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The understanding of the flow pattern from the regional aquifers into the Rift Valley is important in building a conceptual model and in understanding the salinization processes.

From practical point of view, the understanding of the flow mechanism is an important tool for the sustainable exploitation of the groundwater resources to the population in the region. The drainage system of the West Bank is mainly controlled by tectonics. It was initiated by the uplift of mountains through the folding of the Syrian Arc system and rejuvenated through the formation of the Jordan Rift Valley. Between the mid Miocene and Pliocene recent phases a lateral strike slip movement of the African and Arabian plates took place. This movement placed the West Bank in the Sinai sub-plate and led to the development of the rhomb-graben left lateral shear fault system along the line of the Dead Sea. This fault system had a vertical, stepped component, which led to the lowering of the base level for both the surface and phreatic ground water drainage (Rofe & Raffety, 1963

and Andrew, 2000). This new base level of erosion deflected the drainage system from flowing to the Mediterranean Sea to flow towards the Dead Sea. This deflection divided the West Bank into two major basins, Mediterranean basin and Dead Sea basin, divided by the ridge on the Mountain Plateau. This process as a whole leads to the formation of the Jordan River basin. The West Bank area is affected by intensive structural patterns (anticlines and synclines) on which extensive secondary structures of different ages were formed, where the major folds are accompanied by a great number of faults, joints and fractures.

From the hydro-geological point of view, such extensive structural patterns affecting the study area controls the groundwater and surface water flow patterns and makes the West Bank a very good recharge area of the various aquifer systems. Also the highly faulted rock formations, which may reach several kilometers in some areas, increase the possibility of hydraulic connection between the various aquifer formations. For example, most springs of the West Bank formed within structural fault zones where the fault acts as a water barrier which transfers water from the affected aquifer formation to the ground surface. On the other hand, some drilling experiments in the West Bank showed that the groundwater wells have higher yield potential in areas with highly structural fault intersections (Sabbah

& Isaac,1996).

Combined with the topography of the area, the land forms and drainage patterns are highly determined by the geological structures. The predominant feature in the West Bank is the considerable contrast in elevation between the uplands (West Bank Mountains), with an altitude of up to 1200 m.a.s.l, and the great depth of the Jordan Rift Valley, with a depth of

~400 m.b.s.l. This distribution and variation in altitude can be seen in the topographical map of West Bank in figure 3.3. The crest axial line extending from the mountains of Hebron, Jerusalem, Ramallah, and Nablus is parallel to the Jordan Rift Valley in the East of the West Bank. The horizontal distance between the axial line and Jordan River is about 25-30km. This indicates a steep overall topographic gradient of about 1:20 to the East of the West Bank Mountains and at some locations the gradient is much steeper. For example, the gradient is about 1:90 in Jericho area.

Figure 3.3: Topographical map of West Bank which shows the distribution and variation in altitude in the topography of the study area and the West Bank, (SUSMAQ, 2001).

3.2.1 Surface Water Flow Direction of Marsaba-Feshcha Study Area

The flow direction of the surface water in the main streams of Marsaba-Feshcha drainage basin is at most towards the Northeast and to less extent towards the East and Southeast, while in the secondary creeks it is mainly Eastwards. Marsaba-Feshcha, the main wadi discharging this catchment, is a tributary of Wadi Qilt, Wadi Muqalek (Og), Wadi Qumeran and Wadi Al-Nar (Kidron), that flows Northeast, East and Southeast towards the Dead Sea (figure 3.4).

Figure 3.4: A map showing the Marsaba-Feshcha main drainage systems.

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3.2.2 Ground Water Flow Patterns of Marsaba-Feshcha Study Area

Most of the natural replenishment in the study area is from precipitation on the outcrops in the Western part of the basin. Accordingly groundwater flow direction is mainly from the West to the East. Groundwater head varies from +450m level along the Hebron and Ramallah anticlinal axes to –300m in the Jordan Valley and –400m in the Dead Sea. This groundwater head drop of 850m occurs over a distance of approximately 25-30km.

However, this flow pattern is far from being uniform. There are zones with a relatively low groundwater head gradients (Herodion, Ma’ale Edumim and Mizpe Jericho wells) while there are others in which the gradient is rather steep (Jerusalem-5 and Azriya-1 wells). This

variability in the hydraulic gradient is indicative of either a strong heterogeneity of the aquifer or steep changes in the layer geometry (Flexer et al., 2001).

Groundwater flow is governed by the geological structure of the area, uplifting of the secondary anticlinal axes, as well as flexures and fault systems (Rofe & Raffety, 1963;

Bensabat et al., 2004). The Marsaba Anticline in the East is the most dominant tectonic element, which acts as the Eastern model boundary and influences the groundwater flow path and the outlet in the Ein Feshcha Springs (Flexer et al 2001, Ben-Itzhak and Gvirtzman, 2005).

Several studies have focused on the groundwater flow field through the carbonate aquifer beneath the Jerusalem Desert. Arad and Michaeli, (1964) suggested a uniform West to East flow, parallel to the hydraulic gradient, because no contradicted observations were available. Subsequent studies have suggested a non-uniform groundwater hydraulic gradient, where the flow pattern is influenced by the geological structure (Burstein, 1970;

Fink, 1973). Guttman et al (2004), suggested that the groundwater flow bypasses the low conductivity zones, as shown by the fact that groundwater flow from Herodion and Shdema wells is mainly in the direction of Northeast parallel to the Bet Sahur (Beesan) Syncline axis and subsequently East. Ben-Itzhak and Gvirtzman (2005) noted that the groundwater flow is diverted Northward due to the geological folding structure but also they added the drainage basins are not completely separated; meaning that the structural barriers do not block the eastward flow everywhere throughout the area.

Therefore it is questionable why the groundwater flow changes its path from West-East direction to Northeast and/or Southeast direction, while the groundwater drains through the Feshcha springs a few km southern, instead of flowing the direct and short path to the East into the Rift Valley fill.