Vulnerability assessment to define areas critical for the maintenance of groundwater quality has been shown throughout the world to be an important tool for delineating the monitoring networks required for surveillance of potential pollution sites. The objective of this study has been to assess groundwater quality sampled at individual locations by indexing it numerically in a manner parallel to the DRASTIC mode which provides a relative assessment of vulnerability to potential pollution on the part of the vadose zone and aquifer media. The present study develops an indexed assessment of an aquifer's water quality (IAWQ) initially using the chemical parameters chloride (Cl) and nitrate (NO 3 ), implemented in Israel's Sharon region. High values of IAWQ are shown as possible delineators of areas where land usage is already affecting groundwater quality. Similarities of IAWQ results to those of DRASTIC in the same area can be used to validate the DRASTIC model, and delineate areas where vertical percolation appears to be a major factor affecting groundwater deterioration. On the other hand, discrepancies between IAWQ and DRASTIC values can help to delineate areas where parameters such as lateral flow may best explain a decrease in groundwater quality. The IAWQ formula can thus be a beneficial tool towards assessing the degree of land use impact upon groundwater quality.