What is Managed Aquifer Recharge?

MAR is not a new concept and has been used extensively overseas. Managed aquifer recharge in our context refers to the intentional recharge of clean water to aquifers for environmental benefit.

Benefits include the natural treatment of water to enhance quality and the replenishing of over-allocated aquifers

Infiltration basins, which act like big leaky ponds, are filled with high-quality clean water which seeps down and recharges the groundwater.

Clean alpine water from the Rangitata River is delivered to the MAR site via irrigation races and pipes.  The silts carried by the water settle in the forebay before the water is allowed to flow through to the main infiltration basin. From there, the clean water seeps down to recharge the groundwater system. 

Why do we need to do this?

Water quality in some rivers in the catchment is not acceptable- nitrate levels exceed the NZ drinking water maximum acceptable value and we will not meet 2035 targets without taking drastic action. 

This situation is not unique to our catchment and is an unforeseen consequence of historic farming practice alongside other community use of the water resource.  Nutrients from land use activities take a very long time (decades to centuries) to travel through the groundwater system. We need to clean up these legacy nutrients in the groundwater while also significantly reducing the nutrients leaching from current land use.

The NPS and Environment Canterbury Plan Change 2 require a combination of reduced nutrient leaching from current land use and MAR to address legacy nutrients in groundwater and management of abstraction.

We must act now. Leaving these issues for the next generation is not an option.

Where does the nitrate come from?

Nitrates largely come from farming. Before we had our current knowledge about good farming practice the restrictions on farming were not as strenuous. Now we know more, our farming community is required to ensure good farm management practice including reducing their nutrient leaching by 36% by 2035. In addition, other industrial practices and leaky septic tanks also negatively impacted water quality. All these factors have combined to cause the issues we currently face.

Where does the water come from for MAR?

The project uses repurposed Rangitata River water from existing consents.

There is no unnatural mixing between waters.

Who oversees the MAR project?

The project is governed by the Hekeao / Hinds Water Enhancement Trust (HHWET).

Trustees include:

  • Peter Lowe – Chair
  • Alister Argyle
  • Melanie Brooks
  • Neil Brown
  • Craig Fleming
  • Sir Graeme Harrison
  • Vince Lobb
  • Ian Mackenzie
  • Anne Marett
  • Rab McDowell
  • Mark Webb

Will the MAR project achieve the required change?

The trial project has already achieved positive results. You can find the technical detail here. The governance group is confident that the project will make a difference however, it is important to remember that this is not the only solution. We all have a role to play in improving the quality and quantity of water. Farmers are making significant changes to the way they farm to help bring about improvements. Each farm must have a Farm Environment Plan and farmers must farm to good management practice, including reducing their nutrient leaching by 36% by 2035.

What if we don’t get nitrate levels down?

If we don’t reduce nitrate levels to those required by Environment Canterbury and the NPS Freshwater then more drastic measures will need to be taken.

Is there a flood risk from the MAR project?

No. The water required for MAR is small compared to rainfall in the catchment and infiltration ponds are not located close to springs. 

Who is funding and paying for the MAR project?

To date funding for the project has come from:

  • Environment Canterbury
  • The Provincial Growth Fund
  • MHV Water (in kind)
  • Central South Island Fish & Game (in kind)
  • Rangitata Diversion Race Management – RDRML (in kind)
  • Barrhill Chertsey Irrigation – BCI
  • Eiffelton Community Group Irrigation Scheme
  • Hinds Independent Groundwater Users

Funding for the scheme will be from a combination of sources based on ‘who benefits’. This could look like the following

Capital Expenditure

  • National contribution
  • Regional Rates
  • Local rates (ADC or ECan)
  • Benefiting landowners

Operating Costs

  • Local rates (ADC or ECan)
  • Benefiting landowners

What is the cost of the project?

An additional $6M is required for capital expenditure post 2020 and annual operating costs are estimated to be a maximum of $2M.

What is the Hekeao Hinds River project?

The Hekeao Hinds River project is an enhancement project that will bring additional environmental projects to fruition. Projects already underway include:

  • A Kowaro/mudfish wetland site
  • Mahinga kai sites
  • Restoration of a rare New Zealand indigenous lizard habitat

If the issue is caused by the farming community – why don’t they pay to fix it?

The farming community is just one of the contributors to the issue. This is a community problem and requires a community solution. Much of the damage is historical and we are unable to make historical charges. Our community all benefits economically from the agri sector and we all need to be part of the solution.