Marton Water Supply Strategy

At its meeting on Thursday 9 April 2026, Rangitīkei District Council agreed to a new direction for the

Marton Water Strategy, following further testing and independent review.

A decades-long problem

Work on the Marton Water Strategy began in 2019, with a clear goal: To provide safe, reliable drinking water that meets the needs of Marton now and into the future.

While progress has been steady, the journey has been far from straightforward.

Marton has long relied on dam-based water that although is safe to drink, was never designed for long-term use and a growing population. This has led to ongoing issues with colour, taste, and smell – especially in spring and summer seasons.

This is not a new challenge. Council records show decades of investigation into alternative water supplies, with countless reports over the Council’s history exploring potential options.

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December 2025 - March 2026:

With all testing complete, Council worked through a detailed review of all findings. This included:

• Independent peer review and expert analysis of nanofiltration performance
• Assessment of long-term costs
• Evaluation of washwater management options

Council wanted to take a careful, evidence-based approach to reviewing before making a final decision - ensuring the solution is right for Marton both now and into the future.

April 2026:

Based on the review and all the information we now have, Council have decided to pause any further work on the nanofiltration technology for now.

To address the complex nature of the Tūtaenui Reservoir bore water, we would need to introduce additional treatment steps to the Nanofiltration technology resulting in increased capital and operational costs over and above the approved budget for this project.

Taking the time to test and learn has meant we have a great understanding of Marton water (both from the dams and the new bore), and we have been able to explore alternative technologies being trialed in other parts of the country with similar issues.

We have worked incredibly hard to develop an alternative solution that blends new technology with tried and true methods. The proposed alternative solution has 3 components:

1. Installing ultrasonic algae control systems in the Tūtaenui Reservoir Dams to manage algae blooms during warmer months.
2. Constructing a special treatment plant at the Calico Line bore to improve the groundwater quality.
3. Blending water from the reservoir dams with water from the bores during peak demand.

We are hopeful this will improve the quality of water for the short-medium term, while sticking within the project budget, while we continue to investigate long-term permanent solutions.

In 2025, Council moved the small trial treatment plant to the Tūtaenui Reservoir bore site itself in order to test the treatment method in ‘real world’ conditions.

• An “at scale” trial treatment plant was installed at the Tūtaenui Reservoir in July 2025 to:
• Test nanofiltration over a longer period
• Understand its performance during peak demand
• Refine how washwater would be managed

Originally planned for 12 weeks, the testing at this trial treatment plant ran for nearly five months. Council deliberately extended testing to remove uncertainty and ensure the system would perform reliably for Marton residents over the long term.

With a contractor for treatment design secured, the focus shifted to testing how the water from the Tūtaenui Road bore could be treated. A small-scale trial treatment plant for the new bore water was developed next to the Marton Water Treatment Plant. This allowed Council to test different treatment methods in real conditions.

Initial test results confirmed:

• Nanofiltration appeared to be the most suitable method for treating the Tūtaenui Reservoir bore water. However, there were still uncertainties about how it would perform at full scale and over time

Testing also identified some additional challenges with the make-up of the water in combination with the nanofiltration technology. Specifically;

• Iron and manganese levels
• Silica in the water
• Managing washwater from the treatment process

By the end of 2024 testing of the existing Tutaenui bore water was completed. Council had a preferred treatment approach but needed to confirm this approach on the new Tutaenui Reservoir bore water. Nanofiltration was at the core of the treatment process, but we needed to refine the treatment design and test it further and for longer.

Work on developing the new bore continued. In October 2023, a screen was installed on the Tūtaenui Reservoir bore. This screen was part of the initial testing process at this bore site and allows for the maximum water to pass through for treatment without dragging through sands or sediments. The new bore was fully established in November 2023.

During this year, staff also worked through the application process for a resource consent to take water from the new bore.

Throughout the year, staff sought contractors for designing a suitable treatment process. This process faced some delays due to a limited engineering market at the time.

In 2022, the project moved into physical works. Key steps included:

• Confirming Tūtaenui Reservoir as the best bore location
• Completing technical investigations of the aquifer
• Running a procurement process to appoint a contractor to complete the bore drilling work.
• Drilling began in August 2022, with the bore reaching a depth of around 299 metres.

By the end of 2022, Council had broken ground on a new bore water source at Tūtaenui Reservoir that could deliver the volume of water required to serve Marton residents.

In May 2021, Council made a key decision to move away from the dam-based supply and adopt groundwater as Marton’s future water source.

This decision was based on:

• Greater reliability compared to the dam
• Ability to meet drinking water standards with treatment
• Long-term sustainability.

Following this decision, work then focused on:

• Identifying the best location for a new bore – as it was determined the two existing bores would not be suitable for Marton long-term.
• Understanding treatment requirements for bore water.
• Planning how the new system could be delivered.

By the end of 2021, a preferred bore site had been identified at Tūtaenui Reservoir.

Council began detailed investigations into groundwater (bores) as a possible replacement for the dam supply. This work found:

• Groundwater may provide a more reliable long-term source. However, it would require treatment to remove minerals like iron, manganese, and hardness.
• Council already had access to two bores; one on Calico Line and one on Tūtaenui Road. However, more work was needed to identify whether these bores could meet the town’s demand.

By the end of 2020, there was a clear case to move away from the dam - but more work was needed to understand how groundwater could be treated effectively. The impacts of Covid-19 were also felt strongly by Council in 2020 and lockdowns and restrictions on travel significantly impacted fieldwork progress especially.

In 2019, Council endorsed the Marton Water Supply Strategy as a key infrastructure project.

Early work identified that:

• The existing dam-based supply would not meet future demand
• The system would require significant investment to remain compliant
• A more reliable, long-term solution was needed

Council agreed to investigate four key areas:

1. Water source – a reliable long-term supply
2. Water quality and treatment – meeting current and future standards
3. Storage and resilience – managing demand and disruptions
4. Network and infrastructure – required upgrades across the system

As investigations began, issues with the existing dams were identified:

• Damage to the spillway was identified in April 2019 and subsequently repaired.
• The condition of the dam reinforced the need to look seriously at alternative water sources.