The Aquifer System

In Auja area, ground water is part of the Eastern ground water basin in the West Bank which is divided by the Ramallah anticline in the west and the Jordan Valley in the east. In the CSA, geological formation according to physical properties is classified by the hydrogeological system into Aquifer and Aquiclude. Figure 2.18 shows this classification of the Eastern Aquifer which includes the Lower Jordan Valley and Jericho Area. Aquifer in this formation stores and sends water into wells or springs and the low transmitting capacity with insignificant quantities into wells or springs is Aquiclude(Almotazbellah A. Abadi May, 2006). Therefore, according to this hydrogeological system, there is deep carbonate aquifer and Alluvial Shallow Aquifer.

Figure 2.18: Hydrogeological cross section in Jericho area (Ground water Management Model, Task 7, The Jericho Model, CH2MHILL, 2001).

As it has been mentioned in chapter 1, two main Aquifer systems composed the Eastern aquifer, a largely phreatic upper Cenomanian-Turonian Aquifer, and a largely confined lower Cenomanian aquifer. These two aquifers are the most important available water resources in the central hills, the foothills and the Jordan valley. (SUSMAQ,2005) Different historical surveys and many several investigations said that these two Aquifers are not connected systems. However, other new investigations in last years approved some connectivity between these two Aquifers.

2.4.3.1 Deep Carbonate Aquifer

The mountain system layer manifested by Ein Samia and Ein Al Auja is exposed to the east of the lower upper cretaceous layer and in the Hebron anticlinal axis including further east, near the Jordan Valley and in the west by discontinuous fault escarpment reaching a height of 200 m near Jericho and becoming lower northwards. The valley bottom consists of lacustrine

sediments, evaporates and alluvial outwash forming an arid, flat, plane land.

Auja monocline strikes NNE south of wadi Samia and becomes NS northwards and dips up to 30˚E and ESE. It should be noted that Auja monocline is not a rift feature but is rather characterized by intensive fault systems, E-W directions. These fault systems are formed from grabens, horsts and step structures. This is shown by the continuity of the monocline, with almost the same dips from the immediate vicinity of the rift (Faria area) to more than 20 km far from the rift (Z.B. Begin, 1974).

Figure(2.19) shows PWA well drilled in 2011. PWA drilled this well to the west of fault system of about (496 m). This borehole penetrated the chalk unit of Abu Deis, Jerusalem, Bethlehem, Hebron and Upper Beit Kahel formations (Amer Marie,WP4.2: Hydro-geological Settings in the Western Part of the Jordan Graben/Case study: Wadi Al Auja Sub basin, 2013).

The groundwater table in both aquifer systems, according to constructed cross section, shows flow gently eastwards with no evidence of high gradient. From this hydro-geological investigations, groundwater's flow from the mountain aquifer eastwards through the fault system and drains the shallow Plio-Plistocene aquifer system. PWA well and Mekerot No. 2 well are hydro-geologically connected and the static water table in PWA borehole falls gently eastwards into the Plio-Plistocene boreholes. This indicates a hydraulic connectivity of both systems and the fault and Abu Deis formation do not act as a barrier. Therefore, recharge of the shallow aquifer system takes place by lateral flow from the Mountain Aquifer into the shallow aquifer system due to the overexploitation up coning of fresh water from the lower layers into the upper layers of the shallow aquifer system. This causes mixing with salty layers as well as with salty water bodies within the shallow aquifer system and the connection between the two aquifer systems (Figure 2.20), Dr. Amer Marie, (2013).

Figure 2.20: Hydrogeological cross section from west to east showing the groundwater table.

PWA, Amer Marei, 2013.

2.4.3.2 Alluvial Shallow Aquifer

The lower aquifer is formed from Lisan (Pleistocene), gravel and alluvial fans (Holocene) formation. Lisan Formation (Pleistocene Aquifer) extends along the Jordan Rift Valley and near Jericho. It is lithological composed of valve marl which consists of thin layers of gypsum and limestone. It includes three members [Samra coarse clastic, Samra silt and Lisan] of the Pleistocene Samra aquifer which are lateral facies succession from terrestrial/fluvial to deltaic/limbic and limbic/brackish lake environments. The marl, gypsum and silt units were generally considered as aquiclude.

Alluvial and gravel fans (Holocene) are distributed in the Jordan Valley. They cover the flood plains of the Jordan River and are strongly related to the faulted areas which are subjected to erosion. They are unconsolidated in the Rift Valley where they are formed of laminated marls with occasional sands. Gravel fans are widely distributed in the Jordan valley and have the capability of transferring groundwater from the limestone aquifers. The alluvial aquifer often directly overlies the Pleistocene gravel aquifer and is hydraulically interconnected with this aquifer. (Figure 2.21) (Wolfer, 1998)

2.4.3.3 Brackish Ground Water

Brackish water in Jericho District is one of the major obstacles which makes water utilization in irrigation and demotic use too complex and limited. This brackish water has increased causing serious problems.

Saline up coning along the Jordan valley resulted by steep dipping which caused deep circulation of the recharging ground water bringing it into contact with the salinity formation.

Currently, agricultural companies (Themar Company) practices flushing in the CSA with huge quantities of pumped water for long periods of time up to 14 hours in one time flushing.

In the CSA, water quality deterioration has increased during the last 30 years, with salinity becoming much higher by years in irrigated area. (Figure 2.22).

Figure 2.22:Water Salinity distributions in the CSA, Values of EC and Chloride concentration Electrical Conductivity (EC) is greater than 2 MS/dm towards the North east of irrigated area, and also in the southern part of irrigated area close to Wadi, while in the middle of southern area, EC decreases to less than 2 MS/dm.

Chloride concentration starting 500 mg/liter in west and increasing to 1500 mg/lit, Figure (2.23) shows one example of increasing salinity concentration in term of Chloride in Well number 19-15/023, and also the increasing of Electrical conductivity during years (2003- 2011).

Figure 2.23: Chloride concentration and EC during years 2000-2009 ,well no. 19-15/023.