| Construction of Infiltration Galleries
Infiltration galleries can successfully be
constructed if beds and banks of water courses are
covered by permeable deposits. Several types of
infiltration galleries can be designed
according to local conditions; they can be constructed
parallel or across stream beds. For
the first type, a trench is dug parallel to the river
bank to a depth below the river bed and
intercept its underflow flow by collecting pipes. The
pipes can also be connected to a
collector well sited on the river bank; the distance from
the river, or the floodable area,
depends on the nature of the river bank; in some cases
the pipes could be installed directly
in the sand filling the stream bed.
The length of the gallery will depend from the amount of
water required and
the hydraulic characteristics of the water-bearing
sediments. Fig 5 shows a very simple
and cheap type of infiltration gallery tapping the
underflow of an ephemeral stream. The
bottom of the well is interconnected with the underflow
of the stream bed by sorted
gravel. A more technically advanced infiltration
gallery is shown in fig. 6 which could be
constructed across larger streams; the collector well is
equipped by a hand pump.
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Fig.
5 - Hand-dug well tapping the underflow of
ephemeral sand river. Ref. 4
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Fig.
6 Hand-dug well with pump tapping underflow of
dry river bed, Ref. 4.
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