Last updated October 2026
Lake Rotorangi is the hydro lake behind the Pātea Dam in South Taranaki, about 59 kilometres north-west of Whanganui in a straight line and reached by back roads from Pātea. At 46 kilometres it is New Zealand’s longest man-made lake, filling the winding Pātea River valley between steep farmland and bush.
Taranaki Regional Council describes it as popular for boating, swimming and waterskiing, particularly in summer. The swimming spot is at the southern end of the lake beside the council’s Pātea Dam Campground. Taranaki Regional Council tests the water here every week over summer, and the site holds an Excellent long-term grade on LAWA.
Swimming Facts
Before you swim: Tested weekly Nov–Mar by Taranaki Regional Council. Stay out for 48 hours after heavy rain. Latest result on LAWA
Today at Lake Rotorangi
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 (63 per 100 mL from 68 tests).
Practical Information
- Location
- Pātea Dam Campground, Maben Road (off Ball Road), north of Pātea, South Taranaki
- Distance from Whanganui
- About 59 km north-west in a straight line; the campground is about 40 km from Pātea township
- Water
- Freshwater hydro lake, no tides
- Water quality
- Excellent (LAWA long-term grade, summers 2020/21 to 2024/25)
- Testing
- Weekly from November to March by Taranaki Regional Council
- Road
- Final section unsealed
- Dogs
- Allowed at the campground on a lead and under control
- Facilities nearby
- Campground toilets, showers, wood-fire barbecues and a boat ramp; tap water is not suitable for drinking
About Lake Rotorangi
Lake Rotorangi was formed in 1984 when an earth dam was built across the Pātea River east of Hāwera to generate electricity.
DOC records that construction of the dam ran from 1979 to 1984, and Venture Taranaki notes the dam is 82 metres high, which made it the fourth highest dam in New Zealand when it was built. The scheme feeds a 30-megawatt power station.
The lake is the largest in the Taranaki region. Because it follows the old river valley for 46 kilometres, it is long and narrow, with many bends, and Taranaki Regional Council notes that conditions near the head of the lake can be quite different from those at the dam end.
The council has monitored the lake since it was formed, mainly as part of the power scheme’s resource consents and more recently for state of the environment and recreational water quality reporting.
In summer the southern end of the lake is a holiday spot. NewZealand.com describes the lake as suited to water skiing, kayaking and fishing for rainbow and brown trout, and South Taranaki District Council runs a campground by the dam with a boat ramp for getting on the water. A custodian looks after the campground over summer.
The Lake Rotorangi Hydro Walkway starts at the dam. It is an easy 1.5-kilometre loop that crosses the dam from the car park and follows a bend above the lake, with seats along the way. DOC suggests allowing about 40 minutes.
Swimming and Water Quality at Lake Rotorangi
Taranaki Regional Council samples Lake Rotorangi at the Pātea Dam campground as part of its Can I Swim Here programme. Staff take samples every Tuesday from November to the end of March, test them for E. coli, and the results usually appear on LAWA by Thursday evening.
The site has an Excellent LAWA long-term grade, based on 68 routine tests over the summers of 2020/21 to 2024/25. All 68 tests taken between January 2022 and March 2025 were suitable for swimming.
In its report on the 2023/24 summer, the council said Lake Rotorangi at Pātea Dam and Lake Herengawe had the best water quality of all its monitored sites. An Excellent grade means the water has rarely been found unsuitable for swimming, but it is a long-term record, not a guarantee for any given day.
Check the latest result on LAWA before you swim, and stay out of the water for at least 48 hours after heavy rain. Taranaki Regional Council goes further and advises avoiding swimming for three days after heavy or prolonged rainfall.
The council also checks the lake for cyanobacteria (toxic algae). Across 30 checks from 2022/23 to 2024/25, none reached alert or action level, and the council graded the lake Excellent for planktonic cyanobacteria.
Conditions can still change in hot, settled weather. Algae can make people sick and can kill dogs, so keep dogs out of water that looks discoloured or scummy and check LAWA for any algae alerts before you go.
This is a working hydro lake shared with boats and water skiers, so swim close to shore near the campground, stay visible and keep a close watch on children. The council also notes that the invasive water weed hornwort, first recorded in 2012, has been spreading through the lake.
Getting There and Facilities
From Whanganui, follow State Highway 3 to Pātea. The campground road starts at Ball Road, just north of Pātea, and South Taranaki District Council puts the campground about 40 kilometres from Pātea township.
The road is unsealed in places, and the council describes it as not for the faint hearted. Once you reach the dam, continue to the end of the road and the campground is on the right. Leave any farm gates as you find them.
The campground has toilets, showers and wood-fire barbecues, with unpowered sites only, and the boat ramp is close by. Bookings are not needed and the maximum stay is four weeks; fees can be paid online, in cash to the custodian or into the honesty box.
The tap water is not suitable for drinking or cooking, so bring your own, and take your rubbish home. Dogs are welcome on a lead.
Where to Learn More
LAWA and Taranaki Regional Council: the latest Can I Swim Here result, algae alerts and the long-term grade for Lake Rotorangi at the Pātea Dam campground.
South Taranaki District Council: directions, facilities, fees and rules for the Pātea Dam Campground.
Department of Conservation: track details and directions for the Lake Rotorangi Hydro Walkway at the dam.
Frequently Asked Questions
Can you swim at Lake Rotorangi?
Yes. Taranaki Regional Council describes the lake as popular for swimming, boating and waterskiing in summer, and tests the water at the Pātea Dam campground every week from November to March. Check LAWA before you swim.
What is the water quality like at Lake Rotorangi?
The campground site has an Excellent LAWA long-term grade for summers 2020/21 to 2024/25. All 68 tests between January 2022 and March 2025 were suitable for swimming. Stay out for at least 48 hours after heavy rain; the council advises three days.
Does Lake Rotorangi get toxic algae?
None of the council’s 30 cyanobacteria checks from 2022/23 to 2024/25 reached alert or action level, but blooms can form in hot weather. Check LAWA for alerts and keep dogs away from discoloured or scummy water.
How far is Lake Rotorangi from Whanganui?
The dam is about 59 kilometres north-west of Whanganui in a straight line. By road you go via Pātea, and the campground is about 40 kilometres from Pātea township, partly on unsealed road.
How long is Lake Rotorangi?
The lake is 46 kilometres long, making it New Zealand’s longest man-made lake. It was formed in 1984 by damming the Pātea River for hydroelectricity.
Can you camp at Lake Rotorangi?
Yes. South Taranaki District Council runs the Pātea Dam Campground with toilets, showers, barbecues and unpowered sites. No booking is needed, the maximum stay is four weeks, and you need to bring your own drinking water.
Are dogs allowed at Lake Rotorangi?
Dogs are allowed at the Pātea Dam Campground on a lead and must be kept under control. Toxic algae can kill dogs, so check LAWA for alerts before letting them swim.
Is there a walk at Lake Rotorangi?
Yes. The Lake Rotorangi Hydro Walkway is an easy 1.5-kilometre loop from the dam car park that takes about 40 minutes.
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