'File 19/252 Bahrain Water Supply' [‎37r] (77/96)

Normally at sea level on the east coast of Arabia the static head of
the water in the Socene rocks is from about 35 to 50 feet. However, in areas
where there is evidently local leakage the pressure drops below the above
average.
In the Bahrein region the static head ranges from practically sea level
on the southern portion of the Island to about 20 feet in local areas on the
north portion of the Island. In the north portion of the Island the static
level probably averages around 12 feet.
In the eastern Persian Gulf The historical term used to describe the body of water between the Arabian Peninsula and Iran. region the pressures in A, B & C Zones may
be the same in one area or they may all be different. This evidently depend
largely on local porosity of the rocks and the character of the impervious
members separating the major water zones.
SALINITY OF WATERS - REGIONAL ;
Zone C V/ater . - This water is generally high in total salts on the
coastal region except on the central portion of Dammam Dome where the water
has evidently been sweetened by local intake of fresh water. In the interior
of Saudi Arabia near the intake the water is very low in salts - below 250 ppm
in many cases.
Zone B Water , - The salinity of Zone B water varies from place to place.
At Ras Tanura it is highly saline but from Dammam Dome to Jubail it is sweet -
2000 ppm or less. However, west of Jubail and in the Abu Hadriya region it
is highly saline. We have no satisfactory explanation for the erratic regional
distribution of the sweet and salty waters in Zone B,
Zone A Water , - The salinity of waters from Zone A varies considerably
from place to place. However, in general the areal extent of sweet water in
this zone is much larger than that in Zone B, For example, sweet water is
found in Zone A at Ras Tanura and in most of the Abu Hadriya region but Zone B
water is highly saline. On the other hand, upper Zone A (Miocene) might be
extremely salty whereas basal Zone A is sweet. This is evidently due to local
conditions which are caused by intermingling with sea water or solution of
salt in the formation in the vicinity,
LOCAL WATER CONDITION (BAHRAIN) :
Zone C Water , - In Bahrein this water is everywhere too saline to be of
domestic value except possibly for cooling purposes. The hydrostatic head is
evidently a few feet higher than that of Zone A or B, The Chalky Zone and beds
below which contains Zone C water are apparently quite porous and very large
volumes of water could be obtained from this source.
The data at Bahrein indicate that the water of Zone C is isolated to
this zone and that it is stopped from migrating upward by the impervious Shark
Tooth Shale, There is a possibility, however, that the thinness of the Shark
Tooth Shale has allowed migration at Zone C water into higher horizons thereby
contaminating the higher water in the southern portion of the Island,