[1] Salinization in coastal aquifers is a global phenomenon resulting from the overexploitation of scarce water resources. The Gaza Strip is one of the most severe cases of salinization, as accelerated degradation of the water quality endangers the present and future water supply for over 1 million people. We investigate the chemical and isotopic ( 87 Sr/ 86 Sr, d 11 B, d 18 O, d 2 H, and d 34 S SO4 ) compositions of groundwater from the southern Mediterranean coastal aquifer (Israel) and the Gaza Strip in order to elucidate the origin of salinity and boron contamination. The original salinity in the eastern part of the aquifer is derived from discharge of saline groundwater from the adjacent Avedat aquitard (Na/Cl < 1, 87 Sr/ 86 Sr $ 0.7079, and d 11 B $ 40%). As the groundwater flows to the central part of the aquifer, a dramatic change in its composition occurs (Na/Cl > 1, high B/Cl, SO 4 /Cl, and HCO 3 , 87 Sr/ 86 Sr $ 0.7083; d 11 B $ 48%), although the d 18 O-d 2 H slope is identical to that of the Avedat aquitard. The geochemical data suggest that dissolution of pedogenic carbonate and gypsum minerals in the overlying loessial sequence generated the Ca-rich solution that triggered base exchange reactions and produced Na-and B-rich groundwater. The geochemical data show that most of the salinization process in the Gaza Strip is derived from the lateral flow of the Na-rich saline groundwater, superimposed with seawater intrusion and anthropogenic nitrate pollution. The methodology of identification of multiple salinity sources can be used to establish a long-term management plan for the Gaza Strip and can also be implemented to understand complex salinization processes in other similarly stressed coastal aquifers.
Israel and the Palestinian Authority share the southern Mediterranean coastal aquifer. Long-term overexploitation in the Gaza Strip has resulted in a decreasing water table, accompanied by the degradation of its water quality. Due to high levels of salinity and nitrate and boron pollution, most of the ground water is inadequate for both domestic and agricultural consumption. The rapid rate of population growth in the Gaza Strip and dependence upon ground water as a single water source present a serious challenge for future political stability and economic development. Here, we integrate the results of geochemical studies and numerical modeling to postulate different management scenarios for joint management between Israel and the Palestinian Authority. The chemical and isotopic data show that most of the salinity phenomena in the Gaza Strip are derived from the natural flow of saline ground water from Israel toward the Gaza Strip. As a result, the southern coastal aquifer does not resemble a classic "upstream-downstream" dispute because Israel's pumping of the saline ground water reduces the salinization rates of ground water in the Gaza Strip. Simulation of different pumping scenarios using a monolayer, hydrodynamic, two-dimensional model (MARTHE) confirms the hypothesis that increasing pumping along the Gaza Strip border combined with a moderate reduction of pumping within the Gaza Strip would improve ground water quality within the Gaza Strip. We find that pumping the saline ground water for a source of reverse-osmosis desalination and then supplying the desalinated water to the Gaza Strip should be an essential component of a future joint management strategy between Israel and the Palestinian Authority.
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 ...
The flow rate of the Lower Jordan River has changed dramatically during the second half of the 20th century. The diversion of its major natural sources reduced its flow rate and led to drying events during the drought years of 2000 and 2001. Under these conditions of low flow rates, the potential influence of external sources on the river discharge and chemical composition became significant. Our measurements show that the concentrations of chloride, calcium, and sodium in the river water decrease along the first 20-km section, while sulfate and magnesium concentrations increase. These variations were addressed by a recent geochemical study, suggesting that ground water inflow plays a major role. To further examine the role of ground water, we applied mass-balance calculations, using detailed flow rate measurements, water samplings, and chemical analyses along the northern (upstream) part of the river. Our flow-rate measurements showed that the river base-flow during 2000 and 2001 was 500 to 1100 L s(-1), which is about 40 times lower than the historical flow rates. Our measurements and calculations indicate that ground water input was 20 to 80% of the river water flow, and 20 to 50% of its solute mass flow. This study independently identifies the composition of possible end-members. These end-members contain high sulfate concentration and have similar chemical characteristics as were found in agricultural drains and in the "saline" Yarmouk River. Future regional development plans that include the river flow rate and chemistry should consider the interactions between the river and its shallow ground water system.
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