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Four popular swimming spots are not suitable for bathing at any time because of consistently high bacterial levels.
Langs Beach stream (southern end) in Bream Bay, Ocean Beach stream at Whangarei Heads, Otiria stream in Moerewa and Ahipara's Wairoa stream at the southern end of Ninety Mile Beach have all been removed from the Northland Regional Council's annual summer water quality monitoring programme.
Coastal monitoring team leader Bruce Howse says "very poor" water quality at these locations justifies the erection of permanent warning signs and people should avoid contact with water in the four streams.
High levels of bacteria mean an increased risk of people picking up gastrointestinal or respiratory illnesses like colds, as well as possible skin, eye or ear infections.
The council has started its annual summer water monitoring programme and will undertake 12 weeks of sampling at Northland beaches and rivers until mid-February.
Most popular beach and river locations usually get the all-clear for recreational uses including swimming, water skiing, windsurfing and kayaking, but heavy rain can contaminate them with bacteria, Mr Howse warns.
The council intends to further investigate the four high-level bacteria sites through sampling independent of the current programme.
The council warns summer holidaymakers in Northland that coastal and freshwater areas can be contaminated by sources like sewage, septic tank seepage, wastewater discharges from boats, stormwater run-off, run-off from farmland and stock in waterways. People are advised not to gather shellfish from such areas for several days after heavy rain.
Mr Howse says a "useful rule of thumb" is that if the water looks murky and you can't see your feet when it's knee deep, that watermight be contaminated and unsafe for swimming.
Authorities may issue public health warnings if water monitoring shows high bacterial levels anywhere.
