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The Perth metropolitan region is subsiding, research suggests

Media release

Groundwater extraction thought to be contributing to subsidence

Curtin University research indicates that large parts of the Perth Basin are subsiding due to groundwater extraction, which could make parts of Perth more vulnerable to the effects of rising sea levels.

Professor Will Featherstone and Dr Mick Filmer, from Curtin’s Institute for Geoscience Research (TIGeR) and the WA School of Mines Department of Spatial Sciences, completed the research as part of Australian Research Council grants issued to study subsidence in the Perth Basin, its effect on heights and how it impacts sea level change recorded by tide gauges.

The research aims to provide science-based information to planners and managers on coastal vulnerability, determine the land response to groundwater abstraction and highlight any effects on tidal gauge readings.

The study, recently published in the Journal of Geophysical Research – Oceans, uses a combination of different yet complementary datasets to show that the Fremantle tide gauge is, and has been, subsiding in a nonlinear way.

This means that the gauge, which is currently used to judge sea level rise, is sinking itself.

“Groundwater is removed for domestic and horticultural purposes. Due to low rainfalls, the water is being extracted faster than it is being replenished, which is causing the land to subside,” Professor Featherstone said.

“If the land is subsiding, then the rate of sea level rise measured by a tide gauge appears to be larger than it actually is, which seems to be the case at Fremantle.

“However this doesn’t mean that we are at a decreased risk of sea level rise, instead we could be at an increased risk, because the land itself is sinking.

“The research results highlight two important issues:  the need to inspect existing tide gauges to ensure they are measuring sea level change correctly; and the need for planners to consider measures to protect infrastructure from an increased sea level rise,” Professor Featherstone said.

Sea level changes are recorded by tide gauges placed in select areas, which use sensors to measure the level of water in reference to a set height marker on land.

Information collected by the tide gauges is generally used to predict the rate at which sea levels are changing in relation to the specific areas they measure.

The Institute for Geoscience Research (TIGeR) is located within the Western Australian School of Mines, Curtin University.

This research, led by Curtin, also included researchers from Newcastle University, United Kingdom and the National Oceanography Centre in Liverpool, United Kingdom.