Evaluation of geologic and geomorphologic influences on borehole productivity in crystalline bedrock aquifers of Limpopo Province, South Africa

Holland, Martin J.; Witthüser, K.

doi:10.1007/s10040-011-0730-5

Cited by 37 publications

(30 citation statements)

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“…Contact metamorphic rocks are intensively fractured through hydrothermal fracturing, increased brittleness, metasomatism, and cooling induced jointing [ Driesner , ; Ingebritsen et al , ] and exhibit a distinct brittleness contrast relative to the granite and the unaltered rock mass. Especially around young intrusions, permeability is enhanced [ Matter et al , ] and remnants may persist over Mio of years [ Achtziger‐Zupančič et al , ; Baudoin and Gay , ; Holland and Witthüser , ]. Marbles exhibit a steep slope due to high surficial permeabilities, probably resulting from (paleo) karst, and low permeabilities deeper underground, where dissolution of the otherwise low‐porosity rock is minimal.…”

Section: Discussionmentioning

confidence: 99%

“…The influence of lithology on crystalline rock permeability is controversial: some authors state that lithology has only minor influence on rock mass permeability [e.g., Davis and Turk, 1964;Winkler and Reichl, 2014]. However, at some sites, crystalline rocks show systematic variations of hydraulic properties as a function of mineralogical composition [e.g., Davies and Ó Dochartaigh, 2002;Gustafson and Krásný, 1994;Henriksen, 2008;Holland and Witthüser, 2011;Masset and Loew, 2010;Stober, 1995]. In addition, the formation, propagation, and sealing of fractures in crystalline rocks is lithology and rock texture dependent [Hoek and Diederichs, 2006;Hoek and Martin, 2014;Rawling et al, 2002;Wong and Zhu, 2013].…”

Section: Lithologymentioning

confidence: 99%

“…The latter mainly consist of high-grade gneisses and only rarely of granulites (20 measurements). Contact metamorphism includes the transformation of mica schist and gneisses to hornfels and was observed to influence fracture transmissivity [Achtziger-Zupan ci c et al, 2017;Holland and Witthüser, 2011].…”

Section: Lithologymentioning

confidence: 99%

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A new global database to improve predictions of permeability distribution in crystalline rocks at site scale

2017

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A comprehensive worldwide permeability data set has been compiled consisting of 29,000 in situ permeabilities from 221 publications and reports and delineating the permeability distribution in crystalline rocks into depths of 2000 meters below ground surface (mbgs). We analyze the influence of technical factors (measurement method, scale effects, preferential sampling, and hydraulic anisotropy) and geological factors (lithology, current stress regime, current seismotectonic activity, and long‐term tectonogeological history) on the permeability distribution with depth, by using regression analysis and k‐means clustering. The influence of preferential sampling and hydraulic anisotropy are negligible. A scale dependency is observed based on calculated rock test volumes equaling 0.6 orders of magnitude of permeability change per order of magnitude of rock volume tested. Based on the entire data set, permeability decreases as log(k) = −1.5 × log(z) − 16.3 with permeability k (m2) and positively increasing depth z (km), and depth is the main factor driving the permeability distribution. The permeability variance is about 2 orders of magnitude at all depths, presumably representing permeability variations around brittle fault zones. Permeability and specific yield/storage exhibit similar depth trends. While in the upper 200 mbgs fracture flow varies between confined and unconfined, we observe confined fracture and matrix flow below about 600 mbgs depth. The most important geological factors are current seismotectonic activity (determined by peak ground acceleration) and long‐term tectonogeological history (determined by geological province). The impact of lithology is less important. Based on the regression coefficients derived for all the geological key factors, permeability ranges of crystalline rocks at site scale can be predicted. First tests with independent data sets are promising.

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Section: Discussionmentioning

confidence: 99%

Section: Lithologymentioning

confidence: 99%

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A new global database to improve predictions of permeability distribution in crystalline rocks at site scale

2017

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“…Fault zones are characterized by an internal structural complexity (Bense et al, 2013;Caine et al, 1996) which control their capacity to drain or to act as barrier to groundwater flow. High permeable fault zones have been described at relatively great depth (>200 m) in the Armorican Massif Le Borgne et al, 2006;Leray et al, 2013;Roques, 2013;Roques et al, 2014) and in other crystalline basements (Holland and Witthüser, 2011;Mabee, 1999;Masset and Loew, 2010;Neves and Morales, 2006;Seebeck et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Groundwater sources and geochemical processes in a crystalline fault aquifer

Roques

Aquilina

Bour

et al. 2014

Journal of Hydrology

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International audienceThe origin of water flowing in faults and fractures at great depth is poorly known in crystalline media.This paper describes a field study designed to characterize the geochemical compartmentalization of adeep aquifer system constituted by a graben structure where a permeable fault zone was identified. Analysesof the major chemical elements, trace elements, dissolved gases and stable water isotopes reveal theorigin of dissolved components for each permeable domain and provide information on various watersources involved during different seasonal regimes. The geochemical response induced by performinga pumping test in the fault-zone is examined, in order to quantify mixing processes and contributionof different permeable domains to the flow. Reactive processes enhanced by the pumped fluxes are alsoidentified and discussed.The fault zone presents different geochemical responses related to changes in hydraulic regime. Theyare interpreted as different water sources related to various permeable structures within the aquifer.During the low water regime, results suggest mixing of recent water with a clear contribution of olderwater of inter-glacial origin (recharge temperature around 7 C), suggesting the involvement of watertrapped in a local low-permeability matrix domain or the contribution of large scale circulation loops.During the high water level period, due to inversion of the hydraulic gradient between the major permeablefault zone and its surrounding domains, modern water predominantly flows down to the deep bedrockand ensures recharge at a local scale within the graben.Pumping in a permeable fault zone induces hydraulic connections with storage-reservoirs. The overlaidregolith domain ensures part of the flow rate for long term pumping (around 20% in the present case).During late-time pumping, orthogonal fluxes coming from the fractured domains surrounding the majorfault zone are dominant. Storage in the connected fracture network within the graben structure mainlyensures the main part of the flow rate (80% in the present case). Reactive processes are induced by mixingof water from different sources and transfer conditions. A specific approach is applied to quantify thereaction rate involved along the pumping time. Autotrophic denitrification coupled with iron mineralsoxidation is highlighted and water rock interaction is clearly enhanced by the flux changes induced bypumping

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“…Botha and Van Rooy 2001; Dippenaar et al 2009;Holland and Witthüser 2011;Titus et al 2009;Witthüser et al 2010). However, as a critical component of understanding the hydrological cycle, one needs to consider the behaviour of earth materials in all aspects of the hydrological cycle, which includes not only saturated conditions, but also the vadose zone, aquicludes and barriers.…”

Section: Introductionmentioning

confidence: 99%

Review of engineering, hydrogeological and vadose zone hydrological aspects of the Lanseria Gneiss, Goudplaats-Hout River Gneiss and Nelspruit Suite Granite (South Africa)

Dippenaar

Rooy

2014

Journal of African Earth Sciences

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Three major basement granites of South Africa, viz. the Lanseria Gneiss of the Johannesburg Dome Granite, the Goudplaats-Hout River Gneiss and the Nelspruit Suite, are compared in terms of existing and new geotechnical and hydrogeological data.Typical weathering profiles based on landform and climate are deduced, denoting typical engineering and hydrogeological behaviour. Finally, the vadose zone behaviour of the basement granites are described with the aim on better understanding of the behaviour of these systems under variable saturation. Ephemeral hillslope wetlands, seepage lines and catenas are specifically addressed as associated hydrological influences, as well as the associated processes of translocation forming duplex soils and pedogenesis forming ferricrete. The final summarised findings depict low plasticity and expansiveness of granites with the most notable geotechnical influences being collapsibility, dispersive behaviour, seepage and difficult excavation. Hydrologically, secondary porosity prevails and younger structures or intrusions govern groundwater occurrence. The vadose zone comprises thick fractured rock to be included in modelling with the soil zone having saturated conductivity typically in the order of 1 x 10 -4 to 1 x 10 -5 m/d.

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Evaluation of geologic and geomorphologic influences on borehole productivity in crystalline bedrock aquifers of Limpopo Province, South Africa

Cited by 37 publications

References 34 publications

A new global database to improve predictions of permeability distribution in crystalline rocks at site scale

A new global database to improve predictions of permeability distribution in crystalline rocks at site scale

Groundwater sources and geochemical processes in a crystalline fault aquifer

Review of engineering, hydrogeological and vadose zone hydrological aspects of the Lanseria Gneiss, Goudplaats-Hout River Gneiss and Nelspruit Suite Granite (South Africa)

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