2013 – Design of Waimakariri irrigation storage ponds

Nigel Connell, Karina Dahl, Steve Agnew and Brent Walton

The Waimakariri Irrigation scheme was initially built from 1997 to 2001 and irrigates approximately 18,000 hectares in North Canterbury with canals between the Waimakariri and Ashely Rivers. This was an enlargement from an existing stockwater scheme originally constructed in 1890. The owner and operator of the scheme, Waimakariri Irrigation Ltd, propose to construct a storage pond to supplement irrigation supply when take is restricted due to low flow in the Waimakariri River.
The footprint of the proposed pond is approximately 1 km x 1 km, with maximum dam height of 12 m and an 8.2 Mm3 maximum storage capacity. Accommodation for hydro-power development has been incorporated into the design of the irrigation storage ponds to provide multiple use of the reservoir contents.
The embankments are to be constructed from on-site granular material that forms the Canterbury Plains and lined with geomembrane. Careful consideration has been given in the seismic design for this High Potential Impact Classification (PIC) structure, which takes into account lessons from recent major earthquakes in the Canterbury Region. In addition, an understanding of the rapidly growing community downstream of the proposed dam has been crucial to ensuring that the potential risk of the dam is managed appropriately.

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