Dear Experts,
Our property is situated in Bande Mutt, Kengeri Satellite Town. Geologically, the entire layout is kind of rocky and hence the name.
On July 10th, 2012 we dug a borewell. Overall, we got an yield of only 3/4th inch as reported by the Operator (from Kannan Borewells). Since it's only the rock deep below, the casing pipe was inserted for about 26 feet only. At approximately around 160ft, we noticed some moisture coming out while drilling along with with the crushed powder (of rock/boulders). Further, we continued to drill but there was no sign of water. By god's grace, at say 360ft we struck water with an yield of 1/4 inch. We asked the operator to continue to drill and again at around 46oft, we struck water again with an yield of 1/2 an inch. The yield whatsoever mentioned above is as stated by the operator.
We had infact consulted a Water diviner who is a retired professor from BU, he claimed to have a success rate of 99% of the survey he has conducted so far. As per his report/survey, there was only one location where we could have had the borewell dug. Also at this location, the diviner said water would be available from 4 sources and that the yield would be not less than 2 inches. He did say that we should strike the water between 350 to 400 feet which was perfect.
As mentioned above, after striking water at 460ft where the yield was found to be 1/2 an inch, we continued to drill further. But then it was only the rock/boulders we drilled. We thought to stop at 550 ft, before doing so we called-up the diviner. He further advised us to continue drilling till 650 ft while the operator was strictly against it. As per operator's experience, observation he said there won't be any other source available and it was utter waste to drill further. However, since we requested he went up to 625 ft. And this time, the operator was correct we did not strike water again.
Also Kannan borewells had only 31 rods (of 20ft length each) in their vehicle. So we were forced to stop at 625ft, maybe we could have recommended to get the rods so that we could drill one or 2 more lengths. But by then we too had lost confidence of striking yet another water source.
We are bit worried because of the low yield. As far as the daily water consumption is concerned, it would be approximately 3000 litres / day required for 2 families (one family of 6 members and in the let-out portion assumed to be around 4 members).
I would like to know if 3/4 inch yield would suffice the need for 10 members.
Operator did say that the yield would improve once the rains hit. Not sure if that statement is true !!
We are yet to check the static water level. As of now, we have taken a quotation for installing submersible pump / pipes which is estimated at 56k. They have considered installing a 2hp Texmo submersible pump and run around 139 meters of pipe. Please let us know if this quote is reasonable and whether we need to run the pipe for a depth of 400ft (approx 139 mts).
What would be the LPH of 3/4 inch yield bore hole ? I have visited a few sites, where it is stated as 261 LPH. Also few experts say that the drilling yield would be different from pumping yield and also that the pumping yield is expected to be 40% higher than the bore yield. Is that true ? When they say 40%, is that the increase in LPH ?
I'll be looking forward for the comments from experts all over India !!
Regards,
Ashwin