7 Summary and Conclusions
This case study identified the following characteristics of the irrigation system on this cropping farm:
- The irrigation system has insufficient capacity to meet peak crop water demands.
- To make allowance for the inadequate system capacity the Van der Klundert’s have adopted crops and planting dates within their cropping rotation to reduce the peak water requirement during the months of November to January.
- The existing irrigation equipment is not operating as efficiently as it could be.
- The well has additional capacity that could be used.
The preferred irrigation system upgrade consisted of the following features:
- Increasing the total system flow from 187 m3/hour to 220 m3/hour (i.e. 17%).
- Purchasing a hard hose boom irrigator to replace the side-roll irrigator. This would reduce the labour required to shift the irrigator between irrigation runs and give greater flexibility.
- Installing a booster pump at the top of the well to provide additional head for the increased system flow.
- Replacing the rising column at the well with a larger pipe size to reduce the headloss.
- Replacing the mainline in paddock A with a larger pipe size to reduce the headloss to the highest elevation hydrants.
- Running both irrigators on up to two 11-hour shifts per day. This would reduce the irrigation return interval and apply a smaller application depth more frequently to the irrigated area.
- A new water permit from the Canterbury Regional Council to cover the increased volume of water to be taken.
- An estimated capital cost of $66,500 + GST.
Information on the crop yields for the recent average to wetter years and the very dry 1997/98 year were obtained, together with the anticipated yields assuming the irrigation system upgrade was implemented. Gross margin figures for the various crops were obtained, and together with the yield information, used to calculate the anticipated financial benefits.
The increased financial benefits of upgrading the irrigation system were found to range from $7,220 + GST per annum for average to wetter years up to $46,530 + GST per annum for a very dry year.
This case study has demonstrated that improvements to the design of the cropping farm irrigation system are financially beneficial. It is anticipated that the increased financial benefits of upgrading the irrigation system would vary between $7,000 and $46,000 + GST depending on the seasonal rainfall.
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