Our Ideas
Reliable irrigation would allow Hurunui’s community and farmland to become more sustainable as an agricultural district. While the Hurunui River carries a lot of water to the sea, low flows are common in summer restricting irrigation and impacting on productivity. Unless excess flows can be stored in winter and drawn upon in dry periods, Hurunui farmers will continue to struggle and the community will fail to thrive.
We are planning a community irrigation scheme with hydro power generation. The original, preferred sites are Lake Sumner and the South Branch of the Hurunui River. In 2011 we identified at third storage option based on the Waitohi River. More information on this developing option can be found here.
Our proposed scheme would irrigate approximately 42,000 hectares of land in the Hurunui and Upper Waipara catchments (see map top right). Land which may be irrigated includes the Hawarden area, Scargill Valley, North Waipara, Mason Flat and Omihi Valley. The project would also be able to boost irrigation currently supplied by the Amuri Irrigation Company's Balmoral Scheme, via the Hurunui River and areas adjacent to the Balmoral Scheme.
Original proposed storage sites:
Lake Sumner
Lake Sumner has a natural lake level variation of 3.2 metres. By installing a low, underwater control gate near the outlet, we propose to use half of this variability to hold back water for storage in the months prior to irrigation, and then let it return to normal variation in winter. The lake will be held at a height that is within its natural range, but at a slightly higher average than normal during summer months. It is important to note that the lake level will not be outside its normal operating range, which will still leave some beach uncovered, and most of the lake margins unchanged.
South Branch
The proposed dam in the South Branch is NOT in the main stem of the Hurunui River, allowing the vast majority of water to flow from source to sea in the North Branch. We propose to store 111 cubic metres of water in the South Branch reservoir which will effectively create a new 7km high country lake. The maximum dam height would be 75metres above the bottom of the gorge, but only 35metres of this will be seen above ground. The sides will be an earth dam construction and will be planted to reflect the vegetation of the area. Given the remoteness of the location (35km from the nearest village and 19km from the confluence with the main stem), the dam will be unobtrusive to all but a few high country trampers.
If we are able to hold back some (not all) of the freshes that flow through the Hurunui River in spring, we expect to keep flows at normal levels, and may even boost low flows in summer. As a result, Maori Gully will continue to see the full range of fluctuations in flow, and kayakers will still be able to enjoy their recreational pursuits.
|
.jpg){kind=small}
.jpg){kind=small}