Water quality in Kawhia Harbour is good and some aspects are excellent, a year-long study by Environment Waikato has shown.
The harbour was recently studied under Environment Waikato’s regional estuarine monitoring programme, with the results reported to the council’s environment committee meeting in Hamilton today.
Environment Waikato water scientist Bill Vant said water samples taken between winter 2008 and summer 2009 at four different sites showed the estuary was well flushed by clean seawater and generally in good health.
There had been the odd value that exceeded water quality guidelines, but this had not rung any alarm bells.
A winter water sample taken from the harbour area, for example, had exceeded the shellfish gathering guideline for faecal coliforms – but this was expected because of the enclosed nature of the site.
“The exceedance was right up where the river had entered the estuary, so I’m not surprised some contamination was detected there,” Mr Vant said.
“Waikato District Health Board is well aware that bacterial levels in enclosed water bodies often exceed shellfish gathering guidelines, which is why they advise people to take shellfish from the open coast.”
In addition, the water was generally somewhat murky, but this was to be expected due to sediments from the harbour’s large mudflat areas being stirred up by wind and waves.
Mr Vant said although Kawhia’s rivers and streams – like most others in the region – had generally become more polluted over recent years due to human land-use activities, this had not seriously impacted on the estuary’s overall health, due to a “fortunate combination of physical factors at the site”.
“A range of variables, such as the big tides and strong winds we have in New Zealand, mean our estuaries are well flushed with seawater and remain relatively unpolluted.”
Environment committee chair Jane Hennebry said Environment Waikato was working on a range of projects to improve water quality in rivers and streams and reduce the impacts of human land-use activities on waterways, which would further improve water quality in Waikato estuaries over the long term.
“Meanwhile, it’s great to see Kawhia estuary has been given a clean bill of health,” she said.