Armfield S12-MKII, Инструкция по эксплуатации

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53
Exercise H - Water abstraction from a well in an
unconfined aquifer
Theory
Fig. H1 shows an unconfined aquifer situated above an impervious base. There is no
recharge by rainfall or loss of water by evapo-transpiration and the water table is
consequently horizontal. In an unconfined aquifer the piezometric surface coincides
with the upper limit of the saturated zone and this is commonly termed the water
table.
Figure H1
Ground water abstraction from a well will again result in the lowering of the water
table but, in the unconfined aquifer under consideration, this means at the same time
a reduction of the saturated depth available for the flow of water. The equations of
flow thus become:
Darcy
continuity Q = constant = Q
o
combining hdh
integrated h
2
or in the form of the Dupuit Formula
(1)
in which the integration constants Q
o
and R
o
must be determined from the boundary
conditions.
In this case
H = depth of saturated zone before pumping
h = (H - s) where
s = lowering of the water surface due to pumping.