A grassroots environment group is ramping up a lobbying campaign for more stringent "bottom line" rules around freshwater quality.

It comes as Kiwis head for their favourite swimming holes this summer and recently-issued report cards show the water quality in many of the Auckland region's rivers and streams are poor.

The student-led Choose Clean Water group, which this year presented a 12,000-signature petition to Parliament, last week appeared before a parliamentary select committee to discuss its call for freshwater quality bottom lines to be "swimmable" rather than "wadeable".

Spokesperson Marnie Prickett remained hopeful the Government would take its message on board when it consulted further on freshwater reforms.

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"The public has really made it clear that a wadeable bottom line is not good enough," she said.

"There has been a lot of pressure around that and I think the Government is really feeling it."

Prickett said her group would continue its campaigning through summer and would step up lobbying efforts in the coming election year.

"It seems that we had to do this over and over, but we're going say again that we're absolutely not interested in a wadeable bottom line and legislation is a really powerful part of making our values clear and actionable."

Environment Minister Nick Smith wasn't available for comment today but said in a recent lecture the Government was committed to improving the quality and swimmability of New Zealand's lakes and rivers, although it was "cautious of regulatory requirements that are unworkable".

Standards under the Government's National Policy Statement on Freshwater Management, set in 2014, included a requirement for regional councils to manage freshwater bodies so people's health is safeguarded, and carries a bottom line that applies to "wading" and boating.

Smith told the lecture audience the Government was open to strengthening the national requirements on swimmability and had the Land and Water Forum working on options.

But he noted that most of the country's rivers breached the 540 E. coli count required for swimming during heavy rainfall and there were factors, including bird droppings and geothermal activity, that made quality unsuitable.

"We also need to be open about the cost of our regulatory requirements on communities and the fact that many water bodies have long hydrological cycles that mean it is a long time before we see improvement."

The most recent major stocktake of New Zealand's environment - the Government-produced Environment Aotearoa 2015 report - found water quality in rivers that run through intensively-used land has worsened.

While water quality was very good in areas with indigenous vegetation and less intensive use of land, it was a different story in agricultural and urban areas where there was reduced water clarity and aquatic insect life, and higher levels of nutrients and harmful E.coli bacteria.

In the Auckland region, a recent stocktake of freshwater quality in 22 reporting areas showed a mixed bag of results, but in most cases water quality was poor.

The Maungakiekie-Tamaki and Howick areas were given an "F" rating for water quality, the very worst, while Dairy Flat, Henderson-Massey, Manukau, North Shore, Whau, Waitemata, Pukekohe and Orakei had "D" marks.

The best spots were Great Barrier Island, Hibiscus Coast, Waiheke, Wairoa and Waitakere, which received "A" grades for water quality.

Results reported by Government-run website Land, Air, Water and Atmosphere (LAWA) also showed varying results in the 50 monitoring sites, although recreational water quality results for many spots were not available due to lack of data.

The bulk of beach spots in the region were however safe for swimming, except for places with long-term health warnings such as Cox's Bay, Wood Bay, Piha Lagoon, Laingholm Beach, Weymouth Beach, Meola Reef and Te Henga (Bethells) Lagoon.