Defining Groundwater Protection Zones for Wellington Water in the Hutt Valley

Wellington Water Ltd operate two major drinking-water supply wellfields near the coastal end of the Hutt Valley (Waterloo wellfield and the Gear Island wellfield). These bores abstract water from the highly permeable Waiwhetu gravel aquifer derived from the Hutt River. Greater Wellington Regional Councils’ (GWRC) Proposed Natural Resources Plan specifies Groundwater Protection Zones (GPZs) for these bore supplies. GPZs define areas where land use activities and discharges to land and water require special controls to protect the quality of community drinking-water supplies. This example represents a development from sole-source use of a model prediction to an ‘in-concert’ approach where; model predictions, careful hydrogeological investigation, realisation of real-world risks, and sensible use of policy has achieved an outcome that provides a framework to better protect this component of the Wellington water supply. This paper describes the evolving methods that have been used to develop GPZs in the Hutt Valley during the hearings for the proposed plan.