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 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 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 wars (see Invasion of Waikato) and the subsequent illegal confiscations of the 1860s, and are continuing negotiations with the current New Zealand government.
The river was of military significance in the land wars between British and Māori 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.
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 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.
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.
These include an unlined waste dump at Horotiu, just downriver from Hamilton, whose leachates include 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.