Last updated October 2026
The Wairau Diversion is the straight flood channel that carries much of the Wairau River from Tuamarina to Cloudy Bay, with a council reserve along its lower reach off Thomas Road and Neal Road. Its mouth is one of Marlborough’s best-known surfcasting spots.
Kahawai come in to feed at the mouth and are mostly caught on spinning lures, and in summer salmon gather off the mouth before running up the river. It is a different place from the main Wairau River mouth at the Wairau Bar, several kilometres to the south. Fishing is free, but you need a Fish & Game licence to fish for salmon or trout here.
At a Glance
- Location
- Wairau Diversion Reserve, Neal Road, Marshlands, near Blenheim; access from Thomas Road and Neal Road
- Water
- Cloudy Bay and the Wairau Diversion mouth (sea, with fresh water from the river)
- Main species
- Kahawai; quinnat salmon in summer; sea-run trout at times
- Best time
- Around high tide in clearing, moderate river flows; salmon in summer
- Methods
- Spinning with metal lures; surfcasting
- Toilets
- Wairau Diversion public toilets in the reserve
- Camping
- Self-contained vehicles only, in a temporary area while the main site is repaired
- Tide port
- Wellington, via LINZ secondary port Wairau River Entrance
- Rules
- MPI Challenger for sea fish; Fish & Game Nelson/Marlborough licence for salmon and trout
- Cost
- Free (a Fish & Game licence costs extra)
- Low about 3:26 am
- High about 9:39 am
- Low about 4:03 pm
- High about 10:05 pm
Best times today: around 3:26 am, 9:39 am, 4:03 pm and 10:05 pm (2 hours either side of each tide change), and around 3:18 am and 3:43 pm (moon overhead and underfoot).
Moving water around the tide changes usually fishes best. Full 7-day Blenheim tides ›
Tide predictions: LINZ (CC BY 3.0 NZ), adjusted from Wellington using LINZ secondary port offsets. Predictions only; actual tides vary with weather.
About Wairau Diversion
The Diversion was cut in 1963 to stop the lower Wairau plain flooding. A channel was dug from SH1 at Tuamarina straight across country to Cloudy Bay and opened on 30 April 1963.
Marlborough District Council says it is the largest diversion of its kind in New Zealand, able to carry 3,000 cubic metres a second, or about 55% of the river’s flow, on a short, direct path to the sea.
The original river still winds south-east through the lagoons to the Wairau Bar, so there are now two Wairau mouths. Our Wairau River Mouth fishing guide covers the Bar. The Diversion mouth is the one you can reach by road through a council reserve, which is why it is so popular for fishing and picnics.
The reserve is a good fishing site and, in season, a whitebaiting site. It has also been knocked about by the river.
A storm in July 2021 washed away a strip about 30 metres wide and 360 metres long back from the mouth, including the road and trees, and the council has since lined about 600 metres of the bank near Cloudy Bay with roughly 11,000 tonnes of rock.
The wider Wairau plain and lagoons have long been a food basket for Rangitāne o Wairau, who dug kilometres of canals linking the waterways to harvest fish and birds.
How to Fish the Wairau Diversion
Where and when
Most anglers fish at the mouth, where the river meets Cloudy Bay. Local anglers say kahawai push in to feed on the incoming tide and drift out as the tide turns, so the last couple of hours of the incoming tide and the first of the outgoing are the times to be there.
When the river is in flood the kahawai stay well offshore. The best days come as the river clears after rain, with a moderate flow. Seals sometimes move into the mouth and put the fish down.
Salmon wait close to shore at the mouth during low summer flows, often swimming under the kahawai schools, and can spend five to ten days in the mixing zone before a fresh takes them upriver.
What to catch and what to use
- Kahawai: spinning is the main method. A small silver metal lure of about 20 grams on light spin gear works well; if fish follow but do not take, try a smaller lure or add or remove a red tag.
- Salmon: quinnat salmon run up the Wairau in summer. Fish & Game reported a 6.5 kg salmon taken on the third cast at the Diversion. A Fish & Game ranger’s Wairau rig is heavy trout spin gear with braid, about 2 metres of 20 lb fluorocarbon trace and a 22 gram Zed spinner (16 grams in clear water): white on cloudy days, silver on sunny days, with small, sharp treble hooks.
- Whitebait: the reserve is a known whitebaiting spot during the national season, 1 September to 30 October.
What to bring
A selection of metal lures in a few weights, polarised sunglasses to spot fish, and a licence if there is any chance of hooking a salmon or trout.
Getting There and Facilities
- Road: turn off at the Thomas Road and Neal Road intersection, north-east of Blenheim. A gravel road runs along the north bank of the Diversion. It can be rough after rain.
- Walking: since the 2021 flood damage, vehicles have been stopped at the Hinepango stream, with walkers allowed through to the mouth. The council said in 2024 the barrier would stay until repairs were finished, so check the signs.
- Toilets: the council lists public toilets in the reserve.
- Camping: the main responsible camping area is closed because of flood damage, and a temporary area is open elsewhere in the reserve. It is for self-contained vehicles only, with a two-night limit.
- Crowds: expect a few anglers on most days and many more on fine weekends when the kahawai are in.
Rules and Safety
- Sea fish such as kahawai follow MPI’s Challenger rules, and no licence is needed for them. Set netting is banned along this coast from Cape Jackson to the Clarence River, including Cloudy Bay.
- Fish & Game counts a river mouth, and the seashore within 500 metres of it, as fresh water. To fish for salmon or trout here you need a Fish & Game licence, carried with you. The Nelson/Marlborough regulations list the Wairau below Wash Bridge, including the Diversion, as open all year to fly, spinning and bait, with their own bag rules for trout and salmon.
- Whitebaiting follows DOC’s whitebait regulations, not council rules.
- The Diversion takes floodwater fast. When the Wairau at Tuamarina rises more than about 3 metres, the council says the Diversion and the floodway land flood. Do not fish here in a fresh, and watch for rising water after heavy rain up the valley.
- River mouths have strong, changing currents and steep, shifting banks. Do not wade out at the mouth.
Tackle and Bait Nearby
- Hunting & Fishing Marlborough, 46 Main Street, Blenheim: lures, spin gear and Fish & Game licences.
Find Out More
Marlborough District Council: Wairau Diversion Reserve: access, toilets and the current camping arrangements.
Fish & Game Nelson/Marlborough regulations 2026/27: seasons, methods and bag rules for salmon and trout, including the Diversion.
MPI Challenger fishing rules: size and daily limits for kahawai and other sea fish.
Common Questions
Where is the Wairau Diversion?
North-east of Blenheim. Turn off at the Thomas Road and Neal Road intersection; the reserve runs along the north bank to the mouth on Cloudy Bay.
Is it the same as the Wairau River mouth?
No. The Diversion is a 1963 flood channel with its own mouth. The original river reaches the sea at the Wairau Bar, several kilometres to the south.
What can you catch at the Wairau Diversion?
Mainly kahawai, plus quinnat salmon in summer and sea-run trout at times.
What is the best tide?
Local anglers favour the last part of the incoming tide and the start of the outgoing, when the kahawai move into the mouth.
Do I need a licence?
Not for kahawai. You do need a Fish & Game licence to fish for salmon or trout, because the mouth and 500 metres of shore either side count as fresh water.
Can I camp there?
Self-contained vehicles can stay up to two nights in the temporary camping area while the main site is repaired.
When should I stay away?
When the Wairau is in flood. The Diversion carries most of the floodwater and the fishing stops.
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