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Rivers

by  David Young

A river rules my life – the title of a popular book hints at the prominence of New Zealand’s rivers, incising the land at every turn. Often wild and prone to flooding, they claimed the lives of many settlers. But the balance of power soon changed – farming destroyed river habitats, and grand rivers such as the Clutha were harnessed for hydroelectric schemes.


How New Zealand rivers are formed

Rivers are a defining feature of the New Zealand landscape. There are many, and in such a small country they are never far away – for example, as you circle the near-perfect cone of volcanic Mt Taranaki (Mt Egmont), you will cross, on average, one river every kilometre.

The South Island has 40 major river catchments, and the North Island has 30. (A catchment is the land area drained by a river.) Over 180,000 kilometres of rivers have been mapped, and this excludes thousands of small streams.

Mountains and rainfall

Mountains and weather are two major factors affecting the formation of rivers. Much of New Zealand is raised high above the sea, with mountain ranges running along the middle of the North and South islands. Buffeted by the winds of the roaring forties, New Zealand experiences intense rainfall where westerly airflows are driven across the mountains.

The annual 8–10-metre rainfall of Fiordland produces rivers of fearsome force and volatility, while similar rainfalls occur throughout the Southern Alps and feed the short, flash-flooding rivers of Westland.

Some moisture falls as snow, especially in the mountains, and is temporarily stored there. Much water from rain and snow seeps into the ground, to be gradually released back to the surface as it flows downhill in streams and rivers. Unlike many countries, which lose 70% of their precipitation through evaporation, New Zealand loses on average just 30%, ensuring that its river volumes in their natural state are relatively large.

Seasonal variations in rainfall mean that river levels change during the year. Most rivers on the east coast of both islands have lower flows during the dry summers. But in the South Island’s eastern snow-fed rivers, lowest flows occur during winter and spring, before the snow melts.

Geological processes

The headwaters of most of the major rivers in the South Island were once glaciers. During ice ages, glaciers moved down the mountains, carving out river valleys, and carrying down glacial gravels (called outwash). The Canterbury Plains were formed from outwash gravels, which also created the wide beds of braided rivers such as the Rakaia.

A river runs through it

The North Island’s Manawatū River flows through the central mountain range, rather than down it, which is the usual pattern. This is because the river was flowing there before the mountains were formed, and it kept to its course as they rose around it. The South Island’s Clutha and Buller rivers also flow through gorges formed by rising mountain ranges.

Earthquakes and volcanic activity can affect the course of rivers. Wherever faulting occurs and there is enough water flow, rivers will find the faults and cut down along these planes of least resistance. Maruia Falls, on the Maruia River in the Buller area, is a dramatic example of the effects of the Murchison earthquake of 1929. The river was diverted by a landslide during the earthquake, and cut a new channel that causes the river to cascade over a cliff edge.

Rocks and rivers

Rivers are influenced by rock type, which varies greatly throughout the country. For example, the Whanganui River cuts through relatively soft mudstones and sandstones, and its waters slide gently between steep, bush-clad cliffs of papa rock. In contrast, the Clutha and Kawarau rivers in Otago, which have their source in alpine snow and ice, tumble among hard schist boulders and river-worn gravel, through arid gorges.


Types of river

The character of a river is largely determined by the landscape through which it runs. Most New Zealand rivers flow through wild areas such as bush or hill country, and through farmland. Some also pass through towns and cities, such as the Avon in Christchurch and the Leith in Dunedin. Many rivers change in nature as they flow from the mountains to the sea.

Nine large areas of New Zealand, each with different landscape features, have produced distinct types of rivers.

North Island

Northland and Coromandel

These two peninsulas have many short rivers. The lower courses of some have become arms of the sea, as at Hokianga and Whitianga. The longest river in this region, the Northern Wairoa, feeds the large, estuarine Kaipara Harbour.

Waikato

The major rivers in this region are alluvial: they flow through flood plains they have created by depositing sediment. The Waikato (New Zealand’s longest river), Waihou and Piako are the main examples.

Volcanic Plateau and Bay of Plenty

Recent volcanic activity has shaped the course and character of the rivers in these regions. Lakes that formed in volcanic craters are drained by the Tarawera, Kaituna and upper Waikato rivers. Part of the course of the Rangitāiki River is confined between the ranges of the main divide and the edge of the Volcanic Plateau.

The main range and east

Along the main range of the North Island and through the hill country to its east, rivers are incised and some are fast flowing. The major rivers are the Mōtū, Waiapu, Waipaoa, Wairoa, Mōhaka, Ngaruroro, Tukituki and Ruamāhanga. Some, notably the Waipaoa, Ngaruroro, Tukituki and Ruamāhanga, have formed flood plains.

Terrific terraces

While landscape generally determines the character of rivers, sometimes the reverse occurs. After it reaches Marton, the Rangitīkei River flows between sandstone banks that have an extraordinary sequence of terraces. These are the remnants of ancient flood plains that the river built and then cut down over a period of 250,000 years.

Western uplands

In the western uplands of the North Island (Taranaki, Rangitīkei and Manawatū), rivers incise deeply and often flow through long gorges. Examples are the Mōkau, Waitara, Pātea, Waitōtara, Whanganui, Whangaehu, Turakina and Rangitīkei rivers. To the south, the Manawatū River has formed a flood plain.

South Island

West of the main divide

Rivers west of the main divide, in north-west Nelson and Westland, have their headwaters in very mountainous areas and flow swiftly. The major river here is the wild Buller River, known for its white-water rapids and scenic gorges. Other examples are the Motueka, Grey, Taramakau and Arahura rivers.

Marlborough and Canterbury

Marlborough, Canterbury and South Canterbury are famous for their braided rivers, which rise in the Southern Alps and are glacial in origin. Once they reach the plains, the rivers break into many strands, interlaced across broad gravel beds made of glacial outwash. The Wairau, Awatere, Clarence, Waiau, Hurunui, Waimakariri, Rangitātā, Rakaia and Waitaki rivers are the main braided rivers. They are separated by shorter rivers arising in the foothills, notably the Ashley, Selwyn and Ashburton, which are not braided.

Largest river

The Clutha is New Zealand’s largest river by volume. The greatest recorded flow was in 1878, when it surged at an estimated 5,663 cubic metres per second.

Otago

Otago’s rivers also have their origins in the Southern Alps, but they flow through basins in schist blocks. The Clutha, the Taieri and the Shag (Waihemo) are the main examples.

Southland

The rivers in Southland are alluvial, like those in the Waikato region. The main ones are the Mataura, Oreti, Aparima and Waiau rivers.


Māori and rivers

Exploration

For early Māori, rivers offered landing sites, harbours and a source of fresh water. They explored as far as possible upriver on many waterways. Tamatea’s cave on the Whanganui River, for example, marks a journeying point for Tamatea-pōkai-whenua, who circumnavigated New Zealand in the Takitimu canoe.

Transport

It was easier to get from place to place by canoeing up or down rivers than by walking over the mountains or through dense bush. Waka (canoes) made of hollowed-out logs were the main mode of travel along or across rivers. On the many challenging rivers of the South Island, mōkihi (rafts of woven reeds) were favoured. The Mōkihinui River, south of Karamea in north Westland, commemorates this craft in its name, which means ‘large raft of flax stalks’.

Food

Māori often built settlements at the mouth of a river. Food could usually be obtained from the river itself or its estuary. Tuna (eels) and lamprey were harvested with nets or elaborate structures that straddled the flow, and to which nets were secured ( tuna and utu piharau). The eels were either preserved or held live in baskets. A variety of native galaxiids were also taken.

Food sources found inland or at sea could be reached easily by river. In the South Island, rivers were used to transport slaughtered moa from the interior to coastal settlements. The relationship between rivers and the sea was often acknowledged in Māori traditions. Shoals of kahawai migrate annually from the sea to the lower reaches of the Mōtū River on the East Coast of the North Island. Both Te Whānau-ā-Apanui and neighbouring Ngāi Tai tribes believe that this is the fulfillment of an ancient agreement between the sea god, Tangaroa, and their people.

River spirits

Often in Māori tradition taniwha (monsters) lived in rivers. They could be guardians of a place, or upholders of customs and tribal prestige. A famous Tainui proverb runs: ‘Waikato taniwha rau: he piko, he taniwha; he piko, he taniwha.’(Waikato, home of a hundred taniwha: on every bend a taniwha can be found). This refers to the powerful presence of chiefs along the Waikato River.

Pounamu

New Zealand nephrite (known as greenstone or pounamu) is found only on the South Island’s West Coast. Produced deep in the earth, it is brought to the surface by mountain uplift, and then cleaned by river action. Māori prized this stone, which has different shades of colouring. They used it to make tools, weapons and ornaments, and it became a valuable item of trade. Groups made expeditions to the West Coast, where they cut pounamu from boulders and carried it back over paths known as greenstone trails.

Tribal identity and rivers

These long and rich associations help explain why tribes invoke the name of a river to assert their identity. For example, the people of Tainui state as part of a formal greeting: ‘Waikato is the river, Taupiri is the mountain, Pōtatau Te Wherowhero (the first Māori King) is the man.’


The impact of European settlement

Claiming the land

Like Māori, the first European settlers used rivers for exploration and transport. Some major rivers such as the Whanganui and Waikato were used as routes for military conquest, and later as supply lines for isolated settlements.

Rivers were often a source of danger for the unwary. There were so many deaths on river crossings that drowning became known as ‘the New Zealand death’. Once bridges were built, perceptions changed and rivers were no longer seen as barriers.

Gold rushes

In the 1860s, after the gold rushes in California and Australia, New Zealand also had a gold boom. As well as boosting the nation’s population and wealth, the rushes shaped relationships between settlers and some significant river landscapes.

Mainly in Otago and on the West Coast of the South Island, rivers yielded deposits of alluvial gold. The gold was panned, then sluiced. Later in the century, gold dredges did the work, scooping up millions of tonnes of river gravel and boulders. This altered the landscapes of both regions.

Polluting rivers

In the 19th century, gold-mining companies in the North and South islands were allowed to designate rivers as ‘sludge channels’, to discharge debris from gold recovery work. Using rivers to dispose of sewage and waste from farming and industry also became common, and it is still a problem.

The flood threat

Most rivers have steep gradients, but some, especially in the North Island, flowed over gently sloping plains. On the river flats, settlers tried to tame rivers by building drainage works, ports, and flood control systems. Upstream they felled bush, ploughed land and introduced grazing animals, increasing the natural rate of erosion. This led to greater runoff of water, and more sediment being deposited along the lower reaches and flood plains of rivers.

Hazards could develop – for instance, a riverbed could build up between stopbanks until the water level was higher than the surrounding countryside. In heavy rain, serious flooding occurred. Flooding is a growing threat for many rivers that have been modified.

Introduced fish

With recreational fishing in mind, 19th-century acclimatisation societies introduced rainbow and brown trout and quinnat salmon. Today there are trout in most New Zealand rivers. The fisherman’s gain was at some cost to native fish, which were preyed on by trout.

Making lakes

One of the effects of hydroelectric power schemes was the creation of artificial lakes. Dams have formed eight lakes along the Waikato River: Aratiatia, Ōhakuri, Ātiamuri, Whakamaru, Maraetai, Waipapa, Arapuni and Karapiro. They have recreational value. Karapiro, for example, is used for international rowing competitions.

Salmon were systematically introduced by the government for their commercial value. Eventually they were confined to the Rakaia in mid-Canterbury and, to a lesser extent, to some other South Island rivers.

Hydroelectricity

After early schemes in the 1920s, the use of rivers to generate electricity gained pace. Between 1945 and the mid-1970s, New Zealand expanded its electricity generation capacity almost tenfold, mostly through hydroelectric schemes.

By the 1970s many of the country’s major rivers, such as the Waikato, Tongariro, Waiau and Waitaki, had been dammed. Hydroelectric developments were seen as desirable because they produced power from a renewable resource. But they had an impact on water levels in rivers, and sometimes submerged natural features such as waterfalls.


Changes to river environments

Life in and around rivers

Before widespread human settlement, most lowland rivers were bordered by dense native forest with many ferns, mosses, liverworts and fungi. The forested river banks were home to birds, lizards, slugs, snails, flatworms, earthworms and insects. Overhanging vegetation provided shade and food for native fish, and kept water temperatures low so that the growth of algae was controlled.

Human impact

Since the clearance of forest for pasture, these habitats and many native species have been lost because of several factors:

  • With increased light, algae and introduced weeds have spread in rivers, while the warmer water has killed many organisms.
  • Silt from eroding banks threatens water quality and the fish and insects that live in rivers.
  • Hydroelectric developments have flooded or dried up parts of rivers, destroying habitats.
  • Exotic species compete with native plants and fish.
  • Farming leads to runoff of fertiliser and animal waste that has killed native species.

Plants

Untouched river environments can host a range of native plants. Wetland vegetation, including kahikatea, cabbage trees, mānuka, New Zealand flax and rushes, often grows on river margins. Conifer–broadleaf forest grows beside many wild rivers, and mosses, liverworts and ferns can grow both near and in the water.

Around South Island braided rivers, plants such as willowherb, matagouri, silver tussock and many sedge species are common.

Introduced plants such as pines, willows, lupins and hawkweeds are spreading through many river banks and beds. They smother native plants, and harbour pests such as the willow sawfly, and predators such as wild cats, ferrets and hedgehogs. Threatened plants include a forget-me-not (Mysotis uniflora) that forms mats near braided rivers, a river-dwelling moss (Fissidens berteroi) and a liverwort (Schistochila nitidissima).

Fish and crustaceans

Around 40 species of native freshwater fish, including lamprey, eels, smelts, southern graylings, galaxiids, torrentfish, bullies and flounder, are found in New Zealand rivers. They prey mainly on invertebrates including the native crayfish Paranephrops zealandicus and P. planifrons.

Aggressive introduced trout compete for food, and 10 species of native fish, including koaro and the dwarf īnanga, are now considered threatened.

Birds

New Zealand rivers are home to many species of wetland and wading birds. The paradise shelduck is found on wide gravel riverbeds, while the grey duck prefers slow streams. Wading birds such as the pied stilt, banded dotterel, black fronted dotterel and wrybill plover make their nests mostly on the beds of braided rivers in the eastern South Island. Black shags, little black shags and little shags are often seen fishing in rivers as well as coastal waters.

A pretty pest

Russell lupins were planted in front of the Hermitage hotel at Mt Cook in 1930 to cover a rock slide. They soon spread to the Mackenzie Basin, and although they blaze with colour in summer, they are a major threat to braided river environments. Lupins can quickly colonise islands in the riverbed, destroying the habitats of native species.

Some birds that live around braided rivers, notably the black stilt, wrybill and black fronted tern, are threatened by predators and loss of habitat. The whio (blue duck) has to compete with trout for insect species. It is now reduced to a few small populations on remote, fast-flowing rivers in the North and South islands. The brown teal, once common on swampy streams and tidal creeks shaded by overhanging trees, has also been dramatically reduced in numbers, and is now found mainly in Northland.

Insects

Insects such as caddisflies, dragonflies and mayflies are found on the banks of rivers in their adult stage, and in the water during their larval stage. Snails and worms live on the banks and in the water itself. The range of some insects has been limited because of changes to their habitat. For instance, the robust grasshopper (Brachaspis robustus) used to be found in dry, stony riverbeds in Otago and South Canterbury but is now confined to the Tekapo, Pūkaki and lower Ōhau rivers and a few sites further east.


Conserving rivers

Changes in public opinion

Awareness of the need to protect rivers dawned slowly. Efforts to protect river catchments as a way of preventing erosion and limiting floods began in the late 19th century. However, it was not until 1941 that the Soil Conservation and Rivers Control Act was passed. Several decades went by before all districts had set up their own catchment boards. They were supported by a central research and regulation agency based within the former Ministry of Works.

Although there was widespread support for hydroelectricity schemes, in the 1960s some people began to see the environmental threat they posed. The public campaign to save Lake Manapōuri signalled changing attitudes. However, power schemes continued. A second big hydro dam was built on Otago’s magnificent Clutha River during the 1980s at Clyde. The project went ahead despite protests from environmental and community groups.

Recreational groups also formed powerful lobbies. Tranquil rivers have always lured fishermen and swimmers, and boating is a favourite pastime. After the Second World War, canoeing, kayaking and rafting became popular with New Zealanders and overseas tourists. These activities usually took place on the wild scenic rivers that were under increasing threat from power development.

Wild and scenic rivers legislation

In 1981 the Wild and Scenic Rivers Amendment to the Water and Soil Conservation Act was passed. Since then, 12 rivers have been given the protection of national water conservation order status. Groups such as the Living Rivers Coalition continue to campaign for the protection of New Zealand’s waterways.

Flood protection and river management

Catchment boards were replaced by regional councils in 1989. The councils and the National Institute of Water and Atmospheric Research (NIWA) continuously monitor river levels and rainfall, and provide flood warnings if necessary. NIWA has also developed a River Environmental Classification to help manage waterways.

Hamilton jet

The development of the waterjet engine by New Zealander Bill Hamilton in 1954 revolutionised river transport. Using a centrifugal pump that drew in water and expelled it above the waterline, the engine does not extend under the boat like an outboard motor. Jet boats can travel along shallow rivers once inaccessible to power boats. Jet boats are used for tourism on rivers such as the Shotover in Otago.

Riparian protection: restoring the river banks

Since the 1970s, there have been schemes to plant trees and shrubs on river banks. Native species are planted, such as makomako, kotukutuku, kawakawa, māhoe, karo, patē, kōwhai and pōhutukawa. As well as stabilising the banks, they provide food for birds, and so help restore biodiversity.

Māori guardianship

Since the 1980s, Māori have declared their traditional interests in rivers, water and water quality to the Waitangi Tribunal. Cases have been taken to the Environment Court since the passing of the Resource Management Act in 1991. Two of the most significant rivers in New Zealand, the Waikato and Whanganui, both await resolution between the government and the respective tribes over management and protection.

Continuing threats

As well as long-standing pollution and flooding, there are new threats to the health of rivers, in particular:

  • the arrival of invasive species such as didymo (Didymosphenia geminata, also known as ‘rock snot’), which has now spread to many South Island rivers.
  • the growth of dairying in Canterbury. This affects water quality through effluent discharge, and river levels through use of water to irrigate pastures.
  • the increase in numbers of off-road vehicles. Television advertisements often show these vehicles driving through pristine rivers.

Power needs

The demand for electricity is expanding rapidly, and the threat of climate change may limit the use of fossil fuels to generate energy. New Zealanders may face the difficult choice whether to develop more rivers for hydroelectric power, or to retain them in their wild state.


Rivers and culture

Challenging, alluring and sometimes threatening, New Zealand’s ubiquitous rivers weave a thread in the nation’s identity. Since the 19th century, the rivers have inspired artists and writers.

Art

Rivers have been vividly and imaginatively portrayed in some memorable artworks. Petrus van der Velden’s 19th-century paintings of Ōtira Gorge conveyed awe at the power of nature. A later artist, William A. Sutton, depicted the stony bed of a Canterbury river as emblematic of the region. His contemporary, Toss Woollaston, produced expressive paintings of West Coast rivers such as the Grey and the Hokitika.

Writing

Rivers featured in 19th-century fiction and non-fiction writing, but the first novel that made a river its central motif was published by Jane Mander in 1918. The story of a New Zealand river is set in a timber-milling community on the Northern Wairoa River, in the Kaipara region of Northland.

Rivers figured prominently in the fictional landscapes of later novelists such as Vincent O’Sullivan and Maurice Gee. In non-fiction, Mona Anderson’s A river rules my life (1963), an account of life on a South Island high-country station by the Wilberforce River, was a publishing phenomenon in New Zealand.

Frame’s new name

In 1958, novelist Janet Frame changed her name by deed poll to Nene Janet Paterson Clutha. One reason was to protect her privacy in the face of growing public recognition. But she also wanted to acknowledge the importance to her of the Clutha River in Otago. She had seen it as a source of creative inspiration since her student days in the 1940s.

For poets Denis Glover and James K. Baxter, the river held great power. In Glover’s work, this is most evident in his sequences on Arawata Bill, based on the gold prospector William O’Leary, who lived by the Arawata River on the West Coast. The Whanganui River became both muse and location for Baxter’s challenge to modern material life from the late 1960s. In his commune beside the river, Baxter sought to affirm Māori values, a sense of community and traditional spirituality. His Jerusalem sonnets (1970) and Jerusalem daybook (1971) voiced some of the issues faced by a people teetering on the cusp of social change. For a fisherman-poet like Brian Turner, rivers are a recurring theme in his musings on landscape. His near contemporary, Jeff Holman, has enjoyed popular success with The late great Blackball Bridge sonnets (2004), exploring a rich childhood in a West Coast mining town up the Grey River valley.

Film

A few New Zealand feature films have explored the river theme. John O’Shea’s 1981 Pictures depicted the Whanganui as part of intrepid 19th-century surveyor John Rochfort’s story. In his Victorian epic River queen (2005) director Vincent Ward evoked the Whanganui River’s beauty and totemic power with a strong narrative about blood and belonging. The film’s title echoes that of a 1928 short documentary, Queen of rivers. Ironically this one was shot on three rivers besides the Whanganui.


External links and sources

More suggestions and sources


How to cite this page: David Young, 'Rivers', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/en/rivers/print (accessed 18 November 2019)

Story by David Young, published 24 Sep 2007