State of the environment monitoring Auckland water quantity statement 2012/2013 March 2015 Technical Report 2015/005 Auckland Council Technical Report 2015/005 ISSN 2230-4525 (Print) ISSN 2230-4533 (Online) ISBN 978-1-927216-44-6 (Print) ISBN 978-1-927216-45-3 (PDF) This report has been peer reviewed by the Peer Review Panel. Submitted for review on 7 May 2014 Review completed on 27 February 2015 Reviewed by two reviewers Approved for Auckland Council publication by: Name: Regan Solomon Position: Manager, Research and Evaluation Unit Date: 27 February 2015 Recommended citation: Stansfield, B and Holwerda, N (2015). State of the environment monitoring: Auckland water quantity statement 2012/2013. Prepared by EIA Ltd for Auckland Council. Auckland Council technical report, TR2015/005 ©2015 Auckland Council This publication is provided strictly subject to Auckland Council’s copyright and other intellectual property rights (if any) in the publication. 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The publication, information, and data contained within it are provided on an "as is" basis. State of the environment monitoring Auckland water quantity statement 2012/2013 Brett Stansfield EIA Ltd Nicholas Holwerda Research and Evaluation Unit Auckland Council Executive summary The need to understand Auckland’s water resource is crucial for the development in industry, agriculture and the supply of municipal water. This report summarises the hydrological year from June 2012 to May 2013. Consent information is included showing total water allocation and use for each demand type. All information has been split into surface water and groundwater. For the purpose of the report the Auckland region has been split into eight water resource reporting areas: Kaipara River-North Shore, Waitakere, North East, North West, Auckland Central, Gulf Islands, Hunua and South Auckland. The northern part of Auckland was officially declared in drought on 27 February 2013 while the central and southern areas were declared in drought on 6 March 2013 (NIWA 2013). The immediate cause of the 2012/2013 drought was the persistence of slow moving or ‘blocking’ high pressure systems over the Tasman Sea and New Zealand over the summer season. The reason for such persistence will need further research. In this particular instance, the El Niño Southern Oscillation was in its neutral phase and was not a determining factor. Over the period June 2012–May 2013 the region experienced well below average rainfall causing effects on both stream flows and groundwater levels. Rainfall was on average 12.3 per cent less than in the previous year. The reduced rainfall had the consequence of reducing runoff and groundwater base flow discharge to streams and recharge to aquifers. These effects are seen in the stream flow hydrographs and groundwater level charts for most sites. Conversely, above average rainfall was experienced during April and May 2013 during which rainfall rose to 135 per cent and 191 per cent of average rainfall. Seven of the high use stream management areas with long-term monitoring sites had periods during the year where flows dropped below mean annual low flow (MALF). The groundwater levels for 2012/2013 show a typical response to seasonal winter recharge and summer water abstraction loss. The groundwater levels from June 2012 to December 2012 were generally average to above average, due to above average rainfall in 2011/2012. However, these levels became below average from February to May 2013 due to higher than normal summer irrigation demand and low recharge rates. Groundwater levels did rise during April–May 2013; however, whether there was sufficient aquifer recharge to bring groundwater levels back to the long-term mean will not be seen until after spring recovery in October 2013. The groundwater level at the Franklin Kaawa Mauku bore in the south reached near record minimum levels (March 2013). However, there is no management water level for the Franklin Kaawa Mauku bore, and allocation and use was within the availability set in the Auckland Council Regional Plan: Air, Land and Water (ACRP:ALW). The groundwater level for the Waitemata Omaha Flats bore in the north east almost consistently remained below the long term mean level for the June to October recharge period of 2012. However, average water level for the year was well above the management water level, and allocation and use was within the availability set in the ACRP:ALW. Total water allocation for the 2012/2013 year was 107.6Mm3, total water used was 74.3Mm3. Watercare Services Limited allocation was 67m3. Total groundwater allocated in the 2012/2013 hydrological year was slightly greater compared to the previous year (up by 6.6 per cent) and total use was up by 14.2 per cent. The reason for the high water use was likely to be the low rainfall throughout the spring and summer of ______________________________________________________________________________ State of the environment monitoring: Auckland water quantity statement 2012/2013 iv 2012/2013. This low rainfall caused an increase in irrigation water use. Total surface water allocation and use was lower than in the same period the previous year. ______________________________________________________________________________ State of the environment monitoring: Auckland water quantity statement 2012/2013 v Contents 1.0 Background……………………………………………………………………………………….. ................... 5 1.1 Regional rainfall ........................................................................................................................................ 6 1.2 Surface water management ..................................................................................................................... 7 1.3 Groundwater management ....................................................................................................................... 8 1.4 Water use, allocation and compliance...................................................................................................... 9 1.5 Irrigation .................................................................................................................................................. 15 1.6 Industry ................................................................................................................................................... 15 2.0 North West ............................................................................................................................................ 16 2.1 Rainfall .................................................................................................................................................... 16 2.2 Surface water ......................................................................................................................................... 16 2.3 Groundwater ........................................................................................................................................... 19 2.4 Water use and allocation ........................................................................................................................ 19 3.0 North East ............................................................................................................................................. 22 3.1 Rainfall .................................................................................................................................................... 22 3.2 Surface water ......................................................................................................................................... 22 3.3 Groundwater ........................................................................................................................................... 25 3.4 Water allocation and use ........................................................................................................................ 28 4.0 Kaipara River-North Shore .................................................................................................................. 29 4.1 Rainfall .................................................................................................................................................... 29 4.2 Surface water ......................................................................................................................................... 29 4.3 Groundwater ........................................................................................................................................... 32 4.4 Water allocation and