Thread: Ground water
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Old October 29th 15, 10:54 AM posted to uk.sci.weather
Len Wood Len Wood is offline
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Default Ground water

On Thursday, 29 October 2015 02:08:50 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.

In 2011 we had just under 400mm, 60% of normal, and the following year,
despite numerous thunderstorms, deluges and flood alerts along the River
Nene, several springs in the area dried up, and have not flowed since.
Result = steams with no water in them, local lakes well below level,
with any pollution entering them not being diluted sufficiently not to
cause problems. One lake lost all its waterfowl in July due to
contamination from fuel oil from a local industrial estate. What I have
found is enough evidence to prove that the ground water levels are
severely depleted, with the water table at least 300mm below what it was
5 years ago.

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

a very dry and rainless Northampton


Hi Jim,
If you look at the record of annual rainfall for Plymouth 1874 to 2014 you see how variable it is with no longterm trend, but clearly trends on the decadal timescale.

You can see an increasing trend after the drought of the mid seventies, and then a decrease and now slight increase again.

I have also put in dropbox the link to the graph of summer and winter rainfall.
There is a significant increasing trend in winter rainfall and a less convincing decrease in summer rain. Hence no trend in annual rainfall over the longterm.

https://www.dropbox.com/s/u0s7p9kroj...02014.jpg?dl=0

https://www.dropbox.com/s/9lfjie7ko4...0rain.jpg?dl=0

If I was you Jim I would hold fire, but if the water usage has gone up in recent years and/or the surface morphology has changed then you are stuck.

Len
Wembury, SW Devon