A comprehensive groundwater quality report for the entire Otago region was presented by the Otago Regional Council (ORC) science team to a meeting of the council’s data and information committee last week.

The report, which provides baseline information on a region-wide scale about the state of groundwater in Otago, found poor results in a number of areas.

“The results for groundwater quality vary widely across Otago, with degraded water quality particularly in parts of the Lower Clutha and North Otago areas, and better results for the Upper Clutha and Queenstown Lakes areas,” strategy, policy and science general manager Gwyneth Elsum said.

“The types of water quality issues also vary within the region, with E. coli accounting for the majority of poor results in the Lower Waitaki and Lower Taieri, nitrate concentrations being highest in North Otago and the Lower Clutha, and dissolved arsenic detected primarily in the Upper Clutha, Queenstown Lakes, and Central Otago areas – likely derived from schist in the underlying geology.”

Gywneth said E. coli results at bores in the Lower Taieri and Lower Waitaki areas were the biggest concern in the overall findings.

“When E. coli is detected at a monitoring site above national guidelines, ORC works with health authorities to notify anyone who may be using the bore for drinking water,” she said.

The report, which combines data and analysis from 54 bores since the start of monitoring, dating back in some cases over 30 years, provides a good foundation for ORC to benchmark changes in future, and to direct the efforts necessary to address groundwater quality issues, Gwyneth said.

“Having consolidated groundwater information on a regional scale means we can now make informed recommendations about how we address groundwater quality issues in Otago, and work with health authorities and local councils to provide public awareness of the responsibilities involved with private bores.”

The ORC plans to increase its communications to remind and educate the community on the importance of maintaining a secure bore head to prevent contaminants entering groundwater.

The ORC has a number of workstreams underway to address issues raised by the report, including improving consent conditions around bore security, and ramping up education work alongside local councils and health authorities. 

Gwyneth said in the medium-term the ORC will be replacing old SOE bores with new, dedicated monitoring bores at key sites throughout the region and looking at ways to strengthen controls on high-risk activities through the development of the Land and Water Regional Plan.

Advice for bore owners can be found here.