Author:Zeljko Viljevac, Greg Murphy, A Smaill, G Crowcroft, David Bowden
Source:Auckland Regional Council
The aim of this report is to provide guidelines for the management of aquifers in the northern part of Franklin District. Aquifers studied include Bombay, Pukekohe and Glenbrook volcanics, and the Kaawa Formation.
The primary focus of this study was to review the mechanism of groundwater flow within and between the aquifers underlying the Manukau Lowlands and Pukekohe Hill, establish the recharge mechanism, and prepare a model of the recharge. A major component of the work was to estimate the volume of water that can be safely allocated for use (water availability) from the Kaawa aquifer and determine its relationship with other aquifers. The last comprehensive review of the management of these aquifers was completed in 1989 (ARWB, 1989, TP85). Water demand has increased since the late 1980‟s to an extent where some resources were considered fully allocated, based on water availability figures from previous studies. The need for accurate information on water availability from aquifers to satisfy demand led to the review of water management in the area. A major outcome of this work was to provide the technical basis for water availability figures and policy for water management set out in the Proposed Auckland Regional Plan: Air, Land and Water, which was notified in October 2001.
This investigation was focussed on:
(1) The interaction between volcanic aquifers (Pukekohe, Drury-Bombay and Glenbrook) and underlying Kaawa Formation aquifer,
(2) The relationship of the aquifers with stream and spring discharge, and discharge to the sea
(3) The significance of the rainfall/infiltration ratio in the recharge pattern.
(4) The best management approach.
This required a reassessment of geology, hydrogeology and aquifer hydrological parameters. The results of the investigations lead to the management approach as outlined in the Proposed Auckland Regional Plan: Air, Land and Water, 2001 .
Auckland Regional Council technical publication TP133