15th November 2015
TANK newsletter/ panui on the collaborative group developing a Regional Plan to manage land and water in the Tutaekuri, Ahuriri, Ngaruroro and Karamu catchments - TANK.
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Think TANK V

The TANK Group’s November meeting (no. 24) covered groundwater management along with the state and trend of groundwater quality, then a discussion on how to reduce sediment in surface water. 

Dougall Gordon, HBRC Groundwater Scientist, gave a summary of the groundwater system, its geology, re-charge, water use and monitoring programme.  His presentation is online at TANK Resources, or see the TANK Groundwater Fact Sheet for more information.

As with surface water, the Group considered values for groundwater and the attributes it might apply to meet these values, in the diagram below.

HBRC monitors a range of physical and chemical attributes. Some of these can’t be managed directly, such as iron, manganese and hardness – seen in groundwater due to the geology of the aquifer. Iron, manganese and hardness affect water taste and colour, and can affect pipes and pumps.  Levels of these attributes depend on the aquifer material - sand, gravel and rock - and the length of time groundwater spends in the aquifer.  Other attributes - pathogens, pesticides and nutrients - can enter groundwater as a result of land use or discharge activities.

Humans are sensitive to dissolved nutrient levels, such as nitrate, but ecosystem health is much more sensitive.  The threshold for (human) drinking water is 11.3 mg/L nitrate to Nitrogen, while ecosystems rarely have natural nitrate concentrations (annual median) higher than 1.0mg/L nitrate to Nitrogen.

Karamu Stream gains flow from groundwater springs, as do the Raupare and Irongate streams.

Groundwater in the Heretaunga Plains contributes to surface waters in the Karamū, Raupare and Irongate streams.  The degree that ecosystem values are affected by nutrients depends on concentrations and the volume of flows to surface water.  HBRC is in the process of modelling water flows and sources of contaminants, with more information to come on this.
The Group noted several bores showing slightly elevated nitrate concentrations in the unconfined aquifer, where localised land uses are likely to be the cause.  The Group also noted occasional traces of E. coli in some monitoring bores and sought more information about phosphorous trends and levels.  Phosphorus in deeper groundwater results from geology and travel time through the aquifer.  Phosphorus is not normally expected in shallower groundwater - it generally binds to soil particles and doesn’t move into groundwater.   
HBRC’s Regional Policy Statement (RPS) and Regional Resource Management Plan (RRMP) already have objectives, policies and rules in relation to groundwater management, especially for the Heretaunga Plains.  These generally serve the outcomes sought by the group as it seeks to maintain groundwater quality across the Plains.  However, specific attention will be given to the management of storm water discharges to groundwater.  The Stormwater Working Group has yet to report back on this.
TANK Group will develop specific objectives relating to:

  • Nitrogen – details to come as modelling informs on concentration and flows. Levels will be based on NOF and ANZECC guidelines
  • based on The NZ Drinking Water StandardsE. coli –
  • Pesticides – based on NZ Drinking Water Standards 

The Group identified that further monitoring and investigation is needed to examine reasons and possible trends relating to phosphorus, isolated nitrate levels and occasional E. coli measurements.

Managing Sediment

Barry Lynch, HBRC Land Scientist, reminded the Group about the importance of reducing sediment loss from productive farmland.  Sediment reduces the state of some freshwater attributes, it affects water values, especially ecosystems, in estuaries and coastal waters.

Some erosion is natural and occurs regardless of human intervention.  HBRC’s SedNet model - introduced to the Group at meeting 23 - predicted if the catchments were fully forested with no human land use, sediment load would still be about 30% of what is happening now.

Under a pastoral system some sediment loss still occurs, but mitigation measures will reduce the amount.  Measures include good vegetation management, including trees on highly erodible land.  Stock exclusion from waterways will also reduce sediment, nutrients and e. coli in freshwater.

The Group received information about how sediment loss might be reduced and the relative success of different approaches, in Table 1.

Table 1 Estimated sediment loss and mitigation – TANK catchments

Soil protection costs include $800/ ha for hillside stabilisation tree planting, $3 - $36/ metre fencing (dependant on fence type), horticultural setbacks or buffer strips could cost up to $100 - $250/ ha.

The Group discussed needing more information on the wider costs and benefits of soil erosion and soil conservation including lost farm production and impacts on infrastructure.  The costs of sediment to coastal and marine environments were also a concern.  Information from other places in New Zealand is available, with growing local evidence about sediment effects on the region’s marine ecosystem. Flood protection works have channelled sediment in rivers directly to estuaries and the marine environment. This has inhibited the natural meandering habit of our braided river systems, which established the Heretaunga Plains over many thousands of years. A balance needs to be struck. However, HBRC only holds limited long-term information about these effects and is developing a coastal and marine monitoring programme to be better informed.

The Group discussed a management objective for reducing sediment loss over the next 10 years, considering objectives from 10 – 30% reduction.  No decision was made but the group expressed a desire to have both short and longer-term goals.

The TANK Group considered a package of possible management options.  National regulation for stock exclusion and plantation forestry management are due, with draft stock exclusion rules expected by the end of 2016.

Group members expressed particular support for the use of Farm Plans to identify environmental risks and management measures at a property scale.  However, there was no consensus on Farm Plans being a regulatory requirement or being advocated as a useful and beneficial farm management tool, supported by some regulation.

No decisions about any details were made. The Group recommended that the Economic Assessment Working Group examine options and costs, to report back with more detailed options for the group to consider.

Table 2 - Options considered by TANK Group

Behaviour Change

The group also heard some advice on behaviour change, what affects it and how to make it happen.  Key components or drivers for change include:

·         Understanding the problem and the reasons for a change

·         Having ability to change behaviour, including having the knowledge, resources and physical ability to change

·         An imperative/ strong reason to make change – this could include a desire for the outcome being sought, financial advantage, market access, or a regulatory requirement.

NZ GAP and EUREPGAP in horticultural production systems, effluent management plans for dairy, similar programmes in Zespri, Winegrowers, etc. are all relevant. This information is relevant to the choice of measures or tools that might require farm owners and managers to change the way they manage resources over time. More information will be sought on the approach being taken by the Sheep and Beef sector.

Future Considerations

The Group was asked to think about what future changes might impact on water quality or quantity. 

The Group discussed climate change, possible land use changes, the impact of market requirements and what effect changes in society attitudes and environmental awareness might mean to our water management provisions. 

It was noted that some temporary land use change would arise as DoC commenced its wilding pine control programme in the Kaweka Ranges. This could have impacts on water quality downstream, which will need to be carefully managed.

The group was to consider this question and feedback further information as it arises.

Next TANK Meeting

Meeting 25 will focus on values and management of Karamū Stream and its tributaries – including ways to improve the current state.  It will also get a first look at the Heretaunga SOURCE model.  The model looks at how river flow and groundwater levels change under different management regimes and the group will use it to test various quantity and quality management scenarios.

More Info
The TANK Group also considered ways to encourage wider community involvement in this water and land management work.  They voiced a need to share more of the information being considered as part of this plan change process, to also gain wider buy-in to the decisions they make.

As a result, TANK meeting notes will now be publicly available alongside presentations made to each meeting.  See the, search: #tankresources for more details.
NOTE: we want profiles for each newsletter - email a brief bio and photo to to help us show the varied perspectives of TANK Group. 
Please pass this newsletter/ panui on to anyone you think might benefit from it.
Got any comments or questions about this newsletter? Email Mary-Anne Baker
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