Going underground to understand Australia's past climate variability

Posted 12 May 2015

Lead author, Monica Markowska.

University of New South Wales (UNSW), Australian Nuclear Science and Technology Organisation (ANSTO) and National Parks and Wildlife Service (NPWS) researchers working at Yarrangobilly Caves in the Australian Snowy Mountains have found new information from cave deposits that will help reconstruct past climates and groundwater recharge processes.

Given the importance of water in Australia, surprisingly little information is available about the variability of rainfall on this continent in the past. Although there is a good annual record dating back 100 years in Australia, there is nothing much before that period and no known cave deposit records exist for New South Wales.

The newly published research is investigating how to retrieve Australian rainfall records from the past 2000 years from cave deposits. Certain types of cave deposits, including stalagmites, are formed by mineral-rich water in underground caverns. They are important because they can be used to establish a record of past environmental changes, such as rainfall variability.

Understanding past climate can help predict the availability of water resources in the future.

Located in Kosciuszko National Park, the study site is in an important area because it is a source of water for the Murrumbidgee and Murray River systems, two major waterways in southeast Australia. The 440 million year old limestone deposits there contain a system of about 400 caves managed by the NPWS.

Lead author, UNSW Connected Waters Intiative (CWI) and Institute for Environmental Research scientist Monika Markowska and colleagues, have been monitoring dripping water in the cave system, from which stalagmites form, for fifteen months.

“Monitoring the water movement from the surface into the cave is important because this water carries the majority of information about climatic and environmental conditions at the surface,” said Professor Andy Baker of the UNSW CWI, a co-author on the paper.

The research identified the significance of the role of soil moisture content in the formation of stalagmites and the climatic records they contain.

“While rainfall is an essential source of the drip-water that forms stalagmites, at Harrie Wood Cave it was the degree to which soil was saturated with moisture that controlled whether water from individual rainfall events reached the cave system where they could be recorded by the formation of stalagmites” said Markowska.

The research team came to this conclusion after a detailed analysis of drip-waters recorded at 15-minute intervals within the Harrie Wood Cave, along with weather data from the surface above the cave. By monitoring drip rates, researchers determined how long it took the water to get into the cave. They also monitored precipitation, temperature, barometric pressure and soil moisture.

In the cave, dripping water was automatically recorded using Stalagmate® drip logger devices. Drips are recorded by measuring the vibration caused each time a water droplet hit the surface of the miniature drum-like detectors. The data reported in the paper are from 14 sites forming part of a network of fifty devices throughout the cave, one of the largest such studies in the world. Interpreting the data provided by the Stalagmate® loggers provided a unique way to understand water flow from the surface to the cave.

The researchers identified five different types of drip water responses to surface conditions and were surprised to see different flow patterns in drips in close proximity to each other.

The five types of response are due to the many possible flow paths of water from the surface to the cave. Before reaching the cave, water may be stored in the soil, as well as in fractures and solution pockets in the limestone.

Most importantly, the research demonstrates that cave deposits can have very individual relationships to the surface climate due to the specific water flow route.

This information has allowed researchers to identify which speleothems can be used to obtain a rainfall record for the past 2000 years.

The research has been published in the Journal of Hydrology.

Source: ANSTO.

Links:

Latest news

Spotlight on mining and water with Dr Wendy Timms

Spotlight on mining and water with Dr Wendy Timms

10 November 2017

Dr Wendy Timms talks about her many hats and why diversity is critical in sustainable mining practice.

Read more…

Groundwater ‘pit stops’ enabled survival and migration of our ancient ancestors

Groundwater ‘pit stops’ enabled survival and migration of our ancient ancestors

1 June 2017

African groundwater helped kick-start the evolutionary history of humans, with the movement of our ancestors across East Africa shaped by the location of springs, new research suggests.

Read more…

CWI team member gives keynote address at Water Institute for Sustainability Forum in Thailand

CWI team member gives keynote address at Water Institute for Sustainability Forum in Thailand

9 February 2017

Connected Waters Initiative research fellow Dr Landon Halloran was a keynote speaker at the Water Institute for Sustainability Forum in Bangkok, Thailand in January 2017.

Read more…

CWI team member appointed to mining industry advisory panel

CWI team member appointed to mining industry advisory panel

3 November 2016

Dr Wendy Timms was recently appointed to the Independent Expert Scientific Committee on Coal Seam Gas and Large Coal Mining Development (IESC).

Read more…

CWI at IAH 2016

CWI at IAH 2016

6 October 2016

CWI team members presented their research at the recent 43rd annual congress Hydrogeology Congress in Montpellier, France.

Read more…