Evaluation of index-overlay methods for assessing shallow groundwater vulnerability in southeast Hungary

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This study evaluated three index-overlay methods (i.e., DRASTIC, GOD, and susceptibility index (SI)) for their suitability to assessing the vulnerability of shallow aquifer in southeast Hungary to contamination from the land surface. Accordingly, the most recent information on the shallow aquifer depth, recharge rate, land use, and geology/hydrogeology of the groundwater basin was created and integrated in a geographic information system and through a linear combination to compose the methods indices. All three methods delineated approximately 95% of the groundwater basin as being moderately to highly susceptible to contamination, which was mainly due to the sandy soil, high recharge rate, gentle topography, and agricultural activities related to land use. A positive linear correlation was also found, during the validation of the final vulnerability maps, between the vulnerability indices and observed nitrate concentration. The vulnerability indices of SI, DRASTIC, and GOD showed correlations of 0.5635, 0.3615, and 0.3499, respectively, with the available nitrate concentration in the groundwater. Thus, SI was concluded as the most suitable method for assessing the vulnerability of shallow aquifers in southeast Hungary to contamination. The outcomes of this study provide useful information that will help policymakers identify the main contributors to groundwater contamination as well as adopt effective management strategies to avoid further pressure on this invaluable resource.