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The following factors should be carefully studied for ground water development in hard rock areas:
1. In the conditions existing in hard rock areas shallow small diameter wells can at best yield 4 GPM or 250 GPH. The larger diameter wells can store up to 20,000 to 30,000 gallons in a day. A bore well drilled to a depth of 100 to 150 feet may yield 600 to 1000 GPH. Only in exceptional cases yields can be as high as from bore wells in hard rock areas.
2. Hard rock areas, it is not advisable to go deeper than 200 feet.
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3. Drilled wells superior to open wells.
4. Wells should, as far as possible be in the lower sections of the valley.
5. Drainage lines mark the weaker zones in hard rock areas and such regions are to be preferred for locating wells.
6. There are no underground streams. This misconception should be given up.
7. Annual rainfall is likely to be less than 10 per cent of the rainfall.
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8. Rainfall should be conserved by adopting proper methods of cultivation and roof top rain water harvesting.
9. Wells should be distributed on the basis of one well for every 5 acres. On the basis of this 120 wells can be accommodated per square mile in favourable sections of the valley.
New wells should be sink as far away as possible from existing wells and in no case within 300 feet on existing well.
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10. The first and foremost need is to improve the yield from the existing wells.
This can be done by:
i. Deepening through blasting,
ii. Drilling one or two boreholes from the bottom, and
iii. Drilling small diameter radial holes.
11. Demonstration should be arranged to adopt sprinkler irrigation.
12. The recuperation rate in most of the wells being less than 1000 GPH. A 3 HP motor is more than ample for pumping water. The present practice of going for higher horsepower motors should be discouraged.
13. Power lines for giving power I.P. sets should be as far as possible run parallel to stream valley.