The nature and distribution of flowing features in a weakly karstified porous limestone aquifer

Maurice, Louise; Atkinson, T. C.; Barker, John A.; Williams, A. T.; Gallagher, A.J.

doi:10.1016/j.jhydrol.2011.11.050

Cited by 43 publications

(26 citation statements)

References 36 publications

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“…However, in practice, a single isolated conduit is unlikely to persist over long distances in the Chalk. Instead, it is likely to form part of a dense connected network of different flowing features [32]. Therefore, catastrophic drift was likely to have been restricted to within tens of metres of the borehole.…”

Section: Discussionmentioning

confidence: 99%

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Using Boreholes as Windows into Groundwater Ecosystems

et al. 2013

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Groundwater ecosystems remain poorly understood yet may provide ecosystem services, make a unique contribution to biodiversity and contain useful bio-indicators of water quality. Little is known about ecosystem variability, the distribution of invertebrates within aquifers, or how representative boreholes are of aquifers. We addressed these issues using borehole imaging and single borehole dilution tests to identify three potential aquifer habitats (fractures, fissures or conduits) intercepted by two Chalk boreholes at different depths beneath the surface (34 to 98 m). These habitats were characterised by sampling the invertebrates, microbiology and hydrochemistry using a packer system to isolate them. Samples were taken with progressively increasing pumped volume to assess differences between borehole and aquifer communities. The study provides a new conceptual framework to infer the origin of water, invertebrates and microbes sampled from boreholes. It demonstrates that pumping 5 m3 at 0.4–1.8 l/sec was sufficient to entrain invertebrates from five to tens of metres into the aquifer during these packer tests. Invertebrates and bacteria were more abundant in the boreholes than in the aquifer, with associated water chemistry variations indicating that boreholes act as sites of enhanced biogeochemical cycling. There was some variability in invertebrate abundance and bacterial community structure between habitats, indicating ecological heterogeneity within the aquifer. However, invertebrates were captured in all aquifer samples, and bacterial abundance, major ion chemistry and dissolved oxygen remained similar. Therefore the study demonstrates that in the Chalk, ecosystems comprising bacteria and invertebrates extend from around the water table to 70 m below it. Hydrogeological techniques provide excellent scope for tackling outstanding questions in groundwater ecology, provided an appropriate conceptual hydrogeological understanding is applied.

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Section: Discussionmentioning

confidence: 99%

“…Packer testing was undertaken in two Chalk boreholes in which permeable features were identified during previous studies [25], [32], [33], [34]. In each borehole three potential aquifer habitats were selected at varied depths.…”

Section: Methodsmentioning

confidence: 99%

Using Boreholes as Windows into Groundwater Ecosystems

et al. 2013

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“…In the latter case, does it appear to be a parallel-plate fracture opened by tectonic processes or unloading, or has the fracture been enlarged by dissolution, resulting in an elliptical opening with a smooth perimeter (e.g. Maurice et al, 2012;Price et al, 1982;Schürch and Buckley, 2002)?…”

Section: Useful Test Methods For Understanding Flow and Transport In mentioning

confidence: 99%

“…This depicts two conceptual models for an aquifer in sedimentary rocks, with horizontal bedding planes and vertical joints. A 40 m deep pumping well draws most of the flow from open fractures spaced about 10 m apart, which is a common situation in bedrock aquifers (Buckley, 2000;Maurice et al, 2012;Paillet, 2004). In both cases there are sufficient intersecting fractures in three dimensions for a symmetrical drawdown cone to develop.…”

Section: Conceptual Models For Bedrock Aquifersmentioning

confidence: 99%

Diagnostic tests for conceptualizing transport in bedrock aquifers

Worthington¹

2015

Journal of Hydrology

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“…Borehole tools and measurements such as flow metering, packer testing, electrical conductivity, temperature, video and televiewer can reveal local preferential flow (Tate et al, 1970;Paillet, 2001;Maurice et al, 2012). Flow meter measurements often reveal that just a few horizons, spaced meters or tens of meters apart, account for most of the flow into boreholes in carbonate aquifers (Price et al, 1982;Schürch and Buckley, 2002).…”

Section: Preferential Flow Assessment and Modelmentioning

confidence: 99%