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Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

New publications on hypogene speleogenesis

Klimchouk on 26 Mar, 2012
Dear Colleagues, This is to draw your attention to several recent publications added to KarstBase, relevant to hypogenic karst/speleogenesis: Corrosion of limestone tablets in sulfidic ground-water: measurements and speleogenetic implications Galdenzi,

The deepest terrestrial animal

Klimchouk on 23 Feb, 2012
A recent publication of Spanish researchers describes the biology of Krubera Cave, including the deepest terrestrial animal ever found: Jordana, Rafael; Baquero, Enrique; Reboleira, Sofía and Sendra, Alberto. ...

Caves - landscapes without light

akop on 05 Feb, 2012
Exhibition dedicated to caves is taking place in the Vienna Natural History Museum   The exhibition at the Natural History Museum presents the surprising variety of caves and cave formations such as stalactites and various crystals. ...

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That sea level is the average height of the surface of the sea used as a datum for elevations [16].?

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Your search for exchange flow (Keyword) returned 5 results for the whole karstbase:
Modeling of karst aquifer genesis: Influence of exchange flow, 2003, Bauer S, Liedl R, Sauter M,
[1] This paper presents a numerical model study simulating the early karstification of a single conduit embedded in a fissured system. A hybrid continuum-discrete pipe flow model (CAVE) is used for the modeling. The effects of coupling of the two flow systems on type and duration of early karstification are studied for different boundary conditions. Assuming fixed head boundaries at both ends of the conduit, coupling of the two flow systems via exchange flow between the conduit and the fissured system leads to an enhanced evolution of the conduit. This effect is valid over a wide range of initial conduit diameters, and karstification is accelerated by a factor of about 100 as compared to the case of no exchange flow. Parameter studies reveal the influence of the exchange coefficient and of the hydraulic conductivity of the fissured system on the development time for the conduit. In a second scenario the upstream fixed head boundary is switched to a fixed flow boundary at a specified flow rate during the evolution, limiting the amount of water draining toward the evolving conduit. Depending on the flow rate specified, conduit evolution may be slowed down or greatly impaired if exchange flow is considered

Evolution of Karst Aquifers in Natural and Man Made Environments: A Modeling Approach. Ph.D. thesis, 2003, Romanov, Douchko

The evolution of karst aquifers under various hydrological and chemical boundary conditions is studied.
In the first part the influence of exchange flow from a prominent fracture into a two-dimensional network of fissures is compared to the evolution of a fracture isolated from this net. The modeling domain is 742.5 m long and 375 m wide dissected by fractures into 100 by 51 blocks. The wide prominent fracture extends along its center, thus constituting a part of the network. Under constant head conditions between the left and the right hand side of the domain it looses flow into the network. We have studied the influence of the fracture widths of the fine net to the breakthrough time (BT) of the system. Because of loss of flow from the central fracture to the net, aggressive solution from the input enhances dissolution and breakthrough times are reduced. This effect is most effective, when the aperture width of the fine net is only smaller by about 1% than the widths of the prominent fracture, such that a large amount of water can flow into the net. To obtain further information on the processes involved, an isolated one-dimensional fracture with an additional single point of outflow from it, is investigated.
As an application of the results above, the evolution of a karst aquifer below dam sites is studied. The modeling domain is a 2D, 1 m wide vertical section of soluble rock (gypsum and limestone), perpendicular to the dam. The block extends 750 m horizontally and 375 m vertically. It is divided by fractures and fissures into blocks of 7.5 m x 7.5 m x 1m. The chemical composition of the inflowing water is equal at all input points. Because of dissolution along the fractures, a large zone of increasing permeability is created below the structure, causing high unbearable water losses from the dam site and also endangering the mechanical stability of the dam. The dependence of BT on the basic parameters - the height of the impounded water, the depth of the grouting curtain, the initial aperture widths of the fractures and the fissures, and the chemical parameters of the inflowing water (equilibrium concentration with respect to calcite and input concentration) is investigated. For fracture aperture widths larger than 0.02 cm breakthrough occurs within the lifetime of the structure.
In the second part the effect of chemical boundary conditions on the evolution of a karst aquifer is studied. The model domain is 500 m x 225 m, divided into blocks of 5 m x 5 m x 1 m by fracture network. There are two input points at constant head (25 m) at the inflow side of the block. The outflow side is open at constant head – 0 m. The hydrological boundaries are equal for all simulated scenarios. The chemical composition of the inflowing water at both inputs is varied, and the reaction of the aquifer is studied. Mixing corrosion is the reason for zones of increased permeability deep inside the aquifer along the boundary, where the solutions mix. The influence of mixing corrosion for various values of the input Ca concentration is studied. The results show two types of evolution. Breakthrough (BT) governed evolution – for values of cin<0.96?ceq, and mixing corrosion (MC) - governed evolution for values of cin>0.96?ceq. The BT - type is characterized by enlarged pathways connecting an inflow point with the outflow boundary. For increasing values of the input concentrations the effect of MC becomes stronger. For high Ca concentrations, MC is dominating. There is no considerably widened connection between the inflow points and the out flow boundary. but an enlarged channel along the mixing zone is observed. The timescale for this type of evolution is considerably longer. For solutions saturated with respect to calcite, the mixing zone is the only area of widening inside the aquifer.


Modeling the evolution of karst aquifers and speleogenesis. The step from 1-dimensional to 2-dimensional modeling domains, 2004, Romanov D. , Gabrovsek F. , Dreybrodt W.

First models of karst evolution considered a single isolated fracture with no loss of flow along its entire length. Under conditions of constant head dissolution of limestone creates a positive feedback-loop of increase of aperture widths and flow until at breakthrough the flow and aperture width are enhanced dramatically. If a second dimension is added to this model domain, in the simplest case by an exit-tube connected to the isolated channel, water loss from the isolated channel occurs. We have investigated the influence of the water loss on the breakthrough time of the single channel. In all cases, when water loss is present, more aggressive solution enters at the input. The aggressive solutional activity penetrates deeper along the conduit. Therefore dissolutional widening at the exit is enhanced and breakthrough times are reduced. This is discussed in detail by investigating the profiles of hydraulic head, flow rates, aperture widths, and calcium concentrations along the conduit as they evolve in time and comparing them to those of the isolated 1-D conduit.
In a further step the 1-D conduit is embedded into a net of fractures with smaller aperture widths. The conduit is located in the center of the rectangular domain and connected to the 2-D net at equally spaced nodes. By this way exchange flow from the conduit into the net can arise. But also flow from the net to the conduit is possible. We have studied the evolution of this aquifer considering dissolution also in the network of the narrow fissures. Flow from the main central fracture into the net again reduces breakthrough times. After breakthrough, however, a complex exit fan evolves in the net, which later on is overprinted by a net of entrance fans propagating down flow. These fans are related to flow from the net into the central fracture. The evolution of these fans resulting finally in a maze-like structure is significant for high hydraulic gradients (i0.1) as they exist at artificial dam sites. For such situations realistic modeling has to include dissolutional widening in the net. For low hydraulic gradients, i<0.03, the evolution in the net is slow compared to that of the central conduit and therefore the aquifer is dominated by the evolution of the central fracture.


Early karstification in a dual-fracture aquifer: the role of exchange flow between prominent fractures and a dense net of fissures, 2004, Gabrovsek F, Romanov D, Dreybrodt W,

Modeling the influence of epikarst evolution on karst aquifer genesis: A time-variant recharge boundary condition for joint karst-epikarst development, 2005, Bauer S, Liedl R, Sauter M,
The epikarst, a zone of increased weathering near the land surface, determines the distribution of recharge to a karst aquifer in both space and time. It links climatic and near-surface geological conditions with the karstification of a limestone aquifer, defining both the hydraulic and the chemical boundary conditions for the development of the karst system. Realistic modeling of the epikarst is therefore a prerequisite for the simulation of karst aquifer genesis. A conceptual model of the joint karst-epikarst evolution is presented in this paper. An epikarst module is developed and implemented in a numerical continuum-discrete conduit flow model for karst genesis, which accounts for the joint evolution of the epikarst and the main karstic conduit network under unconfined conditions. The influence of epikarst genesis on the evolution of the underlying karst aquifer is investigated in four scenarios. It is found that only the interaction of epikarst and initial heterogeneity in the underlying carbonate rock leads to the development of a dendritic cave system. If no heterogeneity in the initial conduit network or in the recharge distribution is included, maze-type caves develop

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