At the time of sampling, 53 percent of tests (266 of 504) at lakes and rivers in Taranaki revealed water quality issues (file image). Photo: RNZ / Robin Martin
More than half of Taranaki freshwater swimming spots have flunked their latest Can I Swim Here? report card.
The Taranaki Regional Council undertook weekly water quality monitoring at 41 recreational sites across the region, including 23 rivers and lakes, and 18 beaches during the between November 2023 and March this year.
At the time of sampling, 53 percent of tests (266 of 504) at lakes and rivers revealed water quality issues.
Conditions were found to be "unsuitable for swimming" in 32 percent of tests (159) while a further 21 percent of test results (107) were elevated to a "cautionary level" where water quality was generally deemed okay, but "young children, the elderly or those with compromised health may be at increased risk".
Routine testing found lakes and river sites were "suitable for swimming" at the time of sampling 47 percent of the time (238).
Isolating for rivers only, the results were worse still with 42 percent of tests finding waterways "unsuitable for swimming", 27 percent having elevated levels of E. coli where "caution was advised" and only 31 percent of samples returning a deemed "suitable for swimming" score.
By comparison, 83 percent of routine tests (315 of 377) at popular beach sites were found to be "suitable for swimming" at the time of sampling.
The council moved to routine testing in 2021. Prior to this it did not test for three days following a rain event. It will consider the latest testing at its Policy and Planning Committee meeting this week.
Freshwater sites were tested the presence of Escherichia coli (E. coli) and marine sites tested for enterococci. These bacteria were indicators of the presence of faecal contamination in the water and associated pathogens which could make people sick.
Cyanobacteria (potentially toxic algae) were also monitored every two weeks at selected river and lake sites.
Of the monitored freshwater sites, Lake Herengawe and Lake Rotorangi at the Pātea dam had low levels of E. coli on the most occasions, although Lake Herengawe was still deemed unsuitable for swimming due to elevated levels of cyanobacteria.
Te Hēnui Stream mouth in New Plymouth had the poorest water quality with permanent health warnings in place.
At popular beach sites, enterococci numbers exceeded the cautionary guideline in 25 samples (7 percent). In 37 samples (10 percent), water quality was deemed unsuitable for swimming.
Fitzroy Beach, in New Plymouth, had the best water quality of the monitored beaches, followed closely by Ōākura Beach opposite the campground and Middleton Bay.
Waitara East and Waitara West beaches were unsuitable for swimming most often. Urenui Beach was also unsuitable (or caution advised) on several occasions.
For benthic cyanobacteria, 56 out 77 routine surveys (73 percent) found conditions were unsuitable for recreation, while in one survey cyanobacteria reached cautionary levels. In 20 routine surveys (26 percent) monitored rivers were suitable for recreational use.
Exposed mats of benthic cyanobacteria caused the Waiwhakaiho River at Merrilands Domain, Waiwhakaiho River at Meeting of the Waters, and Waingongoro River at Ōhawe Beach to be marked as unsuitable for recreational use throughout the entire monitoring season.
Whereas, benthic cyanobacteria levels remained low at the Te Hēnui Stream site through the summer period.
Long-term grades for freshwater (E. coli and planktonic cyanobacteria) and marine (enterococci) monitoring data were assessed against the National Policy Statement for Freshwater Management 2020 (NPS-FM) and the Microbiological Water Quality Guidelines for Marine and Freshwater Recreational Areas (MfE, 2003).
This assessment found 21 out of 23 (91 percent) of monitored freshwater swimming sites were graded poor with respect to E. Coli and only two (9 percent) were graded excellent, Lake Rotorangi and Lake Herengawe.
With regards to planktonic cyanobacteria in lakes, four out of seven lakes (57 percent) were graded excellent, while three lakes (43 percent) were graded.
poor.
In terms of enterococci long-term grades, 12 marine sites (67 percent) were graded poor, while the remaining six (33 percent) were graded fair.
Under the NPS-FM, sites that had been graded poor were considered to be below the national bottom line; a minimum standard below which action was required to deliver water quality improvements.