``This is reason for concern,'' says an official of the Central Ground Water Authority (CGWA). ``Ground water, if tapped properly, can go a long way to meeting Delhi's water requirements. If not, Delhi's ground water resources will dry up within no time.''

Though the DJB doesn't agree, the CGWA has launched a scheme asking people to register their tube-wells. So far they have listed 40,000 tube-wells in the city, and they expect to register another 15,000 to 20,000 tube-wells within the next two months. But CGWA officials estimate there are at least two lakh unregistered tube-wells and hand-pumps in Delhi.

Delhi's current water requirement is about 800 million gallons daily (MGD), but only 600 MGD is available at any given time, according to the DJB. About 20 per cent of the water is lost during distribution.

``Even if we can't locate all the tube-wells in Delhi, the 40,000 odd that we have found so far can supply about 200 MGD, which is one fourth of Delhi's requirement. This is almost enough to cover Delhi's deficit,'' says S.B. Singh, president of the All India CGWA board officers' association. ``Therefore, the Delhi Jal Board's claim that ground water in Delhi can meet only 10-15 per cent of the requirement does not hold water.''

Officials from the DJB, however, insist that most of the ground water in Delhi is not potable. ``We are aware of several tube-wells, but we have pointed out to the owners that drinking the water without testing it can prove hazardous,'' says a DJB official requesting anonymity.

Singh, on the other hand, points out that the DJB is perhaps not aware that in areas like Chattarpur and Mehrauli ground water is ``very potable and still available at a depth 35 metres''. Besides, there's economics too, he explains: every time the ground water level goes down by one metre, the cost of making the potable increases by 0.5 percent.

Before the CGWA launched the scheme for registration of tube-wells, only 10,000 were in the record books. Now it has increased by another 30,000, CGWA officials have extended the deadline for registration of tube-wells to June 30 this year. They are keeping a close watch on areas like Mehrauli and are not allowing any new tube-wells.