25
EDUCATION
OMAN DAILY Observer
WEDNESDAY, NOVEMBER 16, 2011
Nearly 25 per cent of Oman’s
population is clustered
around the coast, particularly
the Batinah coast, which
constitutes only 10 per cent
of Oman’s total area. This
clustering has caused overexploitation of the groundwater
resources; consequently the
water level in the coastal wells
has decreased rapidly, shallow
wells have dried, and seawater
has intruded into the
coastal aquifer
A study on seawater intrusion in Khabourah
A
study of seawater intrusion in over-pumped
coastal aquifers of the
Batinah region was recently
conducted by a research team
from different Omani institutions. The team was lead by Dr
Osman Abdalla from the College of Science, Department of
Earthsciences, SQU accompanied by Dr Issa al Hussain from
SQU earthquake monitoring
centre, Dr Mubarik Ali and Hilal
al Zeidi from SQU and Khalifa
al Higi and Said al Hinai from
the Ministry of Regional Municipalities and Water Resources. The study aimed at delineating the saline plume, identifying
saline/freshwater zones, and
estimating the migration rate of
the plume in Al Khabourah area
of the Batinah coast. Having in
place a variety of technical surveys, the researchers managed
to define the locus of the saline/
freshwater interface in the area.
One of the findings of the study
was that the 2007 interface position, when compared with that
determined during 2002, indi-
tutes only 10 per cent of Oman’s
total area. This clustering has
caused over-exploitation of the
groundwater resources; consequently the water level in the
coastal wells has decreased rapidly, shallow wells have dried,
and seawater has intruded into
the coastal aquifer.
To tackle this alarming situation, the Government of Oman
now regulates groundwater abstraction in the Batinah region
and has constructed several recharge dams on the major wadies to enhance infiltration into
aquifers and to suppress the
seawater intrusion. One of these
dams is Wadi Al Hawasinah
Dam, which is located in the
study area, Al Khabourah (in
the lowland area of Wadi Al Hawasinah catchment).
The team consisted of academics and experts from the
Earth Sciences Department,
SQU, Ministry of Regional
Municipalities and Water Resources, and SQU earthquake
monitoring centre. Their joint
project, funded by an SQU
time-dependent approach to
estimate the rate of seawater intrusion and assess the replenishment of groundwater resources
under the influence of artificial
recharge from the Al Hawasinah
Dam, constructed in 1995.
Topography, geology
The study area is located in
the northern part of Oman about
140 km north of the capital Muscat. It lies on the coast of the Sea
of Oman and occupies the lower
reach of Wadi Al Hawasinah,
which drains the Rustaq Plateau
(about 2,900 m higher than the
coastal area). The variation of
topography in the area forms
an intricate drainage pattern
involving wadies and seasonal
water courses, originating from
Rustaq Plateau, crossing the
mountainous area and spreading out onto the plain, forming
a wide fan-shaped structure.
The Wadi Al Hawasinah Dam
was constructed in 1995 at the
neck of the fan to prevent most
of the water flow from being
lost to the sea. The catchment
area is almost 1,000 km2; the
divided into two units (near
the coast and 5 km southwest
of the coast), was investigated
systematically, first by resistivity probing and shallow seismic
refraction, to have an initial
knowledge of the impact of
salinity on resistivity and the
impact of lithology on seismic
velocities, followed by extend-
cated a prominent recession in
the saline plume and suggested
an average annual recession rate
of 120m. This recession could
be attributed mainly to the recharging dam of Wadi Al Hawasinah, constructed in 1995,
and the enforcement of water
resources legislation.
Nearly 25 per cent of
Oman’s population is clustered
around the coast, particularly
the Batinah coast, which consti-
grant, was recently published
in the Hydrogeology Journal. It
integrated geophysical methods
— time domain electromagnetic (TDEM) surveys, vertical
resistivity soundings (VES),
and seismic refraction methods.
They tracked the geophysical
survey conducted in the area
during 2002 and marked the
present position of the saline/
freshwater interface. Further,
they tested the ability of the
upper catchment area of Rustaq
Plateau, with average rainfall
of 200 mm/year, serves as the
main contributor to the wadi
flow, whereas the lower catchment, with average rainfall of
50 mm/year, spreads out over
the coastal area. The temperature is quite high (above 40°)
during summer and causes high
evapotranspiration.
Geophysical survey
The study area, which is
ed TDEM surveys along three
NE-SW-oriented
subparallel
lines, orthogonal to the coast,
to investigate the geometry of
the saline/freshwater interface.
This area was studied electromagnetically (TDEM) in 2002.
The present TDEM survey
(conducted in 2007) somewhat
‘foot-printed’ the previous one
with the addition of a new profile (HSW 3) to find out changes
in resistivity signals in 5 years.
Cancer-testis antigens: expression and localisation
A
n SQU academic is
embarking on research
aimed at localising cancertestis antigens MAGE-1
family in relation to CD8+ T
lymphocytes in breast cancer.
According to Professor
Anand Date, at the College of
Medicine, the cancer-testis
antigens (CTAs) represent
potential targets for cancer
immunotherapy
because
these proteins are widely
distributed in tumours but
not in normal tissues, except
testis.
In malignancy, this gene
regulation is disrupted, resulting in CTA expression in
a proportion of tumours of
various types.
Breast cancers are known
to frequently (over) express
several well-characterised
tumour-associated antigens
such as carcinoembryonic
antigen, MUC-1, Her-2/neu
and cancer/testis antigens
such as NY-ESO-1, SSX-2
and members of the MAGE
— family. This was known
in melanoma patients with
the detection of pre-existing
T cell responses to tumour
associated differentiation antigens, he remarks.
Professor Date says, adding that “this was a beginning step to initiate several
vaccination strategies, but
little is known about tumourspecific immunity in breast
cancer patients.”
Dr Osman Abdalla
Resistivity soundings
A resistivity survey is a
suitable geophysical method
to study groundwater, to determine aquifer characteristics,
and to delineate any pollution/
saline encroachment. Resistivity in rocks, as described by
Archie’s law influenced not
only by rock composition and
porosity, but also by water saturation, and water resistivity. So,
the saline water, which has very
low resistivity, if present in a
rock, is expected to considerably reduce the intrinsic resistivity of that rock. Although the
resistivity soundings method is
reliable in delineating saline/
freshwater zones, it has obvious limitations when applied
for identification of subsurface
stratification in zones that are
fully or partially saturated with
saline/freshwater. The same
weakness and strength are observed in the TDEM method.
Therefore, the application of the
seismic method was intended to
constrain the electrical methods
in the interpretation of the layer
geometry in the study area. For
studying resistivity signatures
of saline/freshwater in an area,
the Schlumberger configuration was selected due to its efficiency and control over noises
generally produced by telluric
related ground currents.
The electrical resistivity
soundings were conducted with
a 200-m spread near the coast
(saline zone) and 5 km away
from the coast to differentiate
resistivity signals in both situations. The apparent field resistivity data were analysed
manually and digitally by using
1X1D software which synthesizes apparent resistivities in a
multilayer model through iterations, taking layer thickness and
resistivity as the variables. The
resistivities under the two locations differ significantly: at site1, very low resistivity indicates
the impact of saline water saturation of strata, whereas higher
resistivities at site-2 suggest no
saline intrusion within the depth
of penetration.
Seismic refraction survey
The team also conducted a
seismic refraction experiment
in the two locations near the
resistivity sites to obtain information on subsurface lithology, porosity and/or saturation.
Seismic refraction is known to
be a powerful tool in identifying
subsurface lithological variation
compared to electrical methods
especially in areas with varying
degree of saturation and water
salinity which impair the ability of the electrical methods to
identify the subsurface geology
with accuracy.
Seismically, the surface layer
(3-6 m thick) which is a mixture
of loose and dry wadi deposits
(silt, sand and gravel) is marked
by low velocity (roughly 530
m/s). The velocity increases
to more than 2,000 m/s in the
second layer possibly due to
the compactness of gravels and
sand. However, the role of saturation cannot be overlooked.
The seismic velocity further increases in the third layer under
both locations, which is likely
due to increasing lithology
compactness. The water table,
which is 5 m deep under site-1,
is in a saline environment (resistivity over 5 ohm-m), whereas it
is roughly 20 m deep under site2 but in a freshwater environment (resistivity more than or
equal 60 ohm-m). This means
the freshwater is forming a lens
thicker in the upper-stream part
(site-2) and pinches out towards
site-1 into the underlying saline
water.
The researchers have summarised their findings as follows: “the geophysical surveys,
comprising TDEM, electrical
resistivity, and seismic refraction, were used to comprehend
the lithology variation and obtain an adequate subsurface picture of the saline plume.
The saline/freshwater interface dipping to the southwest
also appears to have steepened
relatively in 2007, dipping to
the southwest at an angle of 3°
and is encountered at a depth of
200 m or more within a distance
of 3.5 km from the coastline.
This suggests thickening of the
freshwater aquifer towards the
southwest.
The most interesting information revealed by this study
is the time-dependent movement of the saline plume. The
saline/freshwater interface that
was traced by TDEM in 2007 in
comparison with the interface
marked in 2002 by a similar
TDEM survey indicates a clear
displacement.
The saline plume in general
has witnessed a recession of
about 600 m in a time span of
5 years at an average rate of 120
m/year which is attributed to artificial recharge induced to the
aquifer by Wadi Al Hawasinah
dam since 1995.
Flow impoundment by the
dam followed by controlled release of water storage from the
dam’s reservoir via spillways
has enhanced water percolation
into the phreatic aquifer and
consequently countered seawater intrusion.”
trusion.” They added that “the
increasing groundwater salinity
that has been observed in the
Batinah region since the 1980s
has caused significant deterioration in water quality and several
wells in numerous farms have
been abandoned as pumped
water is no longer suitable for
irrigation.”
In the south Batinah area,
unpublished data indicated that
the agricultural land that was
lost due to increased salinity
during 2000-2005 was about
27.14 km2.
They pointed out that 116 of
the total 716 wells were abandoned in that particular area,
and 47 per cent of the wells had
salinity in 2005 greater than
6,000 μS/cm. A similar trend
They continued “The regulation of pumping rates of existing
wells, control over drilling new
wells, and other water-management measures adopted by the
Ministry of Regional Municipalities and Water Resources
since 1995 have led to reduction
of the groundwater abstraction
and in turn helped in reducing
the advancement of seawater in-
was also observed in the area of
Al Khabourah which is located
in the north central Batinah.
The team concluded that the
annual groundwater abstraction
declined following the abandonment of these wells, likely
after 2005, and therefore the
water table slightly recovered
contributing to the recession of
the saline/freshwater interface.
Microbial composition of biological soil crusts in Oman
B
iological desert crusts
are relatively common
in the arid deserts in Oman,
however, little is known about
their microbial community
composition and role in soil
stability and fertilisation. Dr
Raid Abid, at the College of
Science, is embarking on a
research work to examine crusts
from geographically different
locations around the Sultanate
(Muscat, Adam and Salalah) for
their soil texture, mineralogy,
trace element composition,
bacterial community structure
and their ability to fix
atmospheric nitrogen.
As to the tools of his study,
the scientist says that “bacterial
diversity will be studied using
state-of-the-art molecular techniques such as denaturing gradient gel electrophoresis (DGGE)
and automated rRNA intergenic
spacer analysis (ARISA)”.
He elaborates that crustal
microorganisms will be cultured in the laboratory and the
obtained isolates will be phylogenetically and physiologically characterised. Further, he
says, the soil characteristics in
crusted and non-crusted areas
will be compared in terms of
their pH, electrical conductivity, total organic matter, trace
elements, nutrients, erosion resistance, evaporation rate and
water holding capacity.
The role of these crusts in
nitrogen fixation will be studied using acetylene reduction
assay technique.
The procedure, the academic goes on, will cover a
comparison of the nitrogenase
rates among different sites un-
der different conditions of light
and dark.
Hopefully, the project will
contribute towards a better understanding of biological soil
crusts in the deserts of Oman
and their role in soil stability
and fertilisation, he concludes.