ASSESSMENT OF PESTICIDE CONTAMINATION OF GROUNDWATER IN NEW-ZEALAND .1. RANKING OF REGIONS FOR POTENTIAL CONTAMINATION

Groundwater contamination by pesticides may be affected by the amounts of pesticide used, the mobility and degradation characteristics of the pesticides, and the vulnerability of an area to pollution. An index of potential pollution was developed based on these factors, with the groundwater vulnerability being measured using the DRASTIC ranking method. Seventeen regions were selected from throughout New Zealand where significant pesticides have been applied and there is an underlying groundwater system. They were ranked according to this index of potential pollution. The sensitivity of the ranking to various formulations and weightings of the index was examined. Three regions (Poverty Bay, Te Puke, and Motueka) were generally highly ranked for a wide range of index formulations. Six of the higher-ranked regions were selected for sampling in the second phase of the study.