The Waikato River is the longest in New Zealand and traces the backbone of the central North Island . Rising from the slopes of Mount Ruapehu in the Tongariro National Park as the Tongariro River , it flows northwards into Lake Taupo. Exiting the lake in the north-eastern corner, it gushes over the Huka Falls at a rate of nearly 300,000 litres per second through a narrow gorge. The Huka Falls are famous, not for their height, but for the speed and volume of gushing water. The Waikato River flows north-west to enter the Tasman Sea just south of Auckland . Totalling 425 kilometres, the river has a fairly gentle gradient, carrying ash from the volcanic plains out to sea. Overall, it drains water from 18,650 km2 or 12% of the total area of the North Island.
The Waikato's principal tributaries are the Waipa and Poutu. The river, which feeds eight power stations between Taupo and Karapiro, is a major source of hydroelectric power. The artificial lakes created by the power stations are popular recreation areas. The river takes its name from the Maori language and means "flowing water". It was the scene of many a conflict between the British and the Waikato tribes in the mid 1800s.