Omaha groundwater risks potential for over use

The ARC will not grant any new groundwater allocations from the Omaha aquifer and will start talks with Omaha’s water users in Rodney to ensure water use stays within a sustainable limit.

The ARC’s Environmental Management Committee meeting on 4 June committed to an action plan that includes community involvement in seeking a solution to ensure the safety of the water supply to all existing users.

“The ARC has a responsibility under the Resource Management Act to safeguard the groundwater supply for existing users,” said ARC Environmental Management Committee chairman, Brian Smith.

There is a finite quantity of water that can be allocated each year, determined by recharge to the aquifer from rainfall. If too much water is taken and the aquifer level lowered, salt water could flow into the aquifer and pollute all of the water source.

The action plan arises from continued monitoring of the aquifer, which has provided information indicating that the current volume of water available each year, 105,000m3, is currently over-allocated by 14%.

“Although the allocations exceed what is available, there are a lot of people who are not using their full allocations, and we need to rationalise this to ensure that the overall allocation ties in with what is actually available,” said Cr Smith.

“We want to talk to water users about what practical approaches can be taken to ensure the amount of water taken stays within the sustainable limit,” added ARC Water Resources Manager, Ken Becker.

“We will need to review existing allocations and to ensure that the most efficient practices for water usage are in place,” said Mr Becker.

“It will be necessary to cease any new allocations to any potential users and we will be talking to the Rodney District Council about the implications for development in the area.”

The Omaha community has long known of concerns about the annual recharge of the aquifer. In the early 1990s, restrictions were imposed on the amount of water allocated to horticultural and market garden users. This led to a reduction in use and a recovery of the aquifer.

Since 1995 the level of rainfall generally has been higher than average and this has resulted in less water being used than allocated. A dry year could see a change in this situation.

Groundwater in the Omaha Flats, Point Wells area is used for domestic purposes (the area is not on reticulated supply), for stock on lifestyle properties, for dairy farms, for horticulture and market gardening and some community type facilities such as a golf course, bowling greens, and public toilets at Omaha.

The amount of water required is divided between 16,000m3/year for domestic and lifestyle properties, 36,000m3/year for dairy farms and 68,000 m3/year for horticulture and other purposes. This total of 120,000m3/year is 14% above ARC’s latest calculations that show that 105,000m3 water is currently available each year.

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