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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 upper confining bed is an impermeable bed overlying an aquifer [16].?

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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 calibration (Keyword) returned 47 results for the whole karstbase:
Showing 31 to 45 of 47
Long-term changes in the cave atmosphere air temperature as a result of periodic heliophysical processes, 2006, Stoeva P. , . Stoev A. , Kiskinovab N. .

Climatic trends connected with short- and long-period variations of the solar activity occur as a reaction even in such conservative media as the air volumes of karst caves. The yearly mean air temperatures in the zone of constant temperatures of four show caves in Bulgaria were studied for a period of 36 years (1968–2003). The examination was made by everyday noon measurements in Ledenika, Saeva dupka, Snezhanka and Uhlovitsa cave. The caves are situated at different altitudes and geographic latitude. Seasonal fluctuations of the yearly mean air temperature in the ZCT of the explored caves have been identified by Fourier analysis. The same analysis has been applied for the Sunspot number and Apmax indices, which are representatives of the solar and geomagnetic activity, for the same period of data available. Autocorrelograms have been used for examination of the seasonal patterns of the air temperatures in the ZCT in every cave and in Sunspot number and Apmax indices. Cross-spectrum analysis has been applied for retrieving the correlations between air ZCT temperatures in the caves and solar and geomagnetic activity. It has been found that the correlation between ZCT temperature time series and sunspot number is better than that between the cave air temperature and Apmax indices. It has been found that View the MathML source is rather connected with the first peak in geomagnetic activity, which is associated with transient solar activity, i.e., coronal mass ejections (CMEs) than with the second one, which is higher and connected with the recurrent high speed streams from coronal holes (Webb, D.F., 2002. CMEs and the solar cycle variation in their geoeffectiveness. In: Wilson, A. (Ed.), Proceedings of the SOHO 11 Symposium on From Solar Min to Max: Half a Solar Cycle with SOHO, 11–15 March 2002, Davos, Switzerland. ESA Publications Division, Noordwijk, 2002, ISBN 92-9092-818-2, pp. 409–419). This work can contribute to studying the mechanisms of atmospheric circulation changes and calibration of long-period climatic data read from cave speleothems and deposits.


Bomb-spike dating of a mummified baboon in Ludwig Cave, Namibia., 2007, Hodgins Greg, Brook George A. , Marais Eugene
In 1982 a mummified adult female baboon was discovered on a ledge in Ludwig Cave in Namibia. A toe bone was removed for dating in July 1995. AMS radiocarbon dating of bone collagen, tendon, and skin indicates a post-modern age. Application of the atomic bomb-spike calibration curve suggests death in late 1977 and an age at death of around 19 years. Baboons roost in the cave and the mummified female, along with a mummified juvenile male discovered in 2002 and three rotting corpses discovered in 1995, were probably chased by other baboons or by leopards down a ca. 6 m drop during the rainy season, and were unable to climb the steep and very slippery slope to escape. The large number of baboons trapped in the cave in less than 20 years, and mummification of two individuals on dry, dusty ledges in the cave, may explain why large numbers of baboon skeletons have been discovered in ancient bone breccias (up to 4 Ma old) in a number of caves throughout Southern Africa.

Bomb-spike dating of a mummified baboon in Ludwig Cave, Namibia., 2007, Hodgins Greg, Brook George A. And Marais Eugene
In 1982 a mummified adult female baboon was discovered on a ledge in Ludwig Cave in Namibia. A toe bone was removed for dating in July 1995. AMS radiocarbon dating of bone collagen, tendon, and skin indicates a post-modern age. Application of the atomic bomb-spike calibration curve suggests death in late 1977 and an age at death of around 19 years. Baboons roost in the cave and the mummified female, along with a mummified juvenile male discovered in 2002 and three rotting corpses discovered in 1995, were probably chased by other baboons or by leopards down a ca. 6 m drop during the rainy season, and were unable to climb the steep and very slippery slope to escape. The large number of baboons trapped in the cave in less than 20 years, and mummification of two individuals on dry, dusty ledges in the cave, may explain why large numbers of baboon skeletons have been discovered in ancient bone breccias (up to 4 Ma old) in a number of caves throughout Southern Africa.

Isotopic Investigations of Cave Drip Waters and Precipitation in Central and Northern Florida, USA, Msc.Thesis, 2007, Pacegraczyk, Kali J

A temperature, drip rate, and stable isotopic study (δ18O and δD) was undertaken in three caves in central and northern Florida. Both surface and cave temperatures were collected, as were precipitation, cave drip water and drip rates. All data were collected on a weekly basis to investigate the isotopic relationships between precipitation and cave drip waters. The objective of this study was to provide a calibration of the oxygen and hydrogen isotopic values in precipitation and cave drip water for future paleoclimate work in the Florida peninsula.Based on the steady annual cave temperature and high relative humidity (95% or above), all three caves are suitable locations for paleoclimate work. A spike in the cave drip rate is seen following precipitation events at both Legend and Jennings Caves. A lag time of 52 days between the date of the storm event and the increase in drip rate was found at Legend Cave.


Legend and Jennings Caves in central Florida show a relationship between the amount of precipitation and the δ18O values. The isotopic values in precipitation were more depleted after a large precipitation event, suggesting the amount effect is influential in this location. At Florida Caverns State Park tourist cave in northern Florida, the association between 18O and precipitation was weak while a relationship between 18O and temperature may be present; here the seasonal effect or latitude effect may be significant.
The monthly mean isotopic values of the drip waters were found to approximate those of the precipitation. The steady isotopic values of the drip water are due to a homogenization of water infiltrating into the epikarst and mixing with water already present in the karst storage. This finding is important for future paleoclimate research in the Florida peninsula. An important assumption in paleoclimate work is that the value of δ18O in calcite at the time of precipitation represents the mean annual δ18O of precipitation at the time of deposition. The ultimate objectives of this research were to assess the isotopic relationship between precipitation and cave drip waters in order to interpret paleoclimate data sets. Although the data were limited to a single year, it appears that a sufficient isotopic signal exists in central-north Florida precipitation and drip water to apply for paleoclimate studies.


How long does evolution of the troglomorphic form take? Estimating divergence times in Astyanax mexicanus, 2007, Porter M. L. , Dittmar K. , Pé, Rezlosada M.

Features including colonization routes (stream capture) and the existence of both epigean and cave-adapted hypogean popula­tions make Astyanax mexicanus an attractive system for investi­gating the subterranean evolutionary time necessary for acqui­sition of the troglomorphic form. Using published sequences, we have estimated divergence times for A. mexicanus using: 1) two different population-level mitochondrial datasets (cyto­chrome b and NADH dehydrogenase 2) with both strict and relaxed molecular clock methods, and 2) broad phylogenetic approaches combining fossil calibrations and with four nuclear (recombination activating gene, seven in absentia, forkhead, and α-tropomyosin) and two mitochondrial (16S rDNA and cytochrome b) genes. Using these datasets, we have estimated divergence times for three events in the evolutionary history of troglomorphic A. mexicanus populations. First, divergence among cave haplotypes occurred in the Pleistocene, possibly correlating with fluctuating water levels allowing the coloni­zation and subsequent isolation of new subterranean habitats. Second, in one lineage, A. mexicanus cave populations expe­rienced introgressive hybridization events with recent surface populations (0.26-2.0 Ma), possibly also correlated with Pleis­tocene events. Finally, using divergence times from surface populations in the lineage without evidence of introgression as an estimate, the acquisition of the troglomorphic form in A. mexicanus is younger than 2.2 (fossil calibration estimates) – 5.2 (cytb estimate) Ma (Pliocene).


Interpretation of pumping tests in a mixed flow karst system, 2008, Maré, Chal J. C. Ladouche B. Dö, Rfliger N. & Lachassagne P.

A long-duration pumping test performed in the conduit of a mixed flow karst system (MFKS) is analyzed and interpreted. It constitutes a unique experiment of catchment wide response of a karst system, with drawdowns measured both in the pumped conduit and in the matrix. A modeling approach is proposed for this interpretation. The developed double continuum model consists of two reservoirs - karst conduits and the surrounding carbonate rocks - between which flow exchange is modeled using the superposition principle and the hypothesis of Darcian flow in the matrix considered as an equivalent porous media. The karst conduits are assumed to have an infinite hydraulic conductivity. Model calibration results in a very good match (relative root mean square [rRMS] = 2.3 %) with drawdown measured at the pumping well (karst conduit). It shows that the matrix hydrodynamic parameters (hydraulic conductivity and storativity) have a greater influence on the drawdown than the storage capacity of the conduit network. The accuracy of the model relies mostly on a very good knowledge of both pumping rate and natural discharge at the spring (with and without pumping). This type of approach represents an advance in double continuum modeling of karst systems. It also provides a methodology for the management of water resources from karst aquifers.


SPELEOTHEM PALAEOCLIMATE RECONSTRUCTIONS FROM NORTH EAST TURKEY, , 2008, Jex, Catherine N

Turkey, in the Near – East, is currently suffering water shortages; with future predictions towards increased aridity. As such, an understanding of past water availability is crucial. This study presents reconstructions of palaeoclimate from stalagmites in north east Turkey over two time periods: 21.6 (± 1.5) ka BP to 7.3 (± 0.3) ka BP; and from ~ 1500 AD to the present day.
Conditions at the LGM (characterised by highest δ18O and δ13C; reduced rate of CaCO3 precipitation) are interpreted as cold and dry with reduced vegetation cover, in line with Israeli and Oman speleothems and Turkish lake core evidence. Towards the Holocene, climate ameliorates and vegetation cover increases. An event centred around 12.4 ka BP is characterised by reduced δ18O, 14C and Sr/Ca and Mg/Ca ratios; and increased δ13C and trace elements (Y, Pb, Cu, Zn and P). This is interpreted as a humid event, contemporaneous with the YD, a time typically associated with arid conditions in the Near- /Middle-East.
A calibration of stable isotopes with climate parameters over the instrumental period is presented; and extrapolated to obtain a record of winter precipitation over the last 500 years. This is the first speleothem reconstruction of its kind in Turkey.


Flank Margin Cave Development in Telogenetic Limestones of New Zealand, 2008, Mylroie J. E. , Mylroie J. R. , Nelson C. S.

Coastal limestone outcrops, typically with advanced levels of diagenetic maturity (i.e., are telogenetic carbonates), were examined on North Island (Raglan Harbour, Kawhia Harbour, Napier, and Waipu Cove) and South Island (Pohara, Paturau River, Punakaiki, Kakanui, and Kaikoura), New Zealand, to determine if flank margin caves, produced by mixing dissolution, were present. In coastal settings, caves in carbonate rock can be the outcome of pseudokarst process, primarily wave erosion, as well as karst processes not associated with fresh and sea-water mixing such as epikarst features and conduit-flow stream caves. Flank margin caves were successfully differentiated from other cave types by the following criteria: phreatic dissolutional morphologies at the wall rock and chamber scales; absence of high- velocity, turbulent-flow wall sculpture and sediment deposits; and lack of integration of adjacent caves into a continuous flow path. The active tectonics of New Zealand creates a variable sea- level situation. The relatively short time of sea-level stability limits the size of the New Zealand flank margin caves compared to tectonically-stable environments, such as the Bahamas, where glacioeustasy alone controls sea-level stability. Uplift events can be identified as slow and steady when the flank margin caves are uniformly elongated in the vertical direction, and episodic when the flank margin caves show widening and tube development at discrete horizons that cut across rock structure. New Zealand flank margin caves contain information on uplift duration and rates independent of other commonly used measures, and therefore can provide a calibration to other methods.


Characterization of Spatial Heterogeneity in Groundwater Applications , 2009, Trinchero, Paolo

Heterogeneity is a salient feature of every natural geological formation. In the past decades a large body of literature has focused on the effects of heterogeneity on flow and transport problems. These works have substantially improved the understanding of flow and transport phenomena but still fail to characterize many of the important features of an aquifer. Among them, preferential flows and solute paths, connectivity between two points of an aquifer, and interpretation of hydraulic and tracer tests in heterogeneous media are crucial points that need to be properly assessed to obtain accurate model predictions. In this context, the aim of this thesis is twofold:

· to improve the understanding of the effects of heterogeneity on flow and transport phenomena
· to provide new tools for characterizing aquifer heterogeneity

First, we start by theoretically and numerically examine the relationship between two indicators of flow and transport connectivity. The flow connectivity indicator used here is based on the time elapsed for hydraulic response in a pumping test (e.g., the storage coefficient estimated by the Cooper-Jacob method, Sest). Regarding transport, we select the estimated porosity from the observed breakthrough curve (Φ est) in a forced-gradient tracer test. Our results allow explaining the poor correlation between these two indicators, already observed numerically by Knudby and Carrera (2005).

Second, a geostatistical framework has been developed to delineate connectivity patterns using a limited and sparse number of measurements. The methodology allows conditioning the results to three types of data measured over different scales, namely: (a) travel times of convergent tracer tests, ta, (b) estimates of the storage coefficient from pumping tests interpreted using the Cooper-a Jacob method, S est, and (c) measurements of transmissivity point values, T. The ability of the methodology to properly delineate capture zones is assessed through estimations (i.e. ordinary cokriging) and sequential gaussian simulations based on different sets of measurements.


Third, a novel methodology for the interpretation of pumping tests in leaky aquifer systems, referred to as the double inflection point (DIP) method, is presented. The real advantage of the DIP method comes when it is applied with all the existing methods independently to a test in a heterogeneous aquifer. In this case each method yields parameter values that are weighted differently, and thus each method provides different information about the heterogeneity distribution. In particular, the combination of the DIP method and Hantush method is shown to lead to the identification of contrasts between the local transmissivity in the vicinity of the well and the equivalent transmissivity of the perturbed aquifer volume.

Fourth, the meaning of the hydraulic parameters estimated from pumping test performed in leaky aquifers is assessed numerically within a Monte Carlo framework. A synthetic pumping test is interpreted using three existing methods. The resulting estimated parameters are shown to be space dependent and vary with the interpretation method, since each method gives different emphasis to different parts of the timedrawdown data. Finally, we show that by combining the parameter estimates obtained from the different analysis procedures, information about the heterogeneity of the leaky aquifer system may be inferred.
Fifth, an unsaturated highly heterogeneous waste rock pile is modeled using a simple linear transfer function (TF) model. The calibration of the parametric model provides information on the characteristic time of the flow through the matrix and on the fraction of the water that, within each section, is channeled through the macropores. An analysis of the influence of the scale on the results is also provided showing that at large scales the behavior of the system tends to that of an equivalent matrix reservoir masking the effects of preferential flow.


Effects of Karst and geological structure on groundwater flow: The case of Yarqon-Taninim Aquifer, Israel, 2010, Dafny Elad, Burg Avi, Gvirtzman Haim

This study demonstrates the significant influences of the geological structure (especially folding and lithology) and the karst system on groundwater flow regime. Folds divert groundwater flow from the general hydraulic gradient; marly layers sustain several perched sub-aquifers above the regional aquifer; and karstification increases the hydraulic conductivity by several orders of magnitude. These phenomena are quantitatively demonstrated within the Yarqon-Taninim (YT) basin, Israel, which is a complex groundwater system, combining several (extremely) opposite characteristics: humid and arid recharge zones, phreatic and confined parts, shallow and deep sub-aquifers, stratified and relatively-homogeneous sub-basins, saline and fresh water bodies, as well as stagnant and fast-flowing groundwater regions.

We have introduced a 3D geological-based grid for the basin (for the first time). It was implemented into a numerical code (FEFLOW), which was used thereafter to analyze quantitatively the flow regime, the groundwater mass balance, and the aquifer hydraulic properties. We present up to date conceptual understanding and numerical modeling of the YT flow field, especially at its mountainous parts.

Based on the calibration procedure and the sensitivity analyses, we obtained the best-fitted hydraulic conductivity values for the aquifer mesh. The general phenomenon observed is that as groundwater flow quantity increases, the hydraulic conductivity also increases. We interpret this result by the karstification mechanism (including paleo-karst). Thus, where groundwater flow-lines converge and where groundwater discharge amount increases, the karstification process intensifies and permeability increases. Consequently, at the mountainous region, along the syncline axes, where groundwater flow-lines converge, higher conductivities are found.

Modeling results also exhibit that at the lowland confined area, the geological structure does not play a major role in directing groundwater flow. Rather, the flow field is controlled by the well-developed karst system and the relatively homogenous carbonate section. It is hypothesizes that the extensive karstification took place at the Messinian Salinity Crises, 5.5 Ma, during which groundwater heads as well as sea level were lowered by several 100 m.


CORA - a dedicated device for carbon dioxide monitoring in cave environments, 2012, Luetscher Marc, Ziegler Felix

High resolution time-series of cave CO2 fluctuations are increasingly demanded to quantify calcite precipitation processes. CORA, an energy-efficient NDIR-device, has been specifically developed for the long-term monitoring of carbon dioxide in remote cave environments. To allow comparison between different cave sites, changes in air pressure and temperature are compensated for using dedicated probes. Laboratory experiments demonstrate that CORAs precision is adapted to the analysis of spatially and temporally variable CO2 regimes and therefore suitable for a large number of applications. Data obtained with 12 independently calibrated instruments are reproducible within 3% (1s). The two-point calibration function is validated using certified reference gases for an overall accuracy determined at 50ppmv, resp.≤3%. Although no significant drift was observed during the test phase a periodic recalibration is recommended. Initial results from field studies show that continuous monitoring over a full annual cycle is possible at 4 hour intervals without specific maintenance.


A method for the stochastic modeling of karstic systems accounting for geophysical data: an example of application in the region of Tulum, Yucatan Peninsula (Mexico), 2012, Vuilleumier C. , Borghi A. , Renard P. , Ottowitz D. , Schiller A. , Supper R. , Cornaton F.

The eastern coast of the Yucatan Peninsula, Mexico, contains one of the most developed karst systems in the world. This natural wonder is undergoing increasing pollution threat due to rapid economic development in the region of Tulum, together with a lack of wastewater treatment facilities. A preliminary numerical model has been developed to assess the vulnerability of the resource. Maps of explored caves have been completed using data from two airborne geophysical campaigns. These electromagnetic measurements allow for the mapping of unexplored karstic conduits. The completion of the network map is achieved through a stochastic pseudo-genetic karst simulator, previously developed but adapted as part of this study to account for the geophysical data. Together with the cave mapping by speleologists, the simulated networks are integrated into the finite-element flow-model mesh as pipe networks where turbulent flow is modeled. The calibration of the karstic network parameters (density, radius of the conduits) is conducted through a comparison with measured piezometric levels. Although the proposed model shows great uncertainty, it reproduces realistically the heterogeneous flow of the aquifer. Simulated velocities in conduits are greater than 1 cm s−1, suggesting that the reinjection of Tulum wastewater constitutes a pollution risk for the nearby ecosystems.


Comparison of a karst groundwater model with and without discrete conduit flow, 2013, Saller S. P. , Ronayne M. J. , Long A. J.

Karst aquifers exhibit a dual flow system characterized by interacting conduit and matrix domains. This study evaluated the coupled continuum pipe-flow framework for modeling karst groundwater flow in the Madison aquifer of western South Dakota (USA). Coupled conduit and matrix flow was simulated within a regional finite-difference model over a 10-year transient period. An existing equivalent porous medium (EPM) model was modified to include major conduit networks whose locations were constrained by dye-tracing data and environmental tracer analysis. Model calibration data included measured hydraulic heads at observation wells and estimates of discharge at four karst springs. Relative to the EPM model, the match to observation well hydraulic heads was substantially improved with the addition of conduits. The inclusion of conduit flow allowed for a simpler hydraulic conductivity distribution in the matrix continuum. Two of the high-conductivity zones in the EPM model, which were required to indirectly simulate the effects of conduits, were eliminated from the new model. This work demonstrates the utility of the coupled continuum pipe-flow method and illustrates how karst aquifer model parameterization is dependent on the physical processes that are simulated


Comparison of a karst groundwater model with and without discrete conduit flow, 2013, Saller S. P. , Ronayne M. J. , Long A. J.

Karst aquifers exhibit a dual flow system characterized by interacting conduit and matrix domains. This study evaluated the coupled continuum pipe-flow framework for modeling karst groundwater flow in the Madison aquifer of western South Dakota (USA). Coupled conduit and matrix flow was simulated within a regional finite-difference model over a 10-year transient period. An existing equivalent porous medium (EPM) model was modified to include major conduit networks whose locations were constrained by dye-tracing data and environmental tracer analysis. Model calibration data included measured hydraulic heads at observation wells and estimates of discharge at four karst springs. Relative to the EPM model, the match to observation well hydraulic heads was substantially improved with the addition of conduits. The inclusion of conduit flow allowed for a simpler hydraulic conductivity distribution in the matrix continuum. Two of the high-conductivity zones in the EPM model, which were required to indirectly simulate the effects of conduits, were eliminated from the new model. This work demonstrates the utility of the coupled continuum pipe-flow method and illustrates how karst aquifer model parameterization is dependent on the physical processes that are simulated.


CONCEPTUALIZATION OF GROUNDWATER FLOW IN THE EDWARDS AQUIFER THROUGH THE KNIPPA GAP HYDROGEOLOGIC CONSTRICTION, UVALDE COUNTY, TEXAS, 2013, Adkins, J.

The Balcones Fault Zone Edwards aquifer (Edwards aquifer) is one of the major regional karst aquifers in the United States, with an average withdrawal of 950 million liters per day (L/d). This study focuses on the connection between the Uvalde pool and the San Antonio pool of the Edwards aquifer, west of the San Antonio metropolitan area in Uvalde County, Texas. This area is known as the Knippa Gap and is located north of the community of Knippa. The Knippa Gap is a major zone controlling the flow from the Uvalde pool to the San Antonio pool. The San Antonio pool is the primary source of water for the greater San Antonio water supply. The Knippa Gap is a restriction where the aquifer narrows to a width estimated to be approximately 4 km, is bounded by northeast trending faults of the Balcones Fault Zone on the north, and uplift from the Uvalde salient and igneous intrusive plugs to the south. (Green et al., 2006). The hydrogeology in the Knippa Gap has been a topic of major interest among researchers in this area for numerous years, yet the exact location, nature of boundaries, and karst hydrogeology are not well defined, and the flow through this area is in need of refinement to improve the aquifer water balance.
This study integrates recent research by other scientists with field studies conducted during the summer of 2012 as part of an M.S. thesis. This paper is limited to a discussion of the water quality as it relates to the southern flow boundary of the Knippa Gap near the Devils River Trend of the Uvalde salient. Water-quality data constrain a revised conceptual model of the flow and karstification in this critical area of recharge to the San Antonio pool, and provide specific lateral boundaries and vertical karstification zones which are being tested in the more comprehensive M.S. thesis. Although current interpretations are tentative, it appears this conceptual model will be readily convertible into a digital model that can test 2hypotheses relating a much broader suite of calibration data, including water levels, water budgets, and spring discharges.


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