Sunday, August 14, 2022

Northland water quality under microscope

Legacy issues to blame for water quality, Northland Regional Council land management officer tells workshop.
Landowner Tim Rose in his eucalypt plantation in the Wekaweka valley, with native undergrowth under mature stringybark eucalypts. Photo: Supplied

E.coli contamination and low levels of macroinvertebrates are two of the most pressing issues in Northland water quality, says Northland Regional Council (NRC) land management officer John Ballinger.

He told a workshop for rural professionals on rural sustainability that the key environmental issues for Northland do not include nitrogen for most rivers and soils but do include E.coli, sediment, phosphorus and the invertebrates.

The National Policy Statement for Freshwater Management has five attribute bands, ranging from A as good to D and E as poor.

In Northland, 94% of waterways are in the D and E bands for E.coli, 22% are D for phosphorus, 50% to 70% are D for macroinvertebrates, 16% are D for sediment and 5% D for periphyton, commonly algae.

Northland also faces loss of its wetlands through drainage and weed infestation and some degradation of its dune lakes.

“We have lots of work to do to turn these environmental indicators around,” Ballinger said.

“What is a problem today may not have been caused today, but is a legacy issue, particularly with sediment.”

He is project manager for the NRC hill country erosion programme and the council-owned and -run poplar and willow nursery.

NRC can help with funding to improve water quality through riparian fencing and planting, supporting catchment groups and retirement of eroding hill country.

“We supply poplar and willow poles at subsidised prices and our land management officers provide free advice,” he said.

Livestock exclusion is a primary tool for protection of waterways and stopping bank erosion and faecal contamination.

NRC will reallocate its funding from the higher slopes to lower slopes as national requirements for freshwater take effect.

Within the Kaipara Harbour catchment in Northland’s region, 23% of land area has been mapped as high erosion risk hill country, modelled to account for approximately 70% of annual sediment loads entering the harbour.

Grants for retirement of eroding hills are available up to $1500/ha for 2ha or greater, capped at $30,000 and planting species other than radiata pine at 2m by 3m spacings.

“We need to diversify our tree species to adapt to climate change, to avoid radiata pests, diseases, storms and drought – we need both exotic and native,” he said.

Northland has a wide choice of species and continuous cover is the ideal regime, where trees are not clear-felled but taken out singly or in small coupes.

Clear-felling every 25 years leads to large sedimentary losses, notwithstanding the improvements in ground disturbance made by the forestry industry.

NRC has three pilots underway – eucalypts in a mānuka nurse crop at Paparoa; totara at Waipapa; and mānuka, tallow wood and redwood at Waitangi.

“We have the opportunity to grow 100% sustainable, NZ-grown hardwoods instead of importing our needs,” he said.

Space planting of poplars and willows on pastures can also be registered in the Emissions Trading Scheme, with new varieties like kawa, for which timber application has been made for building code compliance.

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