total average replenishment volume of 290.3 Â 10 6 m 3 /year. For the Northeastern Basin, the calculated recharge rate ranged between 95.2 and 269.7 mm/year, with a total average recharge volume of 138.5 Â 10 6 m 3 /year. Finally, the recharge rate for the Western Basin was between 122.6 and 323.6 mm/year, with a total average recharge volume of 324.9 Â 10 6 m 3 /year. The data reveal a replenishment potential within the estimated replenishment volumes of previous studies for the same area. Also, the range was between 15 and 50% of total rainfall, which is still within the range of previous studies. The geological structure and the climate conditions of the western slope were clearly play an important role in the increment of total volume. In some cases, such as the geological formations in the Northeastern Basin, the interaction between Eocene and Senonian chalk formations result in minimum recharge rates.Key words mountain aquifer; chloride-mass balance; recharge rate; groundwater replenishment Estimation de la recharge hydrogéologique par la méthode du bilan massique des chlorures en Cisjordanie, Palestine Résumé La quantification de la recharge naturelle est un pré-requis pour une gestion efficace et durable des ressources en eaux souterraines. Puisque l'eau souterraine est la seule source pour l'alimentation en eau de la Cisjordanie, il est primordial d'estimer le taux de renouvellement des aquifères. Nous avons utilisé la méthode du bilan de masse des chlorures afin de calculer la recharge en différents sites du Mountain Aquifer en Cisjordanie, représentatifs des trois bassins hydrogéologiques. La recharge du bassin Est a été estimée entre 130.8 et 269.7 mm/an, avec un volume total de 290.3 Â 10 6 m 3 /an. Pour le bassin Nord-Est, la recharge se situe entre 95.2 et 269.7 mm/an, avec un volume total de 138.5 Â 10 6 m 3 /an. La recharge du bassin Ouest, finalement, s'échelonne entre 125.7 et 323.6 mm/an avec un volume de 324.9 Â 10 6 m 3 /an. Ces données révèlent un potentiel de renouvellement plus important que les volumes estimés lors d'études antérieures dans la même région. La structure géologique et les conditions climatiques sur le versant ouest jouent manifestement un rôle important pour la contribution significative de ce versant au volume total de recharge. Dans certains cas, les formations géologiques, comme la craie Eocène et Sénonienne du bassin Nord-Est, ne favorisent pas la recharge ce qui se traduit par valeurs inférieures.Mots clefs aquifère de ...

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This study describes the impact of septic tanks on the groundwater quality of the shallow Pleistocene aquifer in Jericho area, Westbank, Palestine. Septic tanks are widely used for storage and disposal of sewage in the populated and agricultural city of Jericho. Routine hydrochemical tests for groundwater quality performed for several years identified the problem of a gradual nitrate increase, without pinpointing its definite sources. The geological formations of the Jericho area and the shallow nature of the Pleistocene aquifer, together with the mechanism of recharge, make the groundwater in this aquifer highly susceptible to contamination, particularly along sewers. The lithology of the Samara (high hydraulic conductivity) and the Lisan formation (low conductivity but increased infiltration along fractures) promote easy seepage of agricultural and anthropogenic inputs into the groundwater. Nitrate concentrations are elevated near septic tanks and animal farms, with nitrate values exceeding 74 mg/L. d 15 N nitrate and d 18O nitrate signatures suggest sewage and manure as the main sources of high nitrate concentration in the groundwater. Samples taken during the end of the dry season indicate that a slight denitrification in the aquifer.Keywords: Water quality / nitrate / pollution / isotope / N-15 isotope / O-18 isotope / Westbank, Palestine /

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