Waikato River - Course

Course

The river starts as many small streams on the eastern slopes of Mount Ruapehu. The Mangatoetoenui Glacier (once also called the Waikato Glacier) is one of the principal sources. The southernmost tributary is called the Upper Waikato Stream. The Waipakihi River joins the Waikato from the Kaimanawa Mountains to the west. From the point where the river meets the Waihohonu Stream, down to Lake Taupo, it has been formally named the Tongariro River since 1945.

The Pouto River joins from Lake Rotoaira to the east. The Tongariro flows northward, with State Highway 1 in parallel, through the town of Turangi, and into the southern side of Lake Taupo. Extensive engineering of lakes, tunnels and canals are used to generate hydroelectric power in the Tongariro Power Scheme.

The Waikato River flows out of Lake Taupo at the town of Taupo in Tapuaeharuru Bay at the northeast end of the lake. It flows northeast past the town, alongside State Highway 1, to the Huka Falls. State Highway 5 runs more or less parallel to the river as it flows further northeast. About 40 km from the lake, the river flows west and into the southern end of Lake Ohakuri. It exits from the northwest end of that lake and flows west through the small Lake Atiamuri and into the long east–west oriented Lake Whakamaru, with State Highway 30 following its course. It passes northwest through Lake Maraetai and Lake Waipapa, where it is joined by the Waipapa River, then north through Lake Arapuni and into Lake Karapiro. Pokaiwhenua Stream joins the river in Lake Karapiro. Nine hydroelectric power stations at eight dams extract energy from the river between Taupo and Karapiro. All the lakes in this stretch of the river (apart from Lake Taupo) are artificial.

The river leaves the Volcanic Plateau at Karapiro, where it emerges from the Maungatautari Gorge, and flows northwest into the Waikato Basin, flowing through the towns of Cambridge, Hamilton, and Ngaruawahia. It is joined by its largest tributary, the Waipa River, at Ngaruawahia. It then flows north through the Taupiri Gorge to enter the lower Waikato region. Further north is Huntly and then Meremere, where the Whangamarino and Maramarua Rivers join it. From Mercer, where the Mangatawhiri River joins it, the Waikato flows west and southwest. Just before its mouth at Port Waikato, the Araroa River joins from the north.

The mean discharge of the Waikato River is 340 m3 /s, with the highest flows typically occurring in July and August. Specific mean annual floods are low (60-70 L s-1 km-2), and the frequency of events with greater than 3 times the median flow is 0.4 events / year, due to flow regulation and groundwater storage in pumice.