Last updated October 2026
The Ruamāhanga River at Double Bridges is a river swimming spot in Mel Parkinson Reserve, north of Masterton, about 58 kilometres from Palmerston North in a straight line across the Tararua Range. The swimming area sits just downstream of the road and rail bridges on Opaki Kaiparoro Road, and LAWA describes it as popular for swimming and picnicking.
Greater Wellington Regional Council tests the water every week from November to March, and the site has a Fair long-term grade on LAWA.
A Fair grade means the water is usually suitable, but it is best avoided after rain. Toxic algae also turns up here in some summers, so check LAWA for alerts before you swim, especially if you have a dog.
Swimming Facts
Before you swim: Tested weekly Nov–Mar by Greater Wellington. Stay out for 48 hours after heavy rain. Latest result on LAWA
Today at Ruamāhanga River at Double Bridges
Sunday 25 OctoberWater quality track record
What the grades mean
Excellent and Good: rarely unsafe for swimming. Fair: usually fine, but avoid swimming after rain. Poor: often unsuitable, especially after rain, so check the latest result first.
Grades use LAWA’s method: the 95th percentile of routine E. coli results over the five summers from 2020/21 to 2024/25, with at least 50 tests (440 per 100 mL from 62 tests).
Practical Information
- Location
- Mel Parkinson Reserve, off Stuart Road, north of Masterton, just downstream of the Opaki Kaiparoro Road bridges
- Distance from Palmerston North
- About 58 km in a straight line, on the Wairarapa side of the Tararua Range
- Water
- Freshwater river, no tides; flows change quickly after rain
- Water quality
- Fair (LAWA long-term grade, summers 2020/21 to 2024/25)
- Testing
- Weekly from November to March by Greater Wellington Regional Council, with toxic algae checks over summer
- Facilities nearby
- None mapped close to the swimming spot; Masterton is the nearest town
About the Ruamāhanga River at Double Bridges
The Ruamāhanga is the main river of the Wairarapa. It rises in the Tararua Range north-west of Masterton and runs first south, then south-west, for about 130 kilometres before reaching the sea at Palliser Bay.
On the way it passes close to Masterton and Martinborough and picks up many tributaries, including the Tauweru River near Gladstone. In its lower reaches it winds across a wide floodplain to the wetlands around Lake Wairarapa; the river once flowed into the lake but has since been diverted.
Double Bridges is near the upper end of that journey. The swimming spot is just downstream of the road and rail bridges on Opaki Kaiparoro Road, inside Mel Parkinson Reserve, which is reached from Stuart Road. LAWA describes the reserve as popular for swimming and picnicking.
Here the river has not yet passed through Masterton. Greater Wellington notes that in rural areas the most common source of pollution is farm runoff in wet weather and stock getting into streams in dry weather.
Swimming and Water Quality at Double Bridges
Greater Wellington Regional Council samples the river at Double Bridges every week from November to March as part of its recreational water quality programme, and the results go up on LAWA. The site has a Fair LAWA long-term grade, based on 62 routine tests over the summers of 2020/21 to 2024/25.
Across 74 tests between November 2019 and March 2025, 92% were suitable for swimming. A Fair grade means the water is usually fine for swimming, but the chance of getting sick is higher than at a better-graded site, especially after rain.
Greater Wellington uses a risk model that updates the LAWA swimming rating every hour, combining the site’s test history with recent and forecast rain, so check LAWA right before you swim.
The council’s rule of thumb is to wait 48 hours after heavy rain before getting in the water, and to check that the water is clean and clear. If you notice a water quality problem, you can report it to Greater Wellington’s 24-hour environment hotline on 0800 496 734.
Rivers have their own hazards. Before getting in, check for fast or unpredictable currents, unstable banks and submerged logs, which regional councils list as common river hazards. Check the depth before jumping or diving, and keep children within reach.
Toxic Algae and Dogs
Toxic algae (cyanobacteria) is the main thing to watch for at Double Bridges. Greater Wellington checked the site for it 113 times between the 2019/20 and 2024/25 summers: 12 of those checks reached alert level, and 9 reached action level, when people and animals should stay out of the water. Blooms build up in warm, dry weather and usually last until heavy rain flushes the river.
In rivers, look for black, green or brown slime on the rocks, or brown or black mats at the water’s edge with a leathery texture and an earthy, musty smell.
Greater Wellington warns that dogs are most at risk, because they like the smell and taste of the mats, and that a piece the size of a 50c coin can be enough to kill a dog.
If there is an alert, or you think you can see toxic algae, keep your dog on a lead, keep it out of the water and stop it eating any mats. If you are worried, take your dog to a vet straight away.
Toxic algae can make people sick too, with nausea, vomiting and diarrhoea, and contact can irritate skin and eyes. Keep an eye on children, who may touch algae and then put their fingers in their mouths.
Where to Learn More
LAWA and Greater Wellington Regional Council: the latest “Can I Swim Here?” rating, toxic algae alerts and the long-term grade for the Ruamāhanga River at Double Bridges.
Greater Wellington Regional Council: how to check whether the water is suitable for swimming, with advice on rain and toxic algae.
Greater Wellington Regional Council: toxic algae: how to spot toxic algae in rivers and what to do to protect dogs and children.
Frequently Asked Questions
Can you swim in the Ruamāhanga River at Double Bridges?
Yes. LAWA describes the site in Mel Parkinson Reserve as popular for swimming and picnicking, and Greater Wellington tests it weekly from November to March. Check LAWA for the latest rating and any toxic algae alert, and stay out for 48 hours after heavy rain.
What is the water quality like at Double Bridges?
The site has a Fair LAWA long-term grade, based on 62 routine tests over the summers of 2020/21 to 2024/25. Of 74 tests between November 2019 and March 2025, 92% were suitable for swimming. The risk is higher after rain.
Is there toxic algae in the Ruamāhanga River?
Sometimes. Of 113 toxic algae checks at Double Bridges between 2019/20 and 2024/25, 12 reached alert level and 9 reached action level. Check LAWA for alerts and look for dark mats on the rocks before you swim.
What should dog owners know at Double Bridges?
Watch for toxic algae. Greater Wellington warns that a piece of algal mat the size of a 50c coin can kill a dog. Keep dogs on a lead and out of the water if there is an alert or you see dark mats.
Where exactly is the swimming spot?
It is in Mel Parkinson Reserve off Stuart Road, north of Masterton, just downstream of the road and rail bridges on Opaki Kaiparoro Road.
How far is Double Bridges from Palmerston North?
Double Bridges is about 58 kilometres from Palmerston North in a straight line, on the Wairarapa side of the Tararua Range north of Masterton.
When is the water tested?
Greater Wellington Regional Council samples the site weekly from November to March and checks for toxic algae over summer. Its risk model updates the LAWA rating every hour.
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