Change to Waipara groundwater zone available water
July 11, 2006
Change to Waipara groundwater zone’s available water
The Waipara groundwater zone has changed from a first order to a second order allocation limit, thanks to the completion of new research. This changes the way in which the amount of water available for allocation is calculated.
The first order limit was 16.8 million cubic metres per year, adopted in January 2004 and was based on 15 percent of the mean annual rainfall over the zone together with an estimate of the recharge contribution from streams in the zone. The adopted second order allocation limit for the Waipara groundwater zone is 7.8 million cubic metres per year, half the previous calculation.
The second order approach is based on the availability of additional or more accurate information than was available on adopting the first order approach. This research has recently been completed and incorporates estimates of annual average recharge from rainfall plus irrigation, together with the recharge contributed by streams. The allocation limit is set at 50 percent, or half of the sum of these two sources of water recharging to the ground.
This means that for this zone, the water now
thought to be available for allocation has decreased
dramatically. The predominant reason for the decrease is a
result of a detailed analysis of climate and soil data that
has shown a lower proportion of rainfall recharge,
approximately 52 percent less than the estimate on which the
first order limit was based.
In addition, a revision of the contribution to recharge from the intermittently flowing streams in the zone, as well as further analysis using data from more recent river gauging information, concludes that there is no net gain to groundwater from rivers and streams in the Waipara groundwater allocation zone.
The second order allocation limit of 7.8 million cubic metres per year replaces the first order allocation limit of 16.8 million cubic metres per year. The amount of water currently allocated for use from the Waipara groundwater zone sits at 7.3 million cubic metres per year and therefore the zone status changes to yellow (in other words, actual allocation is greater than 80 percent of water available for irrigation, but less than 100% of the allocation limit).
Environment Canterbury has water use consent applications for a further 1.57 million cubic metres per year which, if granted would take the zone status to red, or more than 100 per cent allocated. “Once consents for allocated water reach 100 percent of the new allocation limit, no further consents will be granted unless applicants can demonstrate to Environment Canterbury that more water is available and can be taken without having a detrimental effect on the environment,” said chief executive Dr Bryan Jenkins.