Macadamia Orchard Micro Irrigation
Canina, Queensland, Australia – Honor Award, Planning & Analysis
Jim Phillips, JP Water P/L
- 25 year old existing Macadamia Orchard with existing irrigation system.
- Current system was inoperable and, had it been, would have had significant pressure and flow variations.
- The property is steeply undulating with contours ranging from 100 to 160 meters.
- The macadamia rows run down the slopes at 90 degrees to the contour lines.
- The soil tends toward red volcanic with a tendency to erode if left without ground cover or mulch.
- Water supply for the orchard is a 30 megaliter dam situated centrally on the property and approximately in the middle contour range.
ROLE OF THE IRRIGATION CONSULTANT
Our role in this project spanned a period of nearly 12 months. As the limitations were confirmed, the cost of the system and the design needs grew. Our scope of services eventually encapsulated the following:
- Calculation of the Peak Irrigation Requirement.
- Sprinkler flow rate and spacing recommendations based on the outcome of the PIR calculations and soil considerations.
- Hydraulic design works. In this the use of the 10mm LDPE pipe was calculated and discussed on site with the client. This is a difficult LDPE pipe size to source and the decision to utilize it was not taken lightly.
- Recommendations as to fertigation and the location of Zone fertigation point as distinct from centralized fertigation. Given the high heads involved and the travel time for fertilizer from the central pump site, it was decided that the local zone system was the best.
- Advice on installed zone headworks, mainline thrust blocking, filter installation and pump shed dimensions.
- Detailed Bill of Materials and suitable suppliers.
- Vetting of tenders for supply and responding to Requests for Information from suppliers. Here the supply of the 10mm LDPE again proved contentious.
- Site visits as the project developed and was commissioned.
- The steep country, the limited availability of water and financial concerns.
- The nature of harvesting the macadamia nuts by sweeping the fallen nuts from under the trees means that, for the 3 month long harvesting period, the ground below the tree out to the drip line is swept bare.
- On this steep topography the irrigation application rate must be high enough to meet the PIR cyclical window but not too high to cause run-off and erosion.
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March 29, 2020
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