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Waikato River
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The Waikato River is the longest river in New Zealand. In the North Island, it runs for 425 kilometres from the eastern slopes of Mount Ruapehu, joining the Tongariro River system and emptying into Lake Taupo, New Zealand's largest lake. It drains Taupo at the lake's northeastern edge, creates the Huka Falls, then flows northwest, through the Waikato Plains.
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The Waikato River is the longest river in New Zealand. In the North Island, it runs for 425 kilometres from the eastern slopes of Mount Ruapehu, joining the Tongariro River system and emptying into Lake Taupo, New Zealand's largest lake. It drains Taupo at the lake's northeastern edge, creates the Huka Falls, then flows northwest, through the Waikato Plains. It empties into the Tasman Sea south of Auckland at Port Waikato. It gives its name to the Waikato region that surrounds the Waikato Plains.
The river's main tributary is the Waipa River, which has its confluence with the Waikato at Ngaruawahia.
The name Waikato comes from Maori and translates as flowing water.
The Waikato River has spiritual meaning for various local Maori tribes including the large Tainui, who regard it as a source of their mana or pride. The widely-respected marae of Turangawaewae is close to its banks at Ngaruawahia.
For many years Tainui tribe have sought to re-establish their links to the river after the New Zealand land wars (see Invasion of Waikato) and the subsequent illegal confiscations of the 1860s, and are continuing negotiations with the current New Zealand government.
Course
The river starts as many small streams on the eastern side of Mount Ruapehu. The Mangatoetoenui Glacier (once called the Waikato glacier) is one of the principal sources. The southernmost tributary is called the Upper Waikato Stream. The Waipakihi River joins the Waikato from the Kaimanawa Mountains to the west. At the point the river meets the Waihohonu Stream, it becomes called the Tongariro River. The Pouto River joins from Lake Rotoaira to the east. The Tongariro flows northward, with State Highway 1 in parallel, through the town of Turangi, and into the southern side of Lake Taupo. Extensive engineering of lakes, tunnels and canals are used to generate hydroelectric power in the Tongariro Power scheme.
At the northeast point of Lake Taupo is Tapuaeharuru Bay and the town of Taupo. The Waikato River leaves the lake and flows northeast past the town, alongside State Highway 1, to the Huka Falls. State Highway 5 runs more or less parallel to the river as it flows further northeast. About 40 km from the lake, the river flows west and into the southern end of Lake Ohakuri. It exits from the northwest end of that lake and flows west through the small Lake Atiamuri and into the long east-west oriented Lake Whakamaru, with State Highway 30 following its course. It passes northwest through Lake Maraetai and Lake Waipapa, where it is joined by the Waipapa River, then north through Lake Arapuni and into Lake Karapiro. Pokaiwhenua Stream joins the river in Lake Karapiro. Many hydroelectric power stations extract energy from the river between Taupo and Karapiro. All the lakes in this stretch of the river (apart from Lake Taupo) are artificial.
Northwest of Lake Karapiro, the river forms the Waikato Basin, flowing through the towns of Cambridge, Hamilton, and Ngaruawahia. It is joined by its largest tributary, the Waipa River, at Ngaruawahia. It then flows north through the Taupiri Gorge to enter the lower Waikato region. Further north is Huntly and then Meremere, where the Whangamarino and Maramarua Rivers join it. From Mercer, where the Mangatawhiri River joins it, the Waikato flows west and southwest. Just before its mouth at Port Waikato, the Araroa River joins from the north.
Uses of the river
As well as being a water and recreation resource, the river has long been a critical communications and transport link for the communities along it. Taupo, Mangakino, Cambridge, Hamilton, Horotiu, Ngaruawahia, Huntly, Hampton Downs, Meremere, Waiuku and Port Waikato are on or close to it.
The river was of military significance in the land wars between British and Maori soldiers around 1863, and significant battles were fought at points including Rangiriri. A cemetery containing the graves of the British military dead can be found there opposite the hotel, shops and cafe.
A ferry service along part of its length was for years conducted by Cesar Roose, several of whose descendants still live beside it.
Electricity generation
The Waikato's first hydro-electric power station was the Horahora Power Station, now located under the deep beneath the surface of Lake Karapiro. Horahora was built to supply electricity for the Martha gold mines at Waihi.
The river has a series of eight hydroelectric power stations that generate electricity for the national grid. Between 1929 and 1971, eight dams and nine powerhouses were built to meet growing demand for electricity.
The power scheme begins at Lake Taupo, which has control gates to regulate the flow of water into the river. Once released through the gates it takes nearly 18 hours for the water to flow to the Tasman Sea. On its journey downstream it passes through power stations at Aratiatia, Ohakuri, Atiamuri, Whakamaru, Maraetai, Waipapa, Arapuni and Karapiro.
Approximately 4000 gigawatt hours (GWh) of electricity is generated annually by the scheme, which is around 13% of New Zealand's total electrical generating capacity.
The river also provides cooling water for the coal/natural gas fired thermal power station at Huntly. However, in order to protect aquatic life, conditions are imposed by its resource consent (see Resource Management Act), specifying the quantity of water that can be removed by the station along with the maximum temperature of the water when returned to the river (25°C). These conditions mean that on very hot summer days the station cannot operate at maximum capacity, sometimes reducing their total output to 40 megawatts (MW). A new cooling tower has been built as part of expansion works at the site, which allows one 250 MW unit to run at full load even during such times.
Recreation
The Waikato is renowned among whitewater kayaking enthusiasts, specifically for the Full James rapid located north of Taupo. The Full James was the site of the 1999 World Whitewater Championships, as well as the pre-World event the year before.
Lake Karapiro (an artificial lake) is regarded as one of New Zealand's best rowing venues. The World Rowing Championships in 1978 and 2010, and the 1950 British Empire Games were hosted at Karapiro.
Ecology
The Waikato River and its hydro lakes are home to at least 19 types of native fish, 10 types of introduced fish. The introduced species include rainbow and brown trout providing what has been call "the finest fly-fishing in the world" . Other introduced species include carp and mosquitofish have become major pests.
Environmental issues
The whole length of the river is administered by the Regional Council, or "Environment Waikato", based in Hamilton. Several major problems currently face the river.
The large catchment area of the Waikato River is highly fertile farmland, so intensive agriculture is present. Due to the agricultural activity within the catchment significant agricultural pollution is leached into groundwater and contained in the runoff. The mismanagement of nitrogen fertilizer and effluent spreading practices in dairy farming is seen as the major causes of this pollution.
The removal of the native vegetation throughout the catchment to accommodate the increasing demand for farmland has also resulted in the silting-up of what was once a navigable channel in the river with loose soils from eroded farmland.
Arsenic is also a major problem in places the content reaches 0.035 greatly exceeding the WHO provisional guideline of 0.01 grams of arsenic per cubic metre. The majority of arsenic in the Waikato River comes from the Wairakei Geothermal Power Station.
Recently controversial was the pumping of water from a point near the seaward end of the river further north to Auckland. This is somewhat purified and used for a portion of the city's domestic water supply.
Slightly-modified human wastes are pumped into the river downriver of several towns, including Hamilton.
A further issue is industrial and metropolitan waste from early-established landfills and waste-emitting factories on the banks of the river.
These include an unlined waste dump at Horotiu, just downriver from Hamilton, whose leachates include persistent organic pollutants such as dieldrin in quantities toxic to freshwater marine life. Tribes at the northern point of the river who took legal action to oppose the continued operation of this dump spoke of finding many dead, disordered and distressed fish near their tribal lands.
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