Improved water quality in Horizons Region shows more rivers more suitable for swimming

An independent report has shown that water quality for sediment and E. coli have improved over the past 7-10 years in the Horizons Region and concluded there are encouraging signs that local scale interventions are collectively contributing to regional scale water quality improvements.

The case study, conducted by LWP Ltd and reviewed by NIWA and StatsNZ, was commissioned jointly by the Ministry for the Environment and Horizons Regional Council as a way to understand improving water quality trends in the Manawatū-Whanganui Region.

Ministry for the Environment Deputy Secretary – Water, Cheryl Barnes, says the study provides useful information for central and regional government.

“It shows that considerable progress can be made in reasonably short timeframes. The key was taking a planned, whole of catchment approach and prioritising effort and investment where it would make the most difference,” says Ms Barnes.

Lead author of the report, Dr Ton Snelder, says the report has shown strong evidence for regional improvement in water quality over the past ten years for sediment (suspended sediment, water clarity, and turbidity), as well as E. coli.

“The reduction in sediment and E. coli has improved water quality for swimming. Overall the modelling concluded there has been a 5 to 8 per cent improvement in ‘swimmability’ in the region in the decade ending in 2016,” says Dr Snelder.

“The study found associations between the proportion of the upstream catchment that was subject to land management interventions and the magnitude of the water quality improvements.”

Horizons Regional Council natural resources and partnership group manager Dr Jon Roygard says the case study demonstrates how regulatory and non-regulatory intervention, including the benefits of supporting farm plans, targeting action on highly erodible land, upgrading point source discharges and undertaking fencing and planting of stream margins, can effectively improve water quality.

Long-term targeted interventions, such as voluntary farm plans to reduce hill country erosion are in place under Horizons’ Sustainable Land Use Initiative (SLUI). SLUI came into effect following a major storm event in 2004. The programme is funded by central government, ratepayers and landowners, with assistance from the Ministry of Primary Industries (MPI). In addition to reducing erosion, SLUI aims to improve water quality and increase the resilience of the regional economy. This initiative includes measures such as tree planting and ‘retiring’ erosion prone land by fencing it off and letting it revert to shrub or native forest.

“To date 683 Whole Farm Plans, covering over 500,000 hectares, has included advising on ‘best’ farm practice and the planting of 14 million trees planted and over 570,000 metres of waterways being fenced,” says Dr Roygard.

“Further fencing and planting has also been completed through Freshwater Grants and a Clean Up Fund project through the Manawatū River Leaders’ Forum.”

The case study highlights strong statistical evidence of association between water quality improvement and point source interventions, this includes significant upgrades to sewage treatment plants under the Clean Up Fund, and point source discharge consents.

Ms Barnes says the study’s results show encouraging signs that local scale interventions, co-funding, and applied science are collectively contributing to regional scale water quality improvement.

“This information will be a useful contribution to national freshwater policy development.”

ENDS

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