The changes in human population often correspond with change in land use, including expansion of urban areas, agriculture and increasing industrialization, which necessitate increasing the available amount of drinking water. As the surface water sources are under the pressure of pollution, it has become necessary to use groundwater at an increasing rate. Groundwater recharge can be abundant in the alluvial plains where the urban areas are often located. Such areas can face danger of pollution of groundwater and the changes in land use are likely to result in change in groundwater quality. Keeping these aspects in view, it was planned to development a groundwater water quality index in the Ganga-Yamuna interfluve area of northern India, The objective of the present study is to develop the Index of Aquifer Water Quality (IAWQ) inside the Geographic information system (GIS) environment, which can be used by the field investigators and modelers in assessing the groundwater vulnerability. The formula to estimate the IAWQ index is adopted from the procedure suggested Melloul and Collin (1998). The procedure developed for this involves weights assigned to these 8 parameters as per their analytical hierarchy in violating the (drinking water) standards and not as an arbitrary means (as taken by Melloul and Collin). The suggested procedure can be extending to include more number of chemical parameters as necessitate in individual case studies. In the modified procedure presented in the present study, the number of measured chemical parameters n is taken as 8 (Cd, Mn, Pb, Fe, NO3-, Total Alkalinity, TDS and Ca2+) as against n=2 (chloride and nitrate) as taken in the Melloul and Collins work.