Water, water everywhere but is it sustainable?

Professor Malcolm Cox
Professor Malcolm Cox

While Brisbane is flush with underground water stores, more needs to be known about refill times to aquifers and the environmental effects of large-scale freshwater extraction to ensure their sustainable use.

Internationally recognised groundwater expert, UNESCO Professor Yongxin Xu is visiting Queensland University of Technology’s Institute for Sustainable Resources on Thursday to speak about the links between surface water and groundwater systems and how to model them.

QUT hydrogeologist Associate Professor Malcolm Cox said Professor Xu had developed models to assess the effect of changing rainfall patterns on the ability of groundwater systems to recharge.

He said Professor Xu’s work had many aspects that could be applied to South- East Queensland conditions to help understand how climate change was affecting our groundwater supplies.

“SEQ has a great variation in groundwater systems which need intensive study before it can be used with confidence as a long-term, sustainable resource,” Professor Cox said.

“Unlike Sydney, which is within a large basin of groundwater, we have groundwater stored in many different rock types with varying porosity and rates of recharge (refill times). Some of the SEQ groundwater may be thousands of years old, some might be only a few weeks.”

He urged caution in utilising South-East Queensland’s subsurface water supplies without fully understanding recharge times, how aquifer systems were linked and how they were connected to the surface.

“For example, The Lockyer Valley, which produces 30 per cent of Brisbane’s vegetables, has used its alluvial groundwater intensively for irrigation,” Professor Cox said.

“The alluvium (river gravel and sand) is not being recharged because rainfall has dropped. Normally it recharges very quickly from rainfall on mountains round the Valley.

Professor Cox said not enough was known about the environmental impact of extracting a lot of freshwater from the ground, especially in coastal areas.

“Stradbroke and Bribie islands, for example, are totally reliant on rainfall recharge for their groundwater supplies therefore groundwater extraction must be carefully monitored.”

Professor Cox said that in both these areas groundwater use must also consider potential problems such as the intrusion of saltwater to replace the fresh groundwater and the effects on ecosystems that rely on groundwater.

He said the Institute for Sustainable Resources had a key focus on water resources and was supporting a number of groundwater research projects in the region.

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