Hydrochemistry and isotope hydrogeology in the Jericho area/Palestine
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3.3.4.1 Introduction
The eastern basin of the West Bank with Jericho in the centre comprises the wadis Malih-Buquei'a, Faria, Auja-Fasail, the area of RamallahJerusalem and the eastern desert sub-basin (Fig. 3.3.4-1). The area is part of the Jordan Rift Valley (Chap. 2.1). Its geology and structure of the area is rather complex (Rofe and Raffety 1963). All sub-basins drain eastward and southeastward to the Jordan Valley. Its wells and springs are used for domestic water supply and irrigation. The continuously increasing demand for water leads to rapid degradation of the quality of freshwater resources by salinization and contamination processes (Vengosh and Rosenthal 1994; Salameh 2002). The lack of sufficient water, combined with rapid deterioration of water quality, presents a serious challenge to the people in the region. Therefore, it is crucial to understand the origin and mechanisms of all contamination processes. Hydrochemical monitoring of aquifers is of great importance for public services and farming. 3.3.3.2 Hydrogeology of the eastern basin
The study area of the Jericho plain is outlined in Fig. 3.3.4-2. It is covered dominantly by Pleistocene Samra (or Samara) and Lisan Formations. In general, the Lisan Formation is the major source of soil and of water salinity in the Jordan Valley (Salameh 2002). Details about the sources of salinity are discussed in Chap. 2.3 and 3.1.4. The climate is semi-arid with low monthly precipitation rates of about 140 mm (ARIJ 1995). The main recharge areas are the Jerusalem Mountains on the western side (Fig. 3.3.41). The Cenomanian-Turonian aquifer system (Fig. 3.3.4-3) in the eastern basin is subdivided into the shallow and relatively thin Upper Cenomanian-Turonian- and the deep Lower Cenomanian sub-aquifer (Chap. 2.2). Additional sub-aquifers are hosted in Quaternary, Neogene and Eocene Formations. These sub-aquifers are described as follows: Pleistocene sub-aquifer consists of unconsolidated sand, gravel, cobbles, and boulders of different sizes separated by impermeable layers of
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Fig. 3.3.4-1. Geological map of the study area with the mountain aquifer in the western part and Quaternary/Pleistocene sediments of the Dead Sea graben to the east
saline lacustrine marl. The alluvial fans consist of gravel with sand and clay and occasionally sandy layers. The beds of the Lisan Formation (Pleistocene subaquifer) as well as alluvial and gravel fans (Holocene) extend along the Jordan Valley. The groundwater in these alluvial fans differs quantitatively and qualitatively depending on its location within the fan. Freshwater occurs around the apex of the fan, whereas saline water occurs at the fringes. Very steep, deep faults in the Jordan Rift Valley may cause deep circulation of groundwater bringing it into contact with salty formations. Brackish springs occur near the Jordan River.
Groundwater in the Jericho area
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Fig. 3.3.4-2. Study area of Jericho. Geological formations are indicated and locations of sampled wells and springs are shown. Note:
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