RESUMEN
Water Quality Index (WQI) has been calculated for underground drinking water at Hasanpur in J. P. Nagar district, Uttar Pradesh, India at ten different sites in the pre-monsoon season as well as after the onset of monsoon. Water quality parameters were selected as per the WHO guidelines and seventeen water quality physico-chemical parameters were estimated following the standard methods and procedures. Drinking water at almost all the sites was found to be highly contaminated, except a few sites, where it was found moderately contaminated for both the periods during the year 2005. In general, to some extent water quality showed deterioration after the onset of monsoon. It was found that some effective measures are urgently required for water quality management in this region.