Saed Khayat

Estimating groundwater recharge using the chloride mass-balance method in the West Bank, Palestine

Abstract 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 × 106 m3/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 × 106 m3/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 × 106 m3/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. Citation Marei, A., Khayat, S., Weise, S., Ghannam, S., Sbaih, M. & Geyer, S. (2010) Estimating groundwater recharge using the chloride mass-balance method in the West Bank, Palestine. Hydrol. Sci. J. 55(5), 780–791.

Sulphur and oxygen isotopic characters of dissolved sulphate in groundwater from the Pleistocene aquifer in the southern Jordan Valley (Jericho area, Palestine)

Sulphate and chloride concentrations in the shallow Pleistocene aquifer systems in the lower Jordan valley area indicate a general trend of increasing salinity eastward and southward. This study was conducted in one of the important sub-basins feeding the Pleo–Pleistocene aquifer in the Jericho area in the southern part of the valley using S and O isotopes of dissolved sulphate. The results show that sulphate has mainly two contributions to the groundwater. One is the surface seepage, which is present as a salty leachate form with the positive δ34Ssulphate values of primary gypsum in Lisan and Samara formations, and the second is the upwelling saline water which was in contact with a deep secondary gypsum, aragonites and salty rocks and rose up under heavy abstraction with depleted 34S in sulphate and relatively high sulphate and chloride content. The latest was clearly shown in the Arab Project wells to the east that is undergoing a continuous heavy abstraction. The isotopic signatures of S and O in these wells to the east show that this depleted 34S and highly concentrated sulphate might also indicate a dissolved sulphate originating from pyrite oxidation that results from the interaction with a pyrite-rich aquifer, which can well up with salty water under heavy abstraction and is oxidised in the upper aerobic shallow aquifer.

Hydrogeological assessments of major springs in Wadi Al Bathan, West Bank, Palestine

Wadi Al Bathan is one of the major tributaries of Wadi Al Faria River. Discharge measurements of six major Wadi springs taken over the past 24 years have been evaluated. The springs drained between 1.27 and 14.2 MCM/year during the hydrological years 1978/1979 (dry year) and 1991/1992 (wet year), respectively. The average calculated recharge area is about 16.8 km2, which actually exceeds the orographic area (10.5 km2), indicating one or more additional feeding water sources. It was found that there is a strong relationship between the discharge of this group and the intensity and distribution of rainfall. These results were confirmed using the hydrological data with the dissolved organic carbon (DOC) and total nitrogen (TN) in the hydrological year 2004/2005. The organic carbon and nitrogen show a flush-out response three and four months after a big rain event, which also reveals a long time until the conduits filled from the bottom to top of the layers.

Investigating the complex hydrogeological settings in the northeastern slope of the West Bank to the Jordan Graben (Malih and Jeftlik)

The northeastern part of the West Bank is located between brackish water sources in the Jordan Rift to the east, and the freshwater drainage from the mountain ridge, where the complex geological structure can facilitate a possible flow-path connecting different fresh and saline water bodies, saline sources, and the regional aquifers, which are the sources of their freshwater. Integrated stable and radioactive isotopic tools of tritium (3H), carbon (14C), carbon (δ13C), sulphur (δ34S) deuterium (δ2H) and oxygen (δ18O) were used to investigate the effect of complex geologic structure on the groundwater residence times, and respective potential sources, mixing, and recharge mechanisms. The low 14C values in the Malih and Marj Najeh area suggest mixing signatures between the old brine and the fresh water that conveyed from Cretaceous rocks and Eocene mountain aquifer in the west through the faults that intersect the water flow path to the north, toward the study area. The study differentiates between two salinity mechanisms, one that is coming from dissolution of saline sediments and salinized the triggered freshwater along with Faria flow path with high 14C pMC values and positive δ34Ssulphate and the second is the deep-seated pressurized CaCl2 brine, the upflow of which causes salinization of fresh groundwater bodies entering the system.

Using stable isotopes to delineate the relations between sub-aquifer systems in the eastern slope of Bethlehem-Hebron to the Dead Sea/Palestine

This study used stable isotopes 18O, 2H, and 3H in addition to hydro chemical and hydraulic data to explain the relations between different sub-aquifer systems in the Bethlehem-Hebron area. This area is suffering from high water shortage. The results indicate different recharge processes which occur within the upper and lower Aquifer systems of the mountain aquifer, and the structural features play an important role in this process. The isotopes emphasize the previous finding about the role of the structure, mainly, the extensive-folded anticlinorium that forces groundwater to flow through synclinal axes up- and downward, with different recharge mechanisms. While the lower aquifer received limited direct recharge from the exposed Bet Kahil formation in the upper part of the mountain, some of the upper aquifer groundwater seeping down through structural axes and faults fed the lower aquifer with additional amount of water. This process is attributed to the lowering of hydraulic head that varied seasonally. On the other hand, the direct recharge for the upper aquifer can be enough unless a huge amount of water from the upper aquifer seeping down due to steep hydraulic gradient to the Dead Sea springs. This process is apparently responsible for the quick drawdown of the groundwater level besides depletion of some wells drilled recently during the last decade in the upper aquifer. Delineating the relations between different aquifer systems within the study area can give further explanation and help the stakeholders to manage the water shortage problem, taking into account the main finding about aquifer relations in the future plans.