Page 173 - Life & Land Use on the Bahrain Islands (Curtis E Larsen)

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manipulation of water distribution, thus it is better to view the evidence from a
different perspective. These combined water resources gave rise to an intermittent
river and lake system rare in this part of the world. Recent drainage attempts have
only reused preexisting natural systems. For our purposes it is best to see
paleoenvironments reflected, not in water flow, but in evidence for surrounding
dessication. For example, movement of existing dune fields may imply a disruption
in surface vegetation on a regional basis, allowing surface sediments to be removed
by the wind. Filling of rivers and marshes by eolian sediments reflects upon such
periods of surface disturbance. For the purpose of extracting paleoenvironmental
information from an unknown area, such geomorphic changes may indicate changes
in rainfall difficult to perceive in this complex environmental setting.
From the evidence at hand, Holocene lakes were high from ca. 7000 to
3000 B.C., with a peak occurring between 5000 and 3800 B.C. Evidence for eolian
activity appeared prior to 4000 B.C., when lakes fell, but based upon the
archeological evidence from site 208-38, lakes were high again through the early
and middle third millennium B.C. Dessication of the area reoccurred prior to 1565
B.C. and again between this date and 750 B.C. No data are available until ca.
A.D. 20, when a paleosol developed on eolian sand indicating dessication in the
intervening period. This period of increased moisture was also followed by aridity
that seems to have lasted until the ninth century. Following A.D. 850, eolian
activity began again blocking drainage channels and ponding water in parts of the
oasis. Final evidence shows medieval moist conditions subsequently interrupted by
dessication after to A.D.1300. A summary of radiocarbon dates is given in Table 4.

Surface Runoff on Bahrain

Wadi systems on Bahrain are poorly developed when compared with those on the
neighboring Arabian Peninsula, yet the drainage patterns are complex, given the
limited surface area of the islands. TTie details of the fluvial geomorphology of the
islands has been recently presented by Doornkamp, Brunsden, and Jones (1980:123-
97). For the general geo morphological perspective required by this study it is only