Natural resources: Continent takes a big drink after 2011 floods

Beef Central, 14/05/2013


Devastating at the time, the major Eastern Australian floods of 2011 have since brought a vital benefit by recharging Australia’s depleted underground water reserves.

Scientists from Australia’s National Centre for Groundwater Research and Training say they have been impressed with recharge rates of groundwater following the 2011 floods in studies in Queensland and Victoria.

“Prior to the floods, water levels in Queensland’s Lockyer Valley were becoming perilously low in this prime agricultural region of southeast Queensland,” said Dr Matthias Raiber, research fellow at the NCGRT and Queensland University of Technology, and now with CSIRO.

“Although the response of groundwater was highly variable owing to the complexity of the Lockyer Valley, in some regions we saw levels rise as much as ten metres,” Dr Raiber said.

“This kind of response is overwhelmingly positive from the perspective of water availability in the region.”

As a dry continent without glaciers or large permanent lakes, groundwater is a critical resource for large parts of Australia, the NCGRT said in a press release.

Its importance is only likely to increase in a future where rainfall patterns are expected to become less predictable, while surface supplies may become ever more stressed due to competing pressures from evaporation, population growth, industry and agriculture.

The Lockyer Valley is a major food bowl for Queensland, with recent shire council figures showing that annual turnover for agriculture, forestry and fishing in the region was $230 million in 2010/11.

“Given the importance of our groundwater reserves, it is crucial that we better understand how our aquifers recharge and at what rate. Even within the Lockyer Valley, there are many different processes for recharge which depend on the hydrology and geology of a location,” Dr Raiber said.

“Using a variety of complementary techniques, we are building a picture of the ways in which groundwater reserves are replenished – something that has been ‘out-of-sight and out-of-mind’ for too long, especially given its importance in Australia’s past, present and future,” he said.


Similar pattern in northern Victoria

Another researcher at NCGRT, PhD candidate at LaTrobe University Sanjeeva Manamperi, is studying recharge rates in a different part of Australia, the Loddon River catchment in Northern Victoria. His results show a similar response followed the flooding in early 2011.

“In most places that I have examined, groundwater levels recovered by about seventy percent in early 2011. This is quite remarkable when you think that this region suffered a thirteen-year drought from 1997 to 2010,” Mr Manamperi said.

A smaller flooding event in 2010 improved the rate at which recharge could occur in 2011 because the surface layers were already saturated when the floods arrived.

“However it was the intensity of the rainfall during the 2011 event that resulted in such spectacular recharge of many of these aquifers. The large volume that accumulated in such a short period of time meant that recharge occurred immediately through fractures in the rocky regions, but also seeped through the soil in other areas.

“Obviously flooding events cause serious problems on the surface – but underground they help replenish stores of water that are running out. For the time being, the 2011 floods have taken the immediate pressure off water use in northern Victoria,” Mr Manamperi said.

“Nevertheless, we cannot be complacent in our conservation of water resources as the long-term availability of groundwater will depend on the frequency of flooding events in Australia, something that is difficult to predict.”

Researchers at the NCGRT are making estimates of Australian groundwater availability in the future based on what they are learning about the processes of recharge during floods. In doing so they hope to provide State and Federal water authorities with a clearer picture of the demands that can be sustainably placed on Australia’s underground reserves.

NCGRT director, Professor Craig Simmons, said most countries did not know the extent of their groundwater resources when they begin extracting them, or how long they take to recharge. Without this vital knowledge they could not be managed effectively.

“Reliable water supply is not only a fundamental element of economic prosperity for any country, but also vital for national security. Research being conducted at the NCGRT is therefore key in providing Australia with the know-how to sustainably exploit its precious underground reserves of fresh water, which are literally Australia’s ‘buried treasure’,” he said.

The National Centre for Groundwater Research and Training is an Australian Government initiative, supported by the Australian Research Council and the National Water Commission.




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