In article
,
nickname writes:
On some of our fields water runs through the field drains into dykes
which then run into swallow holes in a nearby wood.This water then
dissapears underground-i would imagine to recharge the aquifers-we
have a borehole very close by to the swallow holes..I have estimated
from the 150mm of rain we have had in the last 4 weeks -even if only
half of the water went down the swallow hole this could amount to 15
gigaliters going under ground and thats just from 20 hectares.I
dontknow the capacity of the aquifer-but it is a significant amount of
water going intoit.
I would guess that swallow holes are not just found in my neck of the
woods.
Also we have other fields over limestone and i imagine the limestone
acts like a sponge and wont release water till it is saturated.So far
springs running out of this limestone into the guash valley where. i
live have not really increased in flow yet so the limestone must still
be soaking it up.Im not an expert by the way -just a farmer and stand
to be corrected if im wrong-.

Nick


That 150mm of rain is maybe 75mm above normal for April, depending on
where you live. But in the SE rainfall has been deficient over the last
18 months or so. Even if the average monthly shortfall is only 10mm,
that's still a total deficit of 180mm, so there is still a shortfall of
105mm, maybe more if you allow for the increase in transpiration from
plants at this time of year.

Those figures are only very rough guestimates, of course, but I think
they demonstrate why one wet month isn't enough. It's a bit like running
up an overdraft of a couple of hundred pounds, and then paying off 50
quid of it and expecting the bank to be happy.
--
John Hall
Johnson: "Well, we had a good talk."
Boswell: "Yes, Sir, you tossed and gored several persons."
Dr Samuel Johnson (1709-84); James Boswell (1740-95)