It is well known that there is a gradient in average effective rainfall across Great Britain from the north west to the south east. the last 20 years have brought some remarkable variations in the rainfall pattern. In broad terms these have resulted either in exaggeration of the gradient or in short-term reductions in rainfall across the entire island. These variations are at least partly in line with predictions of climate change, which also suggest that there will be increased seasonality in effective rainfall. It is less well known that there is a gradient of water storage which is approximately the reverse of the rainfall gradient, with most storage in the aquifers of the south and east. This is why, in nationwide droughts, it is usually the north and west that suffer the greatest problems with water supplies, despite their lower demand; at these times, transfer of water to the south east is not an option. If the climate-change predictions prove correct, Britain will need to make much greater use of this groundwater storage.