The
Waikato River is the longest river in New Zealand, running for through the
North Island. It rises in 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, and 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 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 Pairere, leaving the old Hinuera channel high and dry. The remains of the old river path can be clearly seen at
Hinuera where the cliffs mark the ancient river edges. The river's main tributary is the
Waipa River, which has its confluence with the Waikato at
Ngaruawahia.