Rangitata River
The Rangitata is one of Canterbury's large braided alpine rivers. While it typically doesn't carry as much water as the Rakaia or Waitaki rivers, it has a long history of large-volume water abstraction.
Water abstracted from the Rangitata is used mainly for irrigation and electricity generation, as well as stock water and managed aquifer recharge.
The main source of water abstraction is through the Rangitata Diversion Race (RDR), which was built in the 1930s and 1940s. The RDR takes water from the Rangitata and feeds several networks of irrigation pipes and channels across the Ashburton district, as well as two hydroelectric plants, before discharging into the Rakaia.
The RDR and the irrigation schemes it provides water to have allowed for greater intensification of farming in the region using water from the Rangitata.
The river is also a significant salmon fishery and jet boating destination.
The Rangitata River Water Conservation Order
The Rangitata is the most recent of Canterbury's four Water Conservation Orders (WCO), and the only one which was applied for under the Resource Management Act 1991 (RMA).
New Zealand and Central South Island Fish and Game applied for the WCO in December 1999, and in 2000, the Ministry for the Environment appointed a special tribunal to hear the application.
The special tribunal report in 2002 recommended that an WCO be applied to the river with the following objectives:
- to preserve headwaters (Clyde and Havelock Rivers and their tributaries) as far as possible in their natural state, and to maintain the waters of the upper river and gorge by minimising abstraction and discharges;
- to maintain the mainstem of Rangitata River as a free-flowing river (prohibiting damming of the river);
- maintain a flow hydrograph as close as practical to the natural regime, including by retaining freshes and floods, setting minimum flows below which no abstraction is permitted, and minimising disturbances in the bed of the river;
- to maintain higher water quality and the mitigating ecological effects of large continuous abstraction;
- to protect salmon spawning waters and access to them.
Environment Court hearings were held in 2003 and 2004, and The Water Conservation (Rangitata River) Order 2006 was passed into law on 19 June 2006.
Minimum flow and the allocation regime
The WCO attempts to achieve these objectives in part by restricting when and how much water can be taken – not just in times of low flow. These restrictions are based on water flow measurement at Klondyke, near the Rangitata Gorge.
- During irrigation season, abstraction cannot lower the river flow to below the summer minimum flow of 20 cumecs.
- Over the winter (non-irrigation) season, abstraction cannot lower the river flow to below the winter minimum flow of 15 cumecs.
- The irrigation regime has three blocks. The minimum flows listed above apply to A block water, while B block water has a more strict minimum flow restriction of 40 cumecs in summer and 30 cumecs in winter, and C block water has a year-round minimum flow restriction of 110 cumecs. Some 95 per cent of the combined A and B allocation is taken through the RDR.
The Rangitata Water Balance model
In February 2025, we published an investigation into the impact of water use on the Rangitata.
The report modelled water abstraction on the river to give a better understanding of how the current water allocation and minimum flows impact the river.
Read the full report here:
Some of the report's major findings include:
- The largest water take is the Rangitata Diversion Race (RDR), which represents 56 percent of total consented allocation, and takes on average 90 percent of its available water. Unlike with other rivers, most of the water consented to be abstracted is taken from the Rangitata.
- The water conservation order does not place a cap on water abstraction during high river flows. This abstraction can limit the river's ability to carry sediment, and lead to more sedimentation in the lower reaches of the river.
- Unlike in the Rakaia and some of our other river systems, natural surface water losses to ground were found to be insignificant (within the eight percent margin of measurement error).
- All consents to take water issued since the water conservation order align with the minimum flow set in the Order, however, some older consents are similar but do not completely align with the Order.
- Climate change is affecting water volumes, with higher temperatures leading to decreasing glacier volumes, and more precipitation falling as rain as opposed to snow. It's projected that alongside fewer snow days, the catchment will also receive more winter rainfall. This would lead to an increase high flows over winter, and lower flows in summer and autumn.
Get in touch
For more information about the Rangitata River, the Rangitata River flow modelling report, or the Rangitata water conservation order, contact our Customer Advisory team by email or by calling 0800 324 636 and we can put you in touch with the water and land science team.
For any media enquiries please email us.