A common way to describe the yield of a new borewell is in ‘inches’ measured by the free, unrestrained flow of water from a borewell over a 90 degree ‘V’ notch. The basic principle is that the discharge is directly related to the height of the water level from the bottom of the V notch.
h – Height of water level from the bottom of the V
Based on certain equations and formulae, the height ‘h’ in inches is converted to discharge rate in litres per hour.
The following table indicates the conversion of the yield in ‘inches’ to a discharge rate in litres per hour.
| V-Notch Reading in Inches | Approximate Discharge Rate in l.p.h. |
Class |
| 1/2 | 95.40 | Low Yield |
| 3/4 | 261.00 | |
| 1 | 597.00 | |
| 1 1/4 | 1,045.00 | Average Yield |
| 1 1/2 | 1,650.00 | |
| 1 3/4 | 2,425.00 | |
| 2 | 3,382.00 | High Yield |
| 2 1/4 | 4,558.80 | |
| 2 1/2 | 5,919.00 | |
| 2 3/4 | 7,501.00 | |
| 3 | 9,329.00 | Very High Yield |
| 3 1/4 | 11,402.60 | |
| 3 1/2 | 13,720.00 | |
| 3 3/4 | 16,284.60 | |
| 4 | 19,148.00 | Superlative Yield |
| 4 1/4 | 22,285.60 | |
| 4 1/2 | 28,695.20 | |
| 4 3/4 | 29,459.20 | |
| 5 | 33,350.00 | |
| 5 1/4 | 37,914.00 | |
| 5 1/2 | 42,551.00 | |
| 5 3/4 | 47,461.00 | |
| 6 | 52,644.00 | |
| 6 1/4 | 58,372.00 | |
| 6 1/2 | 64,373.00 | |
| 6 3/4 | 70,919.00 | |
| 7 | 77,464.00 | |
| 7 1/4 | 84,557.00 | |
| 7 1/2 | 92,195.00 | |
| 7 3/4 | 1,00,105.00 | |
| 8 | 1,08,288.00 |