(1973) n°3 - Royal Academy for Overseas Sciences

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Fig. 9. — Sketch of the situation for a selective withdrawal.
Santing carried out a few field experiments which utilized
this concept ( 2 7 ) . W hile describing the exploitation of water
resources in the Russian deserts, K u n i n ( 1 5 ) stated that great
success was achieved by this method whereby fresh water is
pumped from the upper borehole and saline water from the
lower one. W o l a n sk i and W o o d in g ( 3 5 ) studied the flow
regime close to a pair of wells situated on opposite sides of a
diffusing interface between fresh water overlying saline water.
The interface was assumed horizontal, and gravitational effects
negligible. A uniform flow, parallel to the interface, is included.
To provide a definite starting point for the mixing layer at
the interface, it is further assumed that the fresh and saline
fluids are separated by a thin impermeable layer which extends
from a given distance upstream of the sink to far upstream
(figure 9). This membrane idealised a thin clay membrane
of low permeability. Rather similar concepts exist and solutions
were found for an infinite system of parallel line-sinks located by
pairs at regular distance each from the other, and systematically
one above and one below the interface. Boundary layer theory
was used to treat the growth of the diffusive mixing layer,
modified by the presence of the sinks, and closed-form solutions
were obtained as follows.
The important dimensionless parameters are
(l): uo = -jtU oL / 2 Q ,
where L is the distance upstream of the trailing edge of the