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K. S. Gemail et al.
in the surface salty soils where the Mut Shale is thin in this region (Fig. 10). The
total dissolved salts measured from the shallow wells in that part raised to 2480,
3290 and 1960 mg/L, respectively. In addition to the presence of some clay deposits
within the aquifer materials. Figure 11, shows the aquifer characterization of Taref
sand from resistivity and Gamma ray logs which is illustrated the high shale content
at different depths (Abdallah 2013). While, the northern region of the N-S profiles is
characterized by high electrical resistivity values (176–337 .m) exhibiting a fresh
water prevailing (TDS about 138 mg/L). The thickness of the saturated Taref layer
is increased gradually towards the north direction from 80 m at VES no. 9 to 110 m
at VES no. 2 (Fig. 10).
The 4th geoelectric layer has low resistivities ranging from 1 to 35 .m indicating
the green to black shale layer of Maghrabi Formation which extends to the maximum
depth of investigation. As indicated from borehole logs, the maximum thickness of
this layer is about 70 m and acts as base for the overlying Taref sand aquifer and
splits it from the underlying deep aquifers of Sabaya Formation.
The distribution of thickness and depths of the shallow aquifer is shown in Fig. 12.
In which, the north-western part of the area has the highest aquifer thickness (Fig. 12a)
with shallow depths (Fig. 12b) in addition to high resistivity values to indicate a
good groundwater potentiality as mentioned early in the E-W geoelectrical sections
(Fig. 9). The minimum thickness of this layer (75.8 m) is recorded at the eastern part
of the surveyed area due to the influence of the NE-SW normal faults. Based on the
constructed maps of thickness and depth (Fig. 12) as well as the resistivity sections,
the first priority for groundwater potentially can be given to the northwestern parts
around sounding points 34, 35, 38 and 39 where the interpreted resistivities reach to
the maximum values of water saturated zone reflecting the good water quality with
great thickness and low aquifer depths reducing the drilling cost.
4.2 Faults and Recharge of NSAS
To visualize the role of normal faults which are act as windows for vertical water
flow in the NSAS, the interpreted resistivities with depths from the surface resistivity soundings and resistivity logs (16 boreholes) were employed to construct a 3D
visualization model of Taref aquifer. The inverse distance-anisotropic algorithm was
applied to construct a 3D block of the whole area using Rockworks software package
(Rockware 2014). The anisotropic interpolation of thin strata as in case of clays in
Taref Formation was applied for mapping the lateral discontinuities over large areas
with infrequent data points (FitzGerald et al. 2009; Gemail 2012). The initial inputs
were gathered by sampling of the interpreted resistivity values and elevations of the
subsurface layers from both surface resistivity soundings and resistivity logs. As
in the present case, the primary goal of the regional geophysical interpretation is
to determine the 3D geometry of the effective faults in the aquifer distribution. In
the case of considering the top surface of Maghrabi Fm in the area as marker, the
accuracy of the model can be evaluated by comparing the guesses with the observed
K. S. Gemail et al.
in the surface salty soils where the Mut Shale is thin in this region (Fig. 10). The
total dissolved salts measured from the shallow wells in that part raised to 2480,
3290 and 1960 mg/L, respectively. In addition to the presence of some clay deposits
within the aquifer materials. Figure 11, shows the aquifer characterization of Taref
sand from resistivity and Gamma ray logs which is illustrated the high shale content
at different depths (Abdallah 2013). While, the northern region of the N-S profiles is
characterized by high electrical resistivity values (176–337 .m) exhibiting a fresh
water prevailing (TDS about 138 mg/L). The thickness of the saturated Taref layer
is increased gradually towards the north direction from 80 m at VES no. 9 to 110 m
at VES no. 2 (Fig. 10).
The 4th geoelectric layer has low resistivities ranging from 1 to 35 .m indicating
the green to black shale layer of Maghrabi Formation which extends to the maximum
depth of investigation. As indicated from borehole logs, the maximum thickness of
this layer is about 70 m and acts as base for the overlying Taref sand aquifer and
splits it from the underlying deep aquifers of Sabaya Formation.
The distribution of thickness and depths of the shallow aquifer is shown in Fig. 12.
In which, the north-western part of the area has the highest aquifer thickness (Fig. 12a)
with shallow depths (Fig. 12b) in addition to high resistivity values to indicate a
good groundwater potentiality as mentioned early in the E-W geoelectrical sections
(Fig. 9). The minimum thickness of this layer (75.8 m) is recorded at the eastern part
of the surveyed area due to the influence of the NE-SW normal faults. Based on the
constructed maps of thickness and depth (Fig. 12) as well as the resistivity sections,
the first priority for groundwater potentially can be given to the northwestern parts
around sounding points 34, 35, 38 and 39 where the interpreted resistivities reach to
the maximum values of water saturated zone reflecting the good water quality with
great thickness and low aquifer depths reducing the drilling cost.
4.2 Faults and Recharge of NSAS
To visualize the role of normal faults which are act as windows for vertical water
flow in the NSAS, the interpreted resistivities with depths from the surface resistivity soundings and resistivity logs (16 boreholes) were employed to construct a 3D
visualization model of Taref aquifer. The inverse distance-anisotropic algorithm was
applied to construct a 3D block of the whole area using Rockworks software package
(Rockware 2014). The anisotropic interpolation of thin strata as in case of clays in
Taref Formation was applied for mapping the lateral discontinuities over large areas
with infrequent data points (FitzGerald et al. 2009; Gemail 2012). The initial inputs
were gathered by sampling of the interpreted resistivity values and elevations of the
subsurface layers from both surface resistivity soundings and resistivity logs. As
in the present case, the primary goal of the regional geophysical interpretation is
to determine the 3D geometry of the effective faults in the aquifer distribution. In
the case of considering the top surface of Maghrabi Fm in the area as marker, the
accuracy of the model can be evaluated by comparing the guesses with the observed