Northland has a dense network of rivers and streams. Because of our narrow land mass, most of our rivers are relatively short with small catchments. None of them is considered major on a national scale.
Rivers are channels for floodwaters, a function that is much needed because of Northland's relatively high rainfall.
Our rivers and streams provide habitat for a range of indigenous flora and fauna, as well as being an important water supply for rural communities, horticulture and agricultural demands.
As the majority of Northland’s rivers flow into harbours rather than open coastline, poor river water quality can also affect the health of our harbours.
The Northern Wairoa River is our region’s largest river, draining a catchment area of 3650 square kilometres, or 29 per cent of Northland's land area.
Major catchments in Northland
Northern Wairoa River
The largest Northland river is the Northern Wairoa near Dargaville. It drains a catchment area of 3650 square kilometres. The Northern Wairoa occupies a drowned river valley system and is tidal for about 100km inland.
Rivers that contribute to the Northern Wairoa river are:
- Manganui River:
The Manganui River drains a 90 square kilometre catchment of low rolling hill country, most of which is less than 150m above sea level, except for the northern boundary of the catchment which is formed by the Tangihua Ranges. The Manganui is slow-flowing and meanders through swampy valleys subject to frequent flooding.
- Kaihū River:
The Kaihū catchment, north of Dargaville, includes the western edge of the Tutāmoe Ranges, back to the Tutāmoe settlement, and the edge of the Waipoua Forest. It features a series of rocky gorges and waterfalls. Above Kaihū, the river flows over boulders.
- Awakino River:
This river drains a catchment area of 116 square kilometres, including the western and southern slopes of Tutamoe.
- Tangowahine River:
The Tangowahine has a catchment of 125 square kilometres. It flows through a gorge at the northern end of the Mangaru Range and then opens out into a broad, easy valley.
- Kirikopuni River:
The smallest river in the Northern Wairoa catchment is the Kirikopuni, which drains a narrow valley between the Mangaru Range and the Mangatipa and Houto. The Kirikopuni frequently floods the whole valley floor.
- Mangakāhia River:
The Mangākahia River catchment covers about 800 square kilometres of central Northland, bounded by the Tutāmoe Range in the west and the Wairua River catchment in the east. It has the largest and most rapid flood discharge of any in the Northern Wairoa system.
- Wairua River:
The Wairua River drains the north-eastern corner of the Northern Wairoa Catchment via the Hikurangi Swamp. The large swamp was drained and turned into farmland in the 1970s. Once a lake bed, the swamp is susceptible to heavy rain storms from the north-east and a restricted outlet, making flooding common. The catchment covers 750 square kilometres.
The Awanui River and its tributaries drain the northern side of the Mangamuka Range and flow northwards through Kaitāia and across the Awanui flats to enter the Rangaunu Harbour at Unahi.
The tributaries, Te Puhi stream, Victoria River and Takahue River, are all fast flowing mountain streams with gravel river beds in their upper reaches.
Kaitāia sits on the floodplain at the point where the river is confined, before spilling out on to an alluvial fan and the Awanui flats. Extensive drainage and flood control has been done, over the past 50 years, to lessen most flooding.
The Kerikeri River drains into the Kerikeri Inlet from about 170 square kilometres of land. Streams in the catchment include Rangitāne, Waipapa, Kerikeri and Puketōtara, all of which drain east. Two smaller catchments, Wairoa and Ōkura, drain northward.
With a catchment of 308 square kilometres, the Waitangi River draws water from most of the land between Kaikohe, south of Kerikeri and north of Moerewa. The Waitangi River flows into the Bay of Islands at Waitangi. A tributary, the Waiaruhe River, drains the Ngāwhā Geothermal Field near Kaikohe.
The catchment for the Kawakawa River covers about 820 square kilometres. Its northern boundary runs between Ōpua and Moerewa and its southern boundary is a low ridge separating it from the Hikurangi swamp catchment.
Waipū and Ruakaka rivers
The two main rivers feeding into Bream Bay drain a total area of 310 square kilometres. Most of the rivers flowing to the Waipū River drain from the Brynderwyn Ranges, in the south, through the Ahouroa, Waionehu and Waihoihoi Rivers. The Ruakaka river flows in an easterly direction, draining an area half that of the Waipū river.