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Rangitata River

DOC/LEARNZ helicopter journey to the origins of the Rangitata River. See it’s spectacular origins and find out will happen to the river as the climate changes.

The Māori name ‘Rangitata’ (Rakitata) has been variously translated as ‘day of lowering clouds’, ‘close sky’, and ‘the side of the sky’. With a catchment area (click for interactive map) of 1,773 km2, the Rangitata River begins its journey from the Southern Alps at the confluence of the Clyde and Havelock Rivers, a region made famous because of its location of Edoras and Helm’s Deep in Lord of the Rings.

Before the Rangitata River enters the Canterbury Plains, part of it is diverted to the Rangitata Diversion Race (RDR) for irrigation and hydroelectric generation. Built between 1937 and 1944, the RDR supplies water to the Montalto and Highbank schemes before joining the Rakaia River. The Rangitata River passes through the Rangitata Gorge in the Alpine foothills, and flows southeast for 121km before entering Canterbury Bight 64km northeast of Timaru.

Towards its mouth, the river splits into two streams, forming the large (17km x 5km) lens-shaped delta island, Rangitata Island. 

Upper Rangitata River
Upper Rangitata River
Potts Rivers (in the foreground) is an upper tributary of the Rangitata River, looking up into the Havelock Valley with the Clyde Valley towards the right.
Potts Rivers (in the foreground) is an upper tributary of the Rangitata River, looking up into the Havelock Valley with the Clyde Valley towards the right.

Biodiversity & cultural significance

The Rangitata River is the border between two zone committees with two different Zone Implementation Programmes (ZIPs): Ashburton and Orari-Opihi.

Download the October 2019 report for DOC: Rangitata Catchment Values

Extract from the Ashburton Zone Implementation Program: ‘Water is precious and limited. It must be managed in ways that recognise and balance its importance for cultural, economic and recreational use, aesthetic and landscape values and biodiversity values – and delivers both individual and community good. We affirm and recognise tangata whenua and the value they place on mahinga kai, and the priority of available high quality sources of drinking water in rivers, waterways and aquifers. We also recognise the intrinsic value of aquatic ecosystems and river health (quality and flow), and the need to both prevent further decline and then restore wetlands and waterways. We know that to achieve all the targets of the CWMS within our zone it is necessary to strategically manage the water within our zone and provide opportunities to bring more water into the zone.’

Extract from the Orari-Opihi Zone Implementation Programme (ZIP): ‘The upper reaches of the Rakaia and Rangitata represent relatively weed free glacier fed catchments in almost pristine condition. Throughout their catchments, these rivers have outstanding fishery and habitat values… The Rangitata…provides outstanding habitat for many rare birds, fish, plants and other species, as well as a wide range of recreational values.’

Important Bird Areas on the Rangitata River: links to 6-page PDF file that includes maps, habitat types, and threats relevant to this river. This document was extracted from Forest & Bird’s 177-page 20Mb file on all rivers, lakes, and coastal areas.

Hakatere Conservation Park  straddles sections of the upper Rakaia and Rangitata Rivers, is part of one of the best wetlands in the country. A national wetland restoration project was started in 1997 and involves three premier sites: Whangamarino in Waikato, Awarua/Waituna in Southland and Ō Tū Wharekai here in Canterbury. The rivers, lakes, tarns and swamps of Ō Tū Wharekai have their own special range of species; some of which are rare, for example our kettle holes are home to 23 threatened plants. Although each wetland habitat is unique, all waterways are interconnected, breathing life into the Hakatere basin.

Tenehaun Conservation Area.

Conservation activities

The Rangitata River is one of ECan’s flagship biodiversity programmes.

The Implementation Strategy for the Braided River Flagship Programme – Upper Rakaia and Rangitata Rivers (2011), outlines the initiatives for both rivers.

Havelock River, looking upstream toward Forbes River confluence (part of the Upper Rangitata catchment ). Extensive matagouri provides good cover for wallabies and feral pigs (click the image to see the management plan).
Havelock River, looking upstream toward Forbes River confluence (part of the Upper Rangitata catchment ). Extensive matagouri provides good cover for wallabies and feral pigs (click the image to see the management plan).
Trap lines (blue) in the upper Rangitata River (click image for the full report).
Trap lines (blue) in the upper Rangitata River (click image for the full report).
Bennett’s wallaby, Forest Creek catchment; wallabies and feral pigs are considered the two most important invasive large animal species for immediate management in the upper Rangitata.
Bennett’s wallaby, Forest Creek catchment; wallabies and feral pigs are considered the two most important invasive large animal species for immediate management in the upper Rangitata.

Water flow & floods

Before Image After Image

Images sourced from the CanterburyMaps and partners and licensed for reuse under the CC BY 4.0 (link is external) licence.

“From the ground, it would have seemed like chaos; floods of water rampaging over the plains, damaging anything in its path. But from above, a different picture was emerging. Environment Canterbury (ECan) staff were photographing the floods from the air, later stitching together the images to create a mosaic of the event.

“It showed the floodwaters were following a predetermined pattern. The flood was itself a river, with twists and braids and tributaries, much like the Rangitata itself.

“A zombie river, long ago buried beneath asphalt and housing and irrigators, had been revived.” – The Rewilding Project / Stuff

The December 2019 flood peaked at 2270 cumecs, with a catchment rainfall of 875mm extending over seven days. As the flood was well beyond the design capacity of infrastructure, the outcome was, unexpectedly, considerable and very costly.

This highlights a key problem that river manager are now facing. NIWA has forescast  more frequent and larger floods as the climate change. All the research points to rivers being given more ‘room to move’ to accommodate these future floods. And yet the High Court has ruled that the legal width of a braided river is significantly less than previously defined.

References & research material