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Some water under par

Fourteen of 81 sites tested by Gisborne District Council staff have poor water quality that falls below the national bottom line for ecosystem health, the environmental planning and regulations committee was told yesterday.

The committee was given details of environmental monitoring by water quality science officer Harriet Roil.

The council’s aquatic ecosystem programme collected macroinvertebrae (water insect) samples from 81 sites through the region to assess the ecological health of streams.

Key findings were that 12 percent of the 81 sites had excellent water quality, 37 percent had good water quality, 34 percent had fair quality and 17 percent had poor quality, falling below the national bottom line for ecosystem health, she said.

These poor quality sites were all in the lowland areas.

They included eight sites on the Poverty Bay Flats, Wainui Stream at Heath Johnstone Park, the Waimata River at Goodwins Bridge, two sites on the Pakarae River at Whangara and two at Tolaga Bay.

This was the first assessment from the monitoring programme started by the council in 2015.

The council was required to take action to improve water quality for those streams found to be below the national bottom line for ecosystem health.

The issues on the Poverty Bay Flats were known and the Waipaoa Catchment Plan had mechanisms aimed to address them, she said.

Identification of sites at Whangara and Tolaga Bay below the national bottom line would have implications for future resource consents and freshwater planning in those locations.

Macroinveretbrates, including the larval stages of insects, molluscs, crustaceans and worms, were used nationally and internationally to measure water quality and the ecological condition of streams, she said.

Invertebrates were a vital component to food webs in waterways and provided functions including consuming plant and woody material in-stream. They were predated on to provide food for fish, birds and other insects. They were sensitive to pollution and showed a range of responses to chemical, physical and hydrological conditions over long periods of time.

This was the first analysis of ecological data collected in the aquatic ecosystem state of the environment monitoring programme in Gisborne.

Site tests should reflect what is upstreamThe results highlighted that land use and geology both had a significant effect on the macroinvertebrates present in a stream, water quality science officer Harriet Roil said.

Three years was too short an interval to test for changes but the ecological state across the region was assessed.

Andy Cranston said if a site was shown to have poor quality, it might not mean the whole of a waterway was poor.

Ms Roil said the sites were representative of that place and were also representative of the land use and the geology.

So that site should be representative of what was upstream.

Environmental services and regulations director Nicholas Zaman said staff would come back to the committee with a report providing a more comprehensive picture of what was actually going on.

It was very much related to land use. That would be provided at the next committee meeting.

The Waipaoa River. File picture