الفهرس 
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Abstract
SUMMARY AND CONCLUSIONS
Western desert acts as one of the most vital regions in Egypt
for its size and natural resources. This desert lands owned the
greatest aquifer in Egypt (Nubian Sandstone Aquifer System)
which can use to increase the national income by increasing the
amount of agricultural lands and then amount of crops.
Therefore, intensive studies evaluate the condition of
groundwater aquifer in the study area via geophysical
exploration tools.
The investigated area is located in south Eastern portion
of Western desert of Egypt. It lies between latitudes 22° 15`&
22° 57` N and longitudes 31° 12` & 31° 54` E. It is bounded
by Wadi Halfa road to the west and Tushka Canal to the east
(Figure 1). The area under study covers about 2500 km2
. This
area is accessible through Cairo – Aswan – and Abu-Simbel
asphaltic road.
The present study deals with using the application of
remote sensing and different geophysical tools such as,
magnetic and geoelectrical resistivity to achieve the main
object of groundwater aquifer condition evaluation in the
investigated area.
The geomorphologic features in the study area can be
classified into three morphological units that are the Aswan
High Dam Lake: occupies the southern part of the study area,
Wadi Kurkur Pediplain: covers the area between Aswan
High Dam Lake and Tushka depression, and Tushka
Depression: topographic depression is considered as a
remarkable geomorphologic unit of Tushka area and which
occupies the northern part of the study area.
Stratigraphically, the area under study is covered by
sediments representing three ages (Upper Jurassic – Lower
Cretaceous, Lower Cretaceous, and Quaternary deposits) in
addition to Pre Cambrian basement rocks. The Stratigraphic
formations of the investigated land are subdivided into Nubian
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Sandstone presented by Abu Simbel formation, Lake Nasser
formation, and Sabaya Formation and Quaternary deposits.
Structurally, the study region is affected by fault system.
The fault system is represented by normal faults having four
directions E-W, N-S, NE-SW, and NW-SE.
Two landsat scene images and one scene of digital
elevation model image was used as application of remote
sensing technique to identify the lands affected by
hydrothermal solutions and construct a 3-D view to the surface.
The results of this classification are; 1- the surface of the study
area shows seven types of classes. These is surface water in
lake Nasser, plant cover, dry channels, Nubian sandstone on
the floor or covered by sand sheets, Nubian sandstone as hilly
lands or mountains, basalt and Nubian sandstone affected by
hydrothermal solutions. 2- The effect of hydrothermal solution
was defined at the high lands so it appears as isolated points
not in polygons. 3- The areas covered by sand sheets must
contain some locations affected by hydrothermal solution but
it’s not viewed.
The total intensity of the earth’s magnetic field was
measured along 24 profiles traversing the study area; 10
profiles have N-S direction intersected by 14 profiles with W-E
direction to form more or less grid pattern. The measured total
magnetic values are corrected diurnally and plotted on profiles
and contour maps. The resulting picture represents a total
intensity magnetic map. This map is reduced to the pole by
applying the reduction to the pole technique.
In Quantitative Interpretation of Magnetic Data; the
same direction and location of 24 profiles were extracting from
the total magnetic intensity map reduced to the north magnetic
pole to be modeled to delineate the depth of the basement
surface and the basement tectonic framework of the concerned
area. With the helpful of all available geologic and topographic
information and the obtained results from interpretation of
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magnetic and geoelectrical data; the basement cross-sections
were assumed.
from interpretation of the created magnetic modeled
profiles and maps, it was clear that: the maximum depths to the
basement rocks in the study area reached to 694 m. the area
under study affected by 17 normal faults that represent the two
directions NE-SW, and NW-SE. These faults create many
grabens and basement uplifts. This structural framework affects
the groundwater conditions.
A reasonable coverage for the study area was reached by
a total of 52 Vertical Electrical Soundings (VES). The
sounding stations were distributed, more or less, in the form of
a grid. The Schlumberger 4-electrode configuration was
applied in the present investigation. The maximum current
electrode separation (AB) ranges from 1000m to 3000m. This
electrode separation proved to be sufficient to reach the
required depth that fulfils the aim of the study in view of
evaluating the geologic and hydrogeologic conditions. The
resistivity sounding data has been interpreted qualitatively and
quantitatively.
The qualitative interpretation of the sounding curves
revealed that, the apparent resistivity values on the first, second
and third logarithmic cycles show unsystematic common trend
that is characterized by different apparent resistivity values due
to differences in the surface and near surface layers (irrigation
lands, sand sheets, and/or hard bed sandstone). In the last
terminal, it can be observed that almost all the field curves
terminate with uncompleted or completed H-type, which starts
at different distances (AB/2) in many curves. This indicates
that the main layer (expected water bearing formation) have,
most probably, different depths due to the effected of structural
elements. Three VES’es stations only show H-A-type that
means reaching to the basement rocks.
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The detailed results from the quantitative interpretation
of the geoelectrical resistivity sounding data at the western
portion of the study area are discussed in terms of the
geoelectrical parameters (resistivity and thickness) of the
resulting geoelectrical layers. The interpretation of the
resistivity soundings led to the detection of five main
geoelectrical layers (A, B, C, D and E). Some of these layers
have not been detected at some sounding stations. The first
geoelectrical layer (A) shows average transverse resistivity
ranges from 182 Ohm-m at VES 36 as minimum resistivity to
114858 Ohm-m at VES 22 as maximum resistivity. These big
differences between values are due to lithological changes of
surface layer. The thickness of this layer is ranging from 1.2m
at VES 36 to 6.6m at VES 31. The second geoelectrical layer
(B) has minimum thickness of 47m at VES 32 and maximum
thickness 127m at VES 1. This layer is corresponding to dry
layers of Nubian sandstone. On the other hand, it has a wide
rang of average transverse resistivity from 38.5Ohm-m at VES
39 to 5382.9 Ohm-m at VES 27. The third geoelectrical layer
(C) is corresponding to shall stone and its minimum resistivity
value is 8 Ohm-m at VES No. 17, whereas its maximum
resistivity value is 33 Ohm-m at VES No. 24. This
geoelectrical layer comprises the cape rock of the main aquifer
in the study area. The thickness of this geoelectrical layer
ranges from 8m at VES No. 29 to 19m at VES No. 1. This
layer was not detected through the sounding stations No. 2 and
3 due to the rising of basement rocks in this area. The fourth
geoelectrical layer (D) is the water bearing Nubian sandstone
in western area (formed from successive layers of sand and
shale or clay but the amount of clay is decreasing with depth)
and attains an electrical resistivity range from 56.2 Ohm-m at
VES No. 39 to 367 Ohm-m at VES No. 5. The minimum
thickness was detected for this geoelectrical layer is 56m at
VES No. 32, whereas its base was not reached in many VES’es
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but we use the result of magnetic data to determine the
maximum expected thickness of this layer 442m. The fifth
geoelectrical layer (E) which has higher resistivity values
reached to 11823 Ohm-m at VES 2. So, it’s interpreted as
basement rocks and detected in three VES’es only, which are
VES’es No. 2, 3 and 32.
The detailed results from the quantitative interpretation
of the geoelectrical resistivity sounding data at the north
portion of khor Tushka represented by three main geoelectrical
units (A, B, and C) as a result of geologic correlation. The first
geoelectrical unit “A” mostly is formed from number of thin
layers of different resistance, so, the resistivity of this unit is
result of average transverse resistivity (ρt) and ranges from 22
Ohm-m at VES 51 as minimum resistivity to 14850 Ohm-m at
VES 43 as maximum resistivity. These big differences between
the values are due to heterogeneity of surface layer, which is
change from wade deposits, soil, sand sheets, to compact sand.
The thickness of this layer is ranging from 1.6m at VES 41 to
8.2m at VES 49. The second geoelectrical unit “B”
corresponding to dry layers of Nubian sandstone with thickness
range between 36.5m at VES 49 and 78.1m at VES 46, the
thickness of these layers is increasing and decreasing as factor
of land relief . These dry layers of Nubian sandstone have a
wide range of average transverse resistivity from 92.9 Ohm-m
at VES 42 to 1167 Ohm-m at VES 50. The low resistivity
values reflect high amount of silt and shale intercalated with
sandstone and high resistivity values becomes from gravelly
sand and well sorted sandstone. The third geoelectrical layer
“C” this layer was interpreted as water bearing sandstone. It’s
formed from different types of sand like gravelly sand fine to
medium or medium to coarse sand.
The individual sounding interpretations have been used
to generate 12 geoelectrical cross sections traversing the
investigated area in different directions. Correlation of the
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geoelectrical parameters (resistivity and thickness) helps
inferring the structural elements that affect the succession.
Two sites of 2-D imaging profile with distance between
the unit electrode separation 20m was measured at selected two
small khors in the study area The first profiles have length
600m and it is located at the south of khor gond. It shows; there
is no water invasion from khor Tushka to the dry layers of the
study area. Second the water bearing layers are in contact with
khor Tushka and it’s appearing at depth 90.5m. The second
profiles have length 540m and it is located at the north of the
first one and it shows; first, was their water invasion from khor
Tushka to the dry layers of the study area so, it’s become wet
layer and formed shallow aquifer in this portion with thickness
about 20m. Second the water bearing layers are in contact with
khor Tushka and it’s appearing at depth 49.8m.
One site of 3-D resistivity imaging measurements was
carried out at the eastern portion with 81 electrodes as the
Pole-Pole array. The electrodes are arranged in a 9 by 9 square
grid with a unit spacing of 7 meter between adjacent electrodes
to identify the relationship between khor Tushka water and
aquifer. According to the result of interpretating this 3-D
resistivity imaging; the unconfined aquifer has charged from
khor Tushka.
from all kinds of the previous applications we can
conclude the following result points:
1. There are some locations in the area under study have
impervious Nubian sandstone due to the effect of
hydrothermal solution.
2. The depth to basement rocks in the study area reached
to 694m so, the sedimentary thicknesses is in a positive
condition for ground water accumulation.
3. The study area is formed from many grabens and horsts.
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4. The saturated Nubian sandstone layer which is
represented by the fourth geoelectric unit at the south of
khor Tushka area has thickness from 56m to 442m.
Moreover, the aquifer in this area is defined as confined
aquifer type.
5. The saturated Nubian sandstone layer which is
represented by the third geoelectric unit at the north of
khor Tushka area has thickness range from 160m to
337m. Moreover, the aquifer in this area is defined as
free aquifer type.
6. The study area is affected by different normal fault
systems which are affected by hydrothermal solutions
that make the sediment on its plain impervious rocks.
This classifies the aquifer to isolate and/or semi isolate
aquifers system.
7. There are direct connections between khor Tushka and
the layers above the confined aquifer in some places
formed the shallow aquifer and absent at others.
8. There are similarity between Isoresistivity contour map
and water Salinity map.
9. Some of the drilled water wells in the study.