High Quality Content by WIKIPEDIA articles! The Wairakei River' or Wairakei Stream is a river of the Waikato Region of New Zealand's North Island. It flows southeast to meet the Waikato River, which it does at the town of Wairakei, 10 kilometres north of Taupo.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.