The Green Party say more than 12,000 Kiwis have joined their campaign for rivers that are clean enough to swim in.

The party wants to see a mandate that all water bodies are safe for swimming, an upgrade from the current wadeable standard.

But before that can be achieved there needs to be a focus on fixing the broken stormwater and sewerage systems, flawed urban design and address the

problem of too many cows on New Zealand farms, water spokeswoman Catherine Delahunty says.

"We'll fight for our rivers because that's what New Zealanders want and deserve," she said.

Environment Minister Nick Smith is expected to announce a freshwater policy change this week, which Ms Delahunty hopes will address the concerns of

12,000 New Zealanders who have signed up to the party's campaign.

"Our kids and grand-kids are missing out on an essential experience - swimming in clean, healthy rivers," she said.

The party also wants to cut out industrial irrigation subsidies and put a commercial price on water.

- NZN