This paper reviews and discusses the factors causing the changes of water levels in the aquifers from which Bahrain extracts a large proportion of the water required for human consumption, agriculture and industrial use. These include noteonly geological and climatic features but also the effects of agricultural irrigation, coastal reclamation and leakages from the water supply network, sewer pipes and septic tanks. The results of statistical analyses carried out on water levels obtained from 125 boreholes over a 12-year period, in order to determine any underlying trends in water table movements, are presented and discussed. These analyses have shown that, in general, levels in the deeper aquifers are falling at rates ranging from 78 mm to 277 mm per annum. Variations in the near-surface aquifer are shown to be more complex but with the water table rising under areas associated with land reclaimed from the sea. If levels continue to rise at their present rate, the water table is predicted to be at or very close to the surface by the end of the century. This could lead to various geotechnical, structural, agricultural or health problems.