When swimming in New Zealand oceans, rivers or lakes, water quality standards indicate the safety of doing so.
Such standards are limits set by official agencies, essentially like governments, based on scientists’ advice. Recreational water quality standards define the maximum concentration of a contaminant in water before there is a risk to people or the environment.
While the presence of a small number of bacteria (typically measured in terms of the number of bacteria per 100ml of water) may pose little to no danger to swimmers, higher concentrations may pose a risk to children, the elderly or people with compromised immune systems. Concentrations of bacteria may, and often do, rise to levels where swimming is not recommended for anybody.
Recreational standards focus on water quality in places people are most likely to be in or around the water and its associated risks.
Primary Contact means putting your whole head under the water, like when you swim, surf or dive, and are more strict due to the higher chance of swallowing some of the water. In poor water quality, primary contact can lead to significant negative impacts.
Secondary Contact means you are near the water, like when you paddle, sail or fish. Secondary contact indicates you’re less likely to swallow the water. However, poor water quality can still put you at risk.
Before going swimming, checking for up-to-date information can be crucial, especially in the warmer months. At the monitoring site level, there can be statistical uncertainty associated with each swimming category.
Other factors can have an affect how suitable a waterway is for swimming, including water flor and access, and heavy rain events and weather conditions.
NIWA runs recreational water quality monitoring from November/December to March in most regions throughout New Zealand. Predicated water quality results for Auckland and Wellington regions are available year-round.
Head over to NIWA to find the best places to swim in summer from over 750 beaches, rivers and lake sites monitoring.
Following NIWA’s advice, use the simple swim smart checklist before swimming, including looking for water quality, clarity and hazards.
Check the water quality information for the swim site. Know how to spot potentially toxic algae so you can avoid it. Also, avoid swimming near potential sources of contamination like flocks of birds or near stormwater or wastewater outlets.
Avoid swimming for a minimum of two to three days after heavy or long rainfall, even if sites indicate good water quality. You can check if the water is clean and clear if you can see your toes in calf-deep water, but if not, wait until the water is clear before dipping in.
Look for potential hazards, like strong currents and tidal rips, underwater objects, or even stinging jellyfish near the ocean. Be aware of any warnings and alerts and follow safety advice.
Stay up to date with New Zealand swimming water-related news. As water standards change, we’re committed to ever-developing new, innovative technology to help monitor water quality, which abides by government swimming water regulations.