A Red Zone is where Environment Canterbury's assessment shows that the total amount of groundwater currently allocated exceeds the allocation limit.
A Yellow Zone is where Environment Canterbury's assessment shows that the total amount of groundwater currently allocated is 80% of the allocation limit.
A White Zone is where Environment Canterbury's assessment shows that the total amount of groundwater currently allocated is less than 80% of the allocation limit.
The groundwater allocation limit is determined principally on the basis of allocating up to 15% of the annual average rainfall for the time series of data available. This approach is of use when there is minimal information available. Additional sources of information may be included as outlined in Appendix F of the Groundwater Allocation Report (pdf 960 kB).
The groundwater allocation limit is determined on the basis of 50% of land \-surface recharge (e.g rainfall and irrigation) plus or minus estimates of net stream recharge. This approach is used when there is a moderate amount of information available.
Where there is a high level of hydrogeological knowledge, groundwater is allocated using specific sustainable-yield based calculations, and may involve groundwater modelling. When this approach is used, it is likely the current zones will be divided into sub-zones to take account of the more specific hydrogeological characteristics of these areas.
Groundwater recharge sourced from rainfall infiltrating into the ground.
Groundwater recharge sourced from irrigation water that has infiltrated pas the crop root zone. Such water may be sourced from external sources such as an irrigation scheme using river water or from groundwater pumped from bores.
Streams that do not flow along their entire length all year and often go dry in their middle to lower reaches (for example foothill streams) may contribute to groundwater and hence provide a recharge source. However where the flow in lower reaches is dependent on groundwater a contribution may need to be deducted from the groundwater resource to sustain the lowland flow.
The following are components that may be used to assess groundwater use (known as "effective allocation")
This report assumed that public and commercial/industrial users would use 100% of their consented daily volume over 365 days. Irrigation users were assumed to require an average of 60% of their consented volume over a 150 day period ("the 150 day method").
Where a consent has a seasonal/annual volume of water attached as a condition, 90% of this figure is used for irrigation and drinking water supply users.
Schedule WQN16 of Chapter 5: Water Quantity of the Natural Resources Regional Plan outlines assumptions to estimate an annual volume for consents that do not have a specific seasonal/annual volume allocation as a consent condition. Where an annual volume is assumed using Schedule WQN9, 85% of this figure is used for estimating the "effective allocation".
If a consent has actual metered use data, this can be taken into consideration to determine the effective allocation.
If a consent is hydraulically connected to a surface water body, a component of the total volume of water used will be included in the surface water allocation block. Assessing this volume will lead to reduced estimates of use in the groundwater allocation block where the river affected is a mountain or permanent hill river. Where the river is an intermittent hill river or lowland stream there is to be no reduction in the amount taken from the groundwater allocation block by the take. In this case the take is not considered to be capturing increased surface water recharge, and the total annual volume of the take is to be used to determine the effective allocation from the groundwater zone.
These groundwater reports may be used to provide a full description of groundwater resources in this area. They may include information that will be of use in a consent application, but are not necessarily a comprehensive list.
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