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9 February 2017
TANK newsletter/ panui on the collaborative group developing a plan to manage land and water in the Tutaekuri, Ahuriri, Ngaruroro and Karamu catchments - TANK.
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Meeting 26 started with a kōrero from Marei Apatu, on behalf of the Mana Whenua group, reinforcing TANK’s focus to ‘maintain or improve’. He also stressed the need to air and debate concerns as they arise. TANK Group members acknowledged Marei’s kōrero and that the health of the water, rivers and aquifer is the Group’s first priority.


The Minister for the Environment is appointing a Special Tribunal to consider the WCO application. The group expects further announcements from the Minister in the next month. In a draft submission to the (yet to be appointed) Special Tribunal, HBRC has asked the Tribunal to start their process with the Upper Ngaruroro, leaving the TANK Group to complete their work on deciding about  water use and limits in the lower catchment first.

Naturalised flows - flows for Ngaruroro River at Fernhill that would occur if there was no abstraction - have been reviewed as part of developing the Heretaunga Plains groundwater-surface water model.  New modelling has shown that minimum annual low flows at Fernhill are lower than first estimated. The peer-reviewed reports that support this will follow in due course. This new finding will affect discussions about the most appropriate flow management regime for both the TANK process as well as eventually the WCO process.


Farm drains contain water, which is subject to management through plan rules, but they are not classed as rivers or waterbodies. Rivers include modified watercourses.  Much of the drainage network in the Heretaunga Plains results from draining wetlands and many waterways constructed to do this are therefore modified waterways, i.e. Raupare Stream is a modified watercourse.  
Whatever policy is established to cover farm drains and some of these modified watercourses will also need to consider the flooding and drainage functions they perform.

A short explanatory paper about rivers and drains was given to the Group. This will be available on the TANK webpage once it has been amended and approved for release by the Group.
A discussion paper giving the legal and historical context to water allocation was prepared to help the Group in this process.  This will be available on the TANK webpage once amended and approved for release by the Group.
The TANK Group will be making recommendations about water allocation and the management of water supplies during drought.  This discussion concerns the amount of water that can be sustainably abstracted from waterbodies and is available for allocation through resource consents.

TANK members broke into smaller groups to talk about different ways to prioritise water allocation.  This conversation leads to that reasoning and criteria that helps decide how end uses might be prioritised. The Group considered reasons for end use priority that consider economic values such as productive yield, job creation or retention.  Water use efficiency criteria could be developed or effective social allocation mechanisms could encourage water users to thrive or innovate, or a mix of these could be applied.

The Group first confirmed the existing high priority given to permitted water takes for domestic water supply, an individual’s animals and fire-fighting, through the Resource Management Act.

Other potential reasons for water take priority fell loosely into these categories:
  • Economic value or added value for the regional economy
  • Social wellbeing such as enough water for community or municipal demand
  • Food production and ecological supporting systems
Discussion groups did not come to any particular agreement about end use priority. Community and municipal water supply was highly valued, along with further attention to efficient use and drought management.  A potential connection was made between existing land use policy - recognising the productive nature of irrigable land on the Heretaunga Plains - and water allocation policy. This discussion will continue.

After water has been allocated via water permits, restrictions during droughts require water to be managed more carefully, and should a drought escalate.

During dry summer months, water use is under the most scrutiny. Small groups again discussed how to prioritise for water allocation. The groups listed prioritisation by efficient vs inefficient water use and some had a particular focus on urban water efficiency. Water take priority fell loosely into these categories:
  • Life supporting/ welfare – people and animals
  • Environmental flows
  • Perennial crops
  • Food processing
More discussion on irrigation and other end uses will come as TANK moves to water allocation decisions.


HBRC Scientists Rob Waldron, Jeff Smith and Pawel Rakowski gave presentations to explain water modelling and water use scenarios for the TANK Group to review.
The new groundwater model shows that groundwater and surface water are highly connected across the Heretaunga Plains, with the aquifer described as a slowly affected bathtub. Nearly all groundwater takes are connected in varying degrees to surface water systems.
Stream flow effects from groundwater takes are not localised and combined abstraction effects over the wider Heretaunga Plains add to declining water levels and flows. Every water user has some effect and the effect is cumulative. This in itself represents a big turnaround in the way the TANK Group and wider community have understood and managed abstraction to date.
Modelling (results expected at the March meeting) will simulate the effect of pumping restrictions in different zones on stream flow.  One model scenario will show the effect of no irrigation across the modelled area and another will be based on the current system of groundwater and surface water takes/ restrictions, including the current approach to managing stream depleting groundwater takes.   

Other modelling will use a new way of grouping or classifying groundwater takes.  The model initially ran with the same groundwater depletion categories used for the Tukituki Plan. However all groundwater takes would have been classed as stream depleting and subject to surface flow restrictions. This method of restriction is likely to have little benefit in preventing further river flow losses.  Therefore, other scenarios will model a revised grouping of groundwater takes based on four zone categories – see diagram above.

Mitigating effects of artificial recharge and stream augmentation from groundwater can also be modelled.

Of the 85% of people who live and work on the Heretaunga Plains, drop for drop of water we use, we all have an equal effect on the aquifer and connected rivers.

After feedback from breakout groups, the project team will look at 10 different modelling scenarios based on the classes of groundwater depletion given above.  The scenarios are on the TANK webpage. They cover combinations of low flow management and restrictions.  Modelled scenarios will help the Group to optimise various combinations of groundwater classification, restrictions and mitigations. search #tankresources for more details.
© 2017, HBRC
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