Two out of three rivers monitored in New Zealand contain enough fecal bacteria to make people sick – and the situation is not improving, new data shows.
Crown research agency Land Air and Water Aotearoa (LAWA) this week released its latest national summary of river water quality, along with updated results for more than 1,500 testing sites. rivers across the country.
The data showed that rivers in urban and grazing-dominated areas generally had poorer water quality, while pristine rivers were generally surrounded by native bush.
LAWA measured five indicators: the health of the invertebrate community, the amount of E coli bacteria present to give an idea of fecal contamination, the levels of nutrients toxic to the life of the streams such as nitrates and ammonia, dissolved phosphorus levels (which can lead to algae growth problems) and how much sediment clouded the water.
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E coli levels were so high at two-thirds of the sites monitored that there was a moderate to high risk of disease for swimmers and boaters.
High concentrations of E coli indicated that there were significant upstream sources of faecal matter, such as stock inputs, runoff, birds, or untreated sewage discharge. It also meant that other harmful pathogens could be in the water, according to the report.
They were at a level where local councils were required to put policies in place to try to improve them.
ROSS GIBLIN / STUFF
The Hutt River gets a daily health check, monitoring E. coli, toxic algae and nutrients (first published April 2021)
Almost two-thirds of the river sites tested nationwide had altered ecological health, based on the health of invertebrate communities, according to the report.
Two in five had sediment levels high enough to have an impact, while about half had enough dissolved phosphorus to potentially cause overgrowth of plants in streams.
The toxic effects of nitrates and ammonia on aquatic ecosystems were only a problem at a few sites.
Information on changes in the quality of rivers over the past decade was also available.
For sites with more than 10 years of data available, the number of healthy bedbug communities had slightly decreased.
There was no decline in the number of sites with high levels of fecal bacteria, while nitrate and ammonia levels remained stable.
On a positive note, the water clarity had improved somewhat at some of the darker sites – important as too much sediment in the water could make it harder for river animals to see their food and could clog. the gills of fish.
LAWA Rivers Quality Manager Coral Grant said that overall, the poorest results were found in the most altered environments – like cities.
STACY SQUIRES / STUFF
University of Canterbury biology professor Jack Heinemann and his team have discovered antibiotic-resistant E coli in the River Avon. (Video first published in June 2018)
“While urban rivers and streams make up only 1% of the total river length in New Zealand, they pass through areas of significant land cover transformation, and four of the five urban waterway sites monitored are showing signs. serious pollution or nutrient enrichment. “
She said it was positive to see that the toxic effects of nitrates and ammonia were not a widespread problem.
“However, nitrogen can also stimulate problematic growth of plants and algae at concentrations lower than those causing direct toxicity.”
What does this mean for your region?
Auckland and Waikato
The quality of the river was monitored at 35 sites in the Auckland region.
The Tāmaki River, which flows into the Hauraki Gulf at Otaki Stream, was in the worst 25 percent of sites nationwide by all measures. Lucas Creek on the north coast, which flows into Upper Waitemata Harbor, was one of the worst nationally in terms of E coli levels.
He was doing well in terms of nitrates and phosphates, but nitrogen levels were seen to be on the rise.
Water quality was monitored in 29 watersheds in Waikato District. In the Waikato River watershed alone, scientists have kept track of 114.
Where he entered Lake Taupō, he was doing well in every measure. However, the levels of E. coli were considered to be increasing and trends for nitrates were not assessed.
In the more agricultural parts of the region, such as Mangapiko Creek near Te Awamutu, E coli levels were in the worst 25 percent of riverine sites nationwide. It was also ranked in the worst quarter for total nitrogen levels, clarity, and phosphorus.
In the Wellington area, 51 stream and river sites were monitored in 16 watersheds.
The Hutt River has been monitored at 16 sites. In Boulcott, E coli levels were above national standards and considered to be worsening.
Nitrate levels and clarity were also at good levels for wildlife. While phosphorus levels placed it in the top 50 percent of the country’s rivers, it was seen as on the rise.
Wellington city streams were in trouble. Kaiwharawhara Creek at Ngaio Gorge was also in the worst percentile nationwide for fecal bacteria, as well as nitrates. However, nitrogen levels appear to be improving.
On Canterbury’s vast river system, which included many vulnerable braided rivers, 69 different watersheds were regularly tested for water quality.
The Avon / Ōtākaro River, which runs through Christchurch, has been tested at 18 locations. Of these, several did not meet national safety standards for E coli, including at Mona Vale. It was also in the top 25 percent of the nation’s poorest rivers for nitrates, but most likely improving in both categories.
Christchurch’s other major river, the Heathcote / Ōpāwaho, has been tested at 16 sites. At Clarendon Tce, E coli levels were very high, in the worst 25 percent of sites nationwide, as were nitrates and phosphorus. It was believed that nitrate levels were getting worse.
The important watershed of the Waimakariri River has been tested at 35 sites. At the old road bridge, E coli was at a safe level, but it was probably getting worse. It was in the top 25 percent of the country’s rivers in terms of nitrogen and phosphorus, but in the worst in terms of cloudy sediment.
Further south, the Ashburton / Hakatere River watershed has been tested at 12 locations. On State Highway 1, it had dangerous levels of E coli and was in the worst 25 percent of nitrate sites nationwide. It was also unclear whether these levels were improving or worsening.
Canterbury Environment President Jenny Hughey said data from 2011 to 2021 showed Canterbury was facing challenges similar to those in the rest of the country.
“It’s a mixed picture at a high level showing little change over the past few years. It is clear, however, that the more intensive the land use – the urban being the more intensive – the poorer the water quality.
It was a challenge they had strived to meet for many years, “but there is more to do”.
Hughey said the government’s new Essential Freshwater package included the concept of Te Mana o te Wai (the health of the waterway comes first), which gave a national boost to much of what was already being done in Canterbury. .
Much work was already underway to improve the health of rivers in the region, she said.
“In rural areas we have verifiable agricultural environment plans, nutrient limits and stock exclusion rules. Many rules have been further enforced by local communities focusing on outcomes for their own watersheds, and a new integrated plan for Canterbury will be needed by 2024. “
In both urban and rural areas, restoration work was carried out by the communities.
This work needed to continue, and ECan had the means to support these activities, Hughey said.
“Every step we take will improve our rivers and streams, which we all want.”