When Hau reached what is now known as the Manawatū River, he is said to have stopped and clutched his chest, horrified at the prospect of crossing so mighty an expanse of water.

[1] The Manawatū River has its headwaters northwest of Norsewood in the Tararua District, on the eastern slopes of the Ruahine Range on the North Island of New Zealand.

[2] Beyond the gorge it joins with the Pohangina River at Ashhurst and turns south-west, flowing through the city of Palmerston North.

After Opiki, it slows and has a lower gradient, meandering over the Manawatu Plains; its bed at this point is mud and silty sand.

[2] The Manawatū reaches the Tasman Sea at Foxton Beach, on the west coast of the North Island, creating the Manawatu Estuary.

During glacial times, with the prevalence of ice, snow, and bare mountains, this erosion increases and forms a stony elevated terrace.

[2] The Manawatū Plain was seabed 5 to 6 million years ago, and as it was raised above water by the action of the Australian and Pacific Plates it buckled, forming five long and low ridges (or anticlines) parallel to the mountains, which impede the flow of the Manawatū, Rangitikei, and Oroua Rivers, forcing them to flow southwest rather than directly into the Tasman Sea.

[9] Across the flood plain of the Manawatū and on the low-lying land bordering the river, the predominant vegetation was semi-swamp forest, mostly kahikatea and pukatea.

Results showed that water quality for sediment and E. coli had improved over the previous seven to ten years in the Manawatū-Whanganui region.

Using those measures, they found only four other New Zealand rivers rate worse than the Manawatū (the Waitara, Whanganui, Waipā and Rangitīkei).