Yield issues in a borewell in Medavakkam, Chennai, TN

Dear Sirs

We dug up a borewell in May 2011. This was dug up up to 330 Ft and we went for a Texmo Submersible (1.5 HP) and the pump was help at 270 Ft. This is a 6 inch borewell. For a month or so till end June 2011, we were getting water at all times of the day. Since July 2011, we are getting only 300 litres a day. (we are able to run the motor for 15 mts or so)

What is the way out? What are the next steps we should consider before going for another bore?

Could you pls advice?