"Martin Sykes" wrote in message
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snip


The houses and roads don't help though. I don't understand why new houses
aren't built with underground resevoirs like a big water butt.


Some 'old' houses used to be, e.g. some rural councils installed underground
rainwater cisterns beneath council houses in the 1930s. These became defunct
when the houses were modernised after the second world war. Some private
rural houses were self sufficient in water, too, e.g. I know one which until
the mid 1970s used to have a well to provide drinking water to the kitchen,
and a large tank in the roof space, filled by pumping water up from the
nearby river, providing water for all non-drinking purposes.

If 'mains' water becomes too unreliable or expensive to cope, no doubt your
idea, or something similar, may become necessary again.