On Thursday, October 29, 2015 at 2:08:50 AM UTC, jbm wrote:
I am absolutely and thoroughly stuck on something the local council has
asked me to look into.

Over the last seven years, the rainfall in this area has been well below
normal for 5 of them. Currently, we are over 300mm short of what we
would normally have expected in that time. Doesn't sound a lot, but it
represents 6 months of normal rainfall.

So I would appreciate it if some of you knowledgeable meteorologists out
there would care to hazard a guess at the following. Having experienced
so many dry years recently, what are the chances of getting some
exceptionally wet ones, with steady and moderate rain to start
replenishing the ground water, without the majority of it disappearing
straight into the rivers as surface run-off? What we need is a lot of
water, and I mean a lot, getting down to that water table as quickly as
possible. Any ideas anyone? We have to make a decision shortly as to
what to do with the lakes - leave them as they are, dredge out all the
****e and see what happens, or fill them in and be done with it. And a
reasonably intelligent prediction on future rainfall might help in that
decision.

Jim,

I am not a professional meteorologist, but I have been studying climate change since I retired from engineering about 20 years ago.

As an ex-engineer I would say Sod's Law rules, it is a corollary of the Second Law of Thermodynamics. So what ever you decide will be wrong! For instance when there was a long drought in South East Australia, they built a large desalination plant. As soon as it was built the rain returned. Here in the UK, we had a drought and the minister in charge brought in water rationing. That was followed by the wettest summer ever. So my advice is take preventative measures and with a bit of luck they will not be needed. (If you don't take them they will :-)

As I keep saying, both weather and climate are chaotic. So past performance is not a guide to future behaviour, nor can you rely on the fallacious Law of Averages to buck a trend.

The government produced a book about 20 years ago where they forecast how climate change would affect the UK. The conclusion was that the north would get wetter and the south drier. I can't find my copy of that book but if the dividing line moves south then you could become wetter or vice versa.

HTH,

Cheers, Alastair.