Author:G Crowcroft, R Bannister, Sarah Harvey
Source:Auckland Regional Council
Surface water and groundwater resource information, availability and allocation.
This report is an update of one area in the Auckland Water Resource Quantity Statement 2002 (TP171). That report examined the water resources, both ground and surface, throughout the Auckland Region in eight Management areas. It was then proposed to update that report for two of the areas each year and this document fulfils that objective for the Northwest area. As an update, it covers the 2001 – 2002 hydrological year (from June to May). It may therefore be read in conjunction with TP 171 and does not attempt to reiterate data and information from that earlier report where there have been no changes.
The general picture for 2001 – 2002 was of unusually high spring and summer rainfall, in November and December up to 180% of the long term mean for those months. This was reflected in higher surface stream flows and, in particular, a low level of abstraction from both surface and ground water compared to the allocated levels. One addition to this report from the format in TP 171, is the estimate of water use compared to allocation. For the 2001 – 2002 year approximately 22% of the surface water allocated to consent holders and 61% of the consented groundwater allocation was taken.
Another feature of this type of report is to review outcomes against management objectives and policies. The objectives and policies relating to the taking of water are set out in the Proposed Auckland Regional Plan: Air, Land and Water (PARP:ALW), notified in October 2001. Two particular objectives relevant to Northwest are; to maintain the quality and flow in surface water and maintain the quality, water level and temperature in groundwater. To achieve these objectives there is a policy to take ground water in preference to surface water, where it is available. This is not the case in much of the Northwest where, due to the geology, ground water is less readily available than surface water. This is reflected in the allocation of surface being double that for ground water. However, for the year in review, use of groundwater was higher than surface water by four percent.
The second objective relating to maintaining temperature in the Parakai geothermal aquifer is managed by ensuring the water level in the aquifer is maintained above a prescribed level. Abstraction from the aquifer has been managed to ensure the water level has not fallen below the prescribed limit in the 2001 – 2002 year.
Auckland Regional Council technical publication TP194