Scientists delve into South Dunedin

University of Otago lecturer Sarah Mager (left), masters student Sarah Yeo and GNS Science structural geologist Simon Cox test the water beneath South Dunedin. Photo: Peter McIntosh
University of Otago lecturer Sarah Mager (left), masters student Sarah Yeo and GNS Science structural geologist Simon Cox test the water beneath South Dunedin. Photo: Peter McIntosh
Scientists are busy searching the ground beneath South Dunedin, but it will be a while before the data presents a clear picture about the area's future.

GNS Science is involved with several projects and collaborations assessing the impact of sea-level rise in South Dunedin.

Some preliminary results were presented at a recent community hui in South Dunedin, but scientists say much more work is needed.

As part of a drilling project the company is, alongside the Otago Regional Council and University of Otago geology department, analysing the nature and depth of the sediment underneath the surface.

GNS Principal Scientist Simon Cox said the bedrock was found to be much shallower than expected, based on geophysical soundings.

However, it would take work over the next 12 months to fully understand exactly what that meant for groundwater and seismic issues.

The company was also using piezometers to assess how groundwater levels increased and subsided.

With the university's geography department, including lecturer Dr Sarah Mager and masters student Sarah Yeo, it was collecting water from bores across the area and analysing its chemistry.

The mix of salt and fresh water under different parts of South Dunedin would make clearer where groundwater came from and flowed to.

''This will be used to model what will happen when sea level rises.''

GNS and the Dunedin City Council have also started to evaluate the relationships between sewer and stormwater pipe networks the degree to which they control the level of groundwater, and how this changes in different tides and storms.

A full range of seasonal records was needed, so many of these projects would take years to complete.

Dr Cox said the subsurface of South Dunedin was important because a lot was at stake.

''We need a lot more background information ... In the past we just occupied the land without doing the amount of subsurface work that would be required for modern-day development.''

jono.edwards@odt.co.nz

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