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Worked Examples

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Example 2: For a field pumping test, a well was sunk through a horizontal stratum of sand 14.5 thick and underlain by
a clay stratum.Two observation wells were sunk at horizontal distances of 16 m and 34 m respectively from the pumping
well.The initial position of the water table was 2.2 m below ground level.
At a steady-state pumping rate of 1850 litres/min, the drawdowns in the observation wells were found to be 2.45 m and
1.20 m respectively. Calculate the coefficient of permeability of the sand.
Solution:

q = 1850 litres/min =
r1 = 16 m
r2 = 34 m
h1 = 14.5 - 2.2 - 2.45 = 9.85 m
h2= 14.5 - 2.2 - 1.2 = 11.1 m

k=

= 2.82 x 10-4 m/s = 1.41 x 10-2 cm/s

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