The spelling for the Manawatū-Whanganui region has been officially corrected. …
The change also means the regional council will be known as the Manawatū-Whanganui Regional Council, Horizons Regional Council is the trading name for the council.
The h in Whanganui has now been added to the spelling of the region, which is consistent with the views of local iwi and their dialect or mita.…
A macron or tohutō has been added to the u of Manawatū which has its origins in a waiata, Ka tatū e hine ko Manawatū, describing the search by ancestor, Haunui-a-Nanaia, for his wife.
He named the waterways on his quest and the waiata talks about how his heart (manawa) settled or momentarily stopped (tatū) when he saw the river. Manawatū is an amalgamation of those two words.
Source: Seal of approval for spelling of Manawatū-Whanganui region | RNZ News.