People are advised not to swim at Picton's foreshore, Momorangi, the Wairau Diversion, Ngakuta Bay or in the Taylor and Rai Rivers, the worst sites in Marlborough for water quality after it rains.

The Marlborough District Council's monitoring results show that coastal water quality was of a higher standard than freshwater quality, the environment committee was told yesterday.

The council monitors 31 sites each week during November to March, and posts results on its website as they come through. Data from last summer showed half the monitored river sites were safe to swim at for more than 95 per cent of the time, while nearly 75 per cent of the coastal sites were safe to swim at for more than 95 per cent of the time.

Council advice was that swimming should be avoided during and after wet weather, particularly in urban and intensively farmed areas.

The best water quality at swimming sites was the Pelorus River at the State Highway 6 bridge, the Wairau sites, and the Waihopai, as well as Bobs Bay, Marfells Beach, Mistletoe Bay, Portage, Waikawa Bay and Whites Bay.

Microbial source tracking would be done at several poorly performing sites this summer, including the Wairau Diversion at Neals Rd, the Taylor River at Riverside, Hakahaka Bay, Tirimoana and Picton foreshore, to assess what was causing the poor quality.

Marlborough was identified this week as one of five regions where swimming water quality needs greatest improvement, but Marlborough Mayor Alistair Sowman said Environment Ministry figures do not provide a true national picture because only some councils provided information.

"We don't know how Marlborough really compares to the rest of the country, but we do know we want to improve our local gradings."

Water quality was an important issue for Marlborough and it was closely monitored and results regularly published on the council's website, Mr Sowman said.

It was "well known" that some of Marlborough's rivers were affected by run-off but a great deal of work has been done to identify sources of contamination, he said.

Improvement was occurring, but there would be greater advances in the next year or two as a great deal of effort and resource was now going into improving water quality.

"Earlier this year, I noted that clean water should be one of our region's priorities and I can assure you the council is working on this issue. We want clean rivers which are free from bacterial contamination."

Council staff believed the source of bacteria in the Taylor River, in Blenheim, was likely to be more complex as the river took a lot of run-off from roads and car parking areas as well as from parkland.

- The Marlborough Express

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