3 Existing Irrigation System
3.1 SYSTEM DESCRIPTION
The irrigation system for this farm was designed and installed in 1984. Although details of the original system are sketchy, it is thought that the system was designed for two linear boom irrigators.
The irrigation mainline consists of a 155 mm diameter Class B PVC ring main with hydrants spaced at approximately 100 m in the centre of the paddocks. Water is supplied from a well located near the centre of the property. The layout of the paddocks and irrigation system is displayed in Figure 2.
Figure 2: Layout of farm irrigation system
At the time of the initial investigation (October 1997), the only irrigation machine in use was a Roto-Rainer Model 250, covering 300-550 m runs on 100 m lane spacings.
3.2 WATER SUPPLY
The system is supplied from a 300 mm diameter well located near the centre of the property. The well, drilled in February 1984, is 120 m deep. The static water level when the well was drilled was 96.0 m. A Ritz 6618/6 + 1228b/140/2 (140 kW) electric submersible pump is installed on a 111.4 m long 150 mm diameter galvanised pipe rising column. When supplying one irrigator, the pump has been throttled to about 135-165 m3/hour to protect the class B mainline from pressures greater than 600 kPa. However, the well has the capacity to supply a flow of up to 200 m3/hour. Operating at higher flows than 200 m3/hour would result in insufficient pressure in the mainline. In March 1988, the well was pump tested up to a flow of 258 m3/hour when there was 3.0 m of water above the pump.
3.3 WATER PERMIT
The current water permit, NCY890217, is to take up to 4158 m3/day at a maximum rate of 52 litres/second (187.2 m3/hour) for the spray irrigation of 100 ha of crops and seeds. If the water is taken at the maximum rate, irrigation could occur for up to 22.2 hours per day. The current water permit expires on 30 April 2001.
Contact for Enquiries
MAF Information Services
Pastoral House
25 The Terrace
PO Box 2526
Wellington, NEW ZEALAND
Fax: +64 4 894 0721
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