Hydrochemical investigation of water from the Pleistocene wellsand springs, Jericho area, Palestine

Saed Khayat · Heinz H�tzl · Stefan Geyer · Wasim Ali

Abstract Rising salinity levels is one of the significantsigns of water-quality degradation in groundwater. Thealluvial Pleistocene wells in the Jericho area, Palestineshow high salinity and a high susceptibility to contami-nation. Future exploitation and management of the waterresources under these conditions will require an in-depthunderstanding of the sources and mechanisms of con-tamination. The Jericho area is located in the basin of theJordan Valley. The basin is underlain by alluvial depositsof soil, sand and gravel of Quaternary units Q1 and Q2,and marl clay and evaporites of the upper part of unit Q2.This paper deals with the source of salinity in the wellspenetrating these units, using hydrochemical tracers. Thestudy reveals three main zones of different salinity byusing different diagnostic hydrochemical fingerprinting astracers for elucidating the sources of salinity. It wasconcluded that the most probable sources of salinity are(1) the geological formations of the region, which forminter-fingering layers of both the Samara and Lisan for-mations of Pleistocene age, where the eastern Arab Pro-ject aquifers show the highest amount of sulphate. Thelocation and geological formation of these wells withinthe Lisan suggested that the source of high sulphatecontent is the dissociation of gypsum. (2) The NaCl waterwithin the same area may also be upwelling from a deepbrine aquifer or from a fresh-water aquifer which containssalt-bearing rocks with particles becoming finer fromwest to east. This noticeable high TDS to the east shouldbe affected by the rate of pumping from the upper shallowaquifer, especially in the wells of the Arab Project whichare in continuous pumping during the year. (3) The thirdpossible source of salinity is from anthropogenic influ-

ences. This can be easily shown by the increment of ni-trate, bromide and sulphate, depending on whether thelocation of the well is coincident with urban or agricul-tural areas. This reflects the addition of agriculturalchemical effluents or sewer pollution from adjacent septictanks which are mainly constructed in top gravel in theSamara layer. Further studies are required, using differentgeochemical and isotopic techniques, to confirm thesesuggested salinity sources.

R�sum� Les teneurs croissantes de salinit� est l’un dessignes significatifs de la d�gradation des eaux souter-raines. Les forages des alluvions du Pl�istoc�ne dans lazone de J�richo, Palestine, montrent des degr�s �lev�s ensalinit� et une susceptibilit� aigu� aux contaminations.L’exploitation et la gestion future des ressources en eauxsouterraines sous ses conditions va n�cessiter une bonneconnaissance des m�canismes de la contamination. Lazone de J�richo est localis�e dans le bassin de la vall�e duJourdain. Le bassin est recouvert par les d�p�ts allu-vionnaires de sols, sables, et graviers d’unit�s quater-naires Q1 and Q2 et de marnes, argiles et �vaporites de lapartie sup�rieure de l’unit� Q2. Cet article traite de lasource de salinit� dans les forages p�n�trants ces unit�s,en utilisant des traceurs hydrochimiques. La conclusionest que les sources les plus probables de salinit� sont (1)les formations g�ologiques r�gionales, qui forment desinter-couches des formations de Samara et de Lisan d’�gePl�istoc�ne, pr�sentant des teneurs en sulfate �lev�es dues� la dissolution du gypse. (2) Les eaux chlorur�es-so-diques dans la mÞme zone peuvent remonter en prove-nance d’un aquif�re profond saum�tre ou d’un aquif�red’eau douce de roches salines pr�sentant des particules deplus en plus fines de l’ouest vers l’est. Cette TDS notable� l’est pourrait Þtre affect�e par le taux de pompage desformations superficielles, et notamment dans la zone duProjet Arabe qui est en exploitation continue toute l’an-n�e. (3) La troisi�me source de salinit� est d’origine an-thropique. Ceci est facilement d�montr� par l’incr�men-tation des nitrates, bromides, et sulfates d�pendant de lalocalisation des forages, � proximit� ou non des zonesurbaines et agricoles. Ceci refl�te l’utilisation des ef-fluents agricoles et des pollutions en provenance desfosses septiques qui sont install�es dans la partie sup�-rieure des graviers de la couche de Samara. D’autres�tudes sont requises, utilisant diff�rentes techniques iso-

Received: 27 February 2004 / Accepted: 5 October 2004Published online: 26 January 2005

� Springer-Verlag 2005

S. Khayat ()) · S. GeyerUFZ Environmental Research Centre Leipzig-Halle,Halle, Germanye-mail: saed.khayat@ufz.de

H. H�tzl · W. AliDepartment of Applied Geology,University of Karlsruhe,Karlsruhe, Germany

Hydrogeol J (2006) 14:192–202 DOI 10.1007/s10040-004-0399-0

topiques et g�ochimiques, qui permettraient de confirmerces sources sugg�r�es de salinit�.

Resumen Los niveles ascendentes de salinidad son unade las seales significativas de la degradacin de la ca-lidad del agua en agua subterr�nea. Los pozos aluvialesPleistocenos en el �rea Jeric, Palestina, muestran altasalinidad y alta susceptibilidad por contaminacin. Laexplotacin futura y gestin de los recursos h�dricos bajoestas condiciones requerir� un entendimiento profundo delas fuentes y mecanismos de contaminacin. El �rea Je-ric se localiza en la cuenca del Valle Jordano. La cuencaest� compuesta de depsitos aluviales de suelo, arena, ygrava de unidades Cuaternarias Q1 y Q2, y marga, arcillay evaporitas de la parte superior de la unidad Q2. Esteart�culo se ocupa de la fuente de salinidad en los pozosque penetran estas unidades utilizando trazadores hidro-qu�micos. El estudio revela tres zonas principales de di-ferente salinidad mediante la utilizacin de diferentesindicadores diagnsticos hidro-qu�micos como trazadorespara aclarar las fuentes de salinidad. Se concluy que lasfuentes m�s probables de salinidad son (1) las formacio-nes geolgicas de la regin, las cuales forman capas en-trelazadas de las Formaciones Samara y Lisan de edadPleistoceno, donde los acu�feros del proyecto rabeoriental muestran la cantidad m�s alta de sulfato. La lo-calizacin y formacin geolgica de estos pozos dentro dela Lisan sugieren que la fuente del alto contenido desulfato es la disociacin de yeso. (2) El agua que contieneNaCl dentro de la misma �rea puede estar ascendiendo deun acu�fero profundo salado o de un acu�fero con aguafresca que contiene rocas salinas que ocurren en part�culasfinas de oeste a este. Este contenido notablemente alto deTDS en el oriente deber�a estar afectado por el ritmo debombeo que ocurre en el acu�fero somero superior, es-pecialmente en los pozos del Proyecto rabe el cual seencuentra en bombeo continuo durante el ao. (3) Latercera fuente posible de la salinidad son influencias an-tropog�nicas. Esto puede mostrarse f�cilmente por el in-cremento de nitrato, bromuro y sulfato dependiendo enque si la localizacin del pozo coincide con �reas urbanaso agr�colas. Esto refleja adicin de efluentes qu�micosagr�colas o contaminacin por aguas residuales prove-niente de tanques s�pticos adyacentes que se construyenen la cima de grava en la capa Samara. Se necesitanestudios m�s avanzados utilizando diferentes t�cnicasgeoqu�micas e isotpicas para confirmar estas fuentes desalinidad sugeridas.

Keywords Jericho · Salinity · Lisan, Samara ·Hydrochemistry · Anthropogenic pollution

Introduction

Water is one of the most valuable natural resources in theMiddle East. The combination of population growth,economic and agriculture development, and an arid cli-mate results in overexploitation of the water resources in

the region. The continuous high water demand leads to arapid degradation of the quality of fresh-water resources,as a result of the salinisation and contamination processes(Vengosh and Rosenthal 1994; Salameh 2002). The lackof sufficient water, combined with rapid water-qualitydeterioration, presents a serious challenge to the people inthe region. In order to manage and share these water re-sources under conditions of accelerating degradation, it iscrucial to understand the origin and mechanisms of thecontamination process.

The salinity threatening these fresh-water resources isderived from different sources, both natural and anthro-pogenic. In general, overexploitation of fresh aquifersresults in a rapid decrease of water level, which thentriggers lateral as well as upwelling of deep saline watersfrom adjacent aquifers. Consequently, the overexploitedaquifers become saline due to mixing with saline waters(Vengosh and Rosenthal 1994; Salameh 1996; Marie andVengosh 2001). The other main factor which may have aneffect on water quality is the dissolution of salts from theLisan Samara formations. These layers are composed ofsoil, sand and gravel of the Quaternary units Q1and Q2,and marl clay and evaporites of the upper part of unit Q2which infill the Jordan rift valley to a thickness of at least2,200 m in most of the basin (EXACT 1998). In addition,human activity produces low-quality fluids which enterthe aquifer and further degrade water quality. These fluidsinclude sewage, landfill leachate and agricultural returnflows. The superposition of natural and anthropogeniccontaminants which affect water quality provides a sci-entific challenge, and requires unconventional interpre-tations for the origin of the salinity.

Study area

Jericho is located at the eastern boundary of the WestBank. It extends from 10 km to the north of the Dead Sea,and 7 km to the west of the Jordan River (Fig. 1). Al-though it has a desert climate, its location on the easternslope of the Jerusalem and Ramallah mountains in thewest, in a catchment area with abundant water resources,makes it an important agricultural district. Jericho has anarea of approximately 35,330 ha. The rate of annualprecipitation ranges between 120–250 mm, with an an-nual recharge rate of ~180 MCM (million cubic meter),while the annual consumption rate is ~140 MCM (ARIJ1997).

The geology of the area is characterized by Jordan riftvalley deposits mainly composed of Quaternary marl andalluvial formations. The geological formations in theJericho district are:

1. an alluvial formation (Q2, Fig. 1): this covers theeastern area adjacent to the Jordan. This formation isof Holocene–recent age, and bounded by the rift faultin the east and a fault of 12-km length to the west.

2. the Lisan and Samara formations (Q1, Fig. 1): thiscovers the major part of the Jericho area, and is of

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Hydrogeol J (2006) 14:192–202 DOI 10.1007/s10040-004-0399-0

Pleistocene–recent age. This formation includes threelocal faults up to 3 km long, and is bounded by thealluvial formation in the east and a fault to the west. Itis mainly composed of marl chalk and conglomerates.

3. a chalk and chert formation (Sc, Fig. 1): this formationoccupies the western part of the Jericho district. Theformation is of lower Tertiary–Senonian age. It iscomposed of Senonian chert and chalk deposits,structurally cut by minor faults.

4. a dolomite–limestone formation (K, Fig. 1): this for-mation is of Cenomanian–Turonian age, and covers avery small portion of the south-western and north-western parts of the Jericho district. It is mainlycomposed of limestone, dolomite and marl.

The major aquifer system in Jericho forms part of theeastern basin of the West-Bank which extends along theJordan rift valley. This system is of Quaternary Pleis-tocene Recent age, and mainly composed of the forma-tions described in (1) and (2) above. The main rechargesub-basin for this system is the Jerusalem-RamallahMountains, in which runoff water drains through wadisflowing from the west to the Jordan rift valley in the east.

The lithology of the Pleistocene is varved marl, con-sisting of thin layers of gypsum and limestone, andforming dark and light alternating bands, whereas thealluvium and gravel fan formations are of Holocene ageand cover the flood plains of the Jordan River. Theyconsist of laminated marls and gravel fans.

The main sub-basin feeding the Quaternary aquifersystem in the area is the Jerusalem-Ram Allah sub-basinwhich drains mainly through Wadi Qilt and Wadi Mak-kuk, the Neogene and Pleistocene Lower and Upper

Cenomanian aquifers, and then flows to the east andsoutheast. This sub-basin also contains three major springsystems:

1. the Wadi Qilt spring system: this includes Ein Qilt, EinFara and Ein Fawwar.

2. the Wadi Makkuk (Nuaymah) spring system: this in-cludes Ein Dyouk, Ein Nuaymah and Shosha.

3. the Ein Al-Sultan spring system.

All of the above mentioned springs are used for agricul-tural irrigation, except Ein Al-Sultan which is also usedfor domestic water supply. The water quality of thesesprings is relatively good compared with that of othergroundwater wells in the area. These wells are highlyimpacted by salinisation, an EC of >6,000 �S having beenrecorded in the eastern part of the area (PHG 1999).

The source of increasing salinity in this area is as yetnot well known, although previous studies identified threemajor sources of salinity. These are (1) the in situ dis-solution of salts within the Lisan Formation, (2) salinewater from adjacent deep brine aquifers (related to over-extraction), and (3) anthropogenic effluent mainly ofagricultural backflow and domestic sewer (Marie andVengosh 2001).

In this study, further investigation of the possiblesources of salinity is made, using the behaviour andcharacter of geochemical tracers.

Fig. 1 Study area of Jericho.The sampled wells and springsare shown with the differentgeological formations: Q1Quaternary Pleistocene, Q2Quaternary Holocene, Sc LowerTertiary to Senonian, K Ceno-manian

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Data collection and method

Groundwater sampling and the selection of sample siteswas aimed at providing supplementary analyses of tracersto characterize the chemical signatures of both fresh andsaline groundwater, and their variation with location.

In all, 21 samples from springs and wells were col-lected. Two water samples correspond to springs withrelatively fresh CaCO3 water, in addition to one closedwell which shows the same water type; two wells arelocated to the north of the study area within the alluvialSamara Formation of Wadi Nuw’emeh, 10 wells arealong Wadi Qilt (five west of the wadi and five east of thewadi), while the rest of the wells are located more to theeast of the area.

The samples were collected in the period October–November 2003, this being the end of the dry season.Sampling localities are shown in Fig. 1.

Onsite measurements for physicochemical parameters(pH, temperature, m-value and redox potential) werecarried out. The samples for anions were preserved usingHgCl2 for prolonged preservation of nitrate. For accuratechloride measurement, the chloride concentration wasdetermined in water samples for cation analyses. Most ofthe samples were clear, and thus no filtration was nec-essary. Because the samples were collected in the agri-cultural season, all the sampled wells had been pumpingfor a long period of time. Hence, no further purging wasneeded prior to sampling, and the samples were collectedimmediately. Samples for cations and anions were col-lected in 60-ml polyethylene bottles, and samples fortritium were collected in 500-ml bottles.

Major anions (NO3, SO4, Br, NH4, PO4 and Cl) wereanalysed using HP liquid chromatography. Concentra-tions of the major cations Ca, Mg, Na, Sr and K weredetermined by ICP-OES, and the trace elements Mn, Li,Ba, F, Si, B and Fe were analysed by ICP-MS. Due to thehigh chloride content, most samples needed dilution andtherefore, most trace elements were under the detectionlimits. Alkalinity and HCO3 were measured onsite by ti-tration. Tritium was measured by a liquid scintillationcounter. The sample is mixed with a scintillation mixtureof a solvent, emulsifier and solute. Tritium emits betadecay electrons, which excites the solvent. The solventtransfers its energy to the solute, which emits light photonpulses which are detected and counted.

All chemical and isotope analyses were carried out atthe UFZ Environmental Research Centre Leipzig-Halle.

Results

The chemical data are shown in Table 1. The major cationand anion concentrations of the groundwater from springsand wells in the region are plotted on a Durov diagram inFig. 2.

All the major anions and cations show an increasingtrend with water path from west to east (Fig. 3). Mg, K,Na and Br show good linear correlations with the calcu- T

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Hydrogeol J (2006) 14:192–202 DOI 10.1007/s10040-004-0399-0

lated TDS values, and all follow the west–east pattern,while Ca, Sr, B, SO4 and HCO3 show relatively lowcorrelations and nitrate shows very poor correlation, onlyscattered nitrate values being documented (Fig. 3g).

In general, the data reflect distinctive end members offresh water to the west and saline water further to the east,bordering five distinctive regions.

Springs and fresh-water end memberSprings in the west are characterized by Ca–Mg–CO3water with a low degree of mineralisation (~548 mg TDS/l). Tritium units in the groundwater from the springs are~4.5 TU, while for the adjacent Samed well the value is1 TU. These springs, which correspond to the fresh-waterend member, show low Cl contents with molar ratios of0.0033–0.0039 for B/Cl (Fig. 4b), ~1 for Na/Cl (Fig. 4c),0.0065–0.013 for Br/Cl (Fig. 4d), ~1.2 for Mg/Cl(Fig. 4a), ~0.18 for SO4/Cl (Fig. 4e) and 7.2–7.4*10�4 forSr/Ca (cf. below). The groundwater shows oversaturationindex values for dolomite and calcite, and undersaturationindex values for gypsum and aragonite (Fig. 5a–d).

Wadi Qilt wells (western sector)The groundwater from wells in the west of Wadi Qiltshows intermediate values between the fresh and salineend members, with a water type of Mg–Na–Ca–Cl–HCO3. However, the ion concentrations, mainly chloride,are much lower than in the eastern wells, and sometimesshow values which are close to this in the fresh-water endmember of the springs. Tritium units in the groundwaterfrom these wells are between 3.3–3.9 TU. The ionic molarratios for these wells lie between those of the two endmembers. They show lower saturation indices for dolo-mite and calcite than those of the springs, while the sat-uration indices for anhydrite and gypsum were higher.

These wells show relatively high carbonate, boron andnitrate values.

Wadi Qilt (eastern sector)The hydrochemistry for the springs further to the eastshows trends close to those in the western sector, but withhigher TDS values as well as major ion concentrations.The area is characterized by Lisan and Samara layersoverlapping with the top of the Samara layer. Tritiumunits in the groundwater from these wells are lower thanthose in the wells to the west, with values between 2–3.5 TU. This sector has the same saturation indices fordolomite and calcite as the rest of the Wadi Qilt wells tothe west, and much higher ones for gypsum and anhydrite(Fig. 5). Although the chloride concentrations for thesewells are higher (500–900 mg/l), TDS values are>2,100 mg/l, and the molar ratios for ions are muchlower; most of the molar ratios begin to take on stabletrends when reaching these wells, as do the wells to theeast (Fig. 3).

Wadi Nuwe�meh NorthThe results for the wells in this area to the north showhigh chloride contents (600–>700 mg/l) as well as highconcentrations of major anions and cations relative towells in the west and in Wadi Qilt West. This area ischaracterized by the dominance of the Samara formationwith high hydraulic conductivity. The water type is Mg–Na–Cl–HCO3, the same as that for western wells, bothhaving surplus Mg which originates from dolomite dis-solution of the Samara layer. All the minerals in thegroundwater from these wells are undersaturated. Themolar ratios for the major ions are close to those in theeastern wells. Tritium units in the groundwater from thesewells are around 1.5 TU.

Fig. 2 A Durov plot suggestssimple mixing or dissociation,the trend being from fresh, Ca–Mg–CO3 water in the springsand wells to the west, to Na–Mg–Cl water to the east

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Fig. 3a–k Major anions and cations vs. TDS (mg/l). Salinity increases from west to east in the study area. Mg, K, Na and Br show goodlinear relations, while Ca, Sr, B, SO4 and HCO3 show relatively poor correlations, and nitrate shows very poor correlation

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Fig. 4a–f Ion molar ratios forthe wells and springs. The wellsin the east have stable molarratios for most anions andcations

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East Arab Project wells (saline end member)The groundwater from wells shows the highest salinity inthe Jericho area, with a chloride content of more than1,800 mg/l for well 19-14/067 and a TDS value of3,664 mg/l. This relatively high saline water is of the Na–Mg–Cl and Mg–Ca–Cl type. The SO4 concentration is320 mg/l. The groundwater from these wells is highlysaturated with dolomite and relatively saturated withcalcite, while the saturation indices for gypsum and an-hydrite are higher than the rest of the wells but still un-dersaturated (Fig. 5). The carbonate concentration of440 mg/l (Fig. 2 h) is relatively high. The groundwaterfrom these wells shows the lowest tritium units whichwere below the detection limit of <0.6 TU for well 19-14/067.

Discussion

The chemical data for all the springs and wells show agradual increase for the major elements from the west ofthe area to the east along the water flow path. Thegroundwater salinity varies from fresh Ca–Mg–CO3 waterin the west to relatively high-salinity Na–Mg–Cl and Mg–Ca–Cl water to the east (EC>5,000 �S), differentiatingtwo distinctive end members. The molar ratios for most ofthe elements tend to be stable in the east and in Wadi QiltEast. This may be a result of a dominant source of salinityin the area. Some wells in Wadi Qilt West which showlower chloride contents also show high boron and nitratevalues, while wells to the north show less anthropogenicindicators and higher chloride contents.

The linear correlation in the Durov diagram (Fig. 2)also suggests a type of dissolution or simple mixing whichincreases with distance from west to east and to the north.The water type varies along these paths, from Ca–Mg–HCO3 for the spring water and Mg–Na–Ca–Cl–HCO3 forthe pumped wells in the west and middle of the studiedarea to more saline in the east where the Mg–Ca–Cl andNa–Mg–Cl water type dominates. The variability in bro-mide and nitrate concentrations depends on well locationand agricultural/domestic activities around the borehole.The groundwater mineralisation do not really reflect thespatial trend for the major elements, this being due tovariation in ion input along the water path (Fig. 5). Mostof the groundwater samples show tritium units of 0.8~4.5which reflect a water mixture between sub-modern andrecent recharge (Clark and Fritz 1997). The tritium unitsalso distinguish two differently aged end members whichrepresent this mixing. The groundwater in the westernsprings and wells of the alluvial aquifer comprise mix-tures of recharge from the past few years only (less than5 years). By contrast, groundwater from wells further tothe east with 3H below detection must have been re-charged prior to 1952, and can be considered as sub-modern or older. The tritium level declines with in-creasing distance along the water path through the wadis,and emphasizes that the mechanism of recharge is notrelated to direct infiltration of rainfall but rather of infil-

trated runoff along the wadis which drain from the Jer-usalem-Ramallah Mountains (the main recharge point). Ingeneral, the variation in salinity in the Jericho district canbe due to one or a combination of several sources ofsalinity and pollutants. These can be defined as havingthree main causative factors, as follows.

Saline-water sourceThere is good evidence of brine evolution further to theeast of the study area. It is believed that the overex-ploitation of the wells to the east of the Jericho area hasresulted in upwelling from another, deeper brine aquifer.However, its source, direction and location can not beidentified. The analyses of samples from wells in the eastshow highly saline Ca–Cl and Na–Cl water. A Na/(Na+Cl) ratio less than 0.5 in combination with a highTDS of >500 suggest a reverse softening and a mixing ofbrine water in the east with fresh water in the west.Moreover, the trend of a continuous increment of salinityfrom the west to the middle of the area is demonstrated inthe steady ratios for Na/Cl and B/Cl in the east group,with molar ratios of ~0.5 and 0.0026 (Fig. 4b, c). The lowtritium concentration in the study wells emphasizes thepresence of such a mixing process. The lower tritiumunits between <0.6–1 in the wells to the east may reflect amixing of younger water infiltrated from wadis runoffwith deep old water characterized by high salinity. Thisevidence could be made clearer by further studies of rareearth element concentrations and isotopic signatures.

Evaporites and in situ rock weatheringGenerally, all the wells and springs show HCO3/SiO2ratios of >10 and TDS>500, which suggests carbonateweathering along the water path. The Mg/(Ca+Mg) ratios,which are over 0.5 in most cases (Fig. 4c), indicate do-lomite dissolution, which overlaps with the Lisan layer inmost of the area. In addition to calcite precipitation, es-pecially for the wells in the east where the Ca/(Ca+SO4)ratios are 0.75–0.95, there is surplus calcium from thesuggested Ca–Cl brine, beside gypsum or carbonate dis-solution of the Lisan layer. The results show two mainevaporitic effects. These are mainly the effect of theSamara layer and its dolomite to the west, and the effectof the Lisan layer and its gypsum and calcite to the eastand north. Figure 5 shows that the groundwater in thewest is oversaturated with respect to dolomite and calcite,and becomes less saturated further to the east of Wadi Qiltand Nuw’emeh North. This trend changes for the wells tothe east where another input of Mg-rich salts raises thesaturation indices for dolomite and calcite in a trendwhich increases until it reaches the saline end member atthe eastern Arab Project wells. The Ca and HCO3 con-centrations are lowered by the precipitation of otherminerals such as gypsum and aragonites. Relatively highSO4 concentrations in the east, in parallel with a lowsaturation index of gypsum, indicate gypsum dissolution.Moreover, the increase in ion content, mainly Mg from asuggested brine source to the east, favours dolomitizationof the calcite and aragonite dominating the entire se-

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quence. Sr/Ca molar ratios of 0.0025–0.0155 emphasizethis dolomitization process (Sass and Starinsky 1997).

Except for the springs which show relatively freshwater, the ratios of Na/Cl (0.4 east–0.7 west), Mg/Cl (0.18east–0.5 west) and SO4/Cl (0.015 east–0.15 west) showvalues which are even smaller than the Lisan leaching

ratios which have values of 0.54, 0.23 and 0.05 respec-tively (Salameh 2002), and much lower than seawaterratios. The Br/Cl ratios (0.006 east–0.014 west) are higherthan that of seawater (~0.0016). Although the ground-water from many of the studied wells show different Br/Cl molar ratios which may also have been affected by

Fig. 5a–d Saturation indices(SI) for dolomite, calcite, gyp-sum and anhydrite vs. TDS. Theplots show different trends foreach mineral, the wells to theeast having higher SI valueswith respect to TDS

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dissolution of salts, the variation between this value andthose from the wells is mainly due to more Br input,suggesting two sources of origin: (1) halite dissolutionfrom the evaporitic Lisan layer with Br/Cl molar ratiosdifferent to those of brine water or seawater, and (2) ananthropogenic source of bromide which is used widely inthe form of methyl bromide in this agricultural area.

Anthropogenic influencesThe greatest anthropogenic effect on the groundwaterquality in the Jericho area is due to agricultural activities,which have three main indicators: (1) bromide, which isinjected as a fumigant into the land in the form of methylbromide gas; (2) NO3 from nitrogen fertilizers, pesticidesand manure; and (3) potassium, magnesium and calcium,which may appear in surplus amounts due to irrigationbackflow and infiltration with soil into the groundwater.

The wells in the middle and west of the Jericho areaare susceptible to agricultural influence. This is moreclearly present in the east, although the high chloride

content and the influence of natural evaporites make thisindicator more ambiguous. Figure 6 makes this pictureclearer. The iron factory site, as a non-agricultural area,was taken as an end member for the sewage input, and theArab Project well, where there is extensive agriculturewith less sewage input, was taken as the other endmember. There are two different trend lines for the twoend members and the mixing points of the two influencesin between. Nitrate values vary with activities and loca-tion. NO3 values increase significantly in the wells in theagricultural and animal farm areas or near septic tanks, forexample, Sabiru Rantizi well 19-14/06. This well is foundnear an animal farm, in an area which has widespreadagricultural activities and where pesticides are used ex-tensively. The same values are shown by the iron factorywell which taps the Lisan layer in the east, south ofJericho, but which has essentially no agricultural activi-ties. In this case, the main reason for the high nitrate levelis the common use of septic tanks. Locating the septictanks in this area may not be easy, especially as the area is

Fig. 6 Relationship between Kand NO3. The iron factory wasused as a sewage indicator endmember, and the Arab Project67 as an agricultural endmember. Most of the wells areaffected mainly by sewageinfluences

Fig. 7 Relationship between Sr/Ca molar ratios and Cl concen-trations. The data suggest threeinputs to the groundwater. Thebrine constitutes the most sig-nificant input, with a ratio of~0.008 for the Arab Projectwells in the east. The iron fac-tory well shows a ratio close tothat of the Lisan leachate. Mostof the wells undergo mixingbetween the three end members

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formed mainly by limestone and gypsum. The nature ofthe soft rock reflects a highly fractured texture throughwhich pollutants can easily pass. The continuous input ofpotassium in the groundwater from wells to the east mayreflect an agricultural source; this is a cumulative valueincorporating the potassium coming from sylvite in thisextensive agricultural area within the Arab Project Areato the east of Jericho.

Conclusions

The high salinity in the shallow Pleistocene aquifer in theJericho plain area is a function of three main contributingsources. Figure 7 shows the relation between the molarratios of Sr/Ca versus Cl, and the distribution of thegroundwater samples between the three main end mem-bers with respect to typical brine, freshwater and Lisanleachate Sr/Ca molar ratios.

In general, the hydrochemical and isotopic data clearlyindicate three contributions.

1. The evolution of calcium chloride in the wells to theeast which are relatively rich in strontium and Fe inparallel with low molar ratios for most of the elementscompared to seawater reflect a reverse softening and amixing of brine water.

2. The continuous increment of the major anions andcations, with chloride molar ratios which bear Lisanmolar ratios, suggest the in situ dissolution of rocks asan additional source of salinity. There is a decrease inwater saturation with dolomite and calcite for most ofthe wells in the west, in parallel with an increase ofMg, Ca and HCO3. These elements demineralise underthe effect of the other brine effluent when the waterreaches the eastern wells. The high Mg input favourscalcite dolomization in which the calcium present insurplus amounts forms Ca–Cl brine in the easternwells.

3. The anthropogenic effects from sewage and agricultureare clearly visible in the wells which have low chloridecontent, but by no means low brine effects, this lowerchloride with higher molar ratios, and high Br andnitrate suggesting the input of different water whichcontains pollutants. This water may result from agri-cultural backflow or sewage effluent.

The lithological formation of the area has a two-edgeeffect on the salinity increment in the area, the one being

the in situ weathering of the rock. The other is thestructure of the formation, which consists of dolomite andmarl from the highly transmissive Samara layer withcoarse gravel and high hydraulic conductivity, and theLisan layer with fine silts and low hydraulic conductivitybut highly fractured structure, where both serve as a goodmedium for pollutant transmission and storage.

Many aspects are still not clear and need further re-search using other technical investigations. More sam-pling for isotopes (deuterium, nitrogen15 and sulphur34)and pesticide indications were taken during the course ofthis study. When these analyses are completed, the mode,the tracks and the source of salinity and pollutants in thegroundwater within the Jericho area will be clearer.

Acknowledgements We express our deep gratitude to the GermanFederal Ministry of Science and Research (BMBF) (Dr. S. Kiefferand Dr. H.J. Metzger) for funding and support this Project, and forthe Country of Germany for their continuous support of thePalestinian people. Further thanks goes to all Colleages in PalestineHydrology Group-PHG (Dr. Tamimi and Dr. Ghanem) and all otherPartners in this Project for their joint work activities and Cooper-ation.

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