Chiang Mai Journal of Science

The objective of this paper is to evaluate groundwater vulnerability to contaminants using hydrogeological data and the DRASTIC method. All parameters were prepared in geographic information system as raster grid files. The range and rate of each layer were assigned to parameters according to the degree of vulnerability to contaminants. The groundwater vulnerability map was delineated in five classes to show area relative potential. An area of extremely high degree of vulnerability has the highest range score. The groundwater vulnerability map indicates that extremely high vulnerable areas are along the alluvium flood plain of the Ping River and it tributaries. This flood plain area has high permeability, a flat terrain, and a high amount of rainfall. The high vulnerability of these flood plain areas is indicated by high concentrations of total dissolved solids in subsurface water in dug wells, though some high vulnerability areas are still not contaminated. Therefore, groundwater protection is needed in uncontaminated areas and the groundwater vulnerability map can be used as guidance for controlling groundwater contamination.