Now from the fig.

- = , - = , - =

Let - = - = - ,etc. =

The depths , , of the water level in the casing from the normal water table level can be computed as follows,

= = =

let the corresponding depths of the water table level below the ground surface be , , , etc. we have

= -

= – –

= – –

where, is the depth of water table in the casing from the ground surface at the start of the test. Normally = = = ; if not average value gives .