By: Christopher Cookson
The Omaka River is a small river rising in one of the southern valleys of the Wairau Plain that is a tributary of the Ōpaoa River. Originally, the Omaka flowed into the Ōpaoa in Blenheim, with a course that ran approximately parallel to what is now State Highway Six on Middle Renwick Road. Much of what is now known as the Taylor River where it flows through Blenheim was formerly part of the Omaka River, with the Taylor joining the Omaka as a tributary. Flood engineering works were undertaken that diverted the Omaka to its present course with its confluence with the Ōpaoa near Jacksons Road.
The Omaka River has its source in the mountains to the west of the Blairich and Black Birch Ranges, and flows north into the Waihopai Valley before turning east when it reaches the Wairau Plain. The lower Omaka is a highly modified environment with virtually no indigenous species in the riparian zone, however south of the Wairau Plain, the river flows through mānkua scrub before entering beech forest within the Ferny Gair Conservation Area.
There are bridges over the Omaka at Tyntesfield Road, Hawkesbury Road, and Middle Renwick Road/SH6.