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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. ...

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. ...

Speleology in Kazakhstan

Shakalov on 11 Jul, 2012
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 porosimeter is a device used to measure porosity [16].?

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Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
Engineering challenges in Karst, Stevanović, Zoran; Milanović, Petar
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Geochemical and mineralogical fingerprints to distinguish the exploited ferruginous mineralisations of Grotta della Monaca (Calabria, Italy), Dimuccio, L.A.; Rodrigues, N.; Larocca, F.; Pratas, J.; Amado, A.M.; Batista de Carvalho, L.A.
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
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Your search for rainfall (Keyword) returned 243 results for the whole karstbase:
Showing 226 to 240 of 243
A model for the formation of layered soda-straw stalactites, 2013, Paul Bence, Drysdale R. , Green Helen, Woodhead Jon, Hellstrom John, Eberhard Rolan

Climate records based upon instrumental data such as rainfall measurements are usually only available for approximately the last 150 years at most. To fully investigate decadal-scale climate variation, however, these records must be extended by the use of climate proxies. Soda-straw stalactites (straws) are a previously under-utilised potential source of such data. In this contribution we investigate the structure and formation of straws and look at some issues that may affect the reliability of straw-based palaeoclimate records. We use laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) trace element analysis to document surface contamination features that have the potential to obscure annual trace element variations, and develop a method to reveal the underlying layering. We also use LA- ICP-MS to map the two-dimensional trace element distribution in straws. These maps reveal straw-layer geometry, in which layers are widest at the outside edge of the straw, narrowing and becoming almost parallel on the interior of the straw.

Based upon these observations, we present a model for the formation of straws of this type, where rapid degassing of CO2 from the drip extending below the straw forms the wider outer layers. Summers are defined by increased layer widths and higher trace element contents relative to winter layers. In palaeoclimate studies, where such annual variations can be used to construct time-lines, we suggest that, ideally, the outside surface of the straw be analysed where the trace element content difference is greatest and layering is widest.

The terminal phase of one straw (FC-02) shows decreasing layer widths and increased trace element contents. These features may also be representative of soda-straw responses to drought-induced decreases in percolation water.


Layer-bounding surfaces in stalagmites as keys to better paleoclimatological histories and chronologies, 2013, Railsback L. B. , Akers P. D. , Wang L. , Holdridge G. A. , Riavo Voarintsoa N.

Petrographic recognition of layer-bounding surfaces in stalagmites offers an important tool in constructing paleoclimate records. Previous petrographic efforts have examined thickness of layers (a possible proxy for annual rainfall) and alternation of layers in couplets (a possible indicator of seasonality). Layer-bounding surfaces, in contrast, delimit series of layers and represent periods of non-deposition, either because of exceptionally wet or exceptionally dry conditions.

Two types of layer-bounding surfaces can be recognized according to explicitly defined petrographic criteria. Type E layer-bounding surfaces are surfaces at which layers have been truncated or eroded at the crest of a stalagmite. Keys to their recognition include irregular termination of layers otherwise present on the stalagmite’s flank, dissolutional cavities, and coatings of non-carbonate detrital materials. Type E surfaces are interpreted to represent wet periods during which drip water became so undersaturated as to dissolve pre-existing stalagmite layers, and thus they necessarily represent hiatuses in the stalagmite record. Type L layer-bounding surfaces are surfaces below which layers become thinner upward and/or layers have lesser lateral extent upward, so that the stalagmite’s layer-specific width decreases. They are thus surfaces of lessened deposition and are interpreted to represent drier conditions in which drip rate slowed so much that little deposition occurred. A Type L surface may, but does not necessarily, represent a hiatus in deposition. However, radiometric age data show that Type L surfaces commonly represent significant hiatuses.

These surfaces are significant to paleoclimate research both for their implications regarding climate change (exceptionally wet or dry conditions) and in construction of chronologies in which other data, such as stable isotope ratios, are placed. With regard to climate change, recognition of these surfaces provides paleoclimatological information that can complement or even substitute for geochemical proxies. With regard to chronologies, recognition of layer- bounding surfaces allows correct placement of hiatuses in chronologies and thus correct placement of geochemical data in time series. Attention to changing thickness of annual layers and thus to accumulation rate can also refine a chronology. A chronology constructed with attention to layer-bounding surfaces and to changing layer thickness is much more accurate than a chronology in which hiatuses are not recognized at such surfaces.


CAVES AND KARST HYDROGEOLOGY OF JERUSALEM, ISRAEL, 2013, Frumkin Amos

 

The city of Jerusalem, Israel, is growing for ~4,000 years on karst terrain. Lacking closed depressions, surface topography seems fluvial, but karst is well demonstrated by speleology and subsurface hydrology. Several caves in the city were truncated by construction works, including an 800 m long river cave (longest limestone river cave in Israel), and a 200 × 140 × 90 m isolated chamber cave (largest chamber cave in Israel). Caves are being discovered at a growing rate, as construction works dig deeper into the subsurface in the crowded city. Some of them are eventually destroyed by the construction works; only presently accessible caves are discussed here. The hydrogeology and hydrochemistry of the Gihon, Jerusalem’s main karst spring, was studied in order to understand its behavior, as well as urbanization effects on karst groundwater resources. High-resolution monitoring of the spring discharge, temperature and electrical conductivity, as well as chemical and bacterial analysis demonstrate a rapid response of the spring to rainfall events and human impact. A complex karst system is inferred, including conduit flow, fissure flow and diffuse flow. Electrical conductivity is high compared to nearby springs located at the town margins, indicating considerable urban pollution in the Gihon area. The previously cited pulsating nature of the spring does not exist today. This phenomenon may have ceased due to additional water sources from urban leakage and irrigation feeding the spring. The urbanization of the recharge area thus affects the spring water dramatically, both chemically and hydrologically.


Karstification as a Predisposing Factor of Seismically Triggered Landslides: Case Study from the Crimean Mountains (Ukraine): Introduction to the Problem, 2013, Hradeck J. , Pnek T. , ilhn K. , Smolkov V.

Deep-seated gravitational deformations are significant denudational agents of rock slopes at the margins of karstified plateaus of the Crimean Mountains (CM). The CM evolved during Mesozoic–Cenozoic times as a response to the deformation between the Black Sea domain and East-European platform. The southwestern part of the area is characterized by steep, up to 1000-m-high coastal escarpments consisting of Late Jurassic limestones overlying tuff layers and weak Late Triassic flysch with sporadic small intrusions of Middle Jurassic diorites, gabbros and granites. Steep rock slopes contrast with elevated, highly karstified plateaus situated approximately 500–1300 m a.s.l. The aim of this article is to show long-term evolution of a giant rock slope failure close to the Black Sea coast in the southwestern tip of the CM near Foros Town. The failure evolved in highly anisotropic limestones overlying plastic flysch layers where the main head scarp follows a strike-slip fault. The Foros slope failure is an excellent demonstration of the significance of a preparatory stage in the evolution of large deep-seated slope deformations. Inherited and undisturbed horizontal slickensides on the sub-vertical, inactive fault surface serve as good evidence of significant extensional movement of the surface blocks away from the main headscarp. The studied deformation shows that in a relatively small area tensional (cutting) surfaces can be formed by a great variety of rock discontinuities such as the strike-slip fault, joints and steeply inclined bedding planes. The presence of well-developed, nowadays weathered, speleothems furthermore points to significant karstification that provided additional widening of spaces within rock mass. Gravitational movement destroyed and unroofed several cave systems originally presented at the former edge of a karst plateau. Our findings reveal that large rock slope failures can be added to the factors contributing to the evolution of unroofed caves. Although triggering factors of the activation of individual parts of slope deformations can be determined only hypothetically, lessons learned from widespread landslide activity during and after the 1927 Yalta earthquake and rainfall-driven landslides in the vicinity of Feodosia Town make us consider both seismic loading of slopes and high pore-pressures during heavy winter rainfalls or rapid spring snowmelt to be significant factors. Beside seismic activity, intensive Late Holocene slope processes can be attributed to intensive human activity.

 


COMPLEX EPIKARST HYDROLOGEOLOGY AND CONTAMINANT TRANSPORT IN A SOUTH-CENTRAL KENTUCKY KARST LANDSCAPE, 2013, Polk J. S. , Vanderhoff S. , Groves C. , Miller B. , Bolster C.

 

The movement of autogenic recharge through the shallow epikarstic zone in soil-mantled karst aquifers is important in understanding recharge areas and rates, storage, and contaminant transport processes. The groundwater in agricultural karst areas, such as Kentucky’s Pennyroyal Plateau, which is characterized by shallow epikarst and deeper conduits flow, is susceptible to contamination from organic soil amendments and pesticides. To understand the storage and flow of autogenic recharge and its effects on contaminant transport on water flowing to a single epikarst drain in Crump’s Cave on Kentucky’s Mississippian Plateau, we employed several techniques to characterize the nature and hydrogeology of the system. During 2010–2012, water samples and geochemical data were collected every four hours before, during, and between storm events from a waterfall in Crumps Cave to track the transport and residence time of epikarst water and organic soil amendments during variable flow conditions. Geochemical data consisting of pH, specific conductivity, temperature, and discharge were collected continuously at 10-minute intervals, along with rainfall amounts. In addition, stable isotope data from rainfall, soil water, and epikarst water were collected weekly and during storm events to examine storage and recharge behavior of the system. The changes in geochemistry indicate simultaneous storage and transport of meteoric water through epikarst pathways into the cave, with rapid transport of bacteria occurring through the conduits that bypass storage. The isotopic data indicate that recharge is rapidly homogenized in the epikarst, with storage varying throughout the year based on meteorological conditions. Results indicate current best management practices in agricultural karst areas need to be revisited to incorporate areas that do not have surface runoff, but where contaminants are transported by seepage into local aquifers.


COVER-COLLAPSE SINKHOLE DEVELOPMENT IN THE CRETACEOUS EDWARDS LIMESTONE, CENTRAL TEXAS, 2013, Hunt B. B. , Smith B. A. , Adams M. T. , Hiers S. E. , Brown N.

Sudden cover-collapse sinkhole (doline) development is uncommon in the karstic Cretaceous-age Edwards limestone of central Texas. This paper presents a case-study of a sinkhole that formed within a stormwater retention pond (SWRP) in southwest Austin. Results presented include hydrogeologic characterizations, fate of stormwater, and mitigation of the sinkhole. On January 24, 2012, a 11 cm (4.5 in) rainfall filled the SWRP with about 3 m (10 ft) of stormwater. Subsequently, a sinkhole formed within the floor of a SWRP measuring about 9 m (30 ft) in diameter and 4 m (12 ft) deep. About 26.5 million liters (7 million gallons) of stormwater drained into the aquifer through this opening. To determine the path, velocity, and destination of stormwater entering the sinkhole a dye trace was conducted. Phloxine B was injected into the sinkhole on February 3, 2012. The dye was detected at one well and arrived at Barton Springs in less than 4 days for a minimum velocity of 2 km/day (1.3 mi/day).Review of pre-development 2-foot topographic contour and geologic maps reveals that the SWRP was built within a broad (5,200 m2; 6 acre), shallow depression bounded by two inferred NE-trending fault zones. Photographs taken during SWRP construction showed steep west-dipping bedrock in the northern SWRP wall. Following collapse of the sinkhole, additional hydrogeologic characterization included excavation to a depth of 6.4 m (21 ft), surface geophysics (resistivity), and rock coring. Geologic materials consisted mostly 89of friable, highly altered, clayey limestone consistent with epikarst in-filled with terra rosa providing a cover of the feature. Dipping beds, and fractured bedrock support proximity to the mapped fault zone. Geophysics and surface observations suggested a lateral pathway for stormwater flow at the junction between the wet pond’s impermeable geomembrane and compacted clay liner for the retention pond. The collapse appears to have been caused by stormwater down-washing poorly consolidated sediments from beneath the SWRP and into a pre-existing karst conduit system.

Mitigation of the sinkhole included backfill ranging from boulders to gravel, a geomembrane cover, and reinforced concrete cap. Additional improvements to the SWRP included a new compacted clay liner overlain by a geomembrane liner on the side slopes of the retention pond.


INVESTIGATIONS OF LARGE SCALE SINKHOLE COLLAPSES, LAIBIN, GUANGXI, CHINA, 2013, Gao Yongli, Luo Weiquan, Jiang Xiaozhen, Lei Mingtang, Dai Jianling

A series of sinkholes collapsed at Jili village and Shanbei village, Laibin Guangxi, China in June 2010. A large underground stream exists in the north-south transect of the study area and passes the collapse site. Preliminary investigations revealed that extremely heavy rainfall between May 31 and June 1 2010 may have triggered this collapse event. The precipitation, as high as 469.8 mm within one day, was a record high in the study area. A long period of drought in 2009 followed by extremely heavy rainfall along with cave roof collapse may have caused the collapse event on June 3 2010. The “water hammer” effect and collapse-triggered earthquakes caused severe ground failure and fractures in residential houses and Jili Dam. Several collapse events were caused by extreme weather conditions in Guangxi over the past few years. Further studies of the relationship between extreme weather events and sinkhole collapses will help minimize the damage or impact to human infrastructure by avoiding areas susceptible to collapse or by designing infrastructure to better withstand subsidence


Do carbonate karst terrains affect the global carbon cycle?, 2013, Martin Jonathan B. , Brown Amy, Ezell John

Carbonate minerals comprise the largest reservoir of carbon in the earth’s lithosphere, but they are generally assumed to have no net impact on the global carbon cycle if rapid dissolution and precipitation reactions represent equal sources and sinks of atmospheric carbon. Observations of both terrestrial and marine carbonate systems indicate that carbonate minerals may simultaneously dissolve and precipitate within different portions of individual hydrologic systems. In all cases reported here, the dissolution and precipitation reactions are related to primary production, which fixes atmospheric CO2 as organic carbon, and the subsequent remineralization in watersheds of the organic carbon to dissolved CO2. Deposition of carbonate minerals in the ocean represents a flux of CO2 to the atmosphere. The dissolution of oceanic carbonate minerals can act either as a sink for atmospheric CO2 if dissolved by carbonic acid, or as a source of CO2 if dissolved through sulfide oxidation at the freshwater-saltwater boundary. Since dissolution and precipitation of carbonate minerals depend on ecological processes, changes in these processes due to shifts in rainfall patterns, earth surface temperatures, and sea level should also alter the potential magnitudes of sources and sinks for atmospheric CO2 from carbonate terrains, providing feedbacks to the global carbon cycle that differ from modern feedbacks.


Spring discharge records – a case study, 2013, Wicks, Carol M.

Spring discharge records integrate of all the processes and the reactions occurring within a karst basin. A brief summary of the use of discharge records as a means to constrain the internal structure of karst basins, as means to constrain rainfallrunoff models for karst basin, and as a means to determine the value of hydrodynamic parameters of karst basins is presented. Data collected from Devils Icebox, a karst basin spring in Missouri, USA, were used to assess these approaches to characterizing karst basins. For Devils Icebox, most of the discharge responses do not record information about the internal structure of the basin rather the responses record information about the recharge to the basin. A rainfall-runoff model failed to reproduce the data from which model parameters were derived and has little utility in a predictive mode. Use of conservation of mass equations as a means to derive hydrodynamic parameters is a useful approach, although critical data are lacking. More generally, karst hydrologists need quantitative tracer data and long-term, high-resolution temporal data of the input(s) to and the output(s) from karst basins.


Using hydrogeochemical and ecohydrologic responses to understand epikarst process in semi-arid systems, Edwards plateau, Texas, USA, 2013, Schwartz Benjamin F. , Schwinning Susanne, Gerrard Brett, Kukowski Kelly R. , Stinson Chasity L. , Dammeyer Heather C.

The epikarst is a permeable boundary between surface and subsurface environments and can be conceptualized as the vadose critical zone of epigenic karst systems which have not developed under insoluble cover. From a hydrologic perspective, this boundary is often thought of as being permeable in one direction only (down), but connectivity between the flow paths of water through the epikarst and the root systems of woody plants means that water moves both up and down across the epikarst. However, the dynamics of these flows are complex and highly dependent on variability in the spatial structure of the epikarst, vegetation characteristics, as well as temporal variability in precipitation and evaporative demand. Here we summarize insights gained from working at several sites on the Edwards Plateau of Central Texas, combining isotopic, hydrogeochemical, and ecophysiological methodologies. 1) Dense woodland vegetation at sites with thin to absent soils (0-30 cm) is in part supported by water uptake from the epikarst. 2) However, tree transpiration typically becomes water-limited in dry summers, suggesting that the plant-available fraction of stored water in the epikarst depletes quickly, even when sustained cave drip rates indicate that water is still present in the epikarst. 3) Flow paths for water that feeds cave drips become rapidly disconnected from the evaporation zone of the epikarst and out of reach for plant roots. 4) Deep infiltration and recharge does not occur in these systems without heavy or continuous precipitation that exceeds some threshold value. Thresholds are strongly correlated with antecedent potential evapotranspiration and rainfall, suggesting control by the moisture status of the epikarst evapotranspiration zone. The epikarst and unsaturated zone in this region can be conceptualized as a variably saturated system with storage in fractures, matrix porosity, and in shallow perched aquifers, most of which is inaccessible to the root systems of trees, although woody vegetation may control recharge thresholds.


Temporal variability of karst aquifer response time established by the sliding-windows cross-correlation method, 2013, Delbarta Célestine, Valdesd Danièle, Barbecotg Florent, Tognellia Antoine, Richona Patrick, Couchouxh Laurent

We study the temporal variability of water transfer through the infiltration zone of a karst aquifer by estimating the impulse response of the system using cross-correlogram analyses between rainfall and piezometric level time series. We apply a sliding-window cross-correlation method, which calculates cross-correlograms on partially superposed short time series windows. We apply this method for rainfall and piezometric level time series at six boreholes in a fractured karstic aquifer located in Burgundy, France. Based on cross-correlogram functions, we obtain a time series of response time. At most of the boreholes, the cross-correlation functions change over time, and the response times vary seasonally, being shorter during the summer. This unusual structure can be partly explained by the seasonal variability in rainfall intensity, which is higher during the summer (May–September), inducing the seasonal behaviour of the epikarst. During the summer, when rainfall intensity is higher, the epikarst is more easily and quickly saturated. This induces an increase in lateral water transfer within the epikarst and an increase in concentrated fast flows. We also show that the response time seems to tend towards a limit which represents the maximum saturation of the epikarst.


Paleoflood events recorded by speleothems in caves, 2014, Gazquez F. , Calaforra J. M. , Forti P. , Stoll H. , Ghaleb B. , Delgadohuertas A.

Speleothems are usually composed of thin layers of calcite (or aragonite). However,
cemented detrital materials interlayered between laminae of speleothemic carbonate have been also observed in many caves. Flowstones comprising discontinuous carbonate layers form due to flowing water films,while flood events introduce fluviokarstic sediments in caves that, on occasion,are recorded as clayey layers inside flowstones and stalagmites. This record provides a potential means of understand­ing the frequency of palaeofloods using cave records.In this work,we investigate the origin of this type of detritaldeposit in El Soplao Cave (Northern Spain). The age of the lowest aragonite layer
of a flowstone reveals that the earliest flood period occurred before 500 ka, though most of the flowstone formed between 422 +69/-43 ka and 400 +66/-42 ka. This suggests that the cave was periodically affected by palaeoflood events that introduced detrital sediments from the surface as a result of occasional extreme rainfall events,especially at around 400 ka.The mineralogical data enable an evolutionary modelfor this flowstone to be generated based on the alternation offload events with laminar flows and carbonate layers precipitation that can be extrapolated to other caves in which detrital sediments inside speleothems have been found. 


Hydrological role of karst in the Chalk aquifer of Upper Normandy, France, 2014, Janyani S. El, Dupont J. P. , Massei N. , Slimani S. , Dörfliger N.

The role of karst on large-scale groundwater flow is defined for the Chalk aquifer of Upper Normandy (western Paris Basin), France. In the regional context, chalk plateaus occupy the greater part of watersheds and are the main sites of groundwater recharge. Previous studies focused on karstic output systems in the valleys and less on water-level variations in the recharge zones upstream. This study assesses the relevant hydrogeological processes using time-series data (boreholes and springs) recorded along a down-gradient hydrologeological cross-section in two selected watersheds. These hydrological data are interpreted in the framework of previous descriptions of the morphological organization of the study area’s karst network. The results highlight the hydrological role of (1) the input karst (vertical conduits) which drains recharging water, (2) the output karst (sub-horizontal conduits widely developed in the vicinity of valleys in the surface watersheds) which drains the output flows, and (3) the connections between these two (input and output) networks, which control the upstream water levels and allow quick transfer to springs, particularly after strong rainfall events. A conceptual model of the hydrological functioning of this covered karst aquifer is established, which should serve for the structuring and parameterization of a numerical model


Hydrogeological Characteristics of Carbonate Formations of the Cuddapah Basin, India, 2014, Farooq Ahmad Dar

Karst hydrogeology is an important field of earth sciences as the aquifers in carbonate formations represent vital resource of groundwater that feeds a large part of the world population particularly in semi-arid climates. These unique aquifers posses peculiar characteristics developed by dissolutional activities of water. Karst aquifers possess a typical hydrogeological setup from surface to subsurface. The aquifers are governed by slow groundwater flow in matrix porosity, a medium to fast flow in fractures and rapid flow in conduits and channels. This large variability in their properties makes the prediction and modeling of flow and transport very cumbersome and data demanding. The aquifers are vulnerable to contamination as the pollutants reach the aquifer very fast with little or no attenuation. The geomorphological and hydrogeological properties in these aquifers demand specific techniques for their study. The carbonate aquifers of the semi-arid Cuddapah basin were characterized based on geomorphological, hydrogeological and hydrochemical investigations. All the formations are highly karstified possessing one of the longest and deepest caves of India and few springs along with unique surface features. Karstification is still in progress but at deeper levels indicated by growing speleothems of different architectural size. Model of karstification indicates that lowering of base level of erosion resulted in the dissolution of deeper parts of the limestone as represented by paleo-phreatic conduits in the region. Moist conditions of the past were responsible for the karst development which has been minimized due to the onset of monsoon conditions. Karst has developed at various elevations representing the past base levels in the region.

The recharge processes in these aquifers are complex due to climatic and karst specificities. Point recharge is the major contributor which enters the aquifer as allogenic water. It replenishes the groundwater very rapidly. Diffuse recharge travels through soil and epikarst zone. Average annual recharge of semi-arid Narji limestone aquifer is 29% of the rainfall which occurs during 5-7 rain events in the year.

The hydrogeochemical characteristic of karst aquifers is quite varaible. A significant difference is observed in hydrochemistry. High concentrations of SO42-, Cl-, NO3- suggests the anthropogenic source particularly from agriculture. Local Meteoric Water Line of δ2H and δ18O isotopes of rain and groundwater shows a slope of 7.02. Groundwater isotope data shows more depletion in heavy isotopes -a result of high evaporation of the area. Groundwater samples show a trend with a slope of 4 and 3.1 for δ2H and δ18O respectively. Groundwater during dry months gets more fractionated due to higher temperature and little rainfall. The irrigated water becomes more enriched and then recharges the aquifer as depleted irrigation return flow. The isotopes show large variation in spring water. Few springs are diffuse or mixed type and not purely of conduit type in the area. Tracer results indicate that the tracer output at the sampling location depends on the hydrogeological setup and the nature of karstification.

The study has significantly dealt with in disclosing the typical characteristics of such aquifer systems and bringing out a reliable as well as detailed assessment of various recharges to the system. The groundwater chemistry has been elaborated to establish the nature of possible hydrochemical processes responsible for water chemistry variation in semi-arid karst aquifer. Such study has thrown light on the aquifers that are on one hand very important from social and strategic point of view and on the hand were left unattended from the detailed scientific studies.


Caractérisation et modélisation hydrodynamique des karsts par réseaux de neurones. Application à l’hydrosystème du Lez , 2014, Virgile, Taver

Improving knowledge of karst hydrodynamics represents a global challenge for water resources because karst aquifers provide approximately 25% of the world population in fresh water. Nevertheless, complexity, anisotropy, heterogeneity, non-linearity and possible non-stationarity of these aquifers make them underexploited objects due to the difficulty to characterize their morphology and hydrodynamics. In this context, the systemic paradigm proposes others methods by studying these hydrosystems through input-output (rainfall-runoff) relations.

The approach proposed in this thesis is to use information from field measurement and from systemic analyses to constrain neural network models. The goal is to make these models interpretable in terms of hydrodynamic processes by making model functioning to be similar to natural system in order to obtain a good representation and extract knowledge from model parameters.

This work covers the association of information available on the hydrosystem with correlation and spectral analyses to develop a temporal multiresolution decomposition of variables and to constrain neural network models. A new method for variable selection, adapted to represent long term hydrodynamics of the system, has been proposed. These constrained models show very good results and allow, through their parameters, to study the temporal contribution of inputs variables to the output.

Modeling nonlinear and non-stationary hydrosystems with neural network has been improved by a novel implementation of data assimilation. More precisely, when non-stationarity is attributed to the catchment, data assimilation is used to modify the model parameters. When the inputs are non-stationary, data assimilation can be used to modify the inputs.

The modification of inputs opens considerable scope to: i) fill gaps or homogenizing time series, ii) estimate effective rainfall.

Finally, these various analyses and modeling methods, mainly developed on the karst hydrosystem Lez, can improve the knowledge of the rainfall-runoff relationship at different time scales. These methodological tools thus offer perspectives of better management of the aquifer in terms of floods and resources. The advantage of these analyses and modeling tools is that they can be applicable to other systems.


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