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11.7 Methods of groundwater exploitation*
The groundwater contained in hard rock secondary aquifers in NatallKwaZulu is exploited
by means of boreholes which are normally drilled by pneumatic rotary percussion methods.
The depth of the boreholes varies from 40 - 120 m, with an average depth of about 80 m.
The normal borehole diameter is approximately 150 mm, with variable lengths (3 - 8 m)
of steel casing being required to support soil and weathered rock in the uppermost parts
of the boreholes. In some high yielding boreholes in weak fault breccia, the sides of the
boreholes have to be supported against collapse, either by the use of slotted steel casing,
or well screens inserted in the boreholes.
11.7.1 Borehole depths
Groundwater occurs at shallower depths in topographically lower situations (such as
valleys), by comparison with more elevated terrain. In lower-lying areas, borehole depths
are generally ofthe order of 40 - 50 m, whereas in more elevated surroundings, boreholes
are commonly some 100 - 120 m deep. Water-rest levels in boreholes are often above the
depth at which groundwater is intersected therein. This characteristic is frequently made
use of in deep boreholes in the rural areas of KwaZulu, where it is possible by means of
handpumps installed on the boreholes, to liftgroundwater from a maximum depth of about
50 m. It should be noted that in rural KwaZulu, a borehole yield of 100 - 200 t h- 1 (which
elsewhere might be regarded as a dry borehole on drilling), is entirely acceptable as a
source of domestic water.
11.7.2 Springs
Artesian groundwater conditions in Natal/KwaZulu are relatively rare, and where
encountered, are nearly always associated with a borehole in a topographically depressed
zone, below a very marked elevated area from whence the groundwater is derived. This
situation also frequently applies at the few major cold and thermal springs in the province.
An important cold water spring (used in part, for the water supply of Kokstad), is the
Crystal Spring located just to the north of the town. Notable thermal springs in the
*
Sections 11.7 and 11.8 were written by Maud, R.R., 1993. Drennan Maud and Partners, Durban,
with editorial amendments by Alcock, P.G., 1994.