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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. ...

Did you know?

That free-surface stream is in a cave, a stream that does not completely fill its passage [10].?

Checkout all 2699 terms in the KarstBase Glossary of Karst and Cave Terms

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Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
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Featured articles from other Geoscience Journals
Karst environment, Culver D.C.
Mushroom Speleothems: Stromatolites That Formed in the Absence of Phototrophs, Bontognali, Tomaso R.R.; D’Angeli Ilenia M.; Tisato, Nicola; Vasconcelos, Crisogono; Bernasconi, Stefano M.; Gonzales, Esteban R. G.; De Waele, Jo
Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
Microbial mediation of complex subterranean mineral structures, Tirato, Nicola; Torriano, Stefano F.F;, Monteux, Sylvain; Sauro, Francesco; De Waele, Jo; Lavagna, Maria Luisa; D’Angeli, Ilenia Maria; Chailloux, Daniel; Renda, Michel; Eglinton, Timothy I.; Bontognali, Tomaso Renzo Rezio
Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria), Briestensky, Milos; Rowberry, Matt; Stemberk, Josef; Stefanov, Petar; Vozar, Jozef; Sebela, Stanka; Petro, Lubomir; Bella, Pavel; Gaal, Ludovit; Ormukov, Cholponbek;
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Your search for floods (Keyword) returned 69 results for the whole karstbase:
Showing 1 to 15 of 69
Controversy over the great flood hypotheses in the Black Sea in light of geological, paleontological, and archaeological evidence, ,
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Yankohombach Valentina, Gilbert Allan S. , Dolukhanov Pavel,
Legends describing a Great Flood are found in the narratives of several world religions, and the biblical account of Noah's Flood is the surviving heir to several versions of the ancient Mesopotamian Flood Myth. Recently, the story of the biblical deluge was connected to the Black Sea, together with the suggestion that the story's pre-Mesopotamian origins might be found in the Pontic basin [Ryan, W.B.F., Pitman, III, W.C., 1998. Noah's Flood: The New Scientific Discoveries About the Event That Changed History. Simon and Schuster, New York]. Based on the significance of this flood epic in the Judeo-Christian tradition, popular interest surged following publication of the idea.Currently, two Great Flood scenarios have been proposed for the Black Sea: (1) an Early Holocene event caused by catastrophic Mediterranean inflow at 7.2 ky BP (initial hypothesis of [Ryan et al., 1997. An abrupt drowning of the Black Sea shelf. Marine Geology 138, 119-126]) or 8.4 ky BP (modified hypothesis of [Ryan et al., 2003. Catastrophic flooding of the Black Sea. Annual Review of Earth and Planetary Science 31, 525-554.); and (2) a Late Pleistocene event brought on by Caspian influx between 16 and 13 ky BP [Chepalyga, A.L., 2003. Late glacial Great Flood in the Black Sea and Caspian Sea. GSA Annual Meeting and Exposition, 2-5 November 2003, Seattle, USA, p. 460]. Both hypotheses claim that the massive inundations of the Black Sea basin and ensuing large-scale environmental changes had a profound impact on prehistoric human societies of the surrounding areas, and both propose that the event formed the basis for the biblical Great Flood legend.This paper attempts to determine whether the preponderance of existing evidence sustains support for these Great Floods in the evolution of the Black Sea. Based upon established geological and paleontological data, it finds that the Late Pleistocene inundation was intense and substantial whereas the Early Holocene sea-level rise was not. Between 16 and 13 ky BP, the Late Neoeuxinian lake (the Late Pleistocene water body in the Pontic basin pre-dating the Black Sea) increased rapidly from ~-14 to -50 m (below the present level of the Black Sea), then rose gradually to ~-20 m by about 11 ky BP. At 11-10 ky BP (the Younger Dryas), it dropped to ~-50 m. When the Black Sea re-connected with the Sea of Marmara at about 9.5 ky BP, inflowing Mediterranean water increased the Black Sea level very gradually up to ~-20 m, and in so doing, it raised the salinity of the basin and brought in the first wave of Mediterranean immigrants. These data indicate no major drawdown of the Black Sea after the Younger Dryas, and they do not provide evidence for any catastrophic flooding of the Black Sea in the Early Holocene.In addition, available archaeological and paleoenvironmental evidence from the Pontic region reveal no recognizable changes in population dynamics between 14 and 6 ky BP that could be linked to an inundation of large magnitude [Dolukhanov, P., Shilik, K., 2006. Environment, sea-level changes, and human migrations in the northern Pontic area during late Pleistocene and Holocene times. In: Yanko-Hombach, V., Gilbert, A.S., Panin, N., Dolukhanov, P.M. (Eds.), The Black Sea Flood Question: Changes in Coastline, Climate, and Human Settlement. Springer, Dordrecht, pp. 297-318; Stanko, V.N., 2006. Fluctuations in the level of the Black Sea and Mesolithic settlement of the northern Pontic area. In: Yanko-Hombach, V., Gilbert, A.S., Panin, N., Dolukhanov, P.M. (Eds.), The Black Sea Flood Question: Changes in Coastline, Climate, and Human Settlement. Springer, Dordrecht, pp. 371-385]. More specifically, Mesolithic and early Neolithic archaeological data in southeastern Europe and Ukraine give no indications of shifts in human subsistence or other behavior at the time of the proposed catastrophic flood in the Early Holocene [Anthony, D., 2006. Pontic-Caspian Mesolithic and Early Neolithic societies at the time of the Black Sea Flood: A small audience and small effects. In: Yanko-Hombach, V., Gilbert, A.S., Panin, N., Dolukhanov, P.M. (Eds.), The Black Sea Flood Question: Changes in Coastline, Climate, and Human Settlement. Springer, Dordrecht, pp. 345-370; Dergachev and Dolukhanov, 2006. The Neolithization of the North Pontic area and the Balkans in the context of the Black Sea Floods. In: Yanko-Hombach, V., Gilbert, A.S., Panin, N., Dolukhanov, P.M. (Eds.), The Black Sea Flood Question: Changes in Coastline, Climate, and Human Settlement. Springer, Dordrecht, pp. 489-514]

Phreatobiological researches II., 1965,
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Motas Constantin, Serban Eugne
The present note calls into question the opinion of different authors concerning the presence or lack of adult Niphargus near the phreatic table (superior layer of phreatic water) in zones prospected by Karaman-Chappuis method. Our investigations have proved the reason for which Niphargus adults were less frequent in the superior layer of the phreatic water is rather concerned with our investigation means; which are very approximate -, than with the ecological or ethological requirements of these animals. The assertion that the phreatic fauna performs downward migrations during the floods must be considered as doubtful. During floods it is impossible to dig into the alluvial deposits immediately near the stream, these being completely flooded; so, we are obliged to dig in regions more distant from the riverside, which are not flooded. It is well known that in this zone the biocoenosis contains always a greater number of phreatobius elements. One of the authors (C. Motas) introduce the terms: rithrobios; for the fauna inhabiting the epigean streams, phreatobios; for that inhabiting the phreatic water, and geobios; for the terrestrial world.

Tasmanian Cave Fauna: Character and Distribution, 1967,
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Goede, A.

The geology and nature of the caves is discussed. Cave development has been affected by glacial outwash and periglacial conditions which must be taken into account when considering the development and distribution of cave fauna. The food supply in the caves is limited by the absence of cave-inhabiting bats. Floods while adding to the food supply must be destructive to some forms of terrestrial cave life. The cave fauna consists entirely of invertebrates. The carab genus Idacarabus Lea contains the only troglobites found in Tasmania. A common troglophile throughout the island is Hickmania troglodytes (Higgins and Petterd) which belongs to a very small group of relict spiders. Five species of cave crickets are known from Tasmania and Flinders Island. Three species belong to the genus Micropathus Richards and show an interesting distribution pattern. A single species of glow-worm, Arachnocampa (Arachnocampa) tasmaniensis Ferguson occurs in a number of Tasmanian caves. It is more closely related to the New Zealand species than to glow worms found on the Australian mainland. Other terrestrial cave life is briefly discussed. Aquatic cave life is poorly known. The syncarid Anaspides tasmaniae (Thomson) has been recorded from several caves. It differs from epigean forms in reduction of pigment.

Cave Development during a Catastrophic Storm in the Great Valley of Virginia, 1971,
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Doehring Do, Vierbuchen Rc,
Observations made before aind after a catastrophic storml support the conclutsion that caves receivinig storm recharge may be significantly developed in the vadose zone by the processes of niass transfer. These processes are greatly accelerated during times of major floods. Evidence indicates that in ancient times floods of similar magnitude have occurred

Karst Hydrogeology and Geomorphology of the Sierra de El Abra and the Valles-San Luis Potosí Region, México, PhD Thesis, 1977,
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Fish, Johnnie Edward

The general objective of this work was to develop a basic understanding of the karst hydrology, the nature and origin of the caves, the water chemistry, the surface geomorphology, and relationships among these aspects for a high relief tropical karst region having a thick section of limestone. The Valles-San Luis Potosí region of northeastern México, and in particular, the Sierra de El Abra, was selected for the study. A Cretaceous Platform approximately 200 km wide and 300 km long (N-S) delimits the region of interest. A thick Lower Cretaceous deposit of gypsum and anydrite, and probably surrounded by Lower Cretaceous limestone facies, is overlain by more than 1000 m of the thick-bedded middle Cretaceous El Abra limestone, which has a thick platform-margin reef. The Sierra de El Abra is a greatly elongated range along the eastern margin of the Platform. During the late Cretaceous, the region was covered by thick deposits of impermeable rocks. During the early Tertiary, the area was folded, uplifted, and subjected to erosion. A high relief karst having a wide variety of geomorphic forms controlled by climate and structure has developed. Rainfall in the region varies from 250-2500 mm and is strongly concentrated in the months June-October, when very large rainfalls often occur.
A number of specific investigations were made to meet the general objective given above, with special emphasis on those that provide information concerning the nature of ground-water flow systems in the region. Most of the runoff from the region passes through the karstic subsurface. Large portions of the region have no surface runoff whatsoever. The El Abra Formation is continuous over nearly the whole Platform, and it defines a region of very active ground-water circulation. Discharge from the aquifer occurs at a number of large and many small springs. Two of them, the Coy and the Frío springs group, are among the largest springs in the world with average discharges of approximately 24 m³/sec and 28 m³/sec respectively. Most of the dry season regional discharge is from a few large springs at low elevations along the eastern margin of the Platform. The flow systems give extremely dynamic responses to large precipitation events; floods at springs usually crest roughly one day after the causal rainfall and most springs have discharge variations (0max/0min) of 25-100 times. These facts indicate well-developed conduit flow systems.
The hydrochemical and hydrologic evidence in combination with the hydrogeologic setting demonstrate the existence of regional ground-water flow to several of the large eastern springs. Hydrochemical mixing-model calculations show that the amount of regional flow is at least 12 m³/sec, that it has an approximately constant flux, and that the local flow systems provide the extremely variable component of spring discharge. The chemical and physical properties of the springs are explained in terms of local and regional flow systems.
Local studies carried out in the Sierra de El Abra show that large conduits have developed, and that large fluctuations of the water table occur. The large fossil caves in the range were part of great deep phreatic flow systems which circulated at least 300 m below ancient water tables and which discharged onto ancient coastal plains much higher than the present one. The western margin swallet caves are of the floodwater type. The cave are structurally controlled.
Knowledge gained in this study should provide a basis for planning future research, and in particular for water resource development. The aquifer has great potential for water supply, but little of that potential is presently used.

Investigations of the Troglobitic Crayfish Orconectes inermis testii (Hay) in Mayfield's Cave, Monroe County, Indiana., 1981,
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Hobbs Iii Horton H.
Mark-recapture studies of some aspects of the biology of the cavernicolous crayfish, Orconectes inermis testii (Hay), were conducted from December, 1969 to March, 1970, in Mayfield's Cave, Monroe County, Indiana. Population size was estimated to be 66 +/- 9 (95% C.L.) for the 300 m study area, but because of the small sample size, this is undoubtedly a deflated value. Size of animals, expressed as total length, indicates that the population was comprised primarily of adults. Seventy-four percent of the marked crayfish moved no more than 10.5 m away (total upstream and downstream distances) from the tagging site. Hence, this species appears to restrict its activities to a specific area ("home range") of up to 10.5 m of stream passage. Form I males travelled greater distances than did Form II (15.1 and 3.0 m, respectively), possibly in search of mates. Adult females moved less than juveniles, and males appeared to move greater distances than females (means of 12.9 and 5.9 m, respectively). Upstream movements were more commonly observed than downstream (mainly Form I males), indicating a possible restocking mechanism following floods. Distances travelled were not rebated to the size of individuals or to elapsed time.

Further Studies at the Blue Waterholes, Cooleman Plain, N.S.W., 1969-77, Part I, Climate and Hydrology, 1983,
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Jennings, J. N.

Previous study of the temporal and spatial distribution of limestone solution at Cooleman Plain rested on monthly discharges and water analyses of the Blue Waterholes over 4 years. For this study automatic recording of discharge (8 years), rainfall (8 years), evaporation (7 years) and temperature (4 years) was attended by variable success in the face of interference, rigorous climate and inaccessibility. The most important aspect of the climatic data was the support obtained for the earlier assumption of similar water balances in the forested igneous frame and the grassland limestone plain. Runoff was again shown to be highly variable from year to year and to have an oceanic pluvial regime, with a summer-autumn minimum owing much to evapo-transpiration. The flow duration curve from daily discharges puts this karst amongst those where neither extremely high nor low flows are important. The stream routing pattern offsets the effect of 71% of the catchment being on non-karst rocks, damping flood events. An inflection of 700 l/s in a flow duration plot based on discharge class means is interpreted as the threshold at which surface flow down North Branch reaches the Blue Waterholes. Storages calculated from a generalised recession hydrograph parallel Mendip data where baseflow (fissure) storage provides most of the storage and quickflow (vadose) storage only a secondary part. Water-filled conduit storage (the phreas) could not be determined but is considered small. The baseflow storage seems large, suggesting that it can develop independently of caves in some measure. A quickflow ratio for floods derived by Gunn's modification of the Hewlett and Hibbert separation line method appears relatively low for a mainly non-karst catchment and is again attributed to the routing pattern. For analysis of variation of the solute load over time, estimates of daily discharge during gaps in the record where made for the author by Dr. A.J. Jakeman and Mr. M.A. Greenaway (see Appendix). A small number of discharge measures of two contrasted allogenic catchments of the igneous frame shows a unit area yield close to that for the whole catchment. Together with the guaging of most of the allogenic inputs, this supports the idea that the water yield is much the same from the forested ranges and the grassland plain. This is important for the estimation of limestone removal rates.

Hydrogologie karstique des Alpes-Maritimes, 1984,
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Baissas, P.
Karst hydrogeology in the Alpes-Maritimes - In the Marguareis, the systems penetrate very quickly by transverse faults, to reach the impermeable basement and then follow the dip. All the waters, even those on the French side, belong to the P basin. In the Roya arc, underflows are to be found going round the base of the Argentera-Mercantour. In the Nice arc, the karstification depends principally on tectonic factors and according to the places, the water follows either the overlaps or transverse faults. In the Grasse plateaus, the galleries follow at the outset the slopes and the dips of the synclinal hinges; the tectonic factors determine the location of the resurgences ; at depth, the karst is always phreatic, with relations between tectonic compartments during floods. In the cover of the Tanneron-Esterel basement and Barrot Dome, lithological factors determine flow.

La crue du 18 mai 1994 au Trou qui Souffle (Vercors, France), 1995,
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Lismonde B. , Les_splos_grenoblois_du_c. A. F.
The syncline of Autrans--Maudre is located in Vercors, an alpine region of France. This karstic basin is drained by the resurgence of Goule Noire, located in the gorge of the Bourne River. The surface of this region is 80 km2 and the flow of Goule Noire in low water is 500 1/s. The stage of limestone is urgonian and senonian. The most important cave is the Trou qui Souffle (blowing cave). This cave is 40km long and 450m deep. Down, sumps stop the explorations. The water volume stocked in the phreatic passages between the cave and the spring is about 1,000,000 m3. The Trou qui Souffle has two great fossil galleries, the Franois gallery and the gallery of Easter. The water way of phreatic gallery is actually unknown. In may 1994, a very high rain of 155 mm in a day caused a great flooding. In the cave, the piezometric level went up 100 m over the normal level; 14km of passages are drowned. All the Franois fossil gallery are fill with water. On the contrary, the Gallery of Easter is dry remained. The analysis of this exceptio-nal phenomenon (of 50 years recurren-ce) shows that a very little passage exists between Trou qui Souffle and Goule Noire. The equivalent duct diameter is about 1,5 m. The Trou qui Souffle stocked a water volume of about 300 000 m3. So the karstic system atte-nuates the crest of floods and regula-rizes the flow of resurgence.

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Frumkin A, Ford Dc,
Rock salt is approximately 1000 times more soluble than limestone and thus displays high rates of geomorphic evolution. Cave stream channel profiles and downcutting rates were studied in the Mount Sedom salt diapir, Dead Sea rift valley, Israel. Although the area is very arid (mean annual rainfall approximate to 50 mm), the diapir contains extensive karst systems of Holocene age. In the standard cave profile a vertical shaft at the upstream end diverts water from a surface channel in anhydrite or elastic cap rocks into the subsurface route in the salt. Mass balance calculations in a sample cave passage yielded downcutting rates of 0.2 mm s(-1) during peak flood conditions, or about eight orders of magnitude higher than reported rates in any limestone cave streams. However, in the arid climate of Mount Sedom floods have a low recurrence interval with the consequence that long-term mean downcutting rates are lower: an average rate of 8.8 mm a(-1) was measured for the period 1986-1991 in the same sample passage. Quite independently, long-term mean rates of 6.2 mm a(-1) are deduced from C-14 ages of driftwood found in upper levels of 12 cave passages. These are at least three orders of magnitude higher than rates established for limestone caves. Salt cave passages develop in two main stages: (1) an early stage characterized by high downcutting rates into the rock salt bed, and steep passage gradients; (2) a mature stage characterized by lower downcutting rates, with establishment of a subhorizontal stream bed armoured with alluvial detritus. In this mature stage downcutting rates are controlled by the uplift rate of the Mount Sedom diapir and changes of the level of the Dead Sea. Passages may also aggrade. These fast-developing salt stream channels may serve as full-scale models for slower developing systems such as limestone canyons

Nickpoint recession in karst terrains: An example from the Buchan karst, southeastern Australia, 1996,
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Fabel D, Henricksen D, Finlayson Bl, Webb Ja,
Nickpoint recession in the Buchan karst, southeastern Australia, has resulted in the formation of an underground meander cut-off system in the Murrindal River valley. Three nickpoints have been stranded in the surface channel abandoned by the subterranean piracy, and these can be correlated with river terraces and epiphreatic cave passages in the nearby Buchan River valley. The presence of palaeomagnetically reversed sediments in the youngest cave passage in the Buchan valley implies that the topographically lowest nickpoint in the Murrindal valley is more than 730 ka old, and the other nickpoints are probably several million years old. The nickpoints are occasionally active during floods, but the diversion of most surface flow underground has slowed down their retreat to the extent that they have been effectively stationary for several million years Underground nickpoint migration has been by both incision within major phreatic conduits and their abandonment for lower-level passages. The nickpoints are all present in the upstream part of the cave system, but have not migrated past the sink in the river channel, despite the long period of time available for this to happen. The sink is characterized by collapsed limestone blocks; these filter out the coarse bedload from the river channel. As a result, erosion within the cave passages is dominantly solutional and therefore slower than in the surface channel, where it is mostly mechanical. In addition, to transmit a drop in base level the cave system requires the removal of a larger volume of rock than for the surface migration of a nickpoint, because any roof collapse material in the subsurface system must be removed. These factors have slowed the migration of the base-level changes through the subsurface system, and may be a general feature in caves that have diffuse sinks as their main inputs

Numerical versus statistical modelling of natural response of a karst hydrogeological system, 1997,
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Eisenlohr L, Bouzelboudjen M, Kiraly L, Rossier Y,
Structural and hydrodynamic characteristics of karst aquifers are mostly deduced from studies of global responses of karst springs (hydrographs, chemical or isotopic composition). In this case, global response is often used to make inferences with respect to infiltration and ground water How processes as well as on the hydrodynamic parameters. Obviously, the direct verification of these inferences is very difficult. We have used an indirect method of verification, introducing well defined theoretical karst structures into a finite element model and then analysing the simulated global response according to the currently accepted interpretation schemes. As we know what we are introducing into the numeric model, the consistency of the interpretation may be checked immediately. The results obtained in the hydrogeological study of two karst basins in the Swiss Jura and from 2-D and 3-D numerical simulations show the difficulty of finding structural parameters and hydrodynamic behaviour from statistical methods alone, i.e. correlation analyses discharge-discharge and precipitation-discharge. In effect, our first results show that the form of the correlograms depends on several factors besides the structure of the karst aquifer: (i) on the form of the floods. in other words the contrast between quick Row and base How, (ii) on the frequency of hydrological events during the period analysed and (iii) on the type of infiltration processes, in other words the ratio of diffuse infiltration to concentrated information. Obviously, the variability of a karst hydrograph is a result of a combination of these factors. Distinction between them is not always possible on hydrographs, and therefore on correlations (discharge-discharge and precipitation-discharge). (C) 1997 Elsevier Science B.V

Relations between the structure of storage and the transport of chemical compounds in karstic aquifers, 1997,
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Vaute L. , Drogue C. , Garrelly L. , Ghelfenstein M. ,
Study of the movement of chemical compounds naturally present in the water, or which result from pollution, are examined according to the reservoir structure in karstic aquifers. Structure is represented by a simple geometrical model; slow Row takes place in blocks with a network of low-permeability cracks. The blocks are separated by highly permeable karstic conduits that allow rapid flow, and these form the aquifer drainage system. The karat studied covers 110 km(2). It is fed by an interrupted stream draining a 35 km(2) non-karstic basin, contaminated at the entry to the karst by effluents from a sewage treatment station. The underground water reappears as a resurgence with an annual average flow of approximately 1 m(3) s(-1), after an apparent underground course of 8 km in the karst. Several local sources of pollution (effluent from septic tanks) contaminate the underground water during its course. Sixteen measurement operations were performed at 12 water points, between the interrupted stream and the spring. Some sampling points were at drains, and others were in the low-permeability fissured blocks. Comparison at each point of the concentrations of 14 chemical compounds gave the following results: when pollutant discharge occurs in a permeable zone, movement is rapid in the drainage network formed by the karstic conduits, and does not reach the less permeable fissured blocks which are thus protected; however, if discharge is in a low-permeability zone, the flow does not allow rapid movement of the polluted water, and this increases the pollutant concentration at the discharge, This simple pattern can be upset by a reversal of the apparent piezometric gradient between a block and a conduit during Floods or pumping; this may reverse flow directions and hence modify the movement of contaminants. The study made it possible to site five boreholes whose positions in the karstic structure were unknown, showing the interest of such an approach for the forecasting of the impact of potential pollution.

Storm pulses, thresholds, and fluid mechanics in the transport of clastic sediments in limestone aquifers., 1997,
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White W. B. , White E. L.
Active conduit systems carry a flux of water from recharge regions to discharge downstream at karst springs. They also carry a flux of clastic sediments. Transport of clastic sediments is episodic. Sediment piles are moved mainly during extreme floods. Relationships between sediment panicle sizes and stream flow can be used to determine paleoflow characteristics of caves passages from the clastic sediments and also to calculate the magnitude of flood pulses needed to maintain the sediment flux.

Thalweg variability at bridges along a large karst river: the Suwannee River, Florida, 1998,
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Mossa J. , Konwinski J. ,
Geomorphologists and engineers have different perspectives and approaches for examining river channels and the changes that occur during floods. The field-oriented approach typically adopted by geomorphologists has little predictive ability and design usefulness. In contrast, the empirical approach adopted by engineers is based on predictive equations or models that often differ greatly from reality. Such equations are not based on comprehensive field data and often fail to consider a number of site conditions, especially geology and geomorphology. Yet, in order for geomorphic techniques to be useful to the design and planning of engineering structures such as bridges, it is important that sufficient observations exist in order to characterize long-term and short-term changes in bottom topography and scour potential. Six gaging stations on the Suwannee River, a large river draining karst terrain in the southeastern US, were used to examine the temporal variability in thalweg elevation, the deepest point in a given cross-section. The cross-sections have maximum thalweg variability of just a few meters, despite the occurrence of several large floods. suggesting that the bottoms are fairly stable. Historical approaches can be applied to design the length and depth placement of pilings by providing information on site conditions not considered in engineering equations, such as response of bottom materials to various flow conditions, and thus have potential benefits to public safety and cost effectiveness. (C) 1998 Elsevier Science B.V

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