Mangatainoka River

Its headwaters are on the eastern side of the Tararua Range to the southwest of the town of Eketāhuna, and it roughly parallels the Wairarapa Line railway and State Highway 2 through the Tararua District before meeting the Tiraumea River just before its confluence with the Manawatu River just south of Woodville.

The railway's 162-metre (531 ft) bridge across the river between Newman and Hukanui is the longest on the entire line.

However, large-scale removal of the forest and drainage of the fertile land for agriculture has caused the river to flow faster, deepening its channel, heightening erosion, and encouraging it to meander to try to return to its slower pace.

[3] This has resulted in devastating floods, including one in October 2000 that caused at least NZ$200,000-300,000 of damage to the regional council's scheme to stabilise the river and rehabilitate its environment.

Approximately 50 kilometres (31 mi) of the river is fishable, and easily accessible, due to its proximity to State Highway 2 and major northern Wairarapa towns.