Risks of Coal Seam and Shale Gas Extraction on Groundwater and Aquifers in Eastern Australia

In the developed world there are growing concerns about water security due to the increase in exploration and production of coal seam and shale gas in peri-urban areas using both the hydraulic fracturing (fracking) technique of gas production and the method of extraction of naturally occurring groundwater by pumping it from coal formations to release coal seam gas (CSG). In Australia there is a competing prerequisite to maintain and increase the natural resource base as well as the need to protect and sustain the supply of potable and agricultural groundwater in peri-urban areas. One identified issue for this chapter is whether the increasing popularity of fracking in peri-urban and semi-rural areas in New South Wales (NSW) and Queensland poses a risk to the quality of groundwater supply as well as its contamination. The other main issue is whether the extraction of groundwater from coal seams where fracking is not needed has a major impact on groundwater depletion; and, if so, investigating the appropriate risk assessment and risk management approaches

Classification and comparison of natural and altered flow regimes to support an Australian trial of the Ecological Limits of Hydrologic Alteration framework

The Ecological Limits of Hydrologic Alteration (ELOHA) is a new framework designed to develop environmental flow prescriptions for many streams and rivers in a user-defined geographic region or jurisdiction. This study presents hydrologic classifications and comparisons of natural and altered flows in southeast Queensland, Australia, to support the ecological steps of a field trial of the ELOHA framework. We extended existing protocols for flow classification by assessing the stability of flow classes. Model-based clustering distinguished six Reference classes (based on modelled pre-development flow data) and five Historic classes (based on stream gauge data). The principal flow regime change was loss of some of the original (natural) flow diversity accompanied by the emergence of a perennial flow class in the Historic classification composed mostly of gauges with flow regimes influenced by dams. However, similarities between Reference and Historic classifications indicate that hydrologic changes in southeast Queensland have not totally obscured Reference (pre-development) characteristics. Duration of low flow spells has undergone the greatest absolute change from Reference values.\ud \ud Dams had substantial but variable impacts on downstream flow regimes. Each dam created a unique downstream flow signature, indicating that environmental flow guidance for each regulated river must be tailored to the particulars of flow alterations, the associated ecological impacts and the desired future ecological state of the aquatic ecosystem. Other stressors were implicated in flow regime change, highlighting the need to consider the potential influence of factors other than prominent water infrastructure on flow regime alterations and associated ecological responses

Driving mechanisms for groundwater flow and salt transport in a subterranean estuary

This paper presents field measurements and numerical simulations of groundwater dynamics in the intertidal zone of a sandy meso-tidal beach. The study, focusing on vertical hydraulic gradients and pore water salinities, reveals that tides and waves provide important forcing mechanisms for flow and salt transport in the nearshore aquifer. Such forcing, interacting with the beach morphology, enhances the exchange between the aquifer and ocean. The spatial and temporal variations of vertical hydraulic gradients demonstrate the complexity and dynamic nature of the processes and the extent of mixing between fresh groundwater and seawater in a subterranean estuary''. These results provide evidence of a potentially important reaction zone in the nearshore aquifer driven by oceanic oscillations. Land-derived contaminants may undergo important biogeochemical transformations in this zone prior to discharge