Page 163 - Life & Land Use on the Bahrain Islands (Curtis E Larsen)

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Zarins, personal communication). Important multicomponent sites are found
throughout the area, but the highest examples are of most interest. These are
Burkholders sites 4, 10, 23, and 31. At these sites, 'Ubaid evidence was found at
elevations 9, 10, 20, and 25 meters, respectively. Early Dynastic and Barbar period
ceramics are found as high as 25 meters, but Seleucid and Islamic materials are
found only below the 10-meter contour. A least squares regression line calculated
for these four points yielded an equation y = 3.08 - 0.004x with a correlation
coefficient of r = 0.979. TTiis curve represents the greater range of elevation
effected by the falling potentiometric surface in coastal Saudi Arabia, A
long-term depletion rate calculated from this curve is 0.0048 m/year. TTiese
curves are plotted on Figure 29, where both show more reasonable estimates for
the past elevations of static water levels than provided by extrapolation of the
Italconsult data. Accordingly, the depletion rates calculated from these curves are
far below the modern depletion rates noted by Italconsult. Using the modern data,
the water level at Qatif fell at a rate 2.1 times greater than that for Bahrain. In
the long-term case presented here, the ratio is 2 to 1 for the same areas. Thus,
this paleohydrological reconstruction method shows promise for future more
detailed research.
TTiis investigation implies, first, a long-term decrease in water level over
several thousand years and, second, a revised interpretation of Italconsult!s
findings. There is not a simple case for natural depletion of the aquifer since the
Late Pleistocene. In fact, the higher depletion rates calculated by Italconsult
relate more readily to Wright’s (1967) argument where increased well drilling
resulted in greater extraction of water.

TTie coastal aquifers are also made unique by their direct connection with
the sea. Offshore springs, while an avenue for seawater intrusion, are also a
demonstrable cause of tidal fluctuations in spring levels. This relationship is
verified both in Bahrain and along the coastal plain near Qatif by a direct
correlation between fluctuations in artesian spring level and tidal cycles in the
gulf. Ttie most recent data are contained in Italconsult (1971), which shows a close
relationship between the tidal gauge readings at Ras Tanura, north of Qatif, and