'File 19/252 Bahrain Water Supply' [‎23r] (47/96)

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The flow of water in the drainage ditches was determined
"by selecting a reach of uniform cross-section,measuring the
width of the ditch and the depth of the water and determining
the velocity by timing a surface float over a measured distance
by means of a stop-watch. In calculating the rates of flow
from these figures it has been assumed that the mean velocity
of flow is 0.9.of the surface velocity (a conservative coeffi
cient ). Water samples were obtained from the drainage ditches
for salinity determination and, where possible,water samples
were also obtained from the source of supply in order to observe
the amount of salt taken up into solution during the passage of
the water through the gardens. These data are also shown in
the attached tabulation of results.
This investigation has revealed the fact that over
200^000 barrels/day of water was runni.v* into the sea from the
various ditches at the time measured and, although a certain
amount of salt is picked up by the water, that the salinity is
such that it is still suitable for irrigation purposes.
The amount of water taken from Zellaq wells for Company
operations is approximately 13,000 bbls/day which in comparison
with the amount of water wasted, is veiy small.
Many of the 40 wells referred to above have been drilled
within recent time and the marked decline in static head
apparently coincides with the extensile cultivation which has
developed in this area.
The flow of water through the porous media of the water
bearing strata,whether to a single well or to a number of wells
in an area, must be accompanied by the establishment of a
hydraulic gradient to promote that flow. The hydraulic
gradient depends upon the rate of flow and, a state of equilibri
um will be attained for any one rate of withdrawal. Since the
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