Early development of karst systems: 1. Preferential flow path enlargement under laminar flow

Groves, Christopher G.; Howard, A. D.

doi:10.1029/94wr01303

Cited by 130 publications

(92 citation statements)

References 27 publications

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“…Within the domain of reactive flow in unsaturated soils three main types of interfering instabilities occur: (i) reaction instabilities due to initial heterogeneities in the hydraulic properties with dissolution of wormholes and karst phenomena [1,[96][97][98][99][100][101][102][103][104][105], (ii) flow instabilities with moisture content fingering during the infiltration of a moisture front [106][107][108][109][110][111][112][113][114][115][116] and (iii) density instabilities due to local differences of solution densities [117][118][119][120][121][122][123][124]. However, the scope of this paper is not to investigate instability phenomena, but to propose a new approach that relates changes in mineral volumes and hydraulic properties.…”

Section: General Model Discussionmentioning

confidence: 99%

Effect of mineral reactions on the hydraulic properties of unsaturated soils: Model development and application

Wissmeier

Barry

2009

Advances in Water Resources

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. ACCEPTED MANUSCRIPT AbsThe selective radius shift model was used to relate changes in mineral volume due to precipitation/dissolution reactions to changes in hydraulic properties affecting flow in porous media. The model accounts for (i) precipitation/dissolution taking place only in the water-filled part of the pore space and further that (ii) the amount of mineral precipitation/dissolution within a pore depends on the local pore volume. The pore bundle concept was used to connect pore-scale changes to macroscopic soil hydraulic properties. Precipitation/dissolution induces changes in the pore radii of water-filled pores and, consequently, in the effective porosity. In a time step of the numerical model, mineral reactions lead to a discontinuous pore-size distribution because only the water-filled pores are affected. The pore-size distribution is converted back to a soil moisture characteristic function to which a new water retention curve is fitted under physically plausible constraints. The model equations were derived for the commonly used van Genuchten/Mualem hydraulic properties. Together with a mixed-form solution of Richards' equation for aqueous phase flow, the model was implemented into the geochemical modelling framework PHREEQC, thereby making available PHREEQC's comprehensive geochemical reactions. Example applications include kinetic halite dissolution and calcite precipitation as a consequence of cation exchange. These applications showed marked changes in the soil's hydraulic properties due to mineral precipitation/dissolution and the dependency of these changes on water contents. The simulations also revealed the strong influence of the degree of saturation on the development of the saturated hydraulic conductivity through its quadratic dependency on the van Genuchten parameter . Furthermore, it was shown that the unsaturated hydraulic conductivity at fixed reduced water content can even r tract increase du ing precipitation due to changes in the pore-size distribution.

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Section: General Model Discussionmentioning

confidence: 99%

Effect of mineral reactions on the hydraulic properties of unsaturated soils: Model development and application

Wissmeier

Barry

2009

Advances in Water Resources

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“…In contrast, the role of predesign is less clear for preferential flow in soils and in karstified aquifers. In particular, the formation of conduit patterns in karst has been addressed by several modeling studies (e.g., Groves and Howard, 1994;Howard and Groves, 1995;Siemers and Dreybrodt, 1998;Braun, 1999, 2000;Liedl et al, 2003;Dreybrodt et al, 2005;Kaufmann et al, 2010;Gabrovšek and Dreybrodt, 2011;Hubinger and Birk, 2011), pioneered by early work of Kiraly (1979). Although there may be some predesign, too, it is generally believed that the solution of material by the flow causes a strong tendency towards self-organization of the flow pattern.…”

Section: Introductionmentioning

confidence: 99%

Transferring the concept of minimum energy dissipation from river networks to subsurface flow patterns

Hergarten

Winkler

Birk

2014

Hydrol. Earth Syst. Sci.

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Abstract. Principles of optimality provide an interesting alternative to modeling hydrological processes in detail on small scales and have received growing interest in the last years. Inspired by the more than 20 years old concept of minimum energy dissipation in river networks, we present a corresponding theory for subsurface flow in order to obtain a better understanding of preferential flow patterns in the subsurface. The concept describes flow patterns which are optimal in the sense of minimizing the total energy dissipation at a given recharge under the constraint of a given total porosity. Results are illustrated using two examples: two-dimensional flow towards a spring with a radial symmetric distribution of the porosity and dendritic flow patterns. The latter are found to be similar to river networks in their structure and, as a main result, the model predicts a power-law distribution of the spring discharges. In combination with two data sets from the Austrian Alps, this result is used for validating the model. Both data sets reveal power-law-distributed spring discharges with similar scaling exponents. These are, however, slightly larger than the exponent predicted by the model. As a further result, the distributions of the residence times strongly differ between homogeneous porous media and optimized flow patterns, while the mean residence times are similar in both cases.

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“…Here Groves and Howard [1994b] concluded that enlargement during the early phase under laminar flow conditions is highly selective, favoring the evolution of single passages. After the onset of turbulence, Howard and Groves [1995] showed that enlargement becomes more uniform in the network, resulting in more maze-like cave passage patterns.…”

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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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Early development of karst systems: 1. Preferential flow path enlargement under laminar flow

Cited by 130 publications

References 27 publications

Effect of mineral reactions on the hydraulic properties of unsaturated soils: Model development and application

Effect of mineral reactions on the hydraulic properties of unsaturated soils: Model development and application

Transferring the concept of minimum energy dissipation from river networks to subsurface flow patterns

Karst aquifer evolution in fractured rocks

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