The Role of Dissolution Kinetics in the Development of Karst Aquifers in Limestone: A Model Simulation of Karst Evolution

Dreybrodt, Wolfgang

doi:10.1086/629431

Cited by 175 publications

(186 citation statements)

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“…Here Dreybrodt [1990] and Palmer [1991] have shown that for a fracture approximated by a channel or a pipe with prescribed geometry and fixed pressure drop across the fracture, it is important to account for a calcite dissolution rate, which drops significantly for solutions close to the saturation limit. Both authors concluded that enlargement in the early phase is concentrated around the entrance section of the fracture, and with time more undersaturated solution will penetrate into the fissure farther downstream.…”

mentioning

confidence: 99%

Karst aquifer evolution in fractured rocks

Kaufmann¹,

Braun²

1999

Water Resources Research

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Abstract. We study the large-scale evolution and flow in a fractured karst aquifer by means of a newly developed numerical method. A karst aquifer is discretized into a set of irregularly spaced nodal points, which are connected to their set of natural neighbors to simulate a network of interconnected conduits in two dimensions. The conduits are allowed to enlarge by solutional widening. The geometric flexibility of this method, along with a simplified model for the dissolution kinetics within the system water-carbon dioxide-calcite, enables us to study both laminar and turbulent flow in a karst aquifer during its early phase of evolution. A sensitivity analysis is conducted for parameters such as conduit diameter, hydraulic pressure differences, and recharge conditions along the surface of the aquifer and shows that passage evolution depends strongly on the recharge condition and the amount of water available. Under fixed hydraulic head boundary conditions an early single-passage system develops under laminar conditions and is transformed into a maze-like passage system after the onset of turbulence. Fixed recharge boundary conditions are more likely to result in a branchwork-like passage system, although the addition of distributed recharge may lead to a maze-like system of secondary passages. IntroductionA mature karst landscape is characterized by the virtual absence of surface flow and by subsurface drainage through cave systems. Subsurface flow is often established between sinking streams along the boundaries of insoluble and soluble rocks and major entrenched valleys serving as base level for resurgences. The dissolution of limestone within the system water-carbon dioxide-calcite is a prominent geomorphic process for the evolution of both surface and subsurface morphological features in a karst landscape, and our understanding of the dissolution process and its implications on flow and passage patterns in the karst aquifer is important for the interpretation of large-scale karst landscape evolution.The The widely different passage patterns characterizing the different types of caves lead to several questions, for example, what processes are responsible for cave development, and under which conditions do each of the specific cave passage patterns result. We focus our attention on the two most important cave types, branchwork and network caves, and follow Palmer [1991] in arguing that groundwater recharge is the most important factor controlling cave passage enlargement in these cases. Palmer showed that 67% of the total cave passage length originates from recharge through valleys and sinking streams, and 10% evolved around recharge points located along boundaries between soluble and insoluble rock. He concluded that recharge through discrete, small-catchment sinkholes is likely to result in branchwork caves. On the other hand, network (or 3223

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confidence: 99%

Karst aquifer evolution in fractured rocks

Kaufmann¹,

Braun²

1999

Water Resources Research

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“…The conduit evolves as a typical conduit in soluble rocks often discussed in the literature as classical breakthrough (e.g. Palmer 1991;Dreybrodt 1990;Dreybrodt et al 2005;Kaufmann 2002): The initial enlargement is focussed to the very first part of the conduit, where a typical funnel shape evolves (red solid lines in Fig. 4 top).…”

Section: Limestonementioning

confidence: 94%

Fracture evolution in soluble rocks: From single-material fractures towards multi-material fractures

Kaufmann

Romanov

Gabrovšek

2017

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IzvlečekUDK 551.435.8 Georg Kaufmann, Franci Gabrovšek & Douchko Romanov: Odvisnost kraškega razvoja razpoke od vrste in zaporedja vodotopnih kamnin, skozi katere poteka Z numeričnim modelom smo raziskovali razvoj sekundarne poroznosti v enodimenzionalni razpoki v apnencu, sadri in anhidridu. Cilji raziskav so bili: 1) ugotoviti razlike med razvojem plitvih in globokih razpok v različnih kamninah; 2) oceniti učinek morebitnega izločanja enega od mineralov v razpoki in 3) dinamika rasti razpoke, ki gre skozi plasti različnih kamnin. Rezultati kažejo na primerljiv razvoj razpok v apnencu in sadri, pri čemer je čas razvoja v obeh kamninah precej različen. V anhidridu je zaradi drugačne kinetike raztapljanja razvoj še hitrejši. Izločanje ob spreminjajočih se geokemičnih pogojih lahko hitro zamaši razpoke in posebej v večjih globinah spremeni poti razvoja mreže kraških prevodnikov. V primeru, ko so razpoke v apnencu prekrite s plastjo sadre, kar v naravi pogosto opažamo, je hitrost širjenja najhitrejša, kar daje vodnim potem vzdolž takih razpok izrazito primerjalno prednost pri zajemanju razpoložljivega toka. Ključne besede: vodotopne kamnine, enostavna razpoka, raztapljanje in izločanje, incepcijski horizont. We employ a numerical model describing the evolution of secondary porosity in a single fracture embedded in soluble rock (limestone, gypsum, and anhydrite) to study the evolution of isolated fractures in different rock types. Our main focus is three-fold: The identification of shallow versus deep flow paths and their evolution for different rock types; the effect of precipitation of the dissolved material in the fracture; and finally the complication of fracture enlargement in fractures composed of several different soluble materials. Our results show that the evolution of fractures composed of limestone and gypsum is comparable, but the evolution time scale is drastically different. For anhydrite, owing to its difference from calcite in the kinetical rate law describing the removal of soluble rock, the evolution is even faster. Precipitation of the dissolved rock due to changes in the hydrochemical conditions can clog fractures fairly fast, thus changing the pattern of preferential pathways in the soluble aquifer, especially with depth. Finally, limestone fractures coated with gypsum, as occasionally observed in caves, will result in a substantial increase in fracture enlargement with time, thus giving these fractures a hydraulic advantage over pure limestone fractures in their competition for capturing flow.

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“…By coupling equations of flow in single fractures, networks of fractures or general fractured-porous aquifers, it is possible to simulate conduit evolution in soluble rocks and search for the basic mechanisms guiding the evolution. The early work of Dreybrodt (1990), Palmer (1991) and Palmer et al (1999) showed the feedback mechanisms between flow and dissolution rates in evolving fractures and introduced the breakthrough time as an important indicator of the intensity of conduit evolution. Assembling individual fractures into networks demonstrated how competition between different flow paths results in different geometries of conduit networks.…”

Section: Karst Hydrogeologymentioning

confidence: 99%

Recent advances in karst research: from theory to fieldwork and applications

Parise

Gabrovšek

Kaufmann

et al. 2018

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Karst landscapes and karst aquifers, which are composed of a variety of soluble rocks such as salt, gypsum, anhydrite, limestone, dolomite and quartzite, are fascinating areas of study. As karst rocks are abundant on the Earth's surface, the fast evolution of karst landscapes and the rapid flow of water through karst aquifers present challenges from a number of different perspectives. This collection of 25 papers deals with different aspects of these challenges, including karst geology, geomorphology and speleogenesis, karst hydrogeology, karst modelling, and karst hazards and management. Together these papers provide a state-of-the-art review of the current challenges and solutions in describing karst from a scientific perspective.

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The Role of Dissolution Kinetics in the Development of Karst Aquifers in Limestone: A Model Simulation of Karst Evolution

Cited by 175 publications

References 16 publications

Karst aquifer evolution in fractured rocks

Karst aquifer evolution in fractured rocks

Fracture evolution in soluble rocks: From single-material fractures towards multi-material fractures

Recent advances in karst research: from theory to fieldwork and applications

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