Considering the potential effect of faulting on regional-scale groundwater flow: an illustrative example from Australia’s Great Artesian Basin

Smerdon, Brian D.; Turnadge, Chris

Considering the potential effect of faulting on regional-scale groundwater flow: an illustrative example from Australia’s Great Artesian Basin | De l'effet potentiel de la fracturation sur l’écoulement régional des eaux souterraines : l’exemple illustratif du grand bassin artésien de l'Australie Consideración del efecto potencial del fallamiento sobre el flujo de agua subterránea a escala regional: un ejemplo ilustrativo de la Gran Cuenca Artesiana de Australia 断层作用对区域尺度地下水流的潜在影响: 澳大利亚大自流盆地的例证 Avaliação do provável efeito de falhas no fluxo regional das águas subterrâneas: um exemplo da Grande Bacia Artesiana, Austrália

2015

Smerdon, Brian D. | Turnadge, Chris

Hydraulic head measurements in the Great Artesian Basin (GAB), Australia, began in the early 20th century, and despite subsequent decades of data collection, a well-accepted smoothed potentiometric surface has continually assumed a contiguous aquifer system. Numerical modeling was used to produce alternative potentiometric surfaces for the Cadna-owie–Hooray aquifers with and without the effect of major faults. Where a fault created a vertical offset between the aquifers and was juxtaposed with an aquitard, it was assumed to act as a lateral barrier to flow. Results demonstrate notable differences in the central portion of the study area between potentiometric surfaces including faults and those without faults. Explicitly considering faults results in a 25–50 m difference where faults are perpendicular to the regional flow path, compared to disregarding faults. These potential barriers create semi-isolated compartments where lateral groundwater flow may be diminished or absent. Groundwater management in the GAB relies on maintaining certain hydraulic head conditions and, hence, a potentiometric surface. The presence of faulting has two implications for management: (1) a change in the inferred hydraulic heads (and associated fluxes) at the boundaries of regulatory jurisdictions; and (2) assessment of large-scale extractions occurring at different locations within the GAB.

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