The water may look inviting, but how safe is it to swim in?
Results from the Taranaki Regional Council’s “Can I Swim Here?” annual survey from the 2023/24 season reveal the best places to get wet this summer.
WORDS Irena Brooks. PHOTO: Fitzroy Beach by Roger Richardson
If you’re looking for a clean, clear, unpolluted place to cool off this summer, head to Lake e Rotorangi (at Patea Dam). It is the only site of the 41 beaches, rivers and lakes monitored last summer that achieved a 100% ‘safe to swim’ status.
Of the 18 Taranaki beaches monitored, Fitzroy Beach rated the best — ‘safe’ to swim at 94% of the time. It, and neighbouring East End, were the only two beaches which never logged a ‘not suitable for swimming’ ranking for the entire 2023/24 summer.
For our rivers though, conditions varied widely. The best results were consistently found at the Waiwhakaiho River at Merrilands Domain, getting a green light for swimming 56% of the time. It was the only Taranaki river with a better than even chance of not exposing swimmers to health risks.
However, a few kilometres further downstream adjacent to Lake Rotomanu, the Waiwhakaiho River’s ‘safe to swim’ rating dropped to just 9 percent.
“There are numerous factors that affect water quality,” says Angela Collins, Water Quality Scientist at the Taranaki Regional Council (TRC). “As the river moves through the catchment, it picks up contaminants from both urban areas and natural sources, including the flocks of seagulls and ducks that are present in the lower reaches. This accumulation of pollutants generally results in a decrease in water quality downstream, and is fairly typical for rivers.”
Bathing water quality results depend on several things, like where the readings are taken from and what the weather was like on the day.
There are two gradings used for each of the 41 monitored sites — the weekly readings (which give the current water quality), and Long Term Grades accrued over up to three years’ of weekly samples.
From November to March keep an eye on the LAWA website (lawa.org.nz) for the most up-to-date water quality information for popular swimming spots at lakes, rivers and beaches across the region. Water sampling takes place on a Tuesday and results take 3 days from the time of testing to being published on the website. A traffic light system of green, orange and red is used to indicate whether a site is ‘safe to swim’, caution is advised, or is ‘unsuitable for swimming’.
Because of this lag in up-to-date information, the Council has developed a checklist to use before entering the water (see sidebar).
“The main sources of contamination in rivers come from animals, leaky septic tanks, urban stormwater and at some sites birds are also a contributing factor. Basically, when it rains, faecal matter washes into rivers increasing the health risk for anyone coming into contact with that water,” explains Angela Collins.
Stormwater can contain human and animal waste, toxic materials, debris, agriculture and urban runoff. In town centres, rain is also the leading cause of sewage overflows, and when that happens there should be no shellfish gathering for at least 28 days. When river contamination levels rise, so too do the lakes and beaches they feed into.
“Our main message to swimmers and recreational water users is to stay out of the water for three days after heavy or prolonged rain.”
If you wade into waist deep water and can see your feet, that’s a good sign and the water is probably fine to get into.
Some freshwater sites are also tested for two types of cyanobacteria every two weeks, so while some may rank well in terms of weekly E.coli samples, they may rank badly for cyanobacteria.
Cyanobacteria exists naturally in freshwater, growing as mats on the rocks of a river bed (benthic) or floating and drifting in lakes (planktonic). During the summer months, increased water temperature, reduced rainfall and increased daylight hours provide ideal conditions for cyanobacteria to grow, sometimes resulting in algal blooms. When in bloom, cyanobacteria can produce toxins that can pose a risk to the health of people and animals entering the water.
Sites monitored for benthic cyanobacteria were suitable for recreational use just 26% of the time.
Lake Herengawe may have had the lowest E.coli results of all the monitored sites, but it scored badly in the cyanobacteria results the Council also tests for.
Waiwhakaiho River at Merrilands Domain, Waiwhakaiho River at Meeting of the Waters and Waingongoro River at Ohawe Beach were all unsuitable for recreational use due to exposed mats on the edges of these rivers.
Lakes monitored for planktonic cyanobacteria were suitable for recreational use 80% of the time. Lakes Rātāpiko, Ngangana, Rotomanu and Rotorangi were all safe for recreational use throughout the sampling period
If you spot cyanobacteria, commonly known as blue-green algae, growing in rivers or lakes it is best to avoid all contact with the water. In rivers, cyanobacteria grows as thick black/brown mats on the rocks and can have a distinctive, unpleasant smell, often described as musty, earthy, or swampy. In lakes, cyanobacteria may form algal blooms that are generally green in colour, often turn the water murky, and can produce foam or scum on the water’s surface. Cyanobacteria can be toxic and pose health risks to both people and pets, so it is best to stay out of the water if you see it.
WHAT TO DO IF YOU SEE POLLUTION
If people notice signs of contamination, such as a sediment plume when it hasn’t been raining or unusual changes in the water’s appearance, they can report this to the Taranaki Regional Council pollution hotline 0800 736 222.
If you are concerned about the quality of the bathing water in Taranaki, overall beaches are your best bet. For the vast majority of the time the sea is clear and the water quality is safe to swim in. Stay out of the water for up to three days after heavy rainfall, the TRC advises. If you can’t see your feet knee-deep water, stay out until it clears.