Irrigation


Rakhine, Myanmar - Winter Crop Project

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Assistance with an irrigation development programme on behalf of MFAT, where key issues facing crop farmers include challenging climate effects on local agriculture and consequent economy. The project included the goal of constructing up to five gravity irrigation schemes and eight smaller pump schemes. Site surveys of the proposed dam sites were undertaken, the feasibility of which was assessed by back-solving the required demand and comparing it with the cost of the five storage opportunities. This eliminated two sites. Previously constructed schemes were often abandoned or dug up and sold for parts when a failure occurred that the farmers were unable to fix. This highlighted that engineering input would need to diverge from normal practice to accommodate the goals of development work. The long-term success of these irrigation schemes relies on local farming communities operating and maintaining the infrastructure over its lifespan without dependence on western input, therefore, our scope shifted from directly designing dams and distribution, to assisting a local engineer to deliver a solution and install local expertise to ensure the project’s future. Construction has yet to commence.


Barrhill Chertsey Irrigation

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Barrhill Chertsey Irrigation delivers approximately 5m3/s of Rakaia River water to the Rangitata Diversion Race at Highbank power station.  During the irrigation season, water backflows from the station to the Methven check gates.  A small portion of the flow is utilised in the Barrhill Chertsey area for irrigation, the remainder is conveyed to the Ashburton Lyndhurst Irrigation Scheme for a water swap to enable new irrigation intakes.   Development options were reviewed and a preliminary design proposed, which included five siphon intakes and storage ponds, and new infrastructure at Methven check gates to enable water swap (concrete culverts, gates, canals).  


Rangitata Diversion Race

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A variety of civil, geotechnical, and hydraulic engineering services have been provided for the Rangitata Diversion Race since 2001.  Projects include numerous offtake siphons; new river intakes and fish screens; and designs for sediment basins, canal raising, and offline storage.  Repairs to river armouring at the North Ashburton River siphon, and hydraulic water balances to check for seepage and leaks are amongst a number of investigations undertaken.

 

Central Plains Water Repair Works

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In July 2017, Canterbury was subjected to adverse weather conditions that inflicted significant damage on more than 60 sites along the 16.7km Central Plains Water (CPW) canal. Damage included washed-out bridge abutments, landslides, and direct damage to the canal liner and crest anchors. CPW was faced with the challenge of repairing the canal within three months to meet the approaching irrigation season. In collaboration with contractors and the client, RILEY provided technical support for the full scope of repair works, allowing contractors to maintain the demanding repair pace. CPW met the irrigation season with a fully functional canal.

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Hurunui Water Project

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The Hurunui Water Project proposes to irrigate land in the Amuri Basin, Omihi district, and Scargill.  Involved with the project since 2002, RILEY has:

  • Developed conceptual and feasibility designs for several scheme options to irrigate up to 60,000ha of land using intake from the Hurunui River and water storage provided by a Hurunui Plains reservoir, and damming the Waitohi River.
  • Undertaken canal design and optimisation from the river intake to on-plains storage; the design of dams of various heights at four sites along the Waitohi River storing up to 260Mm3 of water; the design of several pressurised water distribution network options; and associated site visits, geological mapping, and investigation. hydrological studies and dam break assessments.
  • Prepared material for the successful resource consent and upgrading of HWP shareholder records into a spatial GIS database for demand mapping.
   

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