Appendix B: Assumptions and Parameters
The following assumptions and parameters were adopted in the study.
- Consented irrigated area: Consented irrigated area if not listed on the consent record was calculated from the weekly allocation divided by peak weekly crop water requirements for the crop type and region. Peak weekly crop water requirements were as per published values and modelling of irrigation water requirements. Publications and information sources on weekly and annual irrigation water requirements by region included the following:
- Auckland:
- Green S R, Mills T M, Clothier B E. 1996. A Review of Crop Water Requirements for the Auckland Region. A report prepared for Auckland Regional Council by HortResearch, Palmerston North.
- Aqualinc Research Ltd. 2004. Assessment of Water Harvesting in Franklin District. A report prepared for the Franklin Sustainability Group by Aqualinc Research Ltd, Hamilton.
- Bay of Plenty:
- Lincoln Environmental. 2003. Investigating Irrigation Efficiency in the Reporoa Basin. A report prepared for Environment Waikato by Lincoln Environmental, Hamilton.
- Canterbury:
- Lincoln Environment. 2002. Field Proven Irrigation Efficiency Benchmarks. A report prepared for the Ashburton-Lyndhurst Irrigation Society by Lincoln Environmental.
- Environment Canterbury. Proposed Natural Resources Regional Plan, Chapter 5 Water Quantity, Schedule WQN9.
- Manawatu-Wanganui:
- Aqualinc Research Ltd. 2004. Water Allocation Project. A report prepared for Horizons Regional Council by Aqualinc Research Ltd, Hamilton.
- Marlborough:
- Marlborough District Council, irrigation water requirements as listed in the council publication 'Fresh Water'.
- Otago:
- Aqualinc Research Ltd. 2005. Water Requirements for Irrigation Throughout the Otago Region. A report prepared for the Otago Regional Council by Aqualinc Research Ltd, Christchurch.
- Taranaki:
- Lincoln Environmental. 2003. Optimisation of Farm Irrigation. A report prepared for Taranaki Regional Council by Lincoln Environmental, Hamilton.
- Tasman:
- Tasman Resource Management Plan, Table 31.1D page 31. Tasman Regional Council.
- Waikato:
- Watt J, McIndoe I, Green S. 1998. Crop Water Requirements for Irrigation in the Waikato Region. Contract Report LC9798/021. Landcare Research, Hamilton.
- Environment Waikato, Regional Plan, Table 3.7: Estimated Irrigation Water Requirements for Pasture and Crops - Waikato Region.
- Auckland:
- Annual allocation: The allocation, if not listed on the consent record, was calculated as the weekly allocation times the number of weeks of supply per season (52, 50 and 16 weeks for drinking, industrial and irrigation use respectively). The 16 weeks for irrigation is equivalent to the total annual volume for crop type and region as per published information (as above) and modelled irrigation water requirements. For the Auckland region, all data is based on an annual allocation figure supplied by ARC.
- Weekly allocation is expressed as cubic metres per second (m3/s); this is the weekly allocation rate (m3/week) converted to an equivalent take rate of m3/s (ie, m3/week divided by 1.653 x 10-6 (ie, 7 x 24 x 3600)).
- Otago Regional Council mining water rights for irrigation: The determination of weekly allocation and consented irrigated area was based on advice from Otago Regional Council and regional assessment of irrigated area and cumulative take rates. The following approach was adopted:
- Weekly allocations are 60 percent of consented allocation rates (this value is based on the Otago Regional Council estimate of irrigated area and cumulative allocation rate).
- Annual allocations are based on an eight-week irrigation season. The rationale for the shorter supply season is due to the limitations of water availability.
- Consented irrigated area is calculated at an equivalent peak weekly demand of 400 m3/week. This value is based on the assumption that a high proportion of the takes are for flood irrigation.
