Groundwater vulnerability assessment using a composite model combining DRASTIC with extensive agricultural land use in Israelʹs Sharon region

Vulnerability assessment to define areas critical for the maintenance of groundwater quality has been shown throughout the world to be an effective tool for establishing monitoring networks required for surveillance of potential pollution sites. One objective of this study has been to integrate the impact of extensive land use over long periods of time upon aquifer media as an additional parameter to the DRASTIC model to assess the potential level of groundwater vulnerability to pollution. An additional objective involved adaptation of this composite model to a specific region of a coastal aquifer, at a scale commensurate with effective hydrological management needs. The methodology employs empirical means to integrate aquifer media and extensive agriculture land use data covering the study area. The final assessment thus incorporates both the natural state of the vadose zone and aquifer media as well as the potential danger posed by the long-term effect upon the media of existing extensive land usage to the regionʹs groundwater. The assessment utilizes Geographic Information System (GIS) technology. The studyʹs unique contribution involves estimation of a composite index for each cell, enabling comparison with a potential index of vulnerability to groundwater pollution which includes land use impact and the empirical situation of groundwater quality in the field. The results exhibit certain correspondence for Israelʹs coastal Sharon region between the DRASTIC Index, The Composite DRASTIC—Agricultural Land use Index, and high nitrate levels. Such results delineate areas of high pollution risk, and increase the feasibility of applying such models world-wide.