Borehole Measurement Parameters
L1.
Minimum installation depth below
dynamic water level
L2.
Depth to dynamic water level (DWL)
L3.
Depth to static water level (SWL)
L4.
Draw down. This is the difference
between the dynamic and the static
water levels
L5
. Installation depth
L6.
Distance of pump from well bottom
Fig. 4 Borehole Measurements
L5
L4
L1
L2
L3
L6
ii) Pump Position
7
Ÿ
When positioning the pump it is important to ensure adequate motor cooling
through water flow past the motor. This will be achieved by installing the pump
suction above the borehole main aquifer or well screen and if not possible or in
cases of open water installation a cooling sleeve must be used. Recommended
3
minimum flow rate past the motor is 0.2m /sec.
Ÿ
It is recommended that the complete pump is submerged at least 3m the
dynamic water level and if possible the pump should be installed at least 3m
from the bottom of the borehole to prevent silting damage. As a rule the pump
should be positioned mid-way between the bottom of the borehole and the
dynamic water level assuming that the main aquifer is below this level. If in doubt
consult the pump supplier.
iii) Pump Lowering
It is recommended that a fully equipped borehole service vehicle be used for
pump lowering and removal in order to minimize risk of pump dislodging.
However, for shallow boreholes (less than 50m) a manual tripod arrangement
can be used. When moving the pump the following procedures should be
followed:-
Ÿ
Before starting pump lowering it is important to check the borehole depth and
straightness to ensure it is as expected and there is unobstructed passage.
The pump should be carefully lowered into the borehole and if an
