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71-653: Huka Falls is a set of waterfalls on the Waikato River , which drains Lake Taupō in New Zealand . A few hundred metres upstream from Huka Falls, the Waikato River narrows from approximately 100 metres across to a canyon only 15 metres across. The canyon is carved into lake floor sediments laid down before Taupō Volcano 's Oruanui eruption 26,500 years ago. The volume of water flowing through often approaches 220 cubic metres per second, making it one of

142-651: A case for the river before the Waitangi Tribunal as they would not win. An out-of-court settlement was arranged and the deed of settlement signed by the Crown and Waikato-Tainui in August 2008 settled the raupatu claim to the Waikato River, although other claims for land blocks and harbours are still outstanding. Waikato-Tainui now have joint management of the river with Waikato Regional Council . The ancestral Waikato River flowed from an ancient lake (Lake Huka) in

213-525: A catastrophic breakthrough flood causing the river to change course near Piarere . The Hinuera Gap and Waitoa River are evidence of the river's former course. The water level dropped quickly and the river stayed in this new course through the Maungatautari gorge and Hamilton Basin. Deposits show that the Waikato River was already in the Waikato Basin 21,800 years ago. The river starts in

284-513: A day has been drawn from the river at Tuakau, treated and pumped along a 38-kilometre (24 mi) pipe north to Auckland , where it is mixed with local water. This met 8% of Auckland's water needs in 2010/11. In December 2012 capacity was increased to 125 million litres (33,000,000 US gal), and in 2013 work started to increase it to 150 million litres (40,000,000 US gal). The treatment plant meets New Zealand's 2000 drinking water standards according to Water Care NZ. This

355-540: A large part of post-erosional rocks in Tenerife and Gran Canaria islands. Yucca Mountain Repository, a U.S. Department of Energy terminal storage facility for spent nuclear reactor and other radioactive waste, is in a deposit of ignimbrite and tuff. The layering of ignimbrites is used when the stone is worked, as it sometimes splits into convenient slabs, useful for flagstones and in garden edge landscaping. In

426-414: A plug flow, with an essentially non-deforming mass travelling on a thin shear zone, and the en masse freezing occurs when the driving stress falls below a certain level. This would produce a massive unit with an inversely graded base. There are several problems with the en masse model. Since ignimbrite is a deposit, its characteristics cannot completely represent the flow, and the deposit may only record

497-613: A similar chemistry and so must have undergone the same compaction process to have the same foliation. The Green Tuff in Pantelleria contains rheomorphic structures which are held to be a result of post-depositional re-mobilization because at that time the Green Tuff was believed to be a fall deposit which has no lateral transport. Similarities between the structures in the Green Tuff and ignimbrites on Gran Canaria suggest post-depositional re-mobilization. This interpretation of

568-597: A source of their mana , or pride. The widely respected marae of Tūrangawaewae is close to its banks at Ngāruawāhia. For many years the Tainui tribe have sought to re-establish their links to the river after the New Zealand Wars (see Invasion of the Waikato ) and the subsequent confiscations of the 1860s, and are continuing negotiations with the New Zealand government . The Tainui iwi was advised not to bring

639-487: A thickness of 200 metres (660 ft). A new lake was formed – Lake Taupō . The water accumulated until a new outlet was forced 120 metres (390 ft) above the present lake level, near Waihora Bay. Over the next few thousand years the bed of the river was raised by large amounts of eruption debris. Then the original, blocked outlet suddenly gave way; the lake level fell 75 metres (246 ft) as about 80 cubic kilometres (19 cu mi) of water and debris poured out in

710-541: A water and recreation resource, the river was historically a critical communications and transport link for the communities along it. It took about 3 days to paddle a waka from Waiuku to the Cambridge/Te Awamutu area. Taupō , Mangakino , Cambridge , Hamilton , Horotiu , Ngāruawāhia , Huntly , Hampton Downs , Meremere , Waiuku and Port Waikato are on or close to it. The Waikato River in Hamilton

781-444: Is a common form of ignimbrite alteration. There are two types of welding, primary and secondary. If the density current is sufficiently hot the particles will agglutinate and weld at the surface of sedimentation to form a viscous fluid; this is primary welding. If during transport and deposition the temperature is low, then the particles will not agglutinate and weld, although welding may occur later if compaction or other factors reduce

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852-700: Is also theorized that transformation occurs at a boundary layer at the base of the flow and that all the materials pass through this layer during deposition. Another model proposed is that the density current became stationary before the rheomorphic structures form. Structures such as pervasive foliation are a result of load compaction, and other structures are the result of remobilization by load and deposition on inclined topography. The tuff deposited at Wagontire Mountain in Oregon and Bishop Tuff in California show evidence of late stage viscous flow. These tuffs have

923-452: Is currently debate in the field of the relative importance of either mechanism, there is agreement that both mechanisms have an effect. A vertical variation in orientation of the structures is compelling evidence against post-depositional re-mobilization being responsible for the majority of the structures, but more work needs to be carried out to discover if the majority of ignimbrites have these vertical variations in order to say which process

994-410: Is equal to or better than the A standard for Auckland's other water supplies. Slightly-modified human wastes are pumped into the river downriver of several towns. Hamilton city has one of the most modern water treatment systems in the world following a 2003 report by GHB water consultants. In 2007 $ 22 million was spent upgrading the existing intake station south of the city at Riverlea. This will meet

1065-518: Is frequently used by rowers, kayakers and powered pleasure craft. Water-skiers and jet skis have zones outside the city limits where they can be used. The river was of military importance in the land wars between New Zealand settler and Kingitanga forces during 1863–64 and significant battles were fought. Three shallow draft gunboats were designed in New Zealand and built in Sydney in kitset form;

1136-472: 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 . The power station uses river water as a cooling medium for the old steam units, which means that large quantities of warm water is returned to the river. To limit environmental impacts, conditions are imposed by its resource consent , specifying

1207-590: Is largely the result of the massive Hatepe eruption of the Taupō Volcano in 180 AD. The mean discharge of the Waikato River is 340 cubic metres per second (12,000 cu ft/s), with the highest flows typically occurring in July and August. Specific mean annual floods are low (60–70 L s-1 km-2), and the frequency of events with greater than 3 times the median flow is 0.4 events / year, due to flow regulation and groundwater storage in pumice. As well as being

1278-403: Is seen as the major causes of this pollution. Since 2000 Environment Waikato has joined with conservation minded farmers to bring about more efficient and scientific use of fertilizers. The removal of the native vegetation throughout the catchment to accommodate the increasing demand for farmland has contributed to the silting-up of the river with loose soils from eroded farmland, although most of

1349-537: Is the most common. A model based on observations at the Wall Mountain Tuff at Florissant Fossil Beds National Monument in Colorado suggests that the rheomorphic structures such as foliation and pyroclasts were formed during laminar viscous flow as the density current comes to a halt. A change from particulate flow to a viscous fluid could cause the rapid en masse cooling in the last few meters. It

1420-593: The Hinuera Gap into the Firth of Thames and from there into the Hauraki Gulf / Tīkapa Moana . The most recent occasion this is known to have occurred ended some 20,000 years ago, although it is possible that it also flowed north more recently, until about 1800 years ago. A remnant of this former course can be seen as a spur on Lake Karapiro to the south of the settlement of Piarere . The river's current course

1491-786: The North Island . It rises on the eastern slopes of Mount Ruapehu , joining the Tongariro River system and flowing through Lake Taupō , New Zealand's largest lake. It then drains Taupō at the lake's northeastern edge, creates the Huka Falls , and 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

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1562-779: The Sierra Madre Occidental in western Mexico. In the western United States , massive ignimbrite deposits up to several hundred metres thick occur in the Basin and Range Province , largely in Nevada , western Utah , southern Arizona , and north-central and southern New Mexico , and the Snake River Plain . The magmatism in the Basin and Range Province included a massive flare-up of ignimbrite which began about 40 million years ago and largely ended 25 million years ago:

1633-712: 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. Numerous small islands lie in the long, thin delta of the river as it passes through low-lying swampy land between Meremere and

1704-565: The Tongariro River since 1945. The Poutu Stream joins from Lake Rotoaira to the east, as a tributary of the Tongariro, which flows northward, with State Highway 1 in parallel, through the town of Tūrangi , and into the southern side of Lake Taupō. Extensive engineering of lakes, tunnels and canals are used to generate hydroelectric power in the Tongariro Power Scheme . The Waikato River flows out of Lake Taupō at

1775-653: The WHO provisional guideline of 0.01 grams of arsenic per cubic metre and making the water unsuitable for drinking water unless treated. The majority of arsenic in the Waikato River comes from the Wairakei Geothermal Power Station . The amount of arsenic gradually declines as the river flows northwards and is at its lowest at the Waikato River Heads. Since 2002, around 75 million litres (20,000,000 US gal) of water

1846-612: The Avantidrome through St Peter's School of Cambridge and Tamahere was being constructed in 2019/2020, including an underpass at SH21 to Tamahere Park. Te Araroa (the walkway running the length of the country) follows the Waikato for most of its 80 kilometres (50 mi) between Mercer and Hamilton. The Waikato River and its hydro lakes are home to at least 19 types of native fish and 10 types of introduced fish. The introduced species include rainbow and brown trout providing what has been called "the finest fly-fishing in

1917-525: The HCC website. 37°22′10″S 174°42′29″E  /  37.3694°S 174.708°E  / -37.3694; 174.708 Ignimbrite Ignimbrites are made of a very poorly sorted mixture of volcanic ash (or tuff when lithified ) and pumice lapilli , commonly with scattered lithic fragments. The ash is composed of glass shards and crystal fragments. Ignimbrites may be loose and unconsolidated, or lithified (solidified) rock called lapilli-tuff. Near

1988-476: The Waikato Plains. The present course of the river was largely formed about 17,000 years ago. Contributing factors were climate warming, forest being reestablished in the river headwaters and the deepening, rather than widening, of the existing river channel. The channel was gradually eroded as far up river as Piarere , leaving the old Hinuera channel through the Hinuera Gap high and dry. The remains of

2059-400: 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. The 2002 GHD report saw new regulations put in place to make industries comply with a new bylaw which stops hazardous substances entering the water system at all according to

2130-497: The base and top, called lower and upper 'vitrophyres', but central parts are microcrystalline ('lithoidal'). The mineralogy of an ignimbrite is controlled primarily by the chemistry of the source magma. The typical range of phenocrysts in ignimbrites are biotite, quartz, sanidine or other alkali feldspar , occasionally hornblende , rarely pyroxene and in the case of phonolite tuffs, the feldspathoid minerals such as nepheline and leucite . Commonly in most felsic ignimbrites

2201-410: The base of the flow cannot be turbulent . The instantaneous deposition of an entire body of material is not possible because displacement of the fluid is not possible instantaneously. Any displacement of the fluid would mobilize the upper part of the flow, and en masse deposition would not occur. Instantaneously cessation of the flow would cause local compression and extension, which would be evident in

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2272-591: The centre of the North Island through deep gorges of welded ignimbrite and rhyolite , northward through the Hinuera Valley and Hauraki Basin into the Thames Estuary. It is possible that the river flowed through the Waikato Basin about a million years ago before returning to its Hinuera course. After the huge Oruanui eruption 27,000 years ago ignimbrite was showered all over the North Island to

2343-492: The cities demand until 2016. Waste water in its untreated state is 99.9% water and 0.1% other matter. A series of sophisticated machines produce clean water of a high standard getting rid of bad tastes odours and toxins to meet the upgraded NZ water standards. The Pukete 2 project which started in 2002 will upgrade the plant in a series of stages costing $ 24 million. A further issue is industrial and metropolitan waste from early-established landfills and waste-emitting factories on

2414-416: The coast, the largest of which is Motutieke Island . There are also over 40 islands between Ngāruawāhia and Tuakau, depending on the level of the river. Maurea Islands, just south of Rangiriri were subject to a restoration trial to test comparative weed treatments, the main weeds being alder and yellow flag iris . In prehistoric times, the Waikato's course has occasionally shifted to flow north through

2485-411: The density current passed over the forming deposit. Vertical variations in the orientations of sheathfolds are evidence that rheomorphism and welding can occur syn-depositionally. It has been disputed that the shear between the density current and the forming deposit is significant enough to cause all of the rheomorphic structures observed in ignimbrites, although the shear could be responsible for some of

2556-475: The deposition of ignimbrites from a pyroclastic density current: the en masse deposition and the progressive aggradation models. The en masse model was proposed by volcanologist Stephen Sparks in 1976. Sparks attributed the poor sorting in ignimbrites to laminar flows of very high particle concentration. Pyroclastic flows were envisioned as being similar to debris flows, with a body undergoing laminar flow and then stopping en masse . The flow would travel as

2627-424: The deposition of the Green Tuff has been disputed, suggesting that it is an ignimbrite, and structures such as imbricate fiamme , observed in the Green Tuff, were the result of late stage primary viscous flow. Similar structures observed on Gran Canaria had been interpreted as syn-depositional flow. Sheathfolds and other rheomorphic structures may be the result of a single stage of shear. Shear possibly occurred as

2698-409: The depositional process. Vertical chemical zonation in ignimbrites is interpreted as recording incremental changes in the deposition, and the zonation rarely correlates with flow unit boundaries and may occur within flow units. It has been posited that the chemical changes are recording progressive aggradation at the base of the flow from an eruption whose composition changes with time. For this to be so,

2769-453: The edges of the ancient Waikato River course which flowed through the valley before the last major Taupō eruption 1,800 years ago (the Hatepe eruption ). The west cliffs are quarried to get blocks of Hinuera Stone, the name given to welded ignimbrite used for building cladding. The stone is light grey with traces of green and is slightly porous. Huge deposits of ignimbrite form large parts of

2840-759: The end of the Waikato River Trails, via Cambridge and Hamilton to Ngāruawāhia. Completion was planned for 2017, but the Cambridge-Hamilton section opening was further delayed from 2021 and opened on 9 December 2022. North of AFFCO at Horotiu , the route includes the second longest cycle bridge in the country (after the Timber Trail ), a 140 m (150 yd) long cable network arch bridge, budgeted to cost $ 2.6m and to open in August, but opened in November 2017. The section from

2911-428: The falls is a set of small waterfalls dropping about eight metres. The final stage of the falls is a six-metre drop, raised to an effective 11 metre fall by the depth of the water. The falls are a popular tourist attraction, being close to Taupō and readily accessible from State Highway 1 . Waikato River The Waikato River is the longest river in New Zealand, running for 425 kilometres (264 mi) through

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2982-701: The form of many small streams on the eastern slopes of Mount Ruapehu . The Mangatoetoenui Glacier (once also 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. From the point where the river meets the Waihohonu Stream, down to Lake Taupō , it has been formally named

3053-567: The form of tension cracks and small scale thrusting, which is not seen in most ignimbrites. An adaptation of the en masse theory suggests that the ignimbrite records progressive aggradation from a sustained current and that the differences observed between ignimbrites and within an ignimbrite are the result of temporal changes to the nature of the flow that deposited it. Rheomorphic structures are only observed in high grade ignimbrites. There are two types of rheomorphic flow; post-depositional re-mobilization, and late stage viscous flow. While there

3124-701: The graves of the British military dead can be found at Rangiriri opposite the hotel, shops and cafe. The Waikato's first hydro-electric power station was the Horahora Power Station , now located under the Horahora bridge 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 dams and nine hydro-electric power stations that generate electricity for

3195-470: The highest flowing waterfalls in the world. The flow rate is regulated by Mercury NZ Ltd through the Taupō Control Gates as part of their hydro system planning, with Waikato Regional Council dictating flows during periods of downstream flooding in the Waikato River catchment. Mercury NZ have ability to control the flows between 50 cubic metres per second and 319 cubic metres per second. At the top of

3266-497: The hulk of the paddle steamer Rangiriri is preserved at Hamilton . In addition locally sourced barges were rebuilt with steel plating to carry troops and supplies. In support of these invasions, New Zealand developed its first "navy", the Waikato Flotilla , run by an Australian Francis Cadell who was presented with a gold watch and diamonds by the New Zealand government in recognition of his service. A cemetery containing

3337-484: The ignimbrites, like all felsic rocks, and the resultant mineralogy of phenocryst populations within them, is related mostly to the varying contents of sodium, potassium, calcium, the lesser amounts of iron and magnesium. Some rare ignimbrites are andesitic, and may even be formed from volatile saturated basalt , where the ignimbrite would have the geochemistry of a normal basalt. Large hot ignimbrites can create some form of hydrothermal activity as they tend to blanket

3408-451: The land surface. More rarely, clasts are cognate material from the magma chamber. If sufficiently hot when deposited, the particles in an ignimbrite may weld together, and the deposit is transformed into a 'welded ignimbrite' , made of eutaxitic lapilli-tuff . When this happens, the pumice lapilli commonly flatten, and these appear on rock surfaces as dark lens shapes, known as fiamme . Intensely welded ignimbrite may have glassy zones near

3479-576: The magmatism followed the end of the Laramide orogeny , when deformation and magmatism occurred far east of the plate boundary. Additional eruptions of ignimbrite continued in Nevada until roughly 14 million years ago. Individual eruptions were often enormous, sometimes up to thousands of cubic kilometres in volume, giving them a Volcanic Explosivity Index of 8, comparable to Yellowstone Caldera and Lake Toba eruptions. Successions of ignimbrites make up

3550-951: The minimum welding temperature to below the temperature of the glassy particles; this is secondary welding. This secondary welding is most common and suggests that the temperature of most pyroclastic density currents is below the softening point of the particles. The factor that determines whether an ignimbrite has primary welding, secondary welding or no welding is debated: Landscapes formed by erosion in hardened ignimbrite can be remarkably similar to those formed on granitic rocks . In Sierra de Lihuel Calel , La Pampa Province , Argentina, various landforms typical of granites can be observed in ignimbrite. These landforms are inselbergs , flared slopes , domes , nubbins , tors , tafonis and gnammas . In addition, just like in granite landscapes landforms in ignimbrites may be influenced by joint systems . Ignimbrites occur worldwide associated with many volcanic provinces having high-silica content magma and

3621-550: The national grid. These were constructed between 1929 and 1971 to meet growing demand for electricity. The power scheme begins at Lake Taupō, which has control gates to regulate the flow of water into the river. Once released through the gates it takes over 18 hours for the water to flow to the last power station at Karapiro. 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

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3692-500: The old course are seen clearly at Hinuera , where the cliffs mark the ancient river edges. The Waikato's main tributary is the Waipā River , which converges with it at Ngāruawāhia . The name Waikato comes from the Māori language and translates as flowing water . The Waikato River has spiritual meaning for various local Māori tribes , including the large Tainui , who regard it as

3763-601: The process the materials that made up this mixture fused together into a very tough rock of medium density. Ignimbrite also occurs in the Coromandel region of New Zealand , where the striking orange-brown ignimbrite cliffs form a distinctive feature of the landscape. The nearby Taupō Volcanic Zone is covered in extensive flat sheets of ignimbrite erupted from caldera volcanoes during the Pleistocene and Holocene. The exposed ignimbrite cliffs at Hinuera (Waikato) mark

3834-421: 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 (77 °F). These conditions mean that output of the older steam units can be restricted, especially on very hot summer days. In 2006, a cooling tower was installed. This allows one 250 MW unit to run at full load even during such times. After widescale droughts in 1994,

3905-500: The quartz polymorphs cristobalite and tridymite are usually found within the welded tuffs and breccias . In the majority of cases, it appears that these high-temperature polymorphs of quartz occurred post-eruption as part of an autogenic post-eruptive alteration in some metastable form. Thus although tridymite and cristobalite are common minerals in ignimbrites, they may not be primary magmatic minerals. Most ignimbrites are silicic, with generally over 65% SiO 2 . The chemistry of

3976-630: The resulting explosive eruptions. Ignimbrite occurs very commonly around the lower Hunter Region of the Australian state of New South Wales . The ignimbrite quarried in the Hunter region at locations such as Martins Creek, Brandy Hill, Seaham ( Boral ) and at abandoned quarry at Raymond Terrace is a volcanic sedimentation rock of Carboniferous age (280–345 million years). It had an extremely violent origin. This material built up to considerable depth and must have taken years to cool down completely. In

4047-580: The river between Taupō and Karapiro. All the lakes in this stretch of the river (apart from Lake Taupō) are artificial. The river leaves the Volcanic Plateau at Karapiro, where it emerges from the Maungatautari Gorge, and flows northwest into the Waikato Basin, flowing through the towns of Cambridge , Hamilton , and Ngāruawāhia . It is joined by its largest tributary, the Waipā River , at Ngāruawāhia. It then flows north through

4118-458: The river to Orakei Korako , from Hamilton Gardens to Mystery Creek and Fairfield Bridge and, since 2009, from Tuakau to Port Waikato . On 19 July 2021 a ferry service began on the river in Hamilton, linking Swarbrick's Landing and Braithwaite Park with the museum and gardens . Services ended with liquidation of the company in September 2022. Three trails follow parts of

4189-533: The river. Boosted by New Zealand Cycle Trail funding, the Waikato River Trails , a 100-kilometre (62 mi) series of connected river cycling trails in the South Waikato. The River Trail has five sections, open to both walkers or bikes, between Lake Karapiro and Aratiatia. It opened in 2011. Te Awa River Ride runs for 65 km (40 mi) following the river from Horahora, near

4260-995: The river. Jet skis are confined to the city margins because of their noise. Power boats regularly use the river, including manufacturers and boating shops testing and demonstrating boats, especially in summer. In addition there are numerous kayaks and a few waka. There are council boat ramps, run by Waikato District , Hamilton City, South Waikato District and Taupō District , at Port Waikato Rd; Hoods Landing Rd, Otaua; Elbow Rd, Aka aka; River Rd, Tuakau ; Riverbank Rd, Mercer ; Churchill East Rd, Rangiriri ; Ohinewai Landing Rd; Boatie Reserve SH1, Parry St and Riverview Rd, Huntly ; SH1 Taupiri ; Waikato Esplanade, Ngāruawāhia ; Farm and Braithwaite Parks, Pukete ; Swarbricks Landing, Hamilton Pde, Pine Beach, Ferrybank, Memorial Park , Roose Commerce Park, Hayes Paddock , Hamilton Gardens ; Narrows Lane, Tamahere ; Karapiro (6 ramps); Arapuni (4); Maraetai ; Whakamaru (3); Ohakuri and Mangakino . A ferry service along part of its length

4331-420: The silting is due to the construction of the many hydrodams. In its pre-1930s wild state, the silt was flushed from the river every winter by flood surges. The remnants of these can be seen in the silt channels carved out of what is now St Andrews golf course, adjacent to the river in Hamilton. Arsenic enters the river at concentrations that reach 0.035 grams of arsenic per cubic metre in places, exceeding

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4402-539: 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. Nine hydroelectric power stations at eight dams extract energy from

4473-661: The structures such as imbricate fiamme. Ignimbrite is primarily composed of a matrix of volcanic ash ( tephra ) which is composed of shards and fragments of volcanic glass, pumice fragments, and crystals. The crystal fragments are commonly blown apart by the explosive eruption. Most are phenocrysts that grew in the magma, but some may be exotic crystals such as xenocrysts , derived from other magmas, igneous rocks, or from country rock . The ash matrix typically contains varying amounts of pea- to cobble-sized rock fragments called lithic inclusions. They are mostly bits of older solidified volcanic debris entrained from conduit walls or from

4544-493: The town of Taupō in Tapuaeharuru Bay at the northeast end of the lake. It 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 kilometres (25 mi) 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

4615-468: The use of the Waikato River to supply drinking water for Auckland was first considered. In July 2002, a water treatment plant was opened at Tuakau , which was expanded in 2021 after major droughts in 2020. The lower Waikato is popular for duck shooting . The Waikato is renowned among whitewater kayaking enthusiasts, specifically for the Full James rapid located north of Taupō. The Full James

4686-479: The volcanic source, ignimbrites often contain thick accumulations of lithic blocks, and distally, many show meter-thick accumulations of rounded cobbles of pumice. Ignimbrites may be white, grey, pink, beige, brown, or black depending on their composition and density. Many pale ignimbrites are dacitic or rhyolitic . Darker-coloured ignimbrites may be densely welded volcanic glass or, less commonly, mafic in composition. Two main models have been proposed to explain

4757-474: The wet soil and bury watercourses and rivers. The water from such substrates will exit the ignimbrite blanket in fumaroles , geysers and the like, a process which may take several years, for example after the Novarupta tuff eruption. In the process of boiling off this water, the ignimbrite layer may become metasomatised (altered). This tends to form chimneys and pockets of kaolin -altered rock. Welding

4828-464: The world". Other introduced species, like the carp and mosquitofish , have become major pests. 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

4899-508: Was for years conducted by Caesar Roose , several of whose descendants still live beside it. He brought the 1894 400-passenger steamer Manuwai from the Whanganui in 1920. In 1924 a Cambridge to Port Waikato excursion was being run 2 or 3 times a year, taking 12 to 14 hours downstream and a few hours longer upstream; for example steamers in 1939 took about 90 minutes from Ngāruawāhia to Hamilton. Manuwai sank at her moorings in 1938, but

4970-573: Was taken to Mercer for repair in 1939, where she was converted to a barge. Several of the old steamers remain under, or beside the river, including the Manuwai , Rawhiti (built 1925) and Freetrader on the west bank just south of Mercer. A 1928 article listed 14 boats that had provided river services. To improve navigation, rocks in the Narrows at Tamahere were removed in 1919. Public cruises operate from Aratiatia to Huka Falls , across

5041-486: 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. The section of the river that flows through Hamilton has the most diverse river traffic with many schools and clubs using rowing skiffs. Rowing races are also held on

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