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

• Published in: Hydrogeology journal Vol. 14; no. 1-2; pp. 192 - 202
• Main Authors: Khayat, Saed, Hoetzl, Heinz, Geyer, Stefan, Ali, Wasim
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer Nature B.V 01.01.2006
• Subjects: Aquifers; Contamination; Formations; Geology; Position (location); Salinity; Sulfates; Tracers; Wells; Middle East, Jordan Valley; Palestine
• ISSN: 1431-2174; 1435-0157
• DOI: 10.1007/s10040-004-0399-0

Rising salinity levels is one of the significant signs of water-quality degradation in groundwater. The alluvial Pleistocene wells in the Jericho area, Palestine show high salinity and a high susceptibility to contamination. Future exploitation and management of the water resources under these conditions will require an in-depth understanding of the sources and mechanisms of contamination. The Jericho area is located in the basin of the Jordan Valley. The basin is underlain by alluvial deposits of 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 wells penetrating these units, using hydrochemical tracers. The study reveals three main zones of different salinity by using different diagnostic hydrochemical fingerprinting as tracers for elucidating the sources of salinity. It was concluded that the most probable sources of salinity are (1) the geological formations of the region, which form inter-fingering layers of both the Samara and Lisan formations of Pleistocene age, where the eastern Arab Project aquifers show the highest amount of sulphate. The location and geological formation of these wells within the Lisan suggested that the source of high sulphate content is the dissociation of gypsum. (2) The NaCl water within the same area may also be upwelling from a deep brine aquifer or from a fresh-water aquifer which contains salt-bearing rocks with particles becoming finer from west to east. This noticeable high TDS to the east should be affected by the rate of pumping from the upper shallow aquifer, especially in the wells of the Arab Project which are in continuous pumping during the year. (3) The third possible source of salinity is from anthropogenic influences. This can be easily shown by the increment of nitrate, bromide and sulphate, depending on whether the location of the well is coincident with urban or agricultural areas. This reflects the addition of agricultural chemical effluents or sewer pollution from adjacent septic tanks which are mainly constructed in top gravel in the Samara layer. Further studies are required, using different geochemical and isotopic techniques, to confirm these suggested salinity sources.Original Abstract: Les teneurs croissantes de salinite est l'un des signes significatifs de la degradation des eaux souterraines. Les forages des alluvions du Pleistocene dans la zone de Jericho, Palestine, montrent des degres eleves en salinite et une susceptibilite aiguee aux contaminations. L'exploitation et la gestion future des ressources en eaux souterraines sous ses conditions va necessiter une bonne connaissance des mecanismes de la contamination. La zone de Jericho est localisee dans le bassin de la vallee du Jourdain. Le bassin est recouvert par les depots alluvionnaires de sols, sables, et graviers d'unites quaternaires Q1 and Q2 et de marnes, argiles et evaporites de la partie superieure de l'unite Q2. Cet article traite de la source de salinite dans les forages penetrants ces unites, en utilisant des traceurs hydrochimiques. La conclusion est que les sources les plus probables de salinite sont (1) les formations geologiques regionales, qui forment des inter-couches des formations de Samara et de Lisan d'age Pleistocene, presentant des teneurs en sulfate elevees dues a la dissolution du gypse. (2) Les eaux chlorurees-sodiques dans la meme zone peuvent remonter en provenance d'un aquifere profond saumatre ou d'un aquifere d'eau douce de roches salines presentant des particules de plus en plus fines de l'ouest vers l'est. Cette TDS notable a l'est pourrait etre affectee par le taux de pompage des formations superficielles, et notamment dans la zone du Projet Arabe qui est en exploitation continue toute l'annee. (3) La troisieme source de salinite est d'origine anthropique. Ceci est facilement demontre par l'incrementation des nitrates, bromides, et sulfates dependant de la localisation des forages, a proximite ou non des zones urbaines et agricoles. Ceci reflete l'utilisation des effluents agricoles et des pollutions en provenance des fosses septiques qui sont installees dans la partie superieure des graviers de la couche de Samara. D'autres etudes sont requises, utilisant differentes techniques isotopiques et geochimiques, qui permettraient de confirmer ces sources suggerees de salinite.