Waikato River
The Waikato River is the longest river in New Zealand, running for through 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 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 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 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 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. Origin The ancestral Waikato River flowed from an ancient lake (Lake Huka) in 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 a thickness of . A new lake was formed – Lake Taupō. The water accumulated until a new outlet was forced 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 as about of water and debris poured out in a catastrophic breakthrough flood causing the river to change course near Piarere.