ABSTRACT
Conventional regional vulnerability assessments rely on a numerical index and normally assess the probability of detecting generic, non-reactive contaminants. These methods often fail to detect areas subject to groundwater contamination because they do not consider contaminant loading and characteristics. In the Manawatu region of New Zealand, a method was developed to assess vulnerability on the basis of four factors: rainfall recharge, and the properties of the soil, unsaturated zone, and aquifer medium. Results of a spatial correlation between these vulnerability factors and groundwater contamination indicate that the properties of aquifer medium are the major factor that control nitrate distribution. This highlights the need for a new system incorporating pollution characteristics and loading, and the relative value of the aquifer.
