Luke Tipoki, with his son Grayson, 2, at the Turanganui river is south Wairarapa. He used to swim in the river but says it is now too polluted for his own son.

Pollution and irrigation have ruined swimming holes treasured by communities for generations, says a young father frustrated he can't share them with his son.

Swimming holes in Wairarapa's many rivers have long been a favourite part of summer holidays in the region, but pollution and reduced flows now confine most swimmers to the rivers' upper reaches.

supplied Old photographs of how the Turanganui river in South Wairarapa, where Luke Tipoki's family used to swim.

"Especially at this time of year, it's so sad...what breaks my heart is that my son can't enjoy our river the way I did," Lake Ferry Hotel publican Luke Tipoki said.

Tipoki lives on the Turanganui River south of Martinborough and a tributary of Wairarapa's main river, the Ruamahanga, joining it just before it drains into Cook Strait after passing hundreds of farms.

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WAIRARAPA ARCHIVE A 1950s photo shows a family frolicking in Wairarapa's Ruamahanga River, much of which is now too polluted to swim in.

Living at the bottom of the main Wairarapa catchment has convinced Tipoki that recent, drastic intensification of farming is what has changed rivers since his boyhood.

Rocks in rivers below dairy farms were brown and the water smelled bad, but above the farms the water was fresh and the rocks were clean, he said.

"It used to be pristine, you could drink straight out of it, it was full of life. Now it's dead, it stinks... I wouldn't let my boy near it.

Loren Dougan/Fairfax NZ. The Turanganui river in south Wairarapa is now choked with dark brown slime and deemed unsafe for swimming by locals.

"Just watching the rivers being degraded for over 30 years... it bugs the hell out of me."

He used to walk across a paddock and into the river, but now has to drive up a road beside it for 15 minutes into the bush, before it hits farmland, to find a stretch of it clean enough to swim in.

"A lot of farmers are trying to blame the pollution on towns, but here [the Turanganui] there's nothing but farms."

The Ruamahanga is now so contaminated by farming runoff and sewerage discharge from towns it has been dubbed the "Sewer-mahanga". The Waipoua River in Masterton was declared toxic to dogs and people last month, because of an algae bloom.

Other popular swimming holes around Martinborough were also no longer used because of the poor water quality, Tipoki said.

His sister Vanessa Tipoki farms on the nearby Tauanui River, also a tributary of the Ruamahanga, and for years a popular community swimming spot.

Unlike her brother's former swimming hole, it's the water quantity, rather than the quality, that's the problem.

Last summer it simply dried up, and the Tipokis spent hours with friends and family frantically rescuing hundreds of fish, including some rare native species, stranded in shrinking pools.

Vanessa Tipoki's father-in-law had never seen that in 70 years living in the area, she said.

While she let her son Vincent Edge, 3, swim in the Tauanui when it had water, she would not let him near the Ruamahanga.

But as a member of the Greater Wellington Regional Council's Ruamahanga "Whaitua" or catchment management committee, she felt hopeful changes would be made.

"Regional councils are obligated to improve waterways... the good thing about the Whaitua process is that it's decision-making from the ground up, so hopefully the decisions will be something the whole community's bought into."

The regional council could not be reached for comment.