To enhance yield in the bore well, you can opt for multi hydro-fracturing methodology, as it looks like your bore well is surrounded by fractured zones at deeper levels. May be some of the main fractured conduits might not have been feeding into your bore well fractures or some other bore wells are sharing your fractured conduits and they might be sucking water from your bore well owing to their locational advantage.
Alternatively if you have enough space, you can trace the main fractured conduits and drill new deep bore wells. This is an alternate solution. When hydro-fracturing technique was not known or was not being adopted in the Trichy and Coimbatore belt, many bore wells recommended close to such kind of low yield bore wells have given surprisingly higher yield at depth levels of 250 feet during late 80s in Trichy belt and depth ranges below 950 feet in early 2000s in Tiruppur and Coimbatore belt. They were hardly 5 to 8 feet away from the old bore wells.
Your terrain has soft formation at shallow depth and sometimes at intermediate depth the bore well may collapse. If it is hard strata then a new bore well is better. I would recommend hydro-fraturing technique which would be available at Bangalore.
To sustain the yield rainwater harvesting with appropriate designs have to be carried out not only by you but also by your neighbours. Please consult a good rainwater harvesting planner at your place and follow the latest design and technological advents.
A Rajamohamed Ambalam (http://www.indiawaterportal.org/users/rajamohamed-ambalam)
There could be a couple of reasons for something like this to happen.
1) Some one else may have drilled a new well that is affecting the yield.
2) You may have struck a huge pocket/cavity which is connected to the main aquifer but the connectivity is not very good hence initially you got the excess water and then it reduced.
3) The pipeline may have developed a leak, probably where the pipe is joined to the pump and due to this the pump is unable to develop the required back pressure to deliver adequate water to the surface.
4) If you have a three phase motor, you may have a phase reversal and the motor is rotating in the reverse direction.
You may do the following,
Check if some one else has drilled a new well recently in the area.
Check if the amount of current drawn by the motor (In Amperes) goes up and the motor shuts off due to overload if the pump is switched on keeping the delivery tap closed. If it does not shut off then there is a leak in the pipeline. This needs to be done only if you have a good quality control panel with overload safety shut-off.
You can always pull out the pump and pipeline for inspection.
Anil Lalwani (http://www.indiawaterportal.org/users/wellwaterworks)