The fall has been as high as 62 per cent in some districts.
But at the same time, the water level has increased in 38 per cent of the wells monitored by the agency in the same period.
The CGWB had carried out monitoring of 124 wells in the NCT of Delhi ahead of the monsoon season this year.
"Ground water monitoring data of 124 wells in NCT of Delhi for pre-monsoon 2013, compared with decadal mean of pre-monsoon (2003-2012), indicates that there was a rise in water level in respect of 38 per cent (around 47 of 124) of the wells and fall in 62 per cent (over 76 of 124) of the wells analysed," Water Resources Minister Harish Rawat told Rajya Sabha in a written reply.
More From This Section
An analysis of ground water quality data of Delhi reveals that in general the ground water quality in Yamuna flood plain is "within the permissible limit" of Bureau of Indian Standards (BIS).
"However, in some pockets in the flood plain of Yamuna, high salinity, iron, nitrate, arsenic and heavy metal contaminants are found," the minister said.