Waiau-toa / Clarence
The Waiau-toa/Clarence Freshwater Management Unit (FMU) is 1,545 square kilometres in area and takes its name from the largest river in the area, the Waiau-toa/Clarence River. The FMU only covers part of the Waiau-toa/Clarence River’s 3,300-square-kilometre catchment, which traverses the Hurunui, Marlborough, and Kaikoura districts. The FMU is predominately mountainous terrain with the Boddington Range in the north and the Inland Kaikoura Range in the south—with peaks ranging from 1,145 metres to 2,149 metres. The FMU shares a northern boundary with the Wairau FMU, wraps around the western end of the Awatere FMU and shares a southern and western boundary with the Hurunui and Kaikoura.
Approximately 70 kilometres of the Waiau-toa/Clarence River’s 230-kilometre length is situated in the Marlborough region. The Acheron River, a major tributary of the Waiau-toa/Clarence River, and its tributaries dominate the northern half of the FMU. The Acheron River flows from the north-eastern point of the FMU, in a south to south-westerly direction, to join the Waiau-toa/Clarence River on the southwestern boundary of the FMU. At this point, the Waiau-toa/Clarence River flows into the FMU from the west then continues in a north-easterly direction becoming the south-eastern boundary line of the FMU. Here, the Dillon River is the longest northern tributary of the Waiau-toa/Clarence, while the Hossack River its most southerly tributary.
A large proportion of the Rangitahi/Molesworth station, New Zealand’s largest farm, is located within the Waiau-toa/Clarence FMU. The area has a long history of providing access routes between the West Coast, Nelson, Marlborough, and Canterbury regions. Passage across this mountainous region was found along the river valleys and through the open plains associated with the high plateau areas around Isolated Saddle and the Severn and Alma Rivers and Tarndale Brook, tributaries of the Acheron River. These areas also contain many of the lakes, tarns, and wetlands in the FMU.