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In orifice method, an orifice is fitted with the known diam of the delivery pipe.
There is an attachment of manometer. Water from the delivery pipe exerts
pressure during discharge which is reflected on the head of the manometer.
The manometer is calibrated with different head in the column. Discharge can
be directly read by knowing the head in the manometer. Needless to add that the
head will be different for different diameter of the delivery pipe.
V-notch Method :
Discharge from the tubewell is allowed to fall on a stilling basin which has
V-notch on the outlet side of the chamber. Discharge can be directly read from
the calibrated V-notch.
When working in the field, there may not be any accessory like V - notch etc. to
measure the discharge from a tubewell. There is one simple field method which
can approximately give the value of discharges from a tubewell. The method is
shown in the figure 3.6.
Fig. 3.6 : Field Method of measurement of discharge
From a discharging tubewell of known diam. of the delivery pipe, an
imaginary line of 1 ft. or 12" is drawn from the delivery pipe. The distance 'd' is
measured from the point at which the imaginary line falls on the G.L.(Fall) to the
point where discharging water touches the G.L. The distance 'd' and radius 'r' of
the delivery pipe is expressed in inches. Then -
