6 Water Use
The following subsections present the analysis of water use. It should be noted the analysis is presented in a variety of timeframes and scales. This reflects the periods and scale of data submitted by the councils. They show there is considerable seasonal and annual variability in water use.
6.1 Auckland Regional Council
Auckland Regional Council requires all consented water takes be fitted with a water measuring device. Approximately 90 percent of consent holders make water use returns every quarter, and approximately 4 percent of consent holders fail to make a return annually.
Figure 6.1 shows comparison of annual water allocation and actual use for the Auckland Region past three years. This shows that region's annual use ranged from 78 percent up to 90 percent of allocation.
Figure 6.1: Water allocation and use in Auckland Region
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figure at its full size (including the text description).
6.2 Environment Southland
Figure 6.2 is reproduced from the Environment Southland water quantity report card (ES, 2005). As listed, it shows actual use versus allocations for nine consents. The report does not indicate details on the type of water use for the consents, however, it does show low levels of use with all the consents being less than 20 percent of allocation.
Figure 6.2: Environment Southland assessment of water use
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figure at its full size (including the text description).
6.3 Horizons Regional Council (Manawatu-Wanganui Regional Council)
Horizons provided information on metering and water use for the Rangitikei and Upper Manawatu Rivers. In 2003, the Council established a metering telemetry trial in the upper Manawatu. As of July 2005, 10 telemetry units had been installed on 24 of the consents required to meter use within the study zone.
The assessment of water use as a proportion of allocation in the Rangitikei and Upper Manawatu showed a wide variation between consents. Water use for municipal water supplies to several towns was typically up to a maximum of 60 percent of daily allocations (Marton, Halcombe and Ohakea). However, water use for rural water takes was more variable both in daily use and frequency of use, ranging from less than 20 percent to more than 100 percent.
6.4 Marlborough District Council
Figure 6.3 shows use for 11 consecutive seasons from 1995-2006. Note the allocation is based on an irrigated area of 820 ha and annual demand for grapes of 155 mm. The analysis is based on annual use versus calculated annual allocation. As shown, peak use occurred in the 2000-2001 season at 70 percent but on average over the period is 36 percent.
Figure 6.3: Water use Southern Valley aquifer
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figure at its full size (including the text description).
6.5 Otago Regional Council
Otago Regional Council has a monitoring programme for 31 consents in the Kakanui catchment. Annual records for the 2005-2006 season were submitted for this study. Analysis of 21 of the consents indicates average use is just over 50 percent of allocation. However, there appear to be a number of anomalies in the analysis with several consents in excess of 200 percent.
6.6 Taranaki Regional Council
Taranaki Regional Council monitors irrigation takes in the region. Virtually all of the takes are for irrigation of pasture for dairy farming. Water use for the takes for the 2003-2004 and 2004-2005 seasons are presented in annual technical reports (TRC, 2005 and 2006). The analysis of annual use shows that on average it is close to 70 percent of allocation but varies between consents from less than 20 percent to more than 120 percent. Figure 6.4 shows use as percent of annual allocation for 20 of the consents with records for both seasons.
Figure 6.4: Taranaki Regional Council irrigation consents
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figure at its full size (including the text description).
6.7 Tasman District Council
Figures 6.5 to 6.7 present the analysis of water use as a percent of allocation on a weekly basis for three groundwater zones for three irrigation seasons (2000-2001, 2003-2004 and 2005-2006). Use varied within and between seasons for the three zones. Weekly use was up to 80 percent of allocation but at times was as low as 20 percent.
Figure 6.5: Water use for Motueka Hau zone
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figure at its full size (including the text description).
Figure 6.6: Water use Waimea Plains - lower confined aquifer
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figure at its full size (including the text description).
Figure 6.7: Water use Waimea-Waimea west zone - unconfined aquifer
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figure at its full size (including the text description).
Virtually all of the above examples of water use versus allocation are for irrigation water use. They show similar trends in terms of variability in use, that is low use on the irrigation season margins (early and late season) and considerable variations between seasons. This is be expected as allocations are generally issued as a fixed peak take rate intended to provide a high level of supply reliability while demand varies according to climate, crop type and growth stage. On a catchment or groundwater zone, maximum use is up to 80 percent of allocation during periods or seasons of high demand. However, it is on average generally around 50-60 percent of allocation.
