Waitohi Irrigation and Hydro Scheme

NOTE: THIS MATERIAL, WHILE HISTORICAL, REMAINS AN ACCURATE DESCRIPTION OF THE SCHEME AT THE TIME IT WAS WRITTEN (2012).

Background

 

HWP proposes to establish a community irrigation scheme with hydro power generation.

An independent panel was initiated by the Hurunui-Waiau Zone Committee, Hurunui District Council and Environment Canterbury, in August 2011, to ensure whichever scheme was developed, it had the best possible outcomes for the Zone including the least environmental, cultural and recreational impact. HWP's Waitohi Scheme was endorsed in the resulting Waitohi Irrigation Scheme Selection Panel Report, over two competing developers. 

 

HWP's Waitohi scheme ranked the highest against the panel's own criteria, including environmental acceptability, consentability, the potential for hydroelectricity to offset costs, the price per hectare and the value of infrastructure, as well as the ability to proceed at the earliest possible opportunity. While all irrigation scheme options using the Waitohi Basin look expensive, HWP has concentrated on keeping capital costs low and reaching an energy-balanced solution that provides some future proofing around power pricing. By making the Waitohi Scheme affordable, HWP will fast-track water storage for irrigation to the Hurunui-Waiau area.  

 

In December 2011, the Waitohi Valley was chosen as an alternative storage site to the South Branch and Lake Sumner.

 

 

 

 

What will the proposed Scheme look like?

 

The scheme proposed includes four dams along the Upper Waitohi River as well as on-plains storage for distribution of water within the HWP command area. 

 

The proposal involves the abstraction of water from the Waitohi and Hurunui Rivers with storage planned within Waitohi catchment. Water will be pumped from the Hurunui River about 1.5kms below Surveyors Stream, up a rising main and through a short tunnel into a large reservoir at Hurricane Gully in the Waitohi catchment. Initial investigations show that this could hold live storage of around 210Mm3. There will be three further dams down the length of the Waitohi Gorge used primarily for re-regulation during power generation, as well as early stage, small scale storage for irrigation. The main intake canal from the Hurunui River will be situated on the plains somewhere between 305RL and 280RL with an upgrade to the Amuri intake. In total, the scheme will irrigate approximately 58,500ha and generate 82Gwh of power.

 

We believe that we've come up with a simple and cost-effective scheme which has environmental and economic benefits. The first stage of the scheme will irrigate up to 13,500ha to the east of the main canal plus 2,000ha on the North Bank and along the Waitohi River, with close to 60,000ha of potential irrigation over the long-term. 

 

Staging?

It is HWP's intention to develop the scheme in a staged approach. The first stage will be to build the three lower dams at Seven Hills, Inches Road and Lower Gorge for storage from the Waitohi, plus on-plain storage of 6.5Mm3 using Hurunui River water (location yet to be determined). Supplemented with run-of-river supply from the lower intake on the Hurunui River, this will irrigate a potential 15,500ha while providing additional reliability for some existing A Block users.