Adaptations of indigenous bacteria to fuel contamination in karst aquifers in south-central Kentucky

USGS Publications Warehouse

Byl, Thomas D.; Metge, David W.; Agymang, Daniel T.; Bradley, Michael W.; Hileman, Gregg; Harvey, Ronald W.

2014-01-01

The karst aquifer systems in southern Kentucky can be dynamic and quick to change. Microorganisms that live in these unpredictable aquifers are constantly faced with environmental changes. Their survival depends upon adaptations to changes in water chemistry, taking advantage of positive stimuli and avoiding negative environmental conditions. The U.S. Geological Survey conducted a study in 2001 to determine the capability of bacteria to adapt in two distinct regions of water quality in a karst aquifer, an area of clean, oxygenated groundwater and an area where the groundwater was oxygen depleted and contaminated by jet fuel. Water samples containing bacteria were collected from one clean well and two jet fuel contaminated wells in a conduit-dominated karst aquifer. Bacterial concentrations, enumerated through direct count, ranged from 500,000 to 2.7 million bacteria per mL in the clean portion of the aquifer, and 200,000 to 3.2 million bacteria per mL in the contaminated portion of the aquifer over a twelve month period. Bacteria from the clean well ranged in size from 0.2 to 2.5 mm, whereas bacteria from one fuel-contaminated well were generally larger, ranging in size from 0.2 to 3.9 mm. Also, bacteria collected from the clean well had a higher density and, consequently, were more inclined to sink than bacteria collected from contaminated wells. Bacteria collected from the clean portion of the karst aquifer were predominantly (,95%) Gram-negative and more likely to have flagella present than bacteria collected from the contaminated wells, which included a substantial fraction (,30%) of Gram-positive varieties. The ability of the bacteria from the clean portion of the karst aquifer to biodegrade benzene and toluene was studied under aerobic and anaerobic conditions in laboratory microcosms. The rate of fuel biodegradation in laboratory studies was approximately 50 times faster under aerobic conditions as compared to anaerobic, sulfur-reducing conditions. The

Hydrological controls on transient aquifer storage in a karst watershed

NASA Astrophysics Data System (ADS)

Spellman, P.; Martin, J.; Gulley, J. D.

2017-12-01

While surface storage of floodwaters is well-known to attenuate flood peaks, transient storage of floodwaters in aquifers is a less recognized mechanism of flood peak attenuation. The hydraulic gradient from aquifer to river controls the magnitude of transient aquifer storage and is ultimately a function of aquifer hydraulic conductivity, and effective porosity. Because bedrock and granular aquifers tend to have lower hydraulic conductivities and porosities, their ability to attenuate flood peaks is generally small. In karst aquifers, however, extensive cave systems create high hydraulic conductivities and porosities that create low antecedent hydraulic gradients between aquifers and rivers. Cave springs can reverse flow during high discharges in rivers, temporarily storing floodwaters in the aquifer thus reducing the magnitude of flood discharge downstream. To date however, very few studies have quantified the magnitude or controls of transient aquifer storage in karst watersheds. We therefore investigate controls on transient aquifer storage by using 10 years of river and groundwater data from the Suwannee River Basin, which flows over the karstic upper Floridan aquifer in north-central Florida. We use multiple linear regression to compare the effects of three hydrological controls on the magnitude of transient aquifer storage: antecedent stage, recharge and slope of hydrograph rise. We show the dominant control on transient aquifer storage is antecedent stage, whereby lower stages result in greater magnitudes of transient aquifer storage. Our results suggest that measures of groundwater levels prior to an event can be useful in determining whether transient aquifer storage will occur and may provide a useful metric for improving predictions of flood magnitudes.

SWISSKARST Project - how to document the karst aquifers in Switzerland using the KARSYS approach.

NASA Astrophysics Data System (ADS)

Malard, A.; Vouillamoz, J.; Jeannin, P.-Y.; Weber, E.; Eichenberger, U.

2012-04-01

Swiss karst aquifers are poorly documented although they represent a resource estimated to around 120 km3 of fresh water - which is comparable to the water volume of all Swiss lakes. Within the framework of the Swiss National Research Program 61 an opportunity was given to develop a systematic way to characterize karst aquifers and to describe their hydrological behaviour. The project aims at providing methodologies or guidelines to approach karst systems and to improve their management. This covers a large range of fields such as water supply, civil engineering, renewable energies, natural hazards, etc. In this context SISKA developed a dedicated approach named KARSYS for KARst SYStems characterization. It is based on iterations of 3D geological models combined with some basic hydraulic principles taking place in karst media. The main principles are: (i) The 3D geometry of the aquifer set the framework in which flow processes take place (ii) Aquifers are flooded below the level of the main perennial springs (iii) The expansion of the water table upstream of the main springs is lower than 1% (low water stage). High water gradients are simulated according to the elevation of temporary springs or observations in existing boreholes or caves. The approach explicitly shows through 3D visual that some groundwater bodies may be separated at low water stage and connected at high water. Such 3D views bring often explanations to the interpretation of "strange" or "not repeatable" dye tracer's results. A major input of KARSYS approach is to provide a systematic construction of a conceptual model for all hydrological karst systems. It also considers interactions between adjacent systems, providing new concepts on the delineation of karst systems. KARSYS approach can be applied in a quick and approximate way and improved along in order to reach a precision according to the question to be addressed. Results of KARSYS applications are: (i) The delineation of catchment areas of

Nutrient dynamics as indicators of karst processes: Comparison of the Chalk aquifer (Normandy, France) and the Edwards aquifer (Texas, U.S.A.)

USGS Publications Warehouse

Mahler, B.J.; Valdes, D.; Musgrove, M.; Massei, N.

2008-01-01

Karst aquifers display a range of geologic and geomorphic characteristics in a wide range of climatic and land-use settings; identification of transport dynamics representative of karst aquifers in general could help advance our understanding of these complex systems. To this end, nutrient, turbidity, and major ion dynamics in response to storms were compared at multiple sites in two karst aquifers with contrasting characteristics and settings: the Chalk aquifer (Eure Department, Normandy, France) and the Barton Springs segment of the Edwards Aquifer (Texas, U.S.A.). The Chalk aquifer is typified by high matrix porosity, thick surficial deposits (up to 30??m thick), and agricultural land use; the Barton Springs segment is typified by low matrix porosity, outcropping limestone, and urban land use. Following one to three storms, from 5 to 16 samples from springs and wells were analyzed for major ions, and specific conductance and turbidity were monitored continuously. Comparison of the chemographs indicated some generalized responses, including an increase in turbidity and potassium concentrations and a decrease in major ion and nitrate concentrations with infiltrating storm runoff. Factor analysis of major ions and turbidity revealed strikingly similar behavior of the chemical variables for the two aquifers: The first two factors, explaining more than 75% of the variability, illustrate that dynamics of most major ions (including nitrate) are opposed to those of turbidity and of potassium. The results demonstrate that potassium and nitrate are effective tracers of infiltrating storm runoff and resident ground water, respectively, and the similar results for these two highly contrasting aquifers suggest that the dynamics identified might be applicable to karst systems in general. ?? 2008 Elsevier B.V. All rights reserved.

Nutrient dynamics as indicators of karst processes: comparison of the Chalk aquifer (Normandy, France) and the Edwards aquifer (Texas, U.S.A.).

PubMed

Mahler, B J; Valdes, D; Musgrove, M; Massei, N

2008-05-26

Karst aquifers display a range of geologic and geomorphic characteristics in a wide range of climatic and land-use settings; identification of transport dynamics representative of karst aquifers in general could help advance our understanding of these complex systems. To this end, nutrient, turbidity, and major ion dynamics in response to storms were compared at multiple sites in two karst aquifers with contrasting characteristics and settings: the Chalk aquifer (Eure Department, Normandy, France) and the Barton Springs segment of the Edwards Aquifer (Texas, U.S.A.). The Chalk aquifer is typified by high matrix porosity, thick surficial deposits (up to 30 m thick), and agricultural land use; the Barton Springs segment is typified by low matrix porosity, outcropping limestone, and urban land use. Following one to three storms, from 5 to 16 samples from springs and wells were analyzed for major ions, and specific conductance and turbidity were monitored continuously. Comparison of the chemographs indicated some generalized responses, including an increase in turbidity and potassium concentrations and a decrease in major ion and nitrate concentrations with infiltrating storm runoff. Factor analysis of major ions and turbidity revealed strikingly similar behavior of the chemical variables for the two aquifers: The first two factors, explaining more than 75% of the variability, illustrate that dynamics of most major ions (including nitrate) are opposed to those of turbidity and of potassium. The results demonstrate that potassium and nitrate are effective tracers of infiltrating storm runoff and resident ground water, respectively, and the similar results for these two highly contrasting aquifers suggest that the dynamics identified might be applicable to karst systems in general.

Water resources management in karst aquifers - concepts and modeling approaches

NASA Astrophysics Data System (ADS)

Sauter, M.; Schmidt, S.; Abusaada, M.; Reimann, T.; Liedl, R.; Kordilla, J.; Geyer, T.

2011-12-01

Water resources management schemes generally imply the availability of a spectrum of various sources of water with a variability of quantity and quality in space and time, and the availability and suitability of storage facilities to cover various demands of water consumers on quantity and quality. Aquifers are generally regarded as suitable reservoirs since large volumes of water can be stored in the subsurface, water is protected from contamination and evaporation and the underground passage assists in the removal of at least some groundwater contaminants. Favorable aquifer properties include high vertical hydraulic conductivities for infiltration, large storage coefficients and not too large hydraulic gradients / conductivities. The latter factors determine the degree of discharge, i.e. loss of groundwater. Considering the above criteria, fractured and karstified aquifers appear to not really fulfill the respective conditions for storage reservoirs. Although infiltration capacity is relatively high, due to low storativity and high hydraulic conductivities, the small quantity of water stored is rapidly discharged. However, for a number of specific conditions, even karst aquifers are suitable for groundwater management schemes. They can be subdivided into active and passive management strategies. Active management options include strategies such as overpumping, i.e. the depletion of the karst water resources below the spring outflow level, the construction of subsurface dams to prevent rapid discharge. Passive management options include the optimal use of the discharging groundwater under natural discharge conditions. System models that include the superposition of the effect of the different compartments soil zone, epikarst, vadose and phreatic zone assist in the optimal usage of the available groundwater resources, while taking into account the different water reservoirs. The elaboration and implementation of groundwater protection schemes employing well

Estimation of transit times in a Karst Aquifer system using environmental tracers: Application on the Jeita Aquifer system-Lebanon.

NASA Astrophysics Data System (ADS)

Doummar, Joanna; Hamdan, Ahmad

2016-04-01

Estimating transit times is essential for the assessment of aquifer vulnerability to contaminants. Groundwater in karst aquifer is assumed to be relatively young due to fast preferential pathways; slow flow components are present in water stored in the fissured matrix. Furthermore, transit times are site specific as they depend on recharge rates, temperatures, elevation, and flow media; saturated and unsaturated zones. These differences create significant variation in the groundwater age in karst systems as the water sampled will be a mix of different water that has been transported through different flow pathways (fissured matrix and conduits). Several methods can be applied to estimate water transit time of an aquifer such as artificial tracers, which provide an estimate for fast flow velocities. In this study, groundwater residence times in the Jeita spring aquifer (Lebanon) were estimated using several environmental tracers such as Chlorofluorocarbons (CFCs), Sulfur Hexafluoride (SF6), Helium-Tritium (3H, 3H- 3He). Additional stable isotope and major ion analysis was performed to characterize water types. Groundwater samples were collected from six different wells in the Jeita catchment area (Jurassic Kesrouane aquifer) as well as from the spring and cave itself. The results are reproducible for the Tritium-Helium method, unlike for the CFC/SF6 methods that yielded poor results due to sampling problems. Tritium concentrations in all groundwater samples show nearly the same concentration (~2.73 TU) except for one sample with relatively lower tritium concentration (~2.26 TU). Ages ranging from 0.07 ± 0.07 years to 23.59 ± 0.00 years were obtained. The youngest age is attributed to the spring/ cave while the oldest ages were obtained in wells tapping the fissured matrix. Neon in these samples showed considerable variations and high delta Ne in some samples indicating high excess air. Four (4) samples showed extreme excess air (Delta-Ne is greater than 70 %) and

Natural and Artificial (fluorescent) Tracers to Characterise Hydrogeological Functioning and to Protect Karst Aquifers

NASA Astrophysics Data System (ADS)

Andreo, B.; Mudarra, M.; Marin, A. I.; Barberá, J. A.

2012-12-01

The hydrogeological functioning and response of karst aquifers can be determined by the joint use of natural hydrogeochemical tracers, especially total organic carbon (TOC) and intrinsic fluorescence of water, together with artificial (fluorescent) tracers, under the same hydrodynamic conditions. Sharp and rapid variations in discharge, temperature, electrical conductivity and water chemistry, particularly of natural tracers of infiltration (TOC, intrinsic fluorescence and NO3-) recorded in karst spring water, confirm the existence of well developed karst conduits in the sector of the aquifer being drained, with rapid flows and very short water transit times from the surface to the springs (Mudarra et al., 2011). This is in agreement with the evidence obtained from breakthrough curves of fluorescent dye tracers (uranine, eosine, etc.). However, time lags between maximum concentrations of natural (especially TOC and intrinsic fluorescence) and artificial tracers show that the global system response is faster than that produced from a recharge concentrated at a point on the surface, even in karst sinkholes. Response and transit times of water through the karst can be calculated using both natural and artificial tracers, but flow velocities can really only be quantified using artificial tracers. Analysis of the responses obtained by natural tracers of infiltration (global system response) and artificial tracers (single response) in karst waters has revealed the usefulness and complementarity of both techniques for characterising the hydrogeological functioning of karst aquifers and, even more important, for validating contamination vulnerability mapping in these medium (Zwahlen, 2004; Andreo et al., 2006). In recent decades, several methods have been developed for such vulnerability mapping, but little progress has been made in validating their results. This validation is essential for the adequate protection of water resources in karst media, as has been shown in

Simulating flow in karst aquifers at laboratory and sub-regional scales using MODFLOW-CFP

NASA Astrophysics Data System (ADS)

Gallegos, Josue Jacob; Hu, Bill X.; Davis, Hal

2013-12-01

Groundwater flow in a well-developed karst aquifer dominantly occurs through bedding planes, fractures, conduits, and caves created by and/or enlarged by dissolution. Conventional groundwater modeling methods assume that groundwater flow is described by Darcian principles where primary porosity (i.e. matrix porosity) and laminar flow are dominant. However, in well-developed karst aquifers, the assumption of Darcian flow can be questionable. While Darcian flow generally occurs in the matrix portion of the karst aquifer, flow through conduits can be non-laminar where the relation between specific discharge and hydraulic gradient is non-linear. MODFLOW-CFP is a relatively new modeling program that accounts for non-laminar and laminar flow in pipes, like karst caves, within an aquifer. In this study, results from MODFLOW-CFP are compared to those from MODFLOW-2000/2005, a numerical code based on Darcy's law, to evaluate the accuracy that CFP can achieve when modeling flows in karst aquifers at laboratory and sub-regional (Woodville Karst Plain, Florida, USA) scales. In comparison with laboratory experiments, simulation results by MODFLOW-CFP are more accurate than MODFLOW 2005. At the sub-regional scale, MODFLOW-CFP was more accurate than MODFLOW-2000 for simulating field measurements of peak flow at one spring and total discharges at two springs for an observed storm event.

Multitracer experiment to evaluate the attenuation of selected organic micropollutants in a karst aquifer.

PubMed

Hillebrand, Olav; Nödler, Karsten; Sauter, Martin; Licha, Tobias

2015-02-15

The increasing pressure on drinking water resources necessitates an efficient management of potential and actual drinking water resources. Karst aquifers play a key role in the supply of the world's population with drinking water. Around one quarter of all drinking water is produced from these types of aquifers. Unfortunately due to the aquifer characteristics with extremely high hydraulic conductivities and short residence times, these systems are vulnerable to contamination. For successful management, a fundamental understanding of mass transport and attenuation processes with respect to potential contaminants is vital. In this study, a multitracer experiment was performed in a karst aquifer in SW-Germany for determining the attenuation capacity of a karst environment by assessing the environmental fate of selected relevant micropollutants. Uranine, acesulfame and carbamazepine were injected into a sinkhole as reference tracers together with the reactive compounds atenolol, caffeine, cyclamate, ibuprofen and paracetamol (also known as acetaminophen). The breakthrough of the tracers was monitored at a karst spring at a distance of ca. 3 km. The breakthrough curves of the reactive compounds were interpreted relative to the reference substances. No significant retardation was found for any of the investigated micropollutants. The determined half-lives of the reactive compounds range from 38 to 1,400 h (i.e. persistent within the investigation period) in the following order (from high to no observed attenuation): paracetamol>atenolol≈ibuprofen>caffeine≫cyclamate. The attenuation rates are generally in agreement with studies from other environmental compartments. The occurrence of the biotransformation product atenolol acid served as evidence for in-situ biodegradation within the aquifer system. Copyright © 2014 Elsevier B.V. All rights reserved.

Organic and inorganic carbon dynamics in a karst aquifer: Santa Fe River Sink-Rise system, north Florida, USA

NASA Astrophysics Data System (ADS)

Jin, Jin; Zimmerman, Andrew R.; Moore, Paul J.; Martin, Jonathan B.

2014-03-01

Spatiotemporal variations in dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), major ions concentrations and other geochemical parameters including stable carbon isotopes of DIC (δ13CDIC), were measured in surface water and deep and shallow well water samples of the Santa Fe River Sink-Rise eogenetic karst system, north Florida, USA. Three end-member water sources were identified: one DOC-rich/DIC-poor/δ13CDIC-depleted, one DOC-poor/DIC-rich/δ13CDIC-enriched, and one enriched in major ions. Given their spatiotemporal distributions, they were presumed to represent soil water, upper aquifer groundwater, and deep aquifer water sources, respectively. Using assumed ratios of Na+, Cl, and SO42- for each end-member, a mixing model calculated the contribution of each water source to each sample. Then, chemical effects of biogeochemical reactions were calculated as the difference between those predicted by the mixing model and measured species concentrations. In general, carbonate mineral dissolution occurred throughout the Sink-Rise system, surface waters were net autotrophic and the subsurface was in metabolic balance, i.e., no net DOC or DIC production or consumption. However, there was evidence for chemolithoautotrophy, perhaps by hydrogen oxidizing microbes, at some deep aquifer sites. Mineralization of this autochthonous natural dissolved organic matter (NDOM) led to localized carbonate dissolution as did surface water-derived NDOM supplied to shallow well sites during the highest flow periods. This study demonstrates linkages between hydrology, abiotic and microbial processes and carbon dynamics and has important implications for groundwater quality, karst morphologic evolution, and hydrogeologic projects such as aquifer storage and recovery in karst systems.

Occurrence of Pepper Mild Mottle Virus (PMMoV) in Groundwater from a Karst Aquifer System in the Yucatan Peninsula, Mexico.

PubMed

Rosiles-González, Gabriela; Ávila-Torres, Gerardo; Moreno-Valenzuela, Oscar A; Acosta-González, Gilberto; Leal-Bautista, Rosa María; Grimaldo-Hernández, Cinthya D; Brown, Judith K; Chaidez-Quiroz, Cristóbal; Betancourt, Walter Q; Gerba, Charles P; Hernández-Zepeda, Cecilia

2017-12-01

The Yucatan Peninsula of Mexico hosts a karst aquifer system that is the only source of freshwater for the area; however, it is vulnerable to human-mediated contamination. Pepper mild mottle virus (PMMoV) is one of the most abundant RNA viruses associated with human feces, making it a viable indicator for tracking fecal pollution in aquatic environments, including groundwater. In this study, groundwater samples collected from a karst aquifer from fresh and brackish water locations were analyzed for fecal indicator bacteria, somatic and male F+ specific coliphages, and PMMoV during the rainy and dry seasons. Total coliform bacteria were detected at all sites, whereas Escherichia coli were found at relatively low levels <40 MPN/100 ml. The highest average concentrations of somatic and male F+ specific coliphages were 920 and 330 plaque forming units per 100 ml, respectively, detected in freshwater during the rainy season. PMMoV RNA was detected in 85% of the samples with gene sequences sharing 99-100% of nucleotide identity with PMMoV sequences available in GenBank. Quantification of PMMoV genome copies (GC) by quantitative real-time PCR indicated concentrations ranging from 1.7 × 10 1 to 1.0 × 10 4 GC/L, with the highest number of GC detected during the rainy season. No significant correlation was observed between PMMoV occurrence by season or water type (p > 0.05). Physicochemical and indicator bacteria were not correlated with PMMoV concentrations. The abundance and prevalence of PMMoV in the karst aquifer may reflect its environmental persistence and its potential as a fecal indicator in this karst aquifer system.

Modelling karst aquifer evolution in fractured, porous rocks

NASA Astrophysics Data System (ADS)

Kaufmann, Georg

2016-12-01

The removal of material in soluble rocks by physical and chemical dissolution is an important process enhancing the secondary porosity of soluble rocks. Depending on the history of the soluble rock, dissolution can occur either along fractures and bedding partings of the rock in the case of a telogenetic origin, or within the interconnected pore space in the case of eogenetic origin. In soluble rocks characterised by both fractures and pore space, dissolution in both flow compartments is possible. We investigate the dissolution of calcite both along fractures and within the pore space of a limestone rock by numerical modelling. The limestone rock is treated as fractured, porous aquifer, in which the hydraulic conductivity increases with time both for the fractures and the pore spaces. We show that enlargement of pore space by dissolution will accelerate the development of a classical fracture-dominated telogenetic karst aquifer, breakthrough occurs faster. In the case of a pore-controlled aquifer as in eogenetic rocks, enlargement of pores results in a front of enlarged pore spaces migrating into the karst aquifer, with more homogeneous enlargement around this dissolution front, and later breakthrough.

River Intrusion in Karst Springs in Eogenetic Aquifers: Implications for Speleogenesis

NASA Astrophysics Data System (ADS)

Martin, J. B.; Gulley, J.; Screaton, E. J.

2008-12-01

Conceptual models of speleogenesis generally assume uni-directional transport in integrated conduit systems from discrete recharge points to discharge at karst springs. Estavelles, however, are karst springs that function intermittently as discrete recharge points when river stage rises more rapidly than local aquifer heads. As river water chemistry changes between baseflow and floods, estavelles should influence mass transport through (e.g. organic carbon, nutrients, and oxygen) and speleogenesis within karst systems. Estavelles are common in our study area in north-central Florida, particularly along the lower reaches of the Santa Fe River, where it flows across the unconfined karstic Floridan aquifer. River stage in this unconfined region can rise much faster than aquifer heads when large amounts of rain fall on the confined regions in its upper reaches. Backflooding into the estavelles during elevated river stage drives river water into the ground, causing some springs to reverse and other springs to recirculate large volumes of river water. Floodwaters originating in the confined region are highly undersaturated with respect to calcite, and thus river water transitions from slightly supersaturated to highly undersaturated with respect to calcite during flood events. As a result, conduits connected to estavelles are continuously enlarged as springs reverse or recirculate calcite-undersaturated river water. It has been suggested that currently flooded caves (i.e. karst conduits) associated with springs in Florida formed entirely underwater because speleothems, which are prevalent in flooded caves in the Yucatan and Bahamas, have not been observed by cave divers. Results of this study indicate that the absence of speleothems does not necessarily provide evidence of a continuous phreatic history for underwater caves. Instead speleothems that formed in caves while dry could have been dissolved by backflooding of estavelles with undersaturated water

HISTORICAL CONTAMINATION OF GROUNDWATER RESOURCES IN THE NORTH COAST KARST AQUIFERS OF PUERTO RICO

PubMed Central

Padilla, Ingrid; Irizarry, Celys; Steele, Katherine

2012-01-01

The North Coast Karst Aquifer System of Puerto Rico is the island’s most productive aquifer. The characteristics that make it highly productive also make it vulnerable to contamination. This research, which addresses the historical contamination of groundwater resources in the northern karst region was conducted through integration of spatial hydrogeologic and contaminant concentration data in the La Plata-Arecibo area. The study used GIS technologies and focused on phthalates and chlorinated volatile organic compounds (CVOCs) and phthalates due to their ubiquitous presence in the environment as well as their presence in listed and potential superfund sites in Puerto Rico and U.S. and potential for exposure and health impacts. Results show an extensive historical contamination of the groundwater resources in the northern karst aquifers. Long-term contamination indicates the aquifers’ large capacity for storing and releasing contaminants and reflects a long-term potential for exposure. The degradation of this important water resource has resulted in a subsequent reduction of the extraction capacity and an increase in the cost of use. PMID:24772197

Geological structure, recharge processes and underground drainage of a glacierised karst aquifer system, Tsanfleuron-Sanetsch, Swiss Alps

NASA Astrophysics Data System (ADS)

Gremaud, Vivian; Goldscheider, Nico; Savoy, Ludovic; Favre, Gérald; Masson, Henri

2009-12-01

The relationships between stratigraphic and tectonic setting, recharge processes and underground drainage of the glacierised karst aquifer system ‘Tsanfleuron-Sanetsch’ in the Swiss Alps have been studied by means of various methods, particularly tracer tests (19 injections). The area belongs to the Helvetic nappes and consists of Jurassic to Palaeogene sedimentary rocks. Strata are folded and form a regional anticlinorium. Cretaceous Urgonian limestone constitutes the main karst aquifer, overlain by a retreating glacier in its upper part. Polished limestone surfaces are exposed between the glacier front and the end moraine of 1855/1860 (Little Ice Age); typical alpine karrenfields can be observed further below. Results show that (1) large parts of the area are drained by the Glarey spring, which is used as a drinking water source, while marginal parts belong to the catchments of other springs; (2) groundwater flow towards the Glarey spring occurs in the main aquifer, parallel to stratification, while flow towards another spring crosses the entire stratigraphic sequence, consisting of about 800 m of marl and limestone, along deep faults that were probably enlarged by mass movements; (3) the variability of glacial meltwater production influences the shape of the tracer breakthrough curves and, consequently, flow and transport in the aquifer.

Sustainable yield of a karst aquifer system: a case study of Jinan springs in northern China

NASA Astrophysics Data System (ADS)

Kang, Fengxin; Jin, Menggui; Qin, Pinrui

2011-06-01

Based on the long-term monitoring data of rainfall, groundwater levels, groundwater abstraction, spring flow rates and groundwater quality, an assessment has been undertaken of the sustainable yield of a karst aquifer system in Shandong Province, northern China, to maintain perennial outflow of the karst springs while meeting water demands. One of the fundamental indicators for sustainable yield of groundwater is identified as maximum allowable water-level drawdown. A regional three-dimensional finite-difference numerical model has been developed to optimize the schemes associated with well fields and their locations and sustainable yields, in the Jinan spring catchment and its adjacent karst groundwater catchments, with the aim of maintaining the water level higher than the allowable lowest water level of 27.5 m above sea level. Furthermore, measures necessary to move towards sustainable use of the karst groundwater are outlined, drawing on contingency plans of water-source replacement and artificial recharge, dual water supply (based in water quality), use of the spring waters themselves, and groundwater quality protection.

Advances in Dynamic Transport of Organic Contaminants in Karst Groundwater Systems

NASA Astrophysics Data System (ADS)

Padilla, I. Y.; Vesper, D.; Alshawabkeh, A.; Hellweger, F.

2011-12-01

Karst groundwater systems develop in soluble rocks such as limestone, and are characterized by high permeability and well-developed conduit porosity. These systems provide important freshwater resources for human consumption and ecological integrity of streams, wetlands, and coastal zones. The same characteristics that make karst aquifers highly productive make them highly vulnerable to contamination. As a result, karst aquifers serve as an important route for contaminants exposure to humans and wildlife. Transport of organic contaminants in karst ground-water occurs in complex pathways influenced by the flow mechanism predominating in the aquifer: conduit-flow dominated systems tend to convey solutes rapidly through the system to a discharge point without much attenuation; diffuse-flow systems, on the other hand, can cause significant solute retardation and slow movement. These two mechanisms represent end members of a wide spectrum of conditions found in karst areas, and often a combination of conduit- and diffuse-flow mechanisms is encountered, where both flow mechanisms can control the fate and transport of contaminants. This is the case in the carbonate aquifers of northern Puerto Rico. This work addresses advances made on the characterization of fate and transport processes in karst ground-water systems characterized by variable conduit and/or diffusion dominated flow under high- and low-flow conditions. It involves laboratory-scale physical modeling and field-scale sampling and historical analysis of contaminant distribution. Statistical analysis of solute transport in Geo-Hydrobed physical models shows the heterogeneous character of transport dynamics in karstic units, and its variability under different flow regimes. Field-work analysis of chlorinated volatile organic compounds and phthalates indicates a large capacity of the karst systems to store and transmit contaminants. This work is part of the program "Puerto Rico Testsite for Exploring Contamination

Linking climate change and karst hydrology to evaluate species vulnerability: The Edwards and Madison aquifers (Invited)

NASA Astrophysics Data System (ADS)

Mahler, B. J.; Long, A. J.; Stamm, J. F.; Poteet, M.; Symstad, A.

2013-12-01

Karst aquifers present an extreme case of flow along structurally variable pathways, making them highly dynamic systems and therefore likely to respond rapidly to climate change. In turn, many biological communities and ecosystems associated with karst are sensitive to hydrologic changes. We explored how three sites in the Edwards aquifer (Texas) and two sites in the Madison aquifer (South Dakota) might respond to projected climate change from 2011 to 2050. Ecosystems associated with these karst aquifers support federally listed endangered and threatened species and state-listed species of concern, including amphibians, birds, insects, and plants. The vulnerability of selected species associated with projected climate change was assessed. The Advanced Research Weather and Research Forecasting (WRF) model was used to simulate projected climate at a 36-km grid spacing for three weather stations near the study sites, using boundary and initial conditions from the global climate model Community Climate System Model (CCSM3) and an A2 emissions scenario. Daily temperature and precipitation projections from the WRF model were used as input for the hydrologic Rainfall-Response Aquifer and Watershed Flow (RRAWFLOW) model and the Climate Change Vulnerability Index (CCVI) model. RRAWFLOW is a lumped-parameter model that simulates hydrologic response at a single site, combining the responses of quick and slow flow that commonly characterize karst aquifers. CCVI uses historical and projected climate and hydrologic metrics to determine the vulnerability of selected species on the basis of species exposure to climate change, sensitivity to factors associated with climate change, and capacity to adapt to climate change. An upward trend in temperature was projected for 2011-2050 at all three weather stations; there was a trend (downward) in annual precipitation only for the weather station in Texas. A downward trend in mean annual spring flow or groundwater level was projected for

Visualization of conduit-matrix conductivity differences in a karst aquifer using time-lapse electrical resistivity

NASA Astrophysics Data System (ADS)

Meyerhoff, Steven B.; Karaoulis, Marios; Fiebig, Florian; Maxwell, Reed M.; Revil, André; Martin, Jonathan B.; Graham, Wendy D.

2012-12-01

In the karstic upper Floridan aquifer, surface water flows into conduits of the groundwater system and may exchange with water in the aquifer matrix. This exchange has been hypothesized to occur based on differences in discharge at the Santa Fe River Sink-Rise system, north central Florida, but has yet to be visualized using any geophysical techniques. Using electrical resistivity tomography, we conducted a time-lapse study at two locations with mapped conduits connecting the Santa Fe River Sink to the Santa Fe River Rise to study changes of electrical conductivity during times of varying discharge over a six-week period. Our results show conductivity differences between matrix, conduit changes in resistivity occurring through time at the locations of mapped karst conduits, and changes in electrical conductivity during rainfall infiltration. These observations provide insight into time scales and matrix conduit conductivity differences, illustrating how surface water flow recharged to conduits may flow in a groundwater system in a karst aquifer.

Geochemical and statistical evidence of recharge, mixing, and controls on spring discharge in an eogenetic karst aquifer

NASA Astrophysics Data System (ADS)

Moore, Paul J.; Martin, Jonathan B.; Screaton, Elizabeth J.

2009-10-01

SummaryInformation about sources of recharge, distributions of flow paths, and the extent of water-rock reactions in karst aquifers commonly result from monitoring spring chemistry and discharge. To investigate the relationship between spring characteristics and the complexities of karst aquifers, we couple variations in surface- and groundwater chemistry to physical conditions including river stage, precipitation, and evapotranspiration (ET) within a sink-rise system through a 6-km portion of the Upper Floridan aquifer (UFA) in north-central Florida. Principal component analysis (PCA) of time series major-element compositions suggests that at least three sources of water affect spring discharge, including allogenic recharge into a swallet, diffuse recharge through a thin vadose zone, and water upwelling from deep within the aquifer. The deep-water source exerts the strongest influence on water chemistry by providing a majority of Na +, Mg 2+, K +, Cl -, and SO42- to the system. Anomalously high temperature at one of several monitoring wells reflects vertical flow of about 1 m/year. Mass-balance calculations suggest diffuse recharge and deep-water upwelling can provide up to 50% of the spring discharge; however, their contributions depend on head gradients between the conduit and surrounding aquifer matrix, which are influenced by variations in precipitation, ET, and river stage. Our results indicate that upwelling from deep flow paths may provide significant contributions of water to spring discharge, and that monitoring only springs limits interpretations of karst systems by masking critical components of the aquifer, such as water sources and flow paths. These results also suggest the matrix in eogenetic aquifers is a major pathway for flow even in a system dominated by conduits.

Effects of dynamically variable saturation and matrix-conduit coupling of flow in karst aquifers

USGS Publications Warehouse

Reimann, T.; Geyer, T.; Shoemaker, W.B.; Liedl, R.; Sauter, M.

2011-01-01

Well-developed karst aquifers consist of highly conductive conduits and a relatively low permeability fractured and/or porous rock matrix and therefore behave as a dual-hydraulic system. Groundwater flow within highly permeable strata is rapid and transient and depends on local flow conditions, i.e., pressurized or nonpressurized flow. The characterization of karst aquifers is a necessary and challenging task because information about hydraulic and spatial conduit properties is poorly defined or unknown. To investigate karst aquifers, hydraulic stresses such as large recharge events can be simulated with hybrid (coupled discrete continuum) models. Since existing hybrid models are simplifications of the system dynamics, a new karst model (ModBraC) is presented that accounts for unsteady and nonuniform discrete flow in variably saturated conduits employing the Saint-Venant equations. Model performance tests indicate that ModBraC is able to simulate (1) unsteady and nonuniform flow in variably filled conduits, (2) draining and refilling of conduits with stable transition between free-surface and pressurized flow and correct storage representation, (3) water exchange between matrix and variably filled conduits, and (4) discharge routing through branched and intermeshed conduit networks. Subsequently, ModBraC is applied to an idealized catchment to investigate the significance of free-surface flow representation. A parameter study is conducted with two different initial conditions: (1) pressurized flow and (2) free-surface flow. If free-surface flow prevails, the systems is characterized by (1) a time lag for signal transmission, (2) a typical spring discharge pattern representing the transition from pressurized to free-surface flow, and (3) a reduced conduit-matrix interaction during free-surface flow. Copyright 2011 by the American Geophysical Union.

Water exchange and pressure transfer between conduits and matrix and their influence on hydrodynamics of two karst aquifers with sinking streams

NASA Astrophysics Data System (ADS)

Bailly-Comte, Vincent; Martin, Jonathan B.; Jourde, Hervé; Screaton, Elizabeth J.; Pistre, Séverin; Langston, Abigail

2010-05-01

SummaryKarst aquifers are heterogeneous media where conduits usually drain water from lower permeability volumes (matrix and fractures). For more than a century, various approaches have used flood recession curves, which integrate all hydrodynamic processes in a karst aquifer, to infer physical properties of the movement and storage of groundwater. These investigations typically only consider flow to the conduits and thus have lacked quantitative observations of how pressure transfer and water exchange between matrix and conduit during flooding could influence recession curves. We present analyses of simultaneous discharge and water level time series of two distinctly different karst systems, one with low porosity and permeability matrix rocks in southern France, and one with high porosity and permeability matrix rocks in north-central Florida (USA). We apply simple mathematical models of flood recession using time series representations of recharge, storage, and discharge processes in the karst aquifer. We show that karst spring hydrographs can be interpreted according to pressure transfer between two distinct components of the aquifer, conduit and matrix porosity, which induce two distinct responses at the spring. Water exchange between conduits and matrix porosity successively control the flow regime at the spring. This exchange is governed by hydraulic head differences between conduits and matrix, head gradients within conduits, and the contrast of permeability between conduits and matrix. These observations have consequences for physical interpretations of recession curves and modeling of karst spring flows, particularly for the relative magnitudes of base flow and quick flow from karst springs. Finally, these results suggest that similar analyses of recession curves can be applied to karst aquifers with distinct physical characteristics utilizing well and spring hydrograph data, but information must be known about the hydrodynamics and physical properties of

Heterotrophic prokaryotic production in ultra-oligotrophic alpine karst aquifers and ecological implications

PubMed Central

Wilhartitz, Inés C.; Kirschner, Alexander K.T.; Stadler, Hermann; Herndl, Gerhard J.; Dietzel, Martin; Latal, Christine; Mach, Robert L.; Farnleitner, Andreas H.

2011-01-01

Spring waters from alpine karst aquifers are important drinking water resources. To investigate in situ prokaryotic heterotrophic production (HP) and its controlling factors, two alpine karst springs of contrasting hydrogeology but of nearby catchments were studied over two annual cycles. Heterotrophic production in spring water, as determined by [3H]leucine incorporation, was low but revealed strong seasonal variations ranging from 0.06 to 6.83 pmol C l−1 h−1 (DKAS1, dolomitic karst-spring) and from 0.50 to 75.6 pmol C l−1 h−1 (LKAS2, limestone karst-spring). Microautoradiography combined with catalyzed reporter deposition - fluorescence in situ hybridization (MAR-CARD-FISH) showed that only about 7 % of the picoplankton community took up [3H]leucine resulting in generation times of 3 to 684 days. Principal component analysis, applying hydrological, chemical and biological parameters demonstrated that planktonic heterotrophic production in LKAS2 was strongly governed by hydrogeographical components (e.g. discharge), whereas variations in DKAS1 are also strongly influenced by changes within the aquifer itself. Measurements in sediments recovered from LKAS2, DKAS1 and similar alpine karst aquifers (n=12) revealed an 106-fold higher heterotrophic production (average 19 μmol C dm−3 h−1) with significantly lower generation times as compared to the planktonic fraction, highlighting the metabolic potential of surface associated endokarst communities to add to self-purification processes. Estimates of microbially mediated CO2 in this compartment indicated a possible contribution to karstification. PMID:19490127

Prediction, time variance, and classification of hydraulic response to recharge in two karst aquifers

USGS Publications Warehouse

Long, Andrew J.; Mahler, Barbara J.

2013-01-01

additional aquifers, they could contribute to an IRF database and a general classification system for karst aquifers.

Microbial diversity and impact on carbonate geochemistry across a changing geochemical gradient in a karst aquifer.

PubMed

Gray, Cassie J; Engel, Annette S

2013-02-01

Although microbes are known to influence karst (carbonate) aquifer ecosystem-level processes, comparatively little information is available regarding the diversity of microbial activities that could influence water quality and geological modification. To assess microbial diversity in the context of aquifer geochemistry, we coupled 16S rRNA Sanger sequencing and 454 tag pyrosequencing to in situ microcosm experiments from wells that cross the transition from fresh to saline and sulfidic water in the Edwards Aquifer of central Texas, one of the largest karst aquifers in the United States. The distribution of microbial groups across the transition zone correlated with dissolved oxygen and sulfide concentration, and significant variations in community composition were explained by local carbonate geochemistry, specifically calcium concentration and alkalinity. The waters were supersaturated with respect to prevalent aquifer minerals, calcite and dolomite, but in situ microcosm experiments containing these minerals revealed significant mass loss from dissolution when colonized by microbes. Despite differences in cell density on the experimental surfaces, carbonate loss was greater from freshwater wells than saline, sulfidic wells. However, as cell density increased, which was correlated to and controlled by local geochemistry, dissolution rates decreased. Surface colonization by metabolically active cells promotes dissolution by creating local disequilibria between bulk aquifer fluids and mineral surfaces, but this also controls rates of karst aquifer modification. These results expand our understanding of microbial diversity in karst aquifers and emphasize the importance of evaluating active microbial processes that could affect carbonate weathering in the subsurface.

Microbial diversity and impact on carbonate geochemistry across a changing geochemical gradient in a karst aquifer

PubMed Central

Gray, Cassie J; Engel, Annette S

2013-01-01

Although microbes are known to influence karst (carbonate) aquifer ecosystem-level processes, comparatively little information is available regarding the diversity of microbial activities that could influence water quality and geological modification. To assess microbial diversity in the context of aquifer geochemistry, we coupled 16S rRNA Sanger sequencing and 454 tag pyrosequencing to in situ microcosm experiments from wells that cross the transition from fresh to saline and sulfidic water in the Edwards Aquifer of central Texas, one of the largest karst aquifers in the United States. The distribution of microbial groups across the transition zone correlated with dissolved oxygen and sulfide concentration, and significant variations in community composition were explained by local carbonate geochemistry, specifically calcium concentration and alkalinity. The waters were supersaturated with respect to prevalent aquifer minerals, calcite and dolomite, but in situ microcosm experiments containing these minerals revealed significant mass loss from dissolution when colonized by microbes. Despite differences in cell density on the experimental surfaces, carbonate loss was greater from freshwater wells than saline, sulfidic wells. However, as cell density increased, which was correlated to and controlled by local geochemistry, dissolution rates decreased. Surface colonization by metabolically active cells promotes dissolution by creating local disequilibria between bulk aquifer fluids and mineral surfaces, but this also controls rates of karst aquifer modification. These results expand our understanding of microbial diversity in karst aquifers and emphasize the importance of evaluating active microbial processes that could affect carbonate weathering in the subsurface. PMID:23151637

Estimating the proportion of groundwater recharge from flood events in relation to total annual recharge in a karst aquifer

NASA Astrophysics Data System (ADS)

Dvory, N. Z.; Ronen, A.; Livshitz, Y.; Adar, E.; Kuznetsov, M.; Yakirevich, A.

2017-12-01

Sustainable groundwater production from karstic aquifers is primarily dictated by its recharge rate. Therefore, in order to limit over-exploitation, it is essential to accurately quantify groundwater recharge. Infiltration during erratic floods in karstic basins may contribute substantial amount to aquifer recharge. However, the complicated nature of karst systems, which are characterized in part by multiple springs, sinkholes, and losing/gaining streams, present a large obstacle to accurately assess the actual contribution of flood water to groundwater recharge. In this study, we aim to quantify the proportion of groundwater recharge during flood events in relation to the annual recharge for karst aquifers. The role of karst conduits on flash flood infiltration was examined during four flood and artificial runoff events in the Sorek creek near Jerusalem, Israel. The events were monitored in short time steps (four minutes). This high resolution analysis is essential to accurately estimating surface flow volumes, which are of particular importance in arid and semi-arid climate where ephemeral flows may provide a substantial contribution to the groundwater reservoirs. For the present investigation, we distinguished between direct infiltration, percolation through karst conduits and diffused infiltration, which is most affected by evapotranspiration. A water balance was then calculated for the 2014/15 hydrologic year using the Hydrologic Engineering Center - Hydrologic Modelling System (HEC-HMS). Simulations show that an additional 8% to 24% of the annual recharge volume is added from runoff losses along the creek that infiltrate through the karst system into the aquifer. The results improve the understanding of recharge processes and support the use of the proposed methodology for quantifying groundwater recharge.

Unprotected karst resources in western Iran: the environmental impacts of intensive agricultural pumping on the covered karstic aquifer, a case in Kermanshah province

NASA Astrophysics Data System (ADS)

Taheri, Kamal; Taheri, Milad; Parise, Mario

2015-04-01

Bare and covered karst areas, with developed karstic aquifers, cover 35 percent of the Kermanshah province in western Iran. These aquifers are the vital sources for drinking and agricultural water supplies. Over the past decade, intensive groundwater use (exploitation) for irrigation imposed a significant impact on the carbonate environments. The huge amount of groundwater over-exploitations has been carried out and still goes on by local farmers in the absence of appropriate governance monitoring control. Increasing in water demands, for more intense crop production, is an important driving force toward groundwater depletion in alluvial aquifers. Progressive groundwater over-exploitations from underlying carbonate rocks have led to dramatic drawdown in alluvial aquifers and deep karst water tables. Detecting new sources of groundwater extractions and prohibiting the karst water utilization for agricultural use could be the most effective strategy to manage the sustainability of covered karst aquifers. Anthropogenic pressures on covered karst aquifers have magnified the drought impacts and caused dryness of most of the karst springs and deep wells. In this study, the combination of geophysical and geological studies was used to estimate the most intensively exploited agricultural zones of Islam Abad plain in the southwestern Kermanshah province using GIS. The results show that in the past decade a great number of deep wells were drilled through the overburden alluvial aquifer and reached the deep karst water resources. However, the difficulties involved in monitoring deep wells in covered karst aquifer were the main cause of karst water depletion. Overexploitation from both alluvial and karst aquifers is the main reason for drying out the Arkawazi, Sharafshah, Gawrawani karst springs, and the karst drinking water wells 1, 3 and 5 of Islam Abad city. Karst spring landscape destructions, fresh water supply deficit for inhabitants, decreasing of tourism and

A quantitative comparison of moldic and vuggy porosity structure in karst aquifers using image and geospatial analysis

NASA Astrophysics Data System (ADS)

Culpepper, A. R.; Manda, A. K.

2011-12-01

Limestone aquifers are vital sources of groundwater for domestic and industrial use throughout the world. To sustain rising population throughout the southeastern United States, aquifers are increasingly exploited to provide the populace clean and reliable water resources. The moldic Castle Hayne and the vuggy Biscayne aquifer systems are two highly productive aquifers that provide critical water resources to millions of citizens in eastern North Carolina and southeastern Florida, respectively. In order to better understand karst aquifers and evaluate the potential for contaminant transport, detailed investigation of 2D porosity and pore geometry using image and geospatial analysis were undertaken. The objective of this study is to compare and contrast the porosity structure of moldic and vuggy karst aquifers by quantifying 2D porosity and pore geometry from images of slabbed core samples and optical televiewer images. Televiewer images and images of painted core samples from the Spring Garden Member of the Castle Hayne aquifer and Miami Limestone Formation of the Biscayne aquifer were acquired for analysis of porosity structure. The procedure for converting images of slabbed core and televiewer images to a GIS useable format consisted of rectification, calibration, image enhancement, classification, recoding and filtering. In GIS, raster or vector formats were used to assess pore attributes (e.g., area and perimeter) and structure. Preliminary results show that both pore area and perimeter for the Spring Garden Member of the Castle Hayne and Miami Limestone Formation of the Biscayne aquifers can be described by exponential distributions. In both sets of slabbed core images the relatively small pores have the highest occurrence, whereas larger pores occur less frequently. However, the moldic Spring Garden Member of the Castle Hayne aquifer has larger pore sizes derived from cores images than the vuggy Miami Limestone Formation of Biscayne aquifer. Total porosity

Correlation of Spatio-Temporal Contaminant Distribution, Land Use, and Hydrogeological Factors in the Karst Aquifers of Northern Puerto Rico

NASA Astrophysics Data System (ADS)

Torres Torres, N. I.; Padilla, I. Y.

2015-12-01

Karst aquifers are characterized by caves, springs, and sinkholes, and typified by interconnected fissures, fractures and conduits. These characteristics make these aquifers highly productive, and vulnerable to contamination. Previous studies in the northern karst aquifers of Puerto Rico have shown significant distribution of contaminants, including volatile organic compounds, phthalates and other contaminants of emerging concern, beyond demarked sources of contamination. This study develops spatial-temporal distributions of phthalate contaminants in the karst system of northern Puerto Rico and assesses statistical correlations between hydrogeologic factors and groundwater contamination with phthalates. Geographic Information Systems (GIS) tools and technologies, and statistical models are applied to attain these objectives. Results show that there is an extensive contamination with phthalates that varies with time. Contamination is present in the confined and shallow aquifers. Di-(2-ethylhexyl) phthalate (DEHP) is the most detected contaminant (20.6% of the sites). Diethyl phthalate and and dibutyl phthalate are also detected in 6.7% and 8.24% of the sites, respectively. Phthalates detected as mixtures components are significantly detected in areas of high urban and industrial development. They are also detected in areas within 5 miles of superfund sites and landfills. The results indicate that phthalate contamination is highly related to land use. Statistical models show that the hydraulic conductivity of the aquifers, sinkholes density, and time are significantly related to the presence of phthalates in groundwater. The extensive spatio-temporal contamination suggests that contaminants can persist in the environment for long periods of time, and that land use and hydrogeological factors are important factors contributing to the presence of emerging contaminants in karst systems.

Transient deformation of karst aquifers observed by GPS: improved knowledge from Central Apennines (Italy)

NASA Astrophysics Data System (ADS)

Silverii, F.; D'Agostino, N.; Borsa, A. A.

2017-12-01

The redistribution of water masses due to temporal variations of hydrological conditions can produce observable deformation of the shallow crust. Space geodesy, e.g., GPS and InSAR, has provided a considerable improvement in terms of data accuracy and spatial and temporal resolution for the detection and investigation of this kind of deformation. In particular, in the areas where snow and water accumulate for long periods, such as aquifers, relatively high deformation (up to several millimeters) has been observed. Karst aquifers are able to store huge amounts of water and a clear deformation related to the groundwater storage variations has been observed in some regions. In a recent study we showed that the karst aquifers of Southern Apennines deform in response of seasonal and interannual variations of groundwater content, producing a visible transient signal in the time series of the surrounding GPS sites. In this work, we analyze the GPS time series and hydrological data of Central Italy, an interesting and complex area which hosts huge karst aquifers and is characterized by high seismic activity. We show that a noticeable transient signal with features similar to those of Southern Apennines affects also the time series of Central Apennines, suggesting that the large karst aquifers of this region experience a process analogue to the ones in Southern Italy. Thanks to the availability of a dense GPS network and different kinds of hydrological data (rainfall, spring discharge, groundwater level) we focus on the process causing the observed deformation. In particular, we model the observed deformation by inverting the GPS data using Green's functions for finite strain cuboid sources (Barbot et al. 2017). An enhanced understanding of the causes and implications of the highlighted deformation of karst aquifers is of primary interest for an improved management of this important water resource and for a better understanding of the possible interactions between

Intrinsic vulnerability, hazard and risk mapping for karst aquifers: A case study

NASA Astrophysics Data System (ADS)

Mimi, Ziad A.; Assi, Amjad

2009-01-01

SummaryGroundwater from karst aquifers is among the most important resources of drinking water supply of the worldwide population. The European COST action 620 proposed a comprehensive approach to karst groundwater protection, comprising methods of intrinsic and specific vulnerability mapping, hazard and risk mapping. This paper presents the first application of all components of this European approach to the groundwater underlying the Ramallah district, a karst hydrogeology system in Palestine. The vulnerability maps which were developed can assist in the implementation of groundwater management strategies to prevent degradation of groundwater quality. Large areas in the case study area can be classified as low or very low risk area corresponding to the pollution sources due to the absence of hazards and also due to low vulnerabilities. These areas could consequently be interesting for future development as they are preferable in view of ground water protection.

Qtracer Program for Tracer-Breakthrough Curve Analysis for Karst and Fractured-Rock Aquifers (2000)

EPA Science Inventory

Tracer tests are generally regarded as being the most reliable and efficient means of gathering subsurface hydraulic information. This is true for all types of aquifers, but especially so for karst and fractured-rock aquifers. Qualitative tracing tests have been conventionally em...

A new model for simulating spring discharge recession and estimating effective porosity of karst aquifers

NASA Astrophysics Data System (ADS)

Xu, Bin; Ye, Ming; Dong, Shuning; Dai, Zhenxue; Pei, Yongzhen

2018-07-01

Quantitative analysis of recession curves of karst spring hydrographs is a vital tool for understanding karst hydrology and inferring hydraulic properties of karst aquifers. This paper presents a new model for simulating karst spring recession curves. The new model has the following characteristics: (1) the model considers two separate but hydraulically connected reservoirs: matrix reservoir and conduit reservoir; (2) the model separates karst spring hydrograph recession into three stages: conduit-drainage stage, mixed-drainage stage (with both conduit drainage and matrix drainage), and matrix-drainage stage; and (3) in the mixed-drainage stage, the model uses multiple conduit layers to present different levels of conduit development. The new model outperforms the classical Mangin model and the recently developed Fiorillo model for simulating observed discharge at the Madison Blue Spring located in northern Florida. This is attributed to the latter two characteristics of the new model. Based on the new model, a method is developed for estimating effective porosity of the matrix and conduit reservoirs for the three drainage stages. The estimated porosity values are consistent with measured matrix porosity at the study site and with estimated conduit porosity reported in literature. The new model for simulating karst spring hydrograph recession is mathematically general, and can be applied to a wide range of karst spring hydrographs to understand groundwater flow in karst aquifers. The limitations of the model are discussed at the end of this paper.

Pathogen and chemical transport in the karst limestone of the Biscayne aquifer: 1. Revised conceptualization of groundwater flow

USGS Publications Warehouse

Renken, Robert A.; Cunningham, Kevin J.; Shapiro, Allen M.; Harvey, Ronald W.; Zygnerski, Michael R.; Metge, David W.; Wacker, Michael A.

2008-01-01

The Biscayne aquifer is a highly transmissive karst limestone that serves as the sole source of drinking water to over two million residents in south Florida. The aquifer is characterized by eogenetic karst, where the most transmissive void space can be an interconnected, touching‐vug, biogenically influenced porosity of biogenic origin. Public supply wells in the aquifer are in close proximity to lakes established by surface mining. The mining of the limestone has occurred to the same depths as the production wells, which has raised concerns about pathogen and chemical transport from these surface water bodies. Hydraulic and forced gradient tracer tests were conducted to augment geologic and geophysical studies and to develop a hydrogeologic conceptual model of groundwater flow and chemical transport in the Biscayne aquifer. Geologic and geophysical data indicate multiple, areally extensive subhorizontal preferential flow zones of vuggy limestone separated by rock with a matrix pore system. The hydraulic response from an aquifer test suggests that the Biscayne aquifer behaves as a dual‐porosity medium; however, the results of the tracer test showed rapid transport similar to other types of karst. The tracer test and concurrent temperature logging revealed that only one of the touching‐vug flow zones dominates transport near the production wells. On the basis of the rising limb of the breakthrough curve, the dispersivity is estimated to be less than 3% of the tracer travel distance, which suggests that the fastest flow paths in the formation are likely to yield limited dilution of chemical constituents.

Karst hydrology and chemical contamination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Field, M.S.

1993-01-01

Ground-water flow in karst aquifers is very different from flow in granular or fractured aquifers. Chemical contamination may be fed directly to a karst aquifer via overland flow to a sinkhole with little or no attenuation and may contaminate downgradient wells, springs, and sinkholes within a few hours or a few days. Contaminants may also become temporarily stored in the epikarstic zone for eventual release to the aquifer. Flood pulses may flush the contaminants to cause transiently higher levels of contamination in the aquifer and discharge points. The convergent nature of flow in karst aquifers may result in contaminants becomingmore » concentrated in conduits. Once contaminants have reached the subsurface conduits, they are likely to be rapidly transported to spring outlets. Traditional aquifer remediation techniques for contaminated aquifers are less applicable to karst aquifers.« less

Research in karst aquifers developed in high-mountain areas combining KARSYS models with springs discharge records. Picos de Europa, Spain

NASA Astrophysics Data System (ADS)

Ballesteros, Daniel; Meléndez, Mónica; Malard, Arnauld; Jiménez-Sánchez, Montserrat; Heredia, Nemesio; Jeannin, Pierre-Yves; García-Sansegundo, Joaquín

2014-05-01

The study of karst aquifers developed in high-mountain areas is quite complex since the application of many techniques of hydrogeology in these areas is difficult, expensive, and requires many hours of field work. In addition, the access to the study area is usually conditioned by the orography and the meteorological conditions. A pragmatic approach to study these aquifers can be the combination of geometric models of the aquifer with the monitoring of the discharge rate of springs and the meteorological records. KARSYS approach (Jeannin et al. 2013) allows us to elaborate a geometric model of karst aquifers establishing the boundaries of the groundwater bodies, the main drainage axes and providing evidences of the catchment delineation of the springs. The aim of this work is to analyse the functioning of the karst aquifer from the western and central part of the Picos de Europa Mountains (Spain) combining the KARSYS approach, the discharge record from two springs and the meteorological records (rain, snow and temperature). The Picos de Europa (North Spain) is a high-mountains area up to 2.6 km altitude with 2,500 mm/year of precipitations. The highest part of these mountains is covered by snow four to seven months a year. The karst aquifer is developed in Carboniferous limestone which is strongly compartmentalized in, at least, 17 groundwater bodies. The method of work includes: 1) the elaboration of a hydrogeological 3D model of the geometry of the karst aquifers by KARSYS approach, 2) the definition of the springs catchment areas based on the hydrogeological 3D model, 3) the selection of two representative springs emerging from the aquifers to study it, 4) the continuous monitoring of water levels in two karst springs since October 2013, 5) the transformation of the water level values to flow values using height-stream relation curves constructed by measures of the spring discharge, and 5) the comparison of the spring discharge rate records and meteorological

Equivalent Porous Media (EPM) Simulation of Groundwater Hydraulics and Contaminant Transport in Karst Aquifers.

PubMed

Ghasemizadeh, Reza; Yu, Xue; Butscher, Christoph; Hellweger, Ferdi; Padilla, Ingrid; Alshawabkeh, Akram

2015-01-01

Karst aquifers have a high degree of heterogeneity and anisotropy in their geologic and hydrogeologic properties which makes predicting their behavior difficult. This paper evaluates the application of the Equivalent Porous Media (EPM) approach to simulate groundwater hydraulics and contaminant transport in karst aquifers using an example from the North Coast limestone aquifer system in Puerto Rico. The goal is to evaluate if the EPM approach, which approximates the karst features with a conceptualized, equivalent continuous medium, is feasible for an actual project, based on available data and the study scale and purpose. Existing National Oceanic Atmospheric Administration (NOAA) data and previous hydrogeological U. S. Geological Survey (USGS) studies were used to define the model input parameters. Hydraulic conductivity and specific yield were estimated using measured groundwater heads over the study area and further calibrated against continuous water level data of three USGS observation wells. The water-table fluctuation results indicate that the model can practically reflect the steady-state groundwater hydraulics (normalized RMSE of 12.4%) and long-term variability (normalized RMSE of 3.0%) at regional and intermediate scales and can be applied to predict future water table behavior under different hydrogeological conditions. The application of the EPM approach to simulate transport is limited because it does not directly consider possible irregular conduit flow pathways. However, the results from the present study suggest that the EPM approach is capable to reproduce the spreading of a TCE plume at intermediate scales with sufficient accuracy (normalized RMSE of 8.45%) for groundwater resources management and the planning of contamination mitigation strategies.

Equivalent Porous Media (EPM) Simulation of Groundwater Hydraulics and Contaminant Transport in Karst Aquifers

PubMed Central

Ghasemizadeh, Reza; Yu, Xue; Butscher, Christoph; Hellweger, Ferdi; Padilla, Ingrid; Alshawabkeh, Akram

2015-01-01

Karst aquifers have a high degree of heterogeneity and anisotropy in their geologic and hydrogeologic properties which makes predicting their behavior difficult. This paper evaluates the application of the Equivalent Porous Media (EPM) approach to simulate groundwater hydraulics and contaminant transport in karst aquifers using an example from the North Coast limestone aquifer system in Puerto Rico. The goal is to evaluate if the EPM approach, which approximates the karst features with a conceptualized, equivalent continuous medium, is feasible for an actual project, based on available data and the study scale and purpose. Existing National Oceanic Atmospheric Administration (NOAA) data and previous hydrogeological U. S. Geological Survey (USGS) studies were used to define the model input parameters. Hydraulic conductivity and specific yield were estimated using measured groundwater heads over the study area and further calibrated against continuous water level data of three USGS observation wells. The water-table fluctuation results indicate that the model can practically reflect the steady-state groundwater hydraulics (normalized RMSE of 12.4%) and long-term variability (normalized RMSE of 3.0%) at regional and intermediate scales and can be applied to predict future water table behavior under different hydrogeological conditions. The application of the EPM approach to simulate transport is limited because it does not directly consider possible irregular conduit flow pathways. However, the results from the present study suggest that the EPM approach is capable to reproduce the spreading of a TCE plume at intermediate scales with sufficient accuracy (normalized RMSE of 8.45%) for groundwater resources management and the planning of contamination mitigation strategies. PMID:26422202

Effects of projected climate (2011–50) on karst hydrology and species vulnerability—Edwards aquifer, south-central Texas, and Madison aquifer, western South Dakota

USGS Publications Warehouse

Mahler, Barbara J.; Stamm, John F.; Poteet, Mary F.; Symstad, Amy J.; Musgrove, MaryLynn; Long, Andrew J.; Norton, Parker A.

2015-12-22

Karst aquifers—formed by the dissolution of soluble rocks such as limestone—are critical groundwater resources in North America, and karst springs, caves, and streams provide habitat for unique flora and fauna. Springflow and groundwater levels in karst terrane can change greatly over short time scales, and therefore are likely to respond rapidly to climate change. How might the biological communities and ecosystems associated with karst respond to climate change and accompanying changes in groundwater levels and springflow? Sites in two central U.S. regions—the Balcones Escarpment of south-central Texas and the Black Hills of western South Dakota (fig. 1)—were selected to study climate change and its potential effects on the local karst hydrology and ecosystem. The ecosystems associated with the Edwards aquifer (Balcones Escarpment region) and Madison aquifer (Black Hills region) support federally listed endangered and threatened species and numerous State-listed species of concern, including amphibians, birds, insects, and plants. Full results are provided in Stamm and others (2014), and are summarized in this fact sheet.

Three-Dimensional Geologic Framework Model for a Karst Aquifer System, Hasty and Western Grove Quadrangles, Northern Arkansas

USGS Publications Warehouse

Turner, Kenzie J.; Hudson, Mark R.; Murray, Kyle E.; Mott, David N.

2007-01-01

Understanding ground-water flow in a karst aquifer benefits from a detailed conception of the three-dimensional (3D) geologic framework. Traditional two-dimensional products, such as geologic maps, cross-sections, and structure contour maps, convey a mental picture of the area but a stronger conceptualization can be achieved by constructing a digital 3D representation of the stratigraphic and structural geologic features. In this study, a 3D geologic model was created to better understand a karst aquifer system in the Buffalo National River watershed in northern Arkansas. The model was constructed based on data obtained from recent, detailed geologic mapping for the Hasty and Western Grove 7.5-minute quadrangles. The resulting model represents 11 stratigraphic zones of Ordovician, Mississippian, and Pennsylvanian age. As a result of the highly dissected topography, stratigraphic and structural control from geologic contacts and interpreted structure contours were sufficient for effectively modeling the faults and folds in the model area. Combined with recent dye-tracing studies, the 3D framework model is useful for visualizing the various geologic features and for analyzing the potential control they exert on the ground-water flow regime. Evaluation of the model, by comparison to published maps and cross-sections, indicates that the model accurately reproduces both the surface geology and subsurface geologic features of the area.

Transit time distributions to assess present and future contamination risk of karst aquifers over Europe and the Mediterranean

NASA Astrophysics Data System (ADS)

Hartmann, Andreas; Gleeson, Tom; Wada, Yoshihide; Wagener, Thorsten

2016-04-01

Karst develops through the dissolution of carbonate rock. Karst groundwater in Europe is a major source of fresh water contributing up to half of the total drinking water supply in some countries. Climate model projections suggest that in the next 100 years, karst regions will experience a strong increase in temperature and a serious decrease of precipitation - especially in the Mediterranean region. Previous work showed that the karstic preferential recharge processes result in enhanced recharge rates and future climate sensitivity. But as there is fast water flow form the surface to the aquifer, there is also an enhanced risk of groundwater contamination. In this study we will assess the contamination risk of karst aquifers over Europe and the Mediterranean using simulated transit time distributions. Using a new type of semi-distributed model that considers the spatial heterogeneity of the karst system by distribution functions we simulated a range of spatially variable pathways of karstic groundwater recharge. The model is driven by the bias-corrected 5 GCMs of the ISI-MIP project (RCP8.5). Transit time distributions are calculated by virtual tracer experiments. These are repeated several times in the present (1991-2010) and the future (2080-2099). We can show that regions with larger fractions of preferential recharge show higher risks of contamination and that spatial patterns of contamination risk change towards the future.

Analysis of hydrologic and geochemical time-series data at James Cave, Virginia: Implications for epikarst influence on recharge in Appalachian karst aquifers

USGS Publications Warehouse

Eagle, Sarah D.; Orndorff, William; Schwartz, Benjamin F.; Doctor, Daniel H.; Gerst, Jonathan D.; Schreiber, Madeline E.

2016-01-01

The epikarst, which consists of highly weathered rock in the upper vadose zone of exposed karst systems, plays a critical role in determining the hydrologic and geochemical characteristics of recharge to an underlying karst aquifer. This study utilized time series (2007–2014) of hydrologic and geochemical data of drip water collected within James Cave, Virginia, to examine the influence of epikarst on the quantity and quality of recharge in a mature, doline-dominated karst terrain. Results show a strong seasonality of both hydrology and geochemistry of recharge, which has implications for management of karst aquifers in temperate climatic zones. First, recharge (discharge from the epikarst to the underlying aquifer) reaches a maximum between late winter and early spring, with the onset of the recharge season ranging from as early as December to as late as March during the study period. The timing and duration of the recharge season were found to be a function of precipitation in excess of evapotranspiration on a seasonal time scale. Secondly, seasonally variable residence times for water in the epikarst influence rock-water interaction and, hence, the geochemical characteristics of recharge. Overall, results highlight the strong and complex influence that the epikarst has on karst recharge, which requires long-term and high-resolution data sets to accurately understand and quantify.

Effects of karst and geologic structure on the circulation of water and permeability in carbonate aquifers

USGS Publications Warehouse

Stringfield, V.T.; Rapp, J.R.; Anders, R.B.

1979-01-01

acids moves down from bare rock surfaces through cracks to the beds that are more soluble than carbonate rocks. For example, in the area of Carlsbad Caverns in southeastern New Mexico, much of the water responsible for solution that formed the caverns apparently entered the groundwater system through large open fractures and did not form sinkhole topography. East of the Carlsbad Caverns, however, in the Pecos River Valley where the carbonate rocks are overlain by the less soluble Ogallala Formation of Late Tertiary age, solution began along escarpments as the Pecos River and its tributaries cut through the less soluble cover. As these escarpments retreated, sinkholes and other karst features developed. Joints or fractures are essential for initiation of downward percolation of water in compact carbonate rocks such as some Paleozoic limestone in which there is no intergranular permeability. Also joints or fractures and bedding planes may be essential in the initiation of lateral movement of water in the zone of saturation. Where conditions of recharge and discharge are favorable, groundwater may move parallel to the dip. However, the direction of movement of water in most carbonate rocks is not necessarily down dip or parallel to the dip. The general direction of movement of both surface and groundwater may be parallel to the strike in a breached anticline. Faults may restrict the lateral movement of water, especially if water-bearing beds are faulted against relatively impervious beds. Conversely, some fault may serve as avenues through which water may move as, for example, in the Cretaceous Edwards aquifer in the San Antonio area, Texas. Karst aquifers, chiefly carbonate rocks, may be placed in three groups according to water-bearing capacity. Water in aquifers of group 1 occurs chiefly in joints, fractures, and other openings that have not been enlarged by solution. The yield of wells is small. Aquifers in group 2, with low to intermediate yields, are those in which

Water Flow in Karst Aquifer Considering Dynamically Variable Saturation Conduit

NASA Astrophysics Data System (ADS)

Tan, Chaoqun; Hu, Bill X.

2017-04-01

The karst system is generally conceptualized as dual-porosity system, which is characterized by low conductivity and high storage continuum matrix and high conductivity and quick flow conduit networks. And so far, a common numerical model for simulating flow in karst aquifer is MODFLOW2005-CFP, which is released by USGS in 2008. However, the steady-state approach for conduit flow in CFP is physically impractical when simulating very dynamic hydraulics with variable saturation conduit. So, we adopt the method proposed by Reimann et al. (2011) to improve current model, in which Saint-Venant equations are used to model the flow in conduit. Considering the actual background that the conduit is very big and varies along flow path and the Dirichlet boundary varies with rainfall in our study area in Southwest China, we further investigate the influence of conduit diameter and outflow boundary on numerical model. And we also analyze the hydraulic process in multi-precipitation events. We find that the numerical model here corresponds well with CFP for saturated conduit, and it could depict the interaction between matrix and conduit during very dynamic hydraulics pretty well compare with CFP.

Karst connections between unconfined aquifers and the Upper Floridan aquifer in south Georgia: geophysical evidence and hydrogeological models

NASA Astrophysics Data System (ADS)

Thieme, D. M.; Denizman, C.

2011-12-01

Buried karst features in sedimentary rocks of the south Georgia Coastal Plain present a challenge for hydrogeological models of recharge and confined flow within the underlying Upper Floridan aquifer. The Withlacoochee River, the trunk stream for the area, frequently disappears into subsurface caverns as it makes its way south to join the Suwannee River in northern Florida. The Withlacoochee also receives inputs from small ponds and bays which in turn receive spring and seep groundwater inputs. We have mapped karst topography at the "top of rock" using ground-penetrating radar (GPR). Up to seven meters of relief is indicated for the paleotopography on Miocene to Pliocene rocks, contrasting with the more subdued relief of the modern landscape. Current stratigraphic and hydrogeological reconstructions do not incorporate this amount of relief or lateral variation in the confining beds. One "pipe" which is approximately four meters in diameter is being mapped in detail. We have field evidence at this location for rapid movement of surficial pond and river water with a meteoric signature through several separate strata of sedimentary rock into an aquifer in the Hawthorn formation. We use our geophysical and hydrological field evidence to constrain quantitative hydrogeological models for the flow rates into and out of both this upper aquifer and the underlying Upper Floridan aquifer, which is generally considered to be confined by the clays of the Hawthorn.

Preliminary characterization of an alpine karst aquifer in a complex geological setting using the KARSYS approach. Picos de Europa, North Spain

NASA Astrophysics Data System (ADS)

Ballesteros, Daniel; Malard, Arnauld; Jeannin, Pierre-Yves; Jiménez-Sánchez, Montserrat; García-Sansegundo, Joaquín; Meléndez, Mónica; Sendra, Gemma

2013-04-01

Research applied to karst aquifers linked to a homogeneous limestone in high mountain areas affected by several tectonic events is a hard task, due to methodological constraints and the uncertainties of the geological data. The KARSYS approach (Jeannin et al. 2012) is based on the combination of existing geological data and basic principles of karst hydraulic, allowing for characterizing the geometry of an aquifer considering a smaller amount of data than other methods. The Picos de Europa (North Spain) is an alpine karst massif with a surface area of 700 km2, peaks up to 2,648 m and fluvial gorges up to 2,000 m deep, including about 270 km of cave passage. The bedrock is mainly composed of Ordovician quartzite covered by massive Carboniferous limestone and is affected by two systems of thrusts and other faults. The most of the geological structures are from Variscan orogeny (Carboniferous in age), some of them could be originated or modified during the Permian-Mesozoic extensional episode, and the others were originated or reactivated during the Alpine Orogeny. Therefore, the Picos de Europa can be considered as a complex geological environment in which usual hydrogeological methods are difficult to use. The aim of this study is to characterize the geometry of the Picos de Europa aquifers applying the KARSYS approach. The approach includes: 1) the identification of aquifer and aquiclude formations; 2) the inventory of the main springs; 3) the establishment of a 3D geological model, focused on the aquifer boundaries; 4) the implementation of the hydraulic features within the 3D model and the delineation of the karst system. The main aquifer of the Picos de Europa is developed within the Carboniferous limestone and displays a complex geometry generally limited and divided into several unconfined groundwater bodies by Ordovician to Carboniferous rocks related to the thrusts. The lowest limit of the aquifer is marked by the N-dipping detachment level of the thrusts

Using nitrate to quantify quick flow in a karst aquifer

USGS Publications Warehouse

Mahler, B.J.; Garner, B.D.

2009-01-01

In karst aquifers, contaminated recharge can degrade spring water quality, but quantifying the rapid recharge (quick flow) component of spring flow is challenging because of its temporal variability. Here, we investigate the use of nitrate in a two-endmember mixing model to quantify quick flow in Barton Springs, Austin, Texas. Historical nitrate data from recharging creeks and Barton Springs were evaluated to determine a representative nitrate concentration for the aquifer water endmember (1.5 mg/L) and the quick flow endmember (0.17 mg/L for nonstormflow conditions and 0.25 mg/L for stormflow conditions). Under nonstormflow conditions for 1990 to 2005, model results indicated that quick flow contributed from 0% to 55% of spring flow. The nitrate-based two-endmember model was applied to the response of Barton Springs to a storm and results compared to those produced using the same model with ??18O and specific conductance (SC) as tracers. Additionally, the mixing model was modified to allow endmember quick flow values to vary over time. Of the three tracers, nitrate appears to be the most advantageous because it is conservative and because the difference between the concentrations in the two endmembers is large relative to their variance. The ??18O- based model was very sensitive to variability within the quick flow endmember, and SC was not conservative over the timescale of the storm response. We conclude that a nitrate-based two-endmember mixing model might provide a useful approach for quantifying the temporally variable quick flow component of spring flow in some karst systems. ?? 2008 National Ground Water Association.

Analysis of methods to estimate spring flows in a karst aquifer.

PubMed

Sepúlveda, Nicasio

2009-01-01

Hydraulically and statistically based methods were analyzed to identify the most reliable method to predict spring flows in a karst aquifer. Measured water levels at nearby observation wells, measured spring pool altitudes, and the distance between observation wells and the spring pool were the parameters used to match measured spring flows. Measured spring flows at six Upper Floridan aquifer springs in central Florida were used to assess the reliability of these methods to predict spring flows. Hydraulically based methods involved the application of the Theis, Hantush-Jacob, and Darcy-Weisbach equations, whereas the statistically based methods were the multiple linear regressions and the technology of artificial neural networks (ANNs). Root mean square errors between measured and predicted spring flows using the Darcy-Weisbach method ranged between 5% and 15% of the measured flows, lower than the 7% to 27% range for the Theis or Hantush-Jacob methods. Flows at all springs were estimated to be turbulent based on the Reynolds number derived from the Darcy-Weisbach equation for conduit flow. The multiple linear regression and the Darcy-Weisbach methods had similar spring flow prediction capabilities. The ANNs provided the lowest residuals between measured and predicted spring flows, ranging from 1.6% to 5.3% of the measured flows. The model prediction efficiency criteria also indicated that the ANNs were the most accurate method predicting spring flows in a karst aquifer.

Single event time series analysis in a binary karst catchment evaluated using a groundwater model (Lurbach system, Austria).

PubMed

Mayaud, C; Wagner, T; Benischke, R; Birk, S

2014-04-16

The Lurbach karst system (Styria, Austria) is drained by two major springs and replenished by both autogenic recharge from the karst massif itself and a sinking stream that originates in low permeable schists (allogenic recharge). Detailed data from two events recorded during a tracer experiment in 2008 demonstrate that an overflow from one of the sub-catchments to the other is activated if the discharge of the main spring exceeds a certain threshold. Time series analysis (autocorrelation and cross-correlation) was applied to examine to what extent the various available methods support the identification of the transient inter-catchment flow observed in this binary karst system. As inter-catchment flow is found to be intermittent, the evaluation was focused on single events. In order to support the interpretation of the results from the time series analysis a simplified groundwater flow model was built using MODFLOW. The groundwater model is based on the current conceptual understanding of the karst system and represents a synthetic karst aquifer for which the same methods were applied. Using the wetting capability package of MODFLOW, the model simulated an overflow similar to what has been observed during the tracer experiment. Various intensities of allogenic recharge were employed to generate synthetic discharge data for the time series analysis. In addition, geometric and hydraulic properties of the karst system were varied in several model scenarios. This approach helps to identify effects of allogenic recharge and aquifer properties in the results from the time series analysis. Comparing the results from the time series analysis of the observed data with those of the synthetic data a good agreement was found. For instance, the cross-correlograms show similar patterns with respect to time lags and maximum cross-correlation coefficients if appropriate hydraulic parameters are assigned to the groundwater model. The comparable behaviors of the real and the

Single event time series analysis in a binary karst catchment evaluated using a groundwater model (Lurbach system, Austria)

PubMed Central

Mayaud, C.; Wagner, T.; Benischke, R.; Birk, S.

2014-01-01

Summary The Lurbach karst system (Styria, Austria) is drained by two major springs and replenished by both autogenic recharge from the karst massif itself and a sinking stream that originates in low permeable schists (allogenic recharge). Detailed data from two events recorded during a tracer experiment in 2008 demonstrate that an overflow from one of the sub-catchments to the other is activated if the discharge of the main spring exceeds a certain threshold. Time series analysis (autocorrelation and cross-correlation) was applied to examine to what extent the various available methods support the identification of the transient inter-catchment flow observed in this binary karst system. As inter-catchment flow is found to be intermittent, the evaluation was focused on single events. In order to support the interpretation of the results from the time series analysis a simplified groundwater flow model was built using MODFLOW. The groundwater model is based on the current conceptual understanding of the karst system and represents a synthetic karst aquifer for which the same methods were applied. Using the wetting capability package of MODFLOW, the model simulated an overflow similar to what has been observed during the tracer experiment. Various intensities of allogenic recharge were employed to generate synthetic discharge data for the time series analysis. In addition, geometric and hydraulic properties of the karst system were varied in several model scenarios. This approach helps to identify effects of allogenic recharge and aquifer properties in the results from the time series analysis. Comparing the results from the time series analysis of the observed data with those of the synthetic data a good agreement was found. For instance, the cross-correlograms show similar patterns with respect to time lags and maximum cross-correlation coefficients if appropriate hydraulic parameters are assigned to the groundwater model. The comparable behaviors of the real and

Simulating groundwater flow in karst aquifers with distributed parameter models—Comparison of porous-equivalent media and hybrid flow approaches

USGS Publications Warehouse

Kuniansky, Eve L.

2016-09-22

Understanding karst aquifers, for purposes of their management and protection, poses unique challenges. Karst aquifers are characterized by groundwater flow through conduits (tertiary porosity), and (or) layers with interconnected pores (secondary porosity) and through intergranular porosity (primary or matrix porosity). Since the late 1960s, advances have been made in the development of numerical computer codes and the use of mathematical model applications towards the understanding of dual (primary [matrix] and secondary [fractures and conduits]) porosity groundwater flow processes, as well as characterization and management of karst aquifers. The Floridan aquifer system (FAS) in Florida and parts of Alabama, Georgia, and South Carolina is composed of a thick sequence of predominantly carbonate rocks. Karst features are present over much of its area, especially in Florida where more than 30 first-magnitude springs occur, numerous sinkholes and submerged conduits have been mapped, and numerous circular lakes within sinkhole depressions are present. Different types of mathematical models have been applied for simulation of the FAS. Most of these models are distributed parameter models based on the assumption that, like a sponge, water flows through connected pores within the aquifer system and can be simulated with the same mathematical methods applied to flow through sand and gravel aquifers; these models are usually referred to as porous-equivalent media models. The partial differential equation solved for groundwater flow is the potential flow equation of fluid mechanics, which is used when flow is dominated by potential energy and has been applied for many fluid problems in which kinetic energy terms are dropped from the differential equation solved. In many groundwater model codes (basic MODFLOW), it is assumed that the water has a constant temperature and density and that flow is laminar, such that kinetic energy has minimal impact on flow. Some models have

Groundwater vulnerability assessment for the karst aquifer of Tanour and Rasoun spring using EPIK, COP, and travel time methods

NASA Astrophysics Data System (ADS)

Hamdan, Ibraheem; Sauter, Martin; Margane, Armin; Ptak, Thomas; Wiegand, Bettina

2016-04-01

Key words: Karst, groundwater vulnerability, EPIK, COP, travel time, Jordan. Karst aquifers are especially sensitive to short-lived contaminants because of fast water travel times and a low storage capacity in the conduit system. Tanour and Rasoun karst springs located around 75 km northwest of the city of Amman in Jordan represent the main domestic water supply for the surrounding villages. Both springs suffer from pollution events especially during the winter season, either by microbiological contamination due to wastewater leakage from septic tanks or by wastewater discharge from local olive oil presses. To assess the vulnerability of the karst aquifer of Tanour and Rasoun spring and its sensitivity for pollution, two different intrinsic groundwater vulnerability methods were applied: EPIK and COP. In addition, a travel time vulnerability method was applied to determine the time water travels from different points in the catchment to the streams, as a function of land surface gradients and presumed lateral flow within the epikarst. For the application of the COP and EPIK, a detailed geological survey was carried out to determine karst features and the karst network development within the catchment area. In addition, parameters, such as soil data, long term daily precipitation data, land use and topographical data were collected. For the application of the travel time vulnerability method, flow length, hydraulic conductivity, effective porosity, and slope gradient was used in order to determining the travel time in days. ArcGIS software was used for map preparation. The results of the combined vulnerability methods (COP, EPIK and travel time) show a high percentage of "very high" to "moderate" vulnerable areas within the catchment area of Tanour and Rasoun karst springs. Therefore, protection of the catchment area of Tanour and Rasoun springs from pollution and proper management of land use types is urgently needed to maintain the quality of drinking water in the

Analysis of methods to estimate spring flows in a karst aquifer

USGS Publications Warehouse

Sepulveda, N.

2009-01-01

Hydraulically and statistically based methods were analyzed to identify the most reliable method to predict spring flows in a karst aquifer. Measured water levels at nearby observation wells, measured spring pool altitudes, and the distance between observation wells and the spring pool were the parameters used to match measured spring flows. Measured spring flows at six Upper Floridan aquifer springs in central Florida were used to assess the reliability of these methods to predict spring flows. Hydraulically based methods involved the application of the Theis, Hantush-Jacob, and Darcy-Weisbach equations, whereas the statistically based methods were the multiple linear regressions and the technology of artificial neural networks (ANNs). Root mean square errors between measured and predicted spring flows using the Darcy-Weisbach method ranged between 5% and 15% of the measured flows, lower than the 7% to 27% range for the Theis or Hantush-Jacob methods. Flows at all springs were estimated to be turbulent based on the Reynolds number derived from the Darcy-Weisbach equation for conduit flow. The multiple linear regression and the Darcy-Weisbach methods had similar spring flow prediction capabilities. The ANNs provided the lowest residuals between measured and predicted spring flows, ranging from 1.6% to 5.3% of the measured flows. The model prediction efficiency criteria also indicated that the ANNs were the most accurate method predicting spring flows in a karst aquifer. ?? 2008 National Ground Water Association.

Interactions of diffuse and focused allogenic recharge in an eogenetic karst aquifer (Florida, USA)

NASA Astrophysics Data System (ADS)

Langston, Abigail L.; Screaton, Elizabeth J.; Martin, Jonathan B.; Bailly-Comte, Vincent

2012-06-01

The karstic upper Floridan aquifer in north-central Florida (USA) is recharged by both diffuse and allogenic recharge. To understand how recharged water moves within the aquifer, water levels and specific conductivities were monitored and slug tests were conducted in wells installed in the aquifer surrounding the Santa Fe River Sink and Rise. Results indicate that diffuse recharge does not mix rapidly within the aquifer but instead flows horizontally. Stratification may be aided by the high matrix porosity of the eogenetic karst aquifer. Purging wells for sample collection perturbed conductivity for several days, reflecting mixing of the stratified water and rendering collection of representative samples difficult. Interpretive numerical simulations suggest that diffuse recharge impacts the intrusion of allogenic water from the conduit by increasing hydraulic head in the surrounding aquifer and thereby reducing influx to the aquifer from the conduit. In turn, the increase of head within the conduits affects flow paths of diffuse recharge by moving newly recharged water vertically as the water table rises and falls. This movement may result in a broad vertical zone of dissolution at the water table above the conduit system, with thinner and more focused water-table dissolution at greater distance from the conduit.

Assessment of groundwater recharge in an ash-fall mantled karst aquifer of southern Italy

NASA Astrophysics Data System (ADS)

Manna, F.; Nimmo, J. R.; De Vita, P.; Allocca, V.

2014-12-01

In southern Italy, Mesozoic carbonate formations, covered by ash-fall pyroclastic soils, are large karst aquifers and major groundwater resources. For these aquifers, even though Allocca et al., 2014 estimated a mean annual groundwater recharge coefficient at regional scale, a more complete understanding of the recharge processes at small spatio-temporal scale is a primary scientific target. In this paper, we study groundwater recharge processes in the Acqua della Madonna test site (Allocca et al., 2008) through the integrated analysis of piezometric levels, rainfall, soil moisture and air temperature data. These were gathered with hourly frequency by a monitoring station in 2008. We applied the Episodic Master Recharge method (Nimmo et al., 2014) to identify episodes of recharge and estimate the Recharge to Precipitation Ratio (RPR) at both the individual-episode and annual time scales. For different episodes of recharge observed, RPR ranges from 97% to 37%, with an annual mean around 73%. This result has been confirmed by a soil water balance and the application of the Thornthwaite-Mather method to estimate actual evapotranspiration. Even though it seems higher than RPRs typical of some parts of the world, it is very close to the mean annual groundwater recharge coefficient estimated at the regional scale for the karst aquifers of southern Italy. In addition, the RPR is affected at the daily scale by both antecedent soil moisture and rainfall intensity, as demonstrated by a statistically significant multiple linear regression among such hydrological variables. In particular, the recharge magnitude is great for low storm intensity and high antecedent soil moisture value. The results advance the comprehension of groundwater recharge processes in karst aquifers, and the sensitivity of RPR to antecedent soil moisture and rainfall intensity facilitates the prediction of the influence of climate and precipitation regime change on the groundwater recharge process.

Geostatistical Borehole Image-Based Mapping of Karst-Carbonate Aquifer Pores.

PubMed

Sukop, Michael C; Cunningham, Kevin J

2016-03-01

Quantification of the character and spatial distribution of porosity in carbonate aquifers is important as input into computer models used in the calculation of intrinsic permeability and for next-generation, high-resolution groundwater flow simulations. Digital, optical, borehole-wall image data from three closely spaced boreholes in the karst-carbonate Biscayne aquifer in southeastern Florida are used in geostatistical experiments to assess the capabilities of various methods to create realistic two-dimensional models of vuggy megaporosity and matrix-porosity distribution in the limestone that composes the aquifer. When the borehole image data alone were used as the model training image, multiple-point geostatistics failed to detect the known spatial autocorrelation of vuggy megaporosity and matrix porosity among the three boreholes, which were only 10 m apart. Variogram analysis and subsequent Gaussian simulation produced results that showed a realistic conceptualization of horizontal continuity of strata dominated by vuggy megaporosity and matrix porosity among the three boreholes. © 2015, National Ground Water Association.

Geostatistical borehole image-based mapping of karst-carbonate aquifer pores

USGS Publications Warehouse

Michael Sukop,; Cunningham, Kevin J.

2016-01-01

Quantification of the character and spatial distribution of porosity in carbonate aquifers is important as input into computer models used in the calculation of intrinsic permeability and for next-generation, high-resolution groundwater flow simulations. Digital, optical, borehole-wall image data from three closely spaced boreholes in the karst-carbonate Biscayne aquifer in southeastern Florida are used in geostatistical experiments to assess the capabilities of various methods to create realistic two-dimensional models of vuggy megaporosity and matrix-porosity distribution in the limestone that composes the aquifer. When the borehole image data alone were used as the model training image, multiple-point geostatistics failed to detect the known spatial autocorrelation of vuggy megaporosity and matrix porosity among the three boreholes, which were only 10 m apart. Variogram analysis and subsequent Gaussian simulation produced results that showed a realistic conceptualization of horizontal continuity of strata dominated by vuggy megaporosity and matrix porosity among the three boreholes.

Regional-scale analysis of karst underground flow deduced from tracing experiments: examples from carbonate aquifers in Malaga province, southern Spain

NASA Astrophysics Data System (ADS)

Barberá, J. A.; Mudarra, M.; Andreo, B.; De la Torre, B.

2018-02-01

Tracer concentration data from field experiments conducted in several carbonate aquifers (Malaga province, southern Spain) were analyzed following a dual approach based on the graphical evaluation method (GEM) and solute transport modeling to decipher flow mechanisms in karst systems at regional scale. The results show that conduit system geometry and flow conditions are the principal factors influencing tracer migration through the examined karst flow routes. Solute transport is mainly controlled by longitudinal advection and dispersion throughout the conduit length, but also by flow partitioning between mobile and immobile fluid phases, while the matrix diffusion process appears to be less relevant. The simulation of tracer breakthrough curves (BTCs) suggests that diffuse and concentrated flow through the unsaturated zone can have equivalent transport properties under extreme recharge, with high flow velocities and efficient mixing due to the high hydraulic gradients generated. Tracer mobilization within the saturated zone under low flow conditions mainly depends on the hydrodynamics (rather than on the karst conduit development), which promote a lower longitudinal advection and retardation in the tracer migration, resulting in a marked tailing effect of BTCs. The analytical advection-dispersion equation better approximates the effective flow velocity and longitudinal dispersion estimations provided by the GEM, while the non-equilibrium transport model achieves a better adjustment of most asymmetric and long-tailed BTCs. The assessment of karst underground flow properties from tracing tests at regional scale can aid design of groundwater management and protection strategies, particularly in large hydrogeological systems (i.e. transboundary carbonate aquifers) and/or in poorly investigated ones.

U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008

USGS Publications Warehouse

Kuniansky, Eve L.

2008-01-01

*INTRODUCTION AND ACKNOWLEDGMENTS* Karst aquifer systems are present throughout parts of the United States and some of its territories. The complex depositional environments that form carbonate rocks combined with post-depositional tectonic events and the diverse climatic regimes under which these rocks were formed result in unique hydrologic systems. The dissolution of calcium carbonate and the subsequent development of distinct and beautiful landscapes, caverns, and springs have resulted in some karst areas of the United States being designated as national or state parks and commercial caverns. Karst aquifers and landscapes that form in tropical areas, such as the north coast of Puerto Rico, differ greatly from karst areas in more arid climates, such as central Texas or western South Dakota. Many of these public and private lands contain unique flora and fauna associated with the hydrologic systems in these karst areas. As a result, multiple Federal, State, and local agencies have an interest in the study of karst terrains. Carbonate sediments and rocks (limestone and dolomite) are composed of greater than 50 percent carbonate minerals and the predominant carbonate mineral is calcium carbonate or limestone (CaCO3). Unlike terrigenous clastic sedimentation, the depositional processes that produce carbonate rocks are complex, involving both biological and physical processes. These depositional processes impact greatly the development of permeability of the sediments. Carbonate minerals readily dissolve or precipitate depending on the chemistry of the water flowing through the rock, thus the study of both marine and meteoric diagenesis of carbonate sediments is multidisciplinary. Even with a better understanding of the depositional environment and subsequent diagenesis, the dual porosity nature of karst aquifers presents challenges to scientists attempting to study ground-water flow and contaminant transport. Many of the major springs and aquifers in the United

Transport of suspended solids from a karstic to an alluvial aquifer: The role of the karst/alluvium interface

USGS Publications Warehouse

Massei, N.; Lacroix, M.; Wang, H.Q.; Mahler, B.J.; Dupont, J.P.

2002-01-01

This study focuses on the coupled transport of dissolved constituents and particulates, from their infiltration on a karst plateau to their discharge from a karst spring and their arrival at a well in an alluvial plain. Particulate markers were identified and the transport of solids was characterised in situ in porous and karstic media, based on particle size analyses, SEM, and traces. Transport from the sinkhole to the spring appeared to be dominated by flow through karst: particulate transport was apparently conservative between the two sites, and there was little difference in the overall character of the particle size distribution of the particulates infiltrating the sinkhole and of those discharging from the spring. Qualitatively, the mineralogy of the infiltrating and discharging material was similar, although at the spring an autochthonous contribution from the aquifer was noted (chalk particles eroded from the parent rock by weathering). In contrast, transport between the spring and the well appears to be affected by the overlying alluvium: particles in the water from the well, showed evidence of considerable size-sorting. Additionally, SEM images of the well samples showed the presence of particles originating from the overlying alluvial system; these particles were not found in samples from the sinkhole or the spring. The differences between the particulates discharging from the spring and the well indicate that the water pumped from the alluvial plain is coming from the karst aquifer via the very transmissive, complex geologic interface between the underlying chalk formation and the gravel at the base of the overlying alluvial system. ?? 2002 Elsevier Science B.V. All rights reserved.

Anthropogenic contaminants as tracers in an urbanizing karst aquifer

USGS Publications Warehouse

Mahler, B.; Massei, N.

2007-01-01

Karst aquifers are uniquely vulnerable to contamination. In the Barton Springs segment of the karstic Edwards aquifer (Texas, U.S.A.), urban contaminants such as pesticides and volatile organic compounds frequently are detected in spring base flow. To determine whether contaminant concentrations change in response to storms, and if they therefore might act as tracers of focused recharge, samples were collected from Barton Springs at closely spaced intervals following three storms. Two herbicides (atrazine and simazine), two insecticides (carbaryl and diazinon), and a solvent (tetrachloroethene) described breakthrough curves over a 1-week period following one or more storms. The breakthrough curves were decomposed into two to five log-normal subcurves, which were interpreted as representing pulses of contaminants moving through the aquifer. Each subcurve could be used in the same way as an artificial tracer to determine travel time to and recovery at the spring. The contaminants have several advantages over artificial tracers: they represent the actual compounds of interest, they are injected essentially simultaneously at several points, and they are injected under those conditions when transport is of the most interest, i.e., following storms. The response of storm discharge, specific conductance, and contaminant loading at the spring depended on initial aquifer flow conditions, which varied from very low (spring discharge of 0.48??m3/s) to high (spring discharge of 2.7??m3/s): concentrations and recovery were the highest when initial aquifer flow conditions were low. This behavior provides information about aquifer structure and the influence of aquifer flow condition on transport properties. ?? 2006 Elsevier B.V. All rights reserved.

Hydrochemistry and stable isotopes (δ18O and δ2H) tools applied to the study of karst aquifers in southern mediterranean basin (Teboursouk area, NW Tunisia)

NASA Astrophysics Data System (ADS)

Ayadi, Yosra; Mokadem, Naziha; Besser, Houda; Khelifi, Faten; Harabi, Samia; Hamad, Amor; Boyce, Adrian; Laouar, Rabah; Hamed, Younes

2018-01-01

Karst aquifers receive increasing attention in Mediterranean countries as they provide large supplies water used for drinkable and irrigation purposes as well as for electricity production. In Teboursouk basin, Northwestern Tunisia, characterized by a typical karst landscape, the water hosted in the carbonates aquifers provides large parts of water supply for drinkable water and agriculture purposes. Groundwater circulation in karst aquifers is characterized by short residence time and low water-rock interaction caused by high karstification processes in the study area. Ion exchange process, rock dissolution and rainfall infiltration are the principal factors of water mineralization and spatial distribution of groundwater chemistry. The present work attempted to study karstic groundwater in Teboursouk region using hydrochemistry and stable isotopes (δ18O and δ2H) tools. Karst aquifers have good water quality with low salinity levels expressed by TDS values largely below 1.5 g/l with Ca-SO4-Cl water type prevailing in the study area. The aquifers have been recharged by rainfall originating from a mixture of Atlantic and Mediterranean vapor masses.

Fate and Transport of TCE Solvents Through Saturated Karst Aquifer

NASA Astrophysics Data System (ADS)

Padilla, I. Y.; Carmona, M.; Anaya, A. A.

2014-12-01

Dense Nonaqueous-Phase Liquids (DNAPLs) are a group of organic compounds that have been a serious problem for groundwater pollution in karst. The industrial production and utilization of these chemicals spread since 1940, and are present at tens of thousands of contaminated sites worldwide. The physic-chemical properties of DNAPLs in conjunction with the hydraulic properties of the karst systems create the perfect condition for DNAPLs to penetrate the epikarst, reach the groundwater, and more within the karst system to zones of potential exposure, such as wells, streams and wetlands. Trichloroethylene (TCE) is the most common DNPAL found in the subsurface environment. This research studies the fate and transport of TCE DNAPL in a karstified limestone physical model (KLPM). Experiments are carried out in KLPM. The KLPM is an enclosed stainless steel tank packed with a rectangular limestone block (15cm x 15cm x 76cm) that simulates a saturated confine karst aquifer. DNAPL experiment involve the injection of 40 ml of pure TCE into steady groundwater flow at the upstream boundary of the KLPM model, while sampling spatially and temporally along the block. Samples are analyzed for TCE on the pure and dissolved phase. Pure TCE is analyzed volumetrically and dissolved phase concentrations are analyze using a High Performance Liquid Chromatography (HPLC). TCE data is used to construct temporal distributions curves (TDCs) at different spatial locations. Results show that pure TCE volumes are collected at the beginnings of the experiment in sampling ports located near the injection port and along preferential flow paths. TCE concentration TDCs show spatial variations related to the limestone block heterogeneously. Rapid response to TCE concentrations is associated with preferential flow paths. Slow response and long tailing of TCE of TCE concentration are associated with diffusive transport in rock matrix and mass transport rates limitations. Bimodal distributions are

Fractal And Multi-fractal Analysis Of The Hydraulic Property Variations Of Karst Aquifers

NASA Astrophysics Data System (ADS)

Majone, B.; Bellin, A.; Borsato, A.

Karst aquifers are very heterogeneous systems with hydraulic property variations acting at several continuous and discrete scales, as a result of the fact that macro- structural elements, such as faults and karst channels, and fractures are intertwined in a complex, and largely unknown, manner. Many experimental studies on karst springs showed that the recession limb of the typical storm hydrograph can be divided into several regions with different decreasing rate, suggesting that the discharge is com- posed of contributions experiencing different travel times. Despite the importance of karst aquifers as a source of fresh water for most Mediterranean countries fostered the attention of scientists and practitioners, the mechanisms controlling runoff production in such a complex subsurface environment need to be further explored. A detailed sur- vey, lasting for one year and conducted by the Museo Tridentino di Scienze Naturali of Trento, represents a unique opportunity to analyze the imprint of hydraulic prop- erty variations on the hydrological signal recorded at the spring of Prese Val, located in the Dolomiti group near Trento. Data include water discharge (Q), temperature (T) and electric conductivity of water (E). Analysis of the data revealed that the power spectrum of E scales as 1/f, with slightly, but significantly, smaller than 1. The scaling nature of the E-signal has been confirmed by rescaled range analysis of the time series. Since the electric conductivity is proportional to the concentration of ions in the spring water, which increases with the residence time, one may conclude that the fractal structure of the E signal is the consequence of a similar structure in the hydraulic property variations. This finding confirms previous results of Kirchner et al. (2000), who reported a similar behavior for chloride concentration in the streamflow of three small Welsh catchments. A more detailed analysis revealed that E and T are both multifractal signals

Linear model describing three components of flow in karst aquifers using 18O data

USGS Publications Warehouse

Long, Andrew J.; Putnam, L.D.

2004-01-01

The stable isotope of oxygen, 18O, is used as a naturally occurring ground-water tracer. Time-series data for ??18O are analyzed to model the distinct responses and relative proportions of the conduit, intermediate, and diffuse flow components in karst aquifers. This analysis also describes mathematically the dynamics of the transient fluid interchange between conduits and diffusive networks. Conduit and intermediate flow are described by linear-systems methods, whereas diffuse flow is described by mass-balance methods. An automated optimization process estimates parameters of lognormal, Pearson type III, and gamma distributions, which are used as transfer functions in linear-systems analysis. Diffuse flow and mixing parameters also are estimated by these optimization methods. Results indicate the relative proximity of a well to a main conduit flowpath and can help to predict the movement and residence times of potential contaminants. The three-component linear model is applied to five wells, which respond to changes in the isotopic composition of point recharge water from a sinking stream in the Madison aquifer in the Black Hills of South Dakota. Flow velocities as much as 540 m/d and system memories of as much as 71 years are estimated by this method. Also, the mean, median, and standard deviation of traveltimes; time to peak response; and the relative fraction of flow for each of the three components are determined for these wells. This analysis infers that flow may branch apart and rejoin as a result of an anastomotic (or channeled) karst network.

Biodegradation of chlorinated ethenes at a karst site in middle Tennessee

USGS Publications Warehouse

Byl, Thomas Duane; Williams, Shannon D.

2000-01-01

This report presents results of field and laboratory investigations examining the biodegradation of chlorinated ethenes in a karst aquifer contaminated with trichloroethylene (TCE). The study site, located in Middle Tennessee, was selected because of the presence of TCE degradation byproducts in the karst aquifer and available site hydrologic and chlorinated-ethene information. Additional chemical, biological, and hydrologic data were gathered to evaluate whether the occurrence of TCE degradation byproducts in the karst aquifer was the result of biodegradation within the aquifer or simply transport into the aquifer. Geochemical analysis established that sulfate-reducing conditions, essential for reductive dechlorination of chlorinated solvents, existed in parts of the contaminated karst aquifer. Other areas of the aquifer fluctuated between anaerobic and aerobic conditions and contained compounds associated with cometabolism, such as ethane, methane, ammonia, and dissolved oxygen. A large, diverse bacteria population inhabits the contaminated aquifer. Bacteria known to biodegrade TCE and other chlorinated solvents, such as sulfate-reducers, methanotrophs, and ammonia-oxidizers, were identified from karst-aquifer water using the RNA-hybridization technique. Results from microcosms using raw karst-aquifer water found that aerobic cometabolism and anaerobic reductive-dechlorination degradation processes were possible when appropriate conditions were established in the microcosms. These chemical and biological results provide circumstantial evidence that several biodegradation processes are active in the aquifer. Additional site hydrologic information was developed to determine if appropriate conditions persist long enough in the karst aquifer for these biodegradation processes to be significant. Continuous monitoring devices placed in four wells during the spring of 1998 indicated that pH, specific conductance, dissolved oxygen, and oxidation-reduction potentials

A multi-method approach for groundwater resource assessment in coastal carbonate (karst) aquifers: the case study of Sierra Almijara (southern Spain)

NASA Astrophysics Data System (ADS)

Andreo, B.; Barberá, J. A.; Mudarra, M.; Marín, A. I.; García-Orellana, J.; Rodellas, V.; Pérez, I.

2018-02-01

Understanding the transference of water resources within hydrogeological systems, particularly in coastal aquifers, in which groundwater discharge may occur through multiple pathways (through springs, into rivers and streams, towards the sea, etc.), is crucial for sustainable groundwater use. This research aims to demonstrate the usefulness of the application of conventional recharge assessment methods coupled to isotopic techniques for accurately quantifying the hydrogeological balance and submarine groundwater discharge (SGD) from coastal carbonate aquifers. Sierra Almijara (Southern Spain), a carbonate aquifer formed of Triassic marbles, is considered as representative of Mediterranean coastal karst formations. The use of a multi-method approach has permitted the computation of a wide range of groundwater infiltration rates (17-60%) by means of direct application of hydrometeorological methods (Thornthwaite and Kessler) and spatially distributed information (modified APLIS method). A spatially weighted recharge rate of 42% results from the most coherent information on physiographic and hydrogeological characteristics of the studied system. Natural aquifer discharge and groundwater abstraction have been volumetrically quantified, based on flow and water-level data, while the relevance of SGD was estimated from the spatial analysis of salinity, 222Rn and the short-lived radium isotope 224Ra in coastal seawater. The total mean aquifer discharge (44.9-45.9 hm3 year-1) is in agreement with the average recharged groundwater (44.7 hm3 year-1), given that the system is volumetrically equilibrated during the study period. Besides the groundwater resources assessment, the methodological aspects of this research may be interesting for groundwater management and protection strategies in coastal areas, particularly karst environments.

Assessing submarine groundwater discharge (SGD) and nitrate fluxes in highly heterogeneous coastal karst aquifers: Challenges and solutions

NASA Astrophysics Data System (ADS)

Montiel, Daniel; Dimova, Natasha; Andreo, Bartolomé; Prieto, Jorge; García-Orellana, Jordi; Rodellas, Valentí

2018-02-01

Groundwater discharge in coastal karst aquifers worldwide represents a substantial part of the water budget and is a main pathway for nutrient transport to the sea. Groundwater discharge to the sea manifests under different forms, making its assessment very challenging particularly in highly heterogeneous coastal systems karst systems. In this study, we present a methodology approach to identify and quantify four forms of groundwater discharge in a mixed lithology system in southern Spain (Maro-Cerro Gordo) that includes an ecologically protected coastal area comprised of karstic marble. We found that groundwater discharge to the sea occurs via: (1) groundwater-fed creeks, (2) coastal springs, (3) diffuse groundwater seepage through seabed sediments, and (4) submarine springs. We used a multi-method approach combining tracer techniques (salinity, 224Ra, and 222Rn) and direct measurements (seepage meters and flowmeters) to evaluate the discharge. Groundwater discharge via submarine springs was the most difficult to assess due to their depth (up to 15 m) and extensive development of the springs conduits. We determined that the total groundwater discharge over the 16 km of shoreline of the study area was at least 11 ± 3 × 103 m3 d-1 for the four types of discharge assessed. Groundwater-derived nitrate (NO3-) fluxes to coastal waters over ∼3 km (or 20%) in a highly populated and farmed section of Maro-Cerro Gordo was 641 ± 166 mol d-1, or ∼75% of the total NO3- loading in the study area. We demonstrate in this study that a multi-method approach must be applied to assess all forms of SGD and derived nutrient fluxes to the sea in highly heterogeneous karst aquifer systems.

Chemical Source Tracking of Bacterial Contamination Using Micropollutants - A Karst Aquifer Case Study

NASA Astrophysics Data System (ADS)

Zirlewagen, Johannes; Hillebrand, Olav; Nödler, Karsten; Licha, Tobias; Schiperski, Ferry; Stange, Claudia; Tiehm, Andreas; Scheytt, Traugott

2015-04-01

Karst aquifers are important drinking water resources in many parts of the world, though they are well known for their high vulnerability to contamination. Rainfall and snowmelt often trigger temporary contamination of karst water resources. Free-range animal breeding and application of manure on the one hand and sewage leakage or spillage on the other hand are usually regarded as main sources for fecal contamination. But distinction of their respective contributions is difficult. This study investigates the feasibility to track the origin of fecal contamination from the occurrences of indicator bacteria and chemical source indicators in karst spring water. The study site is the 45 km² rural catchment of the perennial karst spring Gallusquelle in SW-Germany (mean discharge: 0.5 m³/s). Overflow events of a stormwater detention basin (combined sewer system) are known to impact water quality at the spring. There is no free-range animal breeding in the catchment but intense application of manure. Following two heavy rainfall events with overflow of the stormwater detention basin, spring water was sampled over several days. Samples were analysed for indicator bacteria (total Coliform, E. coli, Enterococci) and 57 micropollutants, among them cyclamate and metazachlor. For the Gallusquelle catchment the artificial sweetener cyclamate and the herbicide metazachlor have been established as source specific indicators, the former for the sewer system and the latter for cropland. Though recharge in the Gallusquelle catchment is predominantly diffuse, there is a significant portion of direct recharge reflected by distinct breakthrough curves for cyclamate and metazachlor. The breakthrough of indicator bacteria coincides very well with the occurrence of both, cyclamate and metazachlor. However, indicator bacteria cannot be unambiguously tracked back to a specific source.

Effect of irrigation pumpage during drought on karst aquifer systems in highly agricultural watersheds: example of the Apalachicola-Chattahoochee-Flint river basin, southeastern USA

NASA Astrophysics Data System (ADS)

Mitra, Subhasis; Srivastava, Puneet; Singh, Sarmistha

2016-09-01

In the Apalachicola-Chattahoochee-Flint (ACF) river basin in Alabama, Georgia, and Florida (USA), population growth in the city of Atlanta and increased groundwater withdrawal for irrigation in southwest Georgia are greatly affecting the supply of freshwater to downstream regions. This study was conducted to understand and quantify the effect of irrigation pumpage on the karst Upper Floridan Aquifer and river-aquifer interactions in the lower ACF river basin in southwest Georgia. The groundwater MODular Finite-Element model (MODFE) was used for this study. The effect of two drought years, a moderate and a severe drought year, were simulated. Comparison of the results of the irrigated and non-irrigated scenarios showed that groundwater discharge to streams is a major outflow from the aquifer, and irrigation can cause as much as 10 % change in river-aquifer flux. The results also show that during months with high irrigation (e.g., June 2011), storage loss (34 %), the recharge and discharge from the upper semi-confining unit (30 %), and the river-aquifer flux (31 %) are the major water components contributing towards the impact of irrigation pumpage in the study area. A similar scenario plays out in many river basins throughout the world, especially in basins in which underlying karst aquifers are directly connected to a nearby stream. The study suggests that improved groundwater withdrawal strategies using climate forecasts needs to be developed in such a way that excessive withdrawals during droughts can be reduced to protect streams and river flows.

Assessment of vulnerability in karst aquifers using a quantitative integrated numerical model: catchment characterization and high resolution monitoring - Application to semi-arid regions- Lebanon.

NASA Astrophysics Data System (ADS)

Doummar, Joanna; Aoun, Michel; Andari, Fouad

2016-04-01

Karst aquifers are highly heterogeneous and characterized by a duality of recharge (concentrated; fast versus diffuse; slow) and a duality of flow which directly influences groundwater flow and spring responses. Given this heterogeneity in flow and infiltration, karst aquifers do not always obey standard hydraulic laws. Therefore the assessment of their vulnerability reveals to be challenging. Studies have shown that vulnerability of aquifers is highly governed by recharge to groundwater. On the other hand specific parameters appear to play a major role in the spatial and temporal distribution of infiltration on a karst system, thus greatly influencing the discharge rates observed at a karst spring, and consequently the vulnerability of a spring. This heterogeneity can only be depicted using an integrated numerical model to quantify recharge spatially and assess the spatial and temporal vulnerability of a catchment for contamination. In the framework of a three-year PEER NSF/USAID funded project, the vulnerability of a karst catchment in Lebanon is assessed quantitatively using a numerical approach. The aim of the project is also to refine actual evapotranspiration rates and spatial recharge distribution in a semi arid environment. For this purpose, a monitoring network was installed since July 2014 on two different pilot karst catchment (drained by Qachqouch Spring and Assal Spring) to collect high resolution data to be used in an integrated catchment numerical model with MIKE SHE, DHI including climate, unsaturated zone, and saturated zone. Catchment characterization essential for the model included geological mapping and karst features (e.g., dolines) survey as they contribute to fast flow. Tracer experiments were performed under different flow conditions (snow melt and low flow) to delineate the catchment area, reveal groundwater velocities and response to snowmelt events. An assessment of spring response after precipitation events allowed the estimation of the

The development of deep karst in the anticlinal aquifer structure based on the coupling of multistage flow systems

NASA Astrophysics Data System (ADS)

Xu, M.; Zhong, L.; Yang, Y.

2017-12-01

Under the background of neotectonics, the multistage underground flow system has been form due the different responses of main stream and tributaries to crust uplift. The coupling of multistage underground flow systems influences the development of karst thoroughly. At first, the research area is divided into vadose area, shunted area and exorheic area based on the development characteristics of transverse valley. Combining the controlling-drain action with topographic index and analyzing the coupling features of multistage underground flow system. And then, based on the coupling of multistage underground flow systems, the characteristics of deep karst development were verified by the lossing degree of surface water, water bursting and karst development characteristics of tunnels. The vadose area is regional water system based, whose deep karst developed well. It resulted the large water inflow of tunnels and the surface water drying up. The shunted area, except the region near the transverse valleys, is characterized by regional water system. The developed deep karst make the surface water connect with deep ground water well, Which caused the relatively large water flow of tunnels and the serious leakage of surface water. The deep karst relatively developed poor in the regions near transverse valleys which is characterized by local water system. The exorheic area is local water system based, whose the deep karst developed poor, as well as the connection among surface water and deep ground water. It has result in the poor lossing of the surface water under the tunnel construction. This study broadens the application field of groundwater flow systems theory, providing a new perspective for the study of Karst development theory. Meanwhile it provides theoretical guidance for hazard assessment and environmental negative effect in deep-buried Karst tunnel construction.

Hazard connected to tunnel construction in Mt Stena karstic area (Rosandra Valley, Classical Karst)

NASA Astrophysics Data System (ADS)

Cucchi, F.; Boschin, W.; Visintin, L.; Zini, L.

2009-04-01

Rosandra Valley -a unique geomorphological environment- is located in the western side of the Classical Karst plateau. This deep limestone gorge is crossed by a stream that is fed by a large basin located in Slovenia. Rosandra Valley is the only example of Classical Karst river valley with surface hydrography; the torrent digs a deep gully into the rock, rich in rapids, swirl holes, small waterfalls, enclosed meanders and basins; here, the first seepage phenomena occur, and part of the water feeds the underground aquifer. Rosandra Valley is theatre to complex structural situation; the NE slope culminates in the structure of Mt Stena, a limestone tectonic scale located between two faults and firmly rooted in the karst platform. Tectonics is quite important for the development of deep karst in this area; Mt Stena, in particular, hosts a comprehensive net of articulated and diversely shaped caves, basically organised on several levels, which stretches over a total of 9,000 metres, bearing testimony to ancient geological and hydrogeological origins. The deepest areas of the system reach a suspended aquifer that is probably sustained by an overthrust and placed about 100 meters above Rosandra torrent underground aquifer. During feasibility studies about Trieste-Divača high velocity railway link, interaction between project and karst features was examined; in fact the proximity of proposal project and Mt Stena karst system suggest to improve the knowledge related to karst and hydrogeological aspects of the massif. Compatibly with the project requirements, risk of voids intersection and water contamination were analyzed. In fact the Mt Stena suspended aquifer partially feeds Rosandra torrent which flows in a protected natural area. Karst features were represented in a 3D model in order to better understand the spatial relationship between railway project and karst system.

Use of Nitrogen-15-Enriched Escherichia coli as a Bacterial Tracer in Karst Aquifers.

PubMed

Ward, James W; Warden, John G; Bandy, Ashley M; Fryar, Alan E; Brion, Gail M; Macko, Stephen A; Romanek, Christopher S; Coyne, Mark S

2016-11-01

Karst aquifers are susceptible to contamination by microorganisms, but relatively few studies have used bacteria as tracers. We demonstrate the utility of Escherichia coli enriched in the stable isotope nitrogen-15 ( 15 N) as a novel bacterial tracer. Nonpathogenic E. coli from two springs in central Kentucky were grown on 15 N-enriched media. Survival of E. coli and persistence of the isotopic signal were assessed in two sets of laboratory experiments conducted with sterilized spring water in dark microcosms at 14 °C. First, isotopically labeled bacteria survived for 130 d at concentrations within one log unit of the average initial value, and there was no significant difference in δ 15 N values from Day 1 to Day 130. Second, water samples with E. coli were inoculated with either of two different species of protozoa (Tetrahymena pyriformis or Colpoda steinii). During 7 d, δ 15 N values increased in T. pyriformis while bacterial populations decreased. In a field test, following a 2.1-cm rainfall, 15 N-labeled E. coli, solutes (rhodamine WT dye and bromide), and latex microspheres were injected into a sinkhole approximately 530 m upgradient of a spring. Breakthrough of all tracers coincided, but microspheres were remobilized by subsequent storms, unlike other tracers. Enriched E. coli exhibited more tailing than solute tracers during the initial storm-flow recession. These results indicate that 15 N-enriched E. coli is a viable tracer of bacterial transport in karst aquifers, although predation may attenuate the isotopic signal in systems that are not rapidly flushed. © 2016, National Ground Water Association.

Characterizing pharmaceutical, personal care product, and hormone contamination in a karst aquifer of southwestern Illinois, USA, using water quality and stream flow parameters.

PubMed

Dodgen, L K; Kelly, W R; Panno, S V; Taylor, S J; Armstrong, D L; Wiles, K N; Zhang, Y; Zheng, W

2017-02-01

Karst aquifers are drinking water sources for 25% of the global population. However, the unique geology of karst areas facilitates rapid transfer of surficial chemicals to groundwater, potentially contaminating drinking water. Contamination of karst aquifers by nitrate, chloride, and bacteria have been previously observed, but little knowledge is available on the presence of contaminants of emerging concern (CECs), such as pharmaceuticals. Over a 17-month period, 58 water samples were collected from 13 sites in the Salem Plateau, a karst region in southwestern Illinois, United States. Water was analyzed for 12 pharmaceutical and personal care products (PPCPs), 7 natural and synthetic hormones, and 49 typical water quality parameters (e.g., nutrients and bacteria). Hormones were detected in only 23% of samples, with concentrations of 2.2-9.1ng/L. In contrast, PPCPs were quantified in 89% of groundwater samples. The two most commonly detected PPCPs were the antimicrobial triclocarban, in 81% of samples, and the cardiovascular drug gemfibrozil, in 57%. Analytical results were combined with data of local stream flow, weather, and land use to 1) characterize the extent of aquifer contamination by CECs, 2) cluster sites with similar PPCP contamination profiles, and 3) develop models to describe PPCP contamination. Median detection in karst groundwater was 3 PPCPs at a summed concentration of 4.6ng/L. Sites clustered into 3 subsets with unique contamination models. PPCP contamination in Cluster I sites was related to stream height, manganese, boron, and heterotrophic bacteria. Cluster II sites were characterized by groundwater temperature, specific conductivity, sodium, and calcium. Cluster III sites were characterized by dissolved oxygen and barium. Across all sites, no single or small set of water quality factors was significantly predictive of PPCP contamination, although gemfibrozil concentrations were strongly related to the sum of PPCPs in karst groundwater

Caffeine as an indicator for the quantification of untreated wastewater in karst systems.

PubMed

Hillebrand, Olav; Nödler, Karsten; Licha, Tobias; Sauter, Martin; Geyer, Tobias

2012-02-01

Contamination from untreated wastewater leakage and related bacterial contamination poses a threat to drinking water quality. However, a quantification of the magnitude of leakage is difficult. The objective of this work is to provide a highly sensitive methodology for the estimation of the mass of untreated wastewater entering karst aquifers with rapid recharge. For this purpose a balance approach is adapted. It is based on the mass flow of caffeine in spring water, the load of caffeine in untreated wastewater and the daily water consumption per person in a spring catchment area. Caffeine is a source-specific indicator for wastewater, consumed and discharged in quantities allowing detection in a karst spring. The methodology was applied to estimate the amount of leaking and infiltrating wastewater to a well investigated karst aquifer on a daily basis. The calculated mean volume of untreated wastewater entering the aquifer was found to be 2.2 ± 0.5 m(3) d(-1) (undiluted wastewater). It corresponds to approximately 0.4% of the total amount of wastewater within the spring catchment. Copyright © 2011 Elsevier Ltd. All rights reserved.

Using MODFLOW with CFP to understand conduit-matrix exchange in a karst aquifer during flooding

NASA Astrophysics Data System (ADS)

Spellman, P.; Screaton, E.; Martin, J. B.; Gulley, J.; Brown, A.

2011-12-01

Karst springs may reverse flow when allogenic runoff increases river stage faster than groundwater heads and may exchange of surface water with groundwater in the surrounding aquifer matrix. Recharged flood water is rich in nutrients, metals, and organic matter and is undersaturated with respect to calcite. Understanding the physical processes controlling this exchange of water is critical to understanding metal cycling, redox chemistry and dissolution in the subsurface. Ultimately the magnitude of conduit-matrix exchange should be governed by head gradients between the conduit and the aquifer which are affected by the hydraulic conductivity of the matrix, conduit properties and antecedent groundwater heads. These parameters are interrelated and it is unknown which ones exert the greatest control over the magnitude of exchange. This study uses MODFLOW-2005 coupled with the Conduit Flow Processes (CFP) package to determine how physical properties of conduits and aquifers influence the magnitude of surface water-groundwater exchange. We use hydraulic data collected during spring reversals in a mapped underwater cave that sources Madison Blue Spring in north-central Florida to explore which factors are most important in governing exchange. The simulation focused on a major flood in 2009, when river stage increased by about 10 meters over 9 days. In a series of simulations, we varied hydraulic conductivity, conduit diameter, roughness height and tortuosity in addition to antecedent groundwater heads to estimate the relative effects of each parameter on the magnitude of conduit-matrix exchange. Each parameter was varied across plausible ranges for karst aquifers. Antecedent groundwater heads were varied using well data recorded through wet and dry seasons throughout the spring shed. We found hydraulic conductivity was the most important factor governing exchange. The volume of exchange increased by about 61% from the lowest value (1.8x10-6 m/d) to the highest value (6 m

Multitracer test for the determination of transport and in-situ degradation of organic micro-contaminants in karst aquifers on the example of caffeine

NASA Astrophysics Data System (ADS)

Hillebrand, O.; Nödler, K.; Licha, T.; Geyer, T.

2012-04-01

The application of organic micro-contaminants as indicators for contamination sources in aquifers and surface-water bodies has been increasingly discussed in the literature over the last years. One of the proposed substances was caffeine. It served as indicator for wastewater-leakage to various systems. As well, wastewater volumes could be estimated from caffeine concentrations. Although caffeine is known to be degradable, the degradation rates are normally only determined from mass balances or laboratory experiments. Degradation rates obtained from mass balances are relatively uncertain, as the input-function is difficult to be assessed. Laboratory experiments are hardly capable to consider the full complexity of natural systems and can rarely be transferred to those. To solve this problem, in-situ degradation rates of reactive indicators have to be determined. Especially multitracer tests can be used to access compound-specific transport parameters and degradation rates, relative to conservative tracers. A multitracer test with caffeine and uranine has been performed in a karst system (catchment of the Gallusquelle spring, SW Germany). From the breakthrough curves of the tracers, the transport behavior and the in-situ degradation rate of caffeine could be deduced. The tracers were injected into a sinkhole with a linear distance of 3000 m to the spring. The mean residence time of the tracers was found to be 84 h at a flow velocity of 35 m/h. Throughout the whole experiment, the spring discharge was constant at 187 L/s. Uranine served as conservative reference-tracer for the calibration of a one-dimensional transport model with respect to solute-unspecific parameters. Relative to that, the tracer breakthrough curve of caffeine was interpreted. As solute-specific parameters the retardation coefficient as well as degradation rate of caffeine in the investigated karst aquifer could be determined. The results indicate, that caffeine is slightly retarded in the

Viruses and bacteria in karst and fractured rock aquifers in east Tennessee, USA

USGS Publications Warehouse

Johnson, T.B.; McKay, L.D.; Layton, A.C.; Jones, S.W.; Johnson, G.C.; Cashdollar, J.L.; Dahling, D.R.; Villegas, L.F.; Fout, G.S.; Williams, D.E.; Sayler, G.

2011-01-01

A survey of enteric viruses and indicator bacteria was carried out in eight community water supply sources (four wells and four springs) in East Tennessee. Seven sites derived their water from carbonate aquifers and one from fractured sandstone. Four of the sites were deemed "low-risk" based on prior monitoring of fecal indicators and factors such as presence of thick layers of overlying sediments. The remaining sites were deemed "high-risk." Enteric viruses (enterovirus and reovirus) were detected by cell culture at least once in seven of the eight wells or springs including all but one of the four low-risk sites. Viral RNA, however, was not detected in any of the samples by reverse transcription-polymerase chain reaction. Conventional indicators of microbial contamination (Escherichia coli and total coliform bacteria) were detected together with culturable viruses in seven of nine virus positive samples. Bacteroides, an alternative fecal indicator which has not previously been used in groundwater investigations, was also detected in all but one of the samples containing E. coli or total coliform bacteria, as well as in one sample where viruses were present in the absence of other bacterial indicators. The study highlights some of the challenges involved in surveys of virus occurrence and indicates that culturable enteric viruses in East Tennessee karst aquifers may be more widespread than previously observed in studies of karst aquifers in Pennsylvania (8%), the Ozark region of Missouri (< 1%), or several other states covered in a national microbial water quality survey conducted by the U.S. Environmental Protection Agency (43%). Copyright ?? 2010 The Author(s). Journal compilation ?? 2010 National Ground Water Association.

Hydrogeological characterization and environmental effects of the deteriorating urban karst groundwater in a karst trough valley: Nanshan, SW China

NASA Astrophysics Data System (ADS)

Jiang, Yongjun; Cao, Min; Yuan, Daoxian; Zhang, Yuanzhu; He, Qiufang

2018-02-01

The unique hydrogeology of karst makes the associated groundwater respond quickly to rainfall events and vulnerable to anthropogenic pollutions. In this study, high-frequency monitoring of spring discharge, temperature, electrical conductivity (EC) and pH, along with monthly hydrochemical and microbial analyses, was undertaken at the outlet of Laolondong karst underground river in Nanshan, southwestern China. The aim was to explore the environmental effects of the catchment's urban area on the karst groundwater resources. The monitoring data of a tracer test and the response of discharge to rainfall events demonstrate that conduits and narrow fissures coexist in the Laolongdong karst aquifer. The EC, Na+, Cl- and SO4 2- values (840 μS/cm, 33.7, 38.6 and 137.2 μg/L, respectively), along with high concentrations of fecal coliform bacteria, at the outlet indicate considerable urban pollution in this area. The contaminants sulfate and nitrate showed different relationships with discharge and EC in different stages of a rainfall event. This behavior provided information about aquifer structure and the influence of transport properties. Meanwhile, the hydrological processes of groundwater flow could be modified by urbanization and result in increasing magnitude of urban floods in the underground river. In addition, sulfuric and nitric acids introduced by urbanization not only impact the karst groundwater quality, but also result in a significant perturbation to the carbon cycling system in the karst area.

Numerical Study of Groundwater Flow and Salinity Distribution Cycling Controlled by Seawater/Freshwater Interaction in Karst Aquifer Using SEAWAT

NASA Astrophysics Data System (ADS)

Xu, Z.; Hu, B.

2017-12-01

The interest to predict seawater intrusion and salinity distribution in Woodville Karst Plain (WKP) has increased due to the huge challenge on quality of drinkable water and serious environmental problems. Seawater intrudes into the conduit system from submarine karst caves at Spring Creek Spring due to density difference and sea level rising, nowadays the low salinity has been detected at Wakulla Spring which is 18 km from coastal line. The groundwater discharge at two major springs and salinity distribution in this area is controlled by the seawater/freshwater interaction under different rainfall conditions: during low rainfall periods, seawater flow into the submarine spring through karst windows, then the salinity rising at the submarine spring leads to seawater further intrudes into conduit system; during high rainfall periods, seawater is pushed out by fresh water discharge at submarine spring. The previous numerical studies of WKP mainly focused on the density independent transport modeling and seawater/freshwater discharge at major karst springs, in this study, a SEAWAT model has been developed to fully investigate the salinity distribution in the WKP under repeating phases of low rainfall and high rainfall periods, the conduit system was simulated as porous media with high conductivity and porosity. The precipitation, salinity and discharge at springs were used to calibrate the model. The results showed that the salinity distribution in porous media and conduit system is controlled by the rainfall change, in general, the salinity distribution inland under low rainfall conditions is much higher and wider than the high rainfall conditions. The results propose a prediction on the environmental problem caused by seawater intrusion in karst coastal aquifer, in addition, provide a visual and scientific basis for future groundwater remediation.

Baseflow index assessment and master recession curve analysis for karst water management in Kakap Spring, Gunung Sewu

NASA Astrophysics Data System (ADS)

Fatchurohman, H.; Adji, T. N.; Haryono, E.; Wijayanti, P.

2018-04-01

Karst terrain occurs in combination of high solubility rock and well developed secondary porosity. Over the time, groundwater resources have not been well managed including karst aquifers. Karst aquifers formed in a very complex hydrological system. Developed in fracture media and soluble rocks have led karst aquifers into various porosity types and aquifer properties. Karst spring hydrograph is an essential element for water resource management. The form of karst spring hydrograph reflects the aquifer characteristics. The shapes of flood discharge hydrographs represent aquifer responses to recharge and contain information about the interior condition of karst drainage basin. Every year, Gunung Sewu karst area is suffering to severe water scarcity. The development of sub-terrain drainage networks lead into the minimum surface water resources. Kakap Spring is perennial gravity spring that located adjacently to the border of Gunung Sewu and the alluvial formation of Baturetno. Kakap spring play vital role regarding water supply in Giriwoyo sub-district as the spring fulfill most of the water needs in Giriwoyo sub-district. Kakap Spring utilized by the local authorities as the main source for pipeline water and distributed to the households. Water level data series obtained using automatic water level data logger and then correlated with manual discharge measurement to generate stage-discharge rating curve. The stage-discharge rating curve formula for Kakap Spring calculated as y = 14,504e8,9763x with r2 value = 0.8582. From the MRC result, flow regimes formula determined as + 400 (1-0,005t) + 700 (1-0,01t)., indicated that the aquifer dominated by turbulent flow regime. From the MRC formula, the degree of karstification in Kakap Spring classified at eighth scale. The average baseflow index in Kakap Spring calculated using recession curve analysis with the BFI index = 0,7485.

Occurrence and transport of pharmaceuticals in a karst groundwater system affected by domestic wastewater treatment plants.

PubMed

Einsiedl, Florian; Radke, Michael; Maloszewski, Piotr

2010-09-20

The occurrence of two pharmaceuticals, ibuprofen and diclofenac, in a vulnerable karst groundwater system was investigated. The hydrogeology of the karst system was identified by collecting (3)H samples in groundwater over 27years and by performing tracer tests. The isotopes and tracer data were interpreted by mathematical modeling to estimate the mean transit time of water and to characterize the hydrogeological flow paths in the groundwater system. By this approach, a mean (3)H transit time of 4.6 years for the fissured-porous karst aquifer was determined, whereas the fast flowing water in the conduit system showed a mean transit time of days. Both pharmaceuticals which infiltrated along sinkholes and small streams into the karst system were detected in concentrations of up to approximately 1 microg/L in effluent water of the wastewater treatment plants. Diclofenac was present in most samples collected from four springs discharging the karst groundwater to the rivers Altmühl and Anlauter in concentrations between 3.6 and 15.4 ng/L. In contrast, ibuprofen was rarely detected in groundwater. The results of this study suggest that both pharmaceuticals move into the fractured system of the karst system and go into storage. Thus dilution processes are the dominant control on the concentrations of both pharmaceuticals in the fractured system, whereas biodegradation is likely less important. Copyright (c) 2010 Elsevier B.V. All rights reserved.

U.S. Geological Survey Karst Interest Group Proceedings, San Antonio, Texas, May 16–18, 2017

USGS Publications Warehouse

Kuniansky, Eve L.; Spangler, Lawrence E.

2017-05-15

Introduction and AcknowledgmentsKarst aquifer systems are present throughout parts of the United States and some of its territories, and have developed in carbonate rocks (primarily limestone and dolomite) and evaporites (gypsum, anhydrite, and halite) that span an interval of time encompassing more than 550 million years. The depositional environments, diagenetic processes, post-depositional tectonic events, and geochemical weathering processes that form karst aquifers are varied and complex. These factors involve biological, chemical, and physical changes that when combined with the diverse climatic regimes in which karst development has taken place, result in the unique dual- or triple-porosity nature of karst aquifers. These complex hydrogeologic systems typically represent challenging and unique conditions to scientists attempting to study groundwater flow and contaminant transport in these terrains.The dissolution of carbonate rocks and the subsequent development of distinct and beautiful landscapes, caverns, and springs have resulted in the most exceptional karst areas being designated as national or state parks. Tens of thousands of similar areas in the United States have been developed into commercial caverns and known privately owned caves. Both public and private properties provide access for scientists to study the flow of groundwater in situ. Likewise, the range and complexity of landforms and groundwater flow systems associated with karst terrains are enormous, perhaps more than for any other aquifer type. Karst aquifers and landscapes that form in tropical areas, such as the cockpit karst along the north coast of Puerto Rico, differ greatly from karst landforms in more arid climates, such as the Edwards Plateau in west-central Texas or the Guadalupe Mountains near Carlsbad, New Mexico, where hypogenic processes have played a major role in speleogenesis. Many of these public and private lands also contain unique flora and fauna associated with these

Hydrological response and thermal effect of karst springs linked to aquifer geometry and recharge processes

NASA Astrophysics Data System (ADS)

Luo, Mingming; Chen, Zhihua; Zhou, Hong; Zhang, Liang; Han, Zhaofeng

2018-03-01

To be better understand the hydrological and thermal behavior of karst systems in South China, seasonal variations in flow, hydrochemistry and stable isotope ratios of five karst springs were used to delineate flow paths and recharge processes, and to interpret their thermal response. Isotopic data suggest that mean recharge elevations are 200-820 m above spring outlets. Springs that originate from high elevations have lower NO3 - concentrations than those originating from lower areas that have more agricultural activity. Measured Sr2+ concentrations reflect the strontium contents of the host carbonate aquifer and help delineate the spring catchment's saturated zone. Seasonal variations of NO3 - and Sr2+ concentrations are inversely correlated, because the former correlates with event water and the latter with baseflow. The mean annual water temperatures of springs were only slightly lower than the local mean annual surface temperature at the outlet elevations. These mean spring temperatures suggest a vertical gradient of 6 °C/vertical km, which resembles the adiabatic lapse rate of the Earth's stable atmosphere. Seasonal temperature variations in the springs are in phase with surface air temperatures, except for Heilongquan (HLQ) spring. Event-scale variations of thermal response are dramatically controlled by the circulation depth of karst systems, which determines the effectiveness of heat exchange. HLQ spring undergoes the deepest circulation depth of 820 m, and its thermal responses are determined by the thermally effective regulation processes at higher elevations and the mixing processes associated with thermally ineffective responses at lower elevations.

Changes in sources and storage in a karst aquifer during a transition from drought to wet conditions

USGS Publications Warehouse

Wong, C.I.; Mahler, B.J.; Musgrove, M.; Banner, J.L.

2012-01-01

Understanding the sources and processes that control groundwater compositions and the timing and magnitude of groundwater vulnerability to potential surface-water contamination under varying meteorologic conditions is critical to informing groundwater protection policies and practices. This is especially true in karst terrains, where infiltrating surface water can rapidly affect groundwater quality. We analyzed the evolution of groundwater compositions (major ions and Sr isotopes) during the transition from extreme drought to wetconditions, and used inverse geochemical modeling (PHREEQC) to constrain controls on groundwater compositions during this evolution. Spring water and groundwater from two wells dominantly receiving diffuse and conduit flow (termed diffuse site and conduit site, respectively) in the Barton Springs segment of the Edwards aquifer (central Texas, USA) and surface water from losing streams that recharge the aquifer were sampled every 3–4 weeks during November 2008–March 2010. During this period, water compositions at the spring and conduit sites changed rapidly but there was no change at the diffuse site, illustrating the dual nature (i.e., diffuse vs. conduit) of flow in this karst system. Geochemical modeling demonstrated that, within a month of the onset of wetconditions, the majority of spring water and groundwater at the conduit site was composed of surface water, providing quantitative information on the timing and magnitude of the vulnerability of groundwater to potential surface-water contamination. The temporal pattern of increasing spring discharge and changing pattern of covariation between spring discharge and surface-water (steam) recharge indicates that that there were two modes of aquifer response—one with a small amount of storage and a second that accommodates more storage.

Contamination risk and drinking water protection for a large-scale managed aquifer recharge site in a semi-arid karst region, Jordan

NASA Astrophysics Data System (ADS)

Xanke, Julian; Liesch, Tanja; Goeppert, Nadine; Klinger, Jochen; Gassen, Niklas; Goldscheider, Nico

2017-09-01

Karst aquifers in semi-arid regions are particularly threatened by surface contamination, especially during winter seasons when extremely variable rainfall of high intensities prevails. An additional challenge is posed when managed recharge of storm water is applied, since karst aquifers display a high spatial variability of hydraulic properties. In these cases, adapted protection concepts are required to address the interaction of surface water and groundwater. In this study a combined protection approach for the surface catchment of the managed aquifer recharge site at the Wala reservoir in Jordan and the downstream Hidan wellfield, which are both subject to frequent bacteriological contamination, is developed. The variability of groundwater quality was evaluated by correlating contamination events to rainfall, and to recharge from the reservoir. Both trigger increased wadi flow downstream of the reservoir by surface runoff generation and groundwater seepage, respectively. A tracer test verified the major pathway of the surface flow into the underground by infiltrating from pools along Wadi Wala. An intrinsic karst vulnerability and risk map was adapted to the regional characteristics and developed to account for the catchment separation by the Wala Dam and the interaction of surface water and groundwater. Implementation of the proposed protection zones for the wellfield and the reservoir is highly recommended, since the results suggest an extreme contamination risk resulting from livestock farming, arable agriculture and human occupation along the wadi. The applied methods can be transferred to other managed aquifer recharge sites in similar karstic environments of semi-arid regions.

Combined use of natural and artificial tracers to determine the hydrogeological functioning of a karst aquifer: the Villanueva del Rosario system (Andalusia, southern Spain)

NASA Astrophysics Data System (ADS)

Mudarra, M.; Andreo, B.; Marín, A. I.; Vadillo, I.; Barberá, J. A.

2014-08-01

Analysis of natural responses of karst springs provides information on the behavior of the aquifers they drain. Detailed monitoring and qualitative and quantitative analyses of natural responses, and environmental—total organic carbon (TOC), NO3 -, Cl- and intrinsic fluorescence—and artificial (fluorescent dye) tracers, in the water drained by Villanueva del Rosario spring (southern Spain), suggest the existence of a conduit flow system with rapid flows and very short transit times of water through the aquifer. This is in agreement with uranine and eosin breakthrough curves and with simple numerical models done using these data. However, due to the low capacity for natural regulation, not all the recharge effects are simultaneously transmitted to the spring water; given a single input, the system modulates and transfers hydrodynamic variations faster than variations of chemical composition and of water temperature. Additionally, time lags between maximum concentrations of natural and artificial tracers show that the global system response (including diffuse infiltration) is faster and more sensitive than that produced from infiltration concentrated at a single point on the surface (sinkholes).

Results of a hydrogeological and hydrogeochemical study of a semi-arid karst aquifer in Tezbent plateau, Tebessa region, northeast of Algeria

NASA Astrophysics Data System (ADS)

Belfar, Dalila; Fehdi, Chemseddine; Baali, Fethi; Salameh, Elias

2017-06-01

The Hammamet Plain, situated in the northwest of the Tezbent mountain range, northeast of Algeria, drains carbonate aquifers through some important karst springs. The physical and chemical characteristics of spring and well water samples were studied for 2 years to assess the origin of groundwater and determine the factors driving the geochemical composition. The ionic speciation and mineral dissolution/precipitation was calculated. Water wells, characterizing groundwater circulation at shallow depths, are moderate to high mineralized waters of Na-HCO3 type. In contrast to the shallow environment, the CO2-rich, deeper waters are of the Ca-HCO3-SO4 type and undergo significant changes in the baseline chemistry along flow lines with increasing residence time. The main factors controlling the groundwater composition and its seasonal variations are the geology, because of the presence of carbonate formations, the elevation and the rate of karst development. In both groups, the carbonate chemistry is diagnostic of the effect of karst development. The supersaturation with respect to calcite indicates CO2 degassing, occurring either inside the aquifer in open conduits, or at the outlet in reservoirs. The undersaturation with respect to calcite shows the existence of fast flow and short residence time conditions inside the aquifer. Interaction between groundwater and surrounding host rocks is believed to be the main process responsible for the observed chemical characteristics of groundwater in the study area.

Hydrogeological characterization of flow system in a karstic aquifer, Seymareh dam, Iran

NASA Astrophysics Data System (ADS)

Behrouj Peely, Ahmad; Mohammadi, Zargham; Raeisi, Ezzatollah; Solgi, Khashayar; Mosavi, Mohammad J.; Kamali, Majid

2018-07-01

In order to determine the characteristics of the flow system in a karstic aquifer, an extensive hydrogeological study includes dye tracing test was conducted. The aquifer suited left abutment of Seymareh Dam, in Ravandi Anticline and discharges by more than 50 springs in the southern flank. Flow system in the aquifer is mainly controlled by the reservoir of Seymareh Dam. Time variations of the spring discharge and water table in the observation wells were highly correlated with the reservoir water level. The average groundwater velocity ranges from 0.2 to more than 14 m/h based on the dye tracing test. The probable flow paths were differentiated in two groups including the flow paths in the northern and southern flanks of Ravandi Anticline. Types of groundwater flow in the proposed flow paths are determined as diffuse or conduit flow type considering groundwater velocity and shape of the breakthrough curves. An index is proposed for differentiation of diffuse and conduit flow system based on relationship of groundwater velocity and hydraulic gradient. Dominant geometry of the flow routs (e.g., conduit diameter and fracture aperture) is estimated for the groundwater flow paths toward the springs. Based on velocity variations and variance coefficient of the water table and discharge of springs on map view a major karst conduit was probably developed in the aquifer. This research emphasizes applying of an extensive hydrogeological study for characterization of flow system in the karst aquifer.

Existence of both culturable and viable but non culturable (VNC) E. coli populations with distinct settling velocities in karst aquifer

NASA Astrophysics Data System (ADS)

Petit, F.; Ratajczak, M.; Massei, N.; Lafite, R.; Clermont, O.; Denamur, E.; Berthe, T.

2012-12-01

The karst aquifers are particularly vulnerable to contamination by faecal pathogens mainly during rainfall event. In groundwater, the fate of E. coli is dependent on their ability to overcome environmental stresses and on their association with particles. Moreover, some strains can survive leading to the emergence of a sub-population of E. coli which failed to grow on laboratory media, while they were still alive thus designated as viable but non culturable (VNC). The aim of this study was to investigate (i) the structure of culturable E. coli population based on the survival ability, the distribution in four main phylo-groups (A, B1, B2, D) and the phenotypic characteristics; and, (ii) the fate of culturable and VNC E. coli, according to their settling velocities. This work was carried out on a karstic workshop-site for which the microbial quality of water was impaired related to livestock density and septic tanks overflows. Particles characterisation was performed by estimation of their settling velocities combined with electronic microscopy observation, and solid phase cytometry (ChemScan®RDI) was carried out to quantify the viable E. coli, and thus VNC E. coli. In the karst, different populations of E. coli were coexisting related to their survival, their culturability, and their association to particles. At the sinkhole, during a rainfall event with pasture, E. coli rapidly losing their culturability after 2 days have been more frequently isolated. These isolates are mainly multiresistant to antibiotics and harbor several virulence factors. In the same time, a population of VNC E. coli (79%), associated to the "non settleable particles" (settling velocities ranging between 10-5 to 10-2 mm.s-1), mainly corresponding to colloids and organic or organo-mineral microflocs was injected in the karst system, probably corresponding to the runoff of attached-bacteria originating from cowpats. Once in the karst, the relative contribution of culturable and VNC E. coli

Karst in Wadi Bani Khalid, Oman

NASA Astrophysics Data System (ADS)

Abdelaziz, Ramadan

2017-04-01

There are several important in Oman. The main aquifer is surficial aquifer and fractured rocks. In fact, the geology of Oman is complex whichmake the hydraulic continuity of bedrock is limited and formaing localized aquifers. caves in Oman are varying types and length, size and geographic formations. Many caves and valleys founded in Oman. Wadi Bani Khalid hosts complex network of fractured rock. Karst in Wadi Bani Kalid made upof Limestone(Calcium, which is dissolve in water.A rain water pass through the rock it is erode the rock and form caves. The cave located in Miqil. The karst was formed in Calcium Carbonate rocks.

Intrinsic vulnerability assessment of Sette Comuni Plateau aquifer (Veneto Region, Italy).

PubMed

Cucchi, Franco; Franceschini, Giuliana; Zini, Luca; Aurighi, Marina

2008-09-01

Maps illustrating the different degrees of vulnerability within a given area are integral to environmental protection and management policies. The assessment of the intrinsic vulnerability of karst areas is difficult since the type and stage of karst development and the related underground discharge behavior are difficult to determine and quantify. Geographic Information Systems techniques are applied to the evaluation of the vulnerability of an aquifer in the alpine karst area of the Sette Comuni Plateau, in the Veneto Region of northern Italy. The water resources of the studied aquifer are of particular importance to the local communities. This aquifer must therefore be protected from both inappropriate use as well as possible pollution. The SINTACS and SINTACS P(RO) K(ARST) vulnerability assessment methods have been utilized here to create the vulnerability map. SINTACS P(RO) K(ARST) is an adaptation of the parametric managerial model (SINTACS) to karst hydrostructures. The vulnerability map reveals vast zones (81% of the analyzed areas) with a high degree of vulnerability. The presence of well-developed karst structures in these highly vulnerable areas facilitate water percolation, thereby enhancing the groundwater vulnerability risk. Only 1.5 of the studied aquifer have extremely high-vulnerability levels, however these areas include all of the major springs utilized for human consumption. This vulnerability map of the Sette Comuni Plateau aquifer is an indispensable tool for both the effective management of water resources and as support to environmental planning in the Sette Comuni Plateau area.

Application of carbonate cyclostratigraphy and borehole geophysics to delineate porosity and preferential flow in the karst limestone of the Biscayne aquifer, SE Florida

USGS Publications Warehouse

Cunningham, K.J.; Renken, R.A.; Wacker, M.A.; Zygnerski, M.R.; Robinson, E.; Shapiro, A.M.; Wingard, G.L.

2006-01-01

Combined analyses of cores, borehole geophysical logs, and cyclostratigraphy produced a new conceptual hydrogeologic framework for the triple-porosity (matrix, touching-vug, and conduit porosity) karst limestone of the Biscayne aquifer in a 0.65 km2 study area, SE Florida. Vertical lithofacies successions, which have recurrent stacking patterns, fit within high-frequency cycles. We define three ideal high-frequency cycles as: (1) upward-shallowing subtidal cycles, (2) upward-shallowing paralic cycles, and (3) aggradational subtidal cycles. Digital optical borehole images, tracers, and flow meters indicate that there is a predictable vertical pattern of porosity and permeability within the three ideal cycles, because the distribution of porosity and permeability is related to lithofacies. Stratiform zones of high permeability commonly occur just above flooding surfaces in the lower part of upward-shallowing subtidal and paralic cycles, forming preferential groundwater flow zones. Aggradational subtidal cycles are either mostly high-permeability zones or leaky, low-permeability units. In the study area, groundwater flow within stratiform high-permeability zones is through a secondary pore system of touching-vug porosity principally related to molds of burrows and pelecypods and to interburrow vugs. Movement of a dye-tracer pulse observed using a borehole fluid-temperature tool during a conservative tracer test indicates heterogeneous permeability. Advective movement of the tracer appears to be most concentrated within a thin stratiform flow zone contained within the lower part of a high-frequency cycle, indicating a distinctly high relative permeability for this zone. Borehole flow-meter measurements corroborate the relatively high permeability of the flow zone. Identification and mapping of such high-permeability flow zones is crucial to conceptualization of karst groundwater flow within a cyclostratigraphic framework. Many karst aquifers are included in cyclic

Hochauflösendes Monitoring von Karst-Grundwasserressourcen beiderseits des Jordangrabens - Konzepte und Anwendungsbeispiele

NASA Astrophysics Data System (ADS)

Schmidt, Sebastian; Grimmeisen, Felix; Ries, Fabian; Goldscheider, Nico; Sauter, Martin

2018-03-01

In the semi-arid eastern Mediterranean water supply is highly dependent on karst aquifers. The region is characterized by multi-year dry and wet cycles combined with high hydrological dynamics, especially during intense precipitation events. The investigated karst regions in the West Bank and Jordan are experiencing strong urbanization within the groundwater catchments and hence a rising impact on water quality. Therefore, high resolution monitoring data are required for the assessment of available water resources and the hydrogeological characterization of the karst systems. These measurements are focused on the (natural) meteorological input signals and the system output signals at the karst springs. Also soil moisture and ephemeral runoff dynamics are investigated. The monitoring data enable (1) hydrogeological characterization of the aquifers, (2) estimation of groundwater recharge via soil water balance and reservoir models, and (3) assessment of contamination dynamics in groundwater (e. g. nitrate and E. coli concentrations), allowing an optimized raw water management. Several examples illustrate the importance of high-resolution hydrological monitoring data.

Assessment of key transport parameters in a karst system under different dynamic conditions based on tracer experiments: the Jeita karst system, Lebanon

NASA Astrophysics Data System (ADS)

Doummar, Joanna; Margane, Armin; Geyer, Tobias; Sauter, Martin

2018-03-01

Artificial tracer experiments were conducted in the mature karst system of Jeita (Lebanon) under various flow conditions using surface and subsurface tracer injection points, to determine the variation of transport parameters (attenuation of peak concentration, velocity, transit times, dispersivity, and proportion of immobile and mobile regions) along fast and slow flow pathways. Tracer breakthrough curves (TBCs) observed at the karst spring were interpreted using a two-region nonequilibrium approach (2RNEM) to account for the skewness in the TBCs' long tailings. The conduit test results revealed a discharge threshold in the system dynamics, beyond which the transport parameters vary significantly. The polynomial relationship between transport velocity and discharge can be related to the variation of the conduit's cross-sectional area. Longitudinal dispersivity in the conduit system is not a constant value (α = 7-10 m) and decreases linearly with increasing flow rate because of dilution effects. Additionally, the proportion of immobile regions (arising from conduit irregularities) increases with decreasing water level in the conduit system. From tracer tests with injection at the surface, longitudinal dispersivity values are found to be large (8-27 m). The tailing observed in some TBCs is generated in the unsaturated zone before the tracer actually arrives at the major subsurface conduit draining the system. This work allows the estimation and prediction of the key transport parameters in karst aquifers. It shows that these parameters vary with time and flow dynamics, and they reflect the geometry of the flow pathway and the origin of infiltrating (potentially contaminated) recharge.

U.S. Geological Survey Karst Interest Group Proceedings, Carlsbad, New Mexico, April 29-May 2, 2014

USGS Publications Warehouse

Kuniansky, Eve L.; Spangler, Lawrence E.; Kuniansky, Eve L.; Spangler, Lawrence E.

2014-01-01

Karst aquifer systems are present throughout parts of the United States and some of its territories, and have developed in carbonate rocks (primarily limestone and dolomite) that span an interval of time encompassing more than 550 million years. The depositional environments, diagenetic processes, post-depositional tectonic events, and geochemical weathering processes that form karst aquifers are varied and complex, and involve biological, chemical, and physical changes. These factors, combined with the diverse climatic regimes under which karst development in these rocks has taken place, result in the unique dual- or triple-porosity nature of karst aquifers. These complex hydrogeologic systems typically represent challenging and unique conditions to scientists attempting to study groundwater flow and contaminant transport in these terrains.The dissolution of carbonate rocks and the subsequent development of distinct and beautiful landscapes, caverns, and springs has resulted in the most exceptional karst areas of the United States being designated as national or state parks; commercial caverns and known privately owned caves number in the tens of thousands. Both public and private properties provide access for scientists to study the flow of groundwater in situ. Likewise, the range and complexity of landforms and groundwater flow systems associated with karst terrains are enormous, perhaps more than for any other aquifer type. Karst aquifers and landscapes that form in tropical areas, such as the cockpit karst along the north coast of Puerto Rico, differ greatly from karst landforms in more arid climates, such as the Edwards Plateau in west-central Texas or the Guadalupe Mountains near Carlsbad, New Mexico, where hypogenic processes have played a major role in speleogenesis. Many of these public and private lands also contain unique flora and fauna associated with these karst hydrogeologic systems. As a result, numerous federal, state, and local agencies have a

A one-dimensional heat-transport model for conduit flow in karst aquifers

USGS Publications Warehouse

Long, Andrew J.; Gilcrease, P.C.

2009-01-01

A one-dimensional heat-transport model for conduit flow in karst aquifers is presented as an alternative to two or three-dimensional distributed-parameter models, which are data intensive and require knowledge of conduit locations. This model can be applied for cases where water temperature in a well or spring receives all or part of its water from a phreatic conduit. Heat transport in the conduit is simulated by using a physically-based heat-transport equation that accounts for inflow of diffuse flow from smaller openings and fissures in the surrounding aquifer during periods of low recharge. Additional diffuse flow that is within the zone of influence of the well or spring but has not interacted with the conduit is accounted for with a binary mixing equation to proportion these different water sources. The estimation of this proportion through inverse modeling is useful for the assessment of contaminant vulnerability and well-head or spring protection. The model was applied to 7 months of continuous temperature data for a sinking stream that recharges a conduit and a pumped well open to the Madison aquifer in western South Dakota. The simulated conduit-flow fraction to the well ranged from 2% to 31% of total flow, and simulated conduit velocity ranged from 44 to 353 m/d.

Prominence of ichnologically influenced macroporosity in the karst Biscayne aquifer: Stratiform "super-K" zones

USGS Publications Warehouse

Cunningham, K.J.; Sukop, M.C.; Huang, H.; Alvarez, P.F.; Curran, H.A.; Renken, R.A.; Dixon, J.F.

2009-01-01

A combination of cyclostratigraphic, ichnologic, and borehole geophysical analyses of continuous core holes; tracer-test analyses; and lattice Boltzmann flow simulations was used to quantify biogenic macroporosity and permeability of the Biscayne aquifer, southeastern Florida. Biogenic macroporosity largely manifests as: (1) ichnogenic macroporosity primarily related to postdepositional burrowing activity by callianassid shrimp and fossilization of components of their complex burrow systems (Ophiomorpha); and (2) biomoldic macroporosity originating from dissolution of fossil hard parts, principally mollusk shells. Ophiomorpha-dominated ichno-fabric provides the greatest contribution to hydrologic characteristics in the Biscayne aquifer in a 345 km2 study area. Stratiform tabular-shaped units of thalassinidean-associated macroporosity are commonly confined to the lower part of upward-shallowing high-frequency cycles, throughout aggradational cycles, and, in one case, they stack vertically within the lower part of a high-frequency cycle set. Broad continuity of many of the macroporous units concentrates groundwater flow in extremely permeable passage-ways, thus making the aquifer vulnerable to long-distance transport of contaminants. Ichnogenic macroporosity represents an alternative pathway for concentrated groundwater flow that differs considerably from standard karst flow-system paradigms, which describe groundwater movement through fractures and cavernous dissolution features. Permeabilities were calculated using lattice Boltzmann methods (LBMs) applied to computer renderings assembled from X-ray computed tomography scans of various biogenic macroporous limestone samples. The highest simulated LBM permeabilities were about five orders of magnitude greater than standard laboratory measurements using air-permeability methods, which are limited in their application to extremely permeable macroporous rock samples. Based on their close conformance to analytical

Time-series variations in CFC and 3H/3He ages in springs discharging from an eogenetic karst aquifer (Invited)

NASA Astrophysics Data System (ADS)

Martin, J. B.; Kurz, M. J.; Khadka, M. B.; Cohen, M. J.

2013-12-01

One of the hallmarks of karst aquifers is rapid mixing between surface water and groundwater, which results in changes in flow and water chemistry at springs. Aquifers with little matrix porosity (telogenetic karst) tend to respond to storm events within days to weeks (e.g., are flashy) while aquifers characterized by elevated matrix porosity (eogenetic karst) may take months or years to respond. This response time is an important control on remediation of storm-derived contaminants as well as the magnitude of water-rock reactions that may result from mixing of surface water and groundwater with different compositions. Responses of flashy springs may be observed through time-series measurements of various solute compositions of the discharge, but response at springs discharging from eogenetic aquifers are difficult to observe because the chemical composition of the recharged storm water may be altered during its residence in the subsurface. For these aquifers, conservative tracers such as chlorofluorocarbon and 3H/3He ratios may provide useful information on the mixing, residence time, and variation in the average age of discharged water. We are testing this hypothesis at six springs discharging from the Floridan Aquifer to the Ichetucknee River in north Florida. Samples were first collected September 3, 2009 during record low flow when the river was discharging 7.2 m3/sec and subsequently after about 400 mm of rain fell over the springshed from June 23 to 26, 2012 during Tropical Storm Debby. Following the storm, samples were collected July 27, 2012 (all six springs) when flow had increased to 10.5 m3/sec. Three of the six springs were sampled during the recession on October 25, 2012 (Q = 10.3 m3/sec), February 14, 2013 (Q = 8.7 m3/sec), and May 16, 2013 (Q = 8.6 m3/sec). CFC dates are available now for all sampling times but 3H/3He dates are only available through October 25, 2012. The two different tracers yield conflicting results with CFC ages generally

Verification of the karst flow model under laboratory controlled conditions

NASA Astrophysics Data System (ADS)

Gotovac, Hrvoje; Andric, Ivo; Malenica, Luka; Srzic, Veljko

2016-04-01

Karst aquifers are very important groundwater resources around the world as well as in coastal part of Croatia. They consist of extremely complex structure defining by slow and laminar porous medium and small fissures and usually fast turbulent conduits/karst channels. Except simple lumped hydrological models that ignore high karst heterogeneity, full hydraulic (distributive) models have been developed exclusively by conventional finite element and finite volume elements considering complete karst heterogeneity structure that improves our understanding of complex processes in karst. Groundwater flow modeling in complex karst aquifers are faced by many difficulties such as a lack of heterogeneity knowledge (especially conduits), resolution of different spatial/temporal scales, connectivity between matrix and conduits, setting of appropriate boundary conditions and many others. Particular problem of karst flow modeling is verification of distributive models under real aquifer conditions due to lack of above-mentioned information. Therefore, we will show here possibility to verify karst flow models under the laboratory controlled conditions. Special 3-D karst flow model (5.6*2.6*2 m) consists of concrete construction, rainfall platform, 74 piezometers, 2 reservoirs and other supply equipment. Model is filled by fine sand (3-D porous matrix) and drainage plastic pipes (1-D conduits). This model enables knowledge of full heterogeneity structure including position of different sand layers as well as conduits location and geometry. Moreover, we know geometry of conduits perforation that enable analysis of interaction between matrix and conduits. In addition, pressure and precipitation distribution and discharge flow rates from both phases can be measured very accurately. These possibilities are not present in real sites what this model makes much more useful for karst flow modeling. Many experiments were performed under different controlled conditions such as different

Karst Aquifer in Qatar and its bearing on Natural Rainfall Recharge

NASA Astrophysics Data System (ADS)

Baalousha, Husam; Ackerer, Philippe

2017-04-01

Qatar is an arid country with little rainfall and high evaporation. Surface water is non-existent so aquifer is the only source of natural water. The annual long-term averages of rainfall and evaporation are 80 mm and more than 2000 mm, respectively. Despite the low rainfall and high evaporation, natural recharge from rainfall occurs at an average of approximately 50 million m3 per year. Rainfall recharge in Qatar takes in land depressions that occur all over the country. These depressions are a result of land collapse due to sinkholes and cavity in the limestone formation. In the northern part of the country, karst features occur as a result of dissolution of limestone, which leads to land depressions. Results of this study shows groundwater recharge occurs in land depression areas, especially in the northern part of the country, where surface runoff accumulates in these land depressions and recharges the aquifer. This paper was made possible by NPRP grant # [NPRP 9-030-1-008] from the Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the author[s]."

Characterization of the porosity distribution in the upper part of the karst Biscayne aquifer using common offset ground penetrating radar, Everglades National Park, Florida

NASA Astrophysics Data System (ADS)

Mount, Gregory J.; Comas, Xavier; Cunningham, Kevin J.

2014-07-01

the direct porosity values from the whole-core samples confirms the ability of GPR common offset surveys to provide rapid characterization of porosity variability in the Biscayne aquifer. The common offset survey method has several advantages: (1) improved time efficiency in comparison to other GPR acquisition modes such as common midpoints; and (2) enhanced lateral continuity of porosity estimates, particularly when compared to porosity measurements on 1-D samples such as rock cores. The results also support the presence of areas of low EM wave velocity or high porosity under saturated conditions, causing velocity pull-down areas and apparent sag features in the reflection record. This study shows that GPR can be a useful tool for improving understanding of the petrophysical properties of highly heterogeneous systems such as karst aquifers, and thus may assist with the development of more accurate groundwater flow models, such as those used for restoration efforts in the Everglades.

Characterization of the porosity distribution in the upper part of the karst Biscayne aquifer using common offset ground penetrating radar, Everglades National Park, Florida

USGS Publications Warehouse

Mountain, Gregory S.; Cunningham, Kevin J.; Comas, Xavier

2014-01-01

the direct porosity values from the whole-core samples confirms the ability of GPR common offset surveys to provide rapid characterization of porosity variability in the Biscayne aquifer.The common offset survey method has several advantages: (1) improved time efficiency in comparison to other GPR acquisition modes such as common midpoints; and (2) enhanced lateral continuity of porosity estimates, particularly when compared to porosity measurements on 1-D samples such as rock cores. The results also support the presence of areas of low EM wave velocity or high porosity under saturated conditions, causing velocity pull-down areas and apparent sag features in the reflection record. This study shows that GPR can be a useful tool for improving understanding of the petrophysical properties of highly heterogeneous systems such as karst aquifers, and thus may assist with the development of more accurate groundwater flow models, such as those used for restoration efforts in the Everglades.

Joining direct and indirect inverse calibration methods to characterize karst, coastal aquifers

NASA Astrophysics Data System (ADS)

De Filippis, Giovanna; Foglia, Laura; Giudici, Mauro; Mehl, Steffen; Margiotta, Stefano; Negri, Sergio

2016-04-01

Parameter estimation is extremely relevant for accurate simulation of groundwater flow. Parameter values for models of large-scale catchments are usually derived from a limited set of field observations, which can rarely be obtained in a straightforward way from field tests or laboratory measurements on samples, due to a number of factors, including measurement errors and inadequate sampling density. Indeed, a wide gap exists between the local scale, at which most of the observations are taken, and the regional or basin scale, at which the planning and management decisions are usually made. For this reason, the use of geologic information and field data is generally made by zoning the parameter fields. However, pure zoning does not perform well in the case of fairly complex aquifers and this is particularly true for karst aquifers. In fact, the support of the hydraulic conductivity measured in the field is normally much smaller than the cell size of the numerical model, so it should be upscaled to a scale consistent with that of the numerical model discretization. Automatic inverse calibration is a valuable procedure to identify model parameter values by conditioning on observed, available data, limiting the subjective evaluations introduced with the trial-and-error technique. Many approaches have been proposed to solve the inverse problem. Generally speaking, inverse methods fall into two groups: direct and indirect methods. Direct methods allow determination of hydraulic conductivities from the groundwater flow equations which relate the conductivity and head fields. Indirect methods, instead, can handle any type of parameters, independently from the mathematical equations that govern the process, and condition parameter values and model construction on measurements of model output quantities, compared with the available observation data, through the minimization of an objective function. Both approaches have pros and cons, depending also on model complexity. For

Karstification of an aquifer along the Birs River, Switzerland - from natural to anthropogenic dominated boundary conditions

NASA Astrophysics Data System (ADS)

Romanov, D.; Epting, J.; Huggenberger, P.; Kaufmann, G.

2009-04-01

Karst aquifers are very sensitive to environmental changes. Small variations of boundary conditions can trigger significant and fast changes of the basic properties of these geological formations. Furthermore, a large number of hydraulic structures have been built in Karst terrains and close to urban areas. Within such settings it is of primary importance to understand the basic processes governing the system and to predict the evolution of Karst aquifers in order to mitigate hazards. There has been great progress in numerical modeling of the evolution of Karst during the last decades. We are now able to model early karstification of locations with complicated geological and geochemical settings and our knowledge about basic processes governing Karst evolution has increased significantly. However, there are still not many modeling attempts with data from real Karst aquifers. A model describing the evolution of a gypsum Karst aquifer along the Birs River in Switzerland is presented in this study. The initial and boundary conditions for the simulations are taken from results of geophysical and geological field studies and a detailed 3D hydrogeological model of the area. Three time intervals of the aquifer's development are discussed in details. The first covers the natural karstification for a period between several hundreds up to a few thousands years. The results from this evolution period are used as initial conditions for the second interval, which covers the time between 1890 and 2007 AD. This period is characterized by anthropogenic alterations of the system through a man-made river dam, which considerably changes the evolution of the aquifer. In 2006 and 2007 AD - after serious subsidence of a nearby highway has been observed - technical measures have been conducted and thus the boundary conditions have changed once again. This is the beginning for the third modeled interval. A forecast for the following 100 years is developed. Our results correlate very well

Geo-Hydro Statistical Characterization of Preferential Flow and Transport Processes in Karst Groundwater Systems

NASA Astrophysics Data System (ADS)

Anaya, A. A.; Padilla, I. Y.; Macchiavelli, R. E.

2011-12-01

Karst groundwater systems are highly productive and provide an important fresh water resource for human development and ecological integrity. Their high productivity is often associated with conduit flow and high matrix permeability. The same characteristics that make these aquifers productive also make them highly vulnerable to contamination and a likely for contaminant exposure. Of particular interest are chlorinated organic contaminants and phthalates derived from industrial solvents and plastic by-products. These chemicals have been identified as potential precursors of pre-term birth, a leading cause of neonatal complications with a significant health and societal cost. The general objectives of this work are to: (1) develop fundamental knowledge and determine the processes controlling the release, mobility, persistence, and possible pathways of contaminants in karst groundwater systems, and (2) characterize transport processes in conduit and diffusion-dominated flow under base flow and storm flow conditions. The work presented herein focuses on the development of geo-hydro statistical tools to characterize flow and transport processes under different flow regimes. Multidimensional, laboratory-scale Geo-Hydrobed models were developed and tested for this purpose. The models consist of stainless-steel tanks containing karstified limestone blocks collected from the karst aquifer formation of northern Puerto Rico. The models a network of sampling wells to monitor flow, pressure, and solute concentrations temporally and spatially. Experimental work entailed making a series of point injections in wells while monitoring the hydraulic response in other wells. Statistical mixed models were applied to spatial probabilities of hydraulic response and weighted injected volume data, and were used to determinate the best spatial correlation structure to represent paths of preferential flow in the limestone units under different groundwater flow regimes. Preliminary testing

Lanthanide-labeled clay: A new method for tracing sediment transport in Karst

USGS Publications Warehouse

Mahler, B.J.; Bennett, P.C.; Zimmerman, M.

1998-01-01

Mobile sediment is a fundamental yet poorly characterized aspect of mass transport through karst aquifers. Here the development and field testing of an extremely sensitive particle tracer that may be used to characterize sediment transport in karst aquifers is described. The tracer consists of micron-size montmorillonite particles homoionized to the lanthanide form; after injection and retrieval from a ground water system, the lanthanide ions are chemically stripped from the clay and quantified by high performance liquid chromatography. The tracer meets the following desired criteria: low detection limit; a number of differentiable signatures; inexpensive production and quantification using standard methods; no environmental risks; and hydrodynamic properties similar to the in situ sediment it is designed to trace. The tracer was tested in laboratory batch experiments and field tested in both surface water and ground water systems. In surface water, arrival times of the tracer were similar to those of a conservative water tracer, although a significant amount of material was lost due to settling. Two tracer tests were undertaken in a karst aquifer under different flow conditions. Under normal flow conditions, the time of arrival and peak concentration of the tracer were similar to or preceded that of a conservative water tracer. Under low flow conditions, the particle tracer was not detected, suggesting that in low flow the sediment settles out of suspension and goes into storage.Mobile sediment is a fundamental yet poorly characterized aspect of mass transport through karst aquifers. Here the development and field testing of an extremely sensitive particle tracer that may be used to characterize sediment transport in karst aquifers is described. The tracer consists of micron-size montmorillonite particles homoionized to the lanthanide form; after injection and retrieval from a ground water system, the lanthanide ions are chemically stripped from the clay and

Solute transport characterization in karst aquifers by tracer injection tests for a sustainable water resource management

NASA Astrophysics Data System (ADS)

Morales, T.; Angulo, B.; Uriarte, J. A.; Olazar, M.; Arandes, J. M.; Antiguedad, I.

2017-04-01

Protection of water resources is a major challenge today, given that territory occupation and land use are continuously increasing. In the case of karst aquifers, its dynamic complexity requires the use of specific methodologies that allow establishing local and regional flow and transport patterns. This information is particularly necessary when springs and wells harnessed for water supply are concerned. In view of the present state of the art, this work shows a new approach based on the use of a LiCl based tracer injection test through a borehole for transport characterization from a local to a regional scale. Thus a long term tracer injection test was conducted in a particularly sensitive sector of the Egino karst massif (Basque Country, Spain). The initial displacement of tracer in the vicinity of the injection was monitored in a second borehole at a radial distance of 10.24 m. This first information, assessed by a radial divergent model, allows obtaining transport characteristic parameters in this immediate vicinity during injection. At a larger (regional) scale, the tracer reaches a highly transmissive network with mean traveling velocities to the main springs being from 4.3 to 13.7 m/h. The responses obtained, particularly clear in the main spring used for water supply, and the persistence of part of the tracer in the injection zone, pose reconsidering the need for their protection. Thus, although the test allows establishing the 24-h isochrone, which is the ceiling value in present European vulnerability approaches, the results obtained advise widening the zone to protect in order to guarantee water quality in the springs. Overall, this stimulus-response test allows furthering the knowledge on the dynamics of solute transport in karst aquifers and is a particularly useful tool in studies related to source vulnerability and protection in such a complex medium.

Resilience of Groundwater Impacted by Land Use and Climate Change in a Karst Aquifer, South China.

PubMed

Guo, Fang; Jiang, Guanghui; Polk, Jason S; Huang, Xiufeng; Huang, Siyu

2015-11-01

Changes of groundwater flow and quality were investigated in a subtropical karst aquifer to determine the driving mechanism. Decreases in groundwater flow are more distinct in discharge zones than those in recharge and runoff zones. Long-term measurement of the represented regional groundwater outlet reveals that groundwater discharge decrease by nearly 50% during the dry season. The hydrochemistry of groundwater in the runoff and discharge zones is of poorer quality than in the recharge zone. Indications of intensive land resource exploitation and changes in land use patterns were attributed to changes in groundwater conditions since 1990, but the influence of climate change was likely from 2001, because the water temperature exhibited increasing trends at a mean rate of 0.02 °C/yr even though groundwater depth was high in the aquifer. These conclusions imply the need for further groundwater monitoring and reevaluation to understand the resilience of aquifer during urbanization and development.

Stochastic simulation of karst conduit networks

NASA Astrophysics Data System (ADS)

Pardo-Igúzquiza, Eulogio; Dowd, Peter A.; Xu, Chaoshui; Durán-Valsero, Juan José

2012-01-01

Karst aquifers have very high spatial heterogeneity. Essentially, they comprise a system of pipes (i.e., the network of conduits) superimposed on rock porosity and on a network of stratigraphic surfaces and fractures. This heterogeneity strongly influences the hydraulic behavior of the karst and it must be reproduced in any realistic numerical model of the karst system that is used as input to flow and transport modeling. However, the directly observed karst conduits are only a small part of the complete karst conduit system and knowledge of the complete conduit geometry and topology remains spatially limited and uncertain. Thus, there is a special interest in the stochastic simulation of networks of conduits that can be combined with fracture and rock porosity models to provide a realistic numerical model of the karst system. Furthermore, the simulated model may be of interest per se and other uses could be envisaged. The purpose of this paper is to present an efficient method for conditional and non-conditional stochastic simulation of karst conduit networks. The method comprises two stages: generation of conduit geometry and generation of topology. The approach adopted is a combination of a resampling method for generating conduit geometries from templates and a modified diffusion-limited aggregation method for generating the network topology. The authors show that the 3D karst conduit networks generated by the proposed method are statistically similar to observed karst conduit networks or to a hypothesized network model. The statistical similarity is in the sense of reproducing the tortuosity index of conduits, the fractal dimension of the network, the direction rose of directions, the Z-histogram and Ripley's K-function of the bifurcation points (which differs from a random allocation of those bifurcation points). The proposed method (1) is very flexible, (2) incorporates any experimental data (conditioning information) and (3) can easily be modified when

Laboratory analog and numerical study of groundwater flow and solute transport in a karst aquifer with conduit and matrix domains.

PubMed

Faulkner, Jonathan; Hu, Bill X; Kish, Stephen; Hua, Fei

2009-11-03

New mathematical and laboratory methods have been developed for simulating groundwater flow and solute transport in karst aquifers having conduits imbedded in a porous medium, such as limestone. The Stokes equations are used to model the flow in the conduits and the Darcy equation is used for the flow in the matrix. The Beavers-Joseph interface boundary conditions are adopted to describe the flow exchange at the interface boundary between the two domains. A laboratory analog is used to simulate the conduit and matrix domains of a karst aquifer. The conduit domain is located at the bottom of the transparent plexiglas laboratory analog and glass beads occupy the remaining space to represent the matrix domain. Water flows into and out of the two domains separately and each has its own supply and outflow reservoirs. Water and solute are exchanged through an interface between the two domains. Pressure transducers located within the matrix and conduit domains of the analog provide data that is processed and stored in digital format. Dye tracing experiments are recorded using time-lapse imaging. The data and images produced are analyzed by a spatial analysis program. The experiments provide not only hydraulic head distribution but also capture solute front images and mass exchange measurements between the conduit and matrix domains. In the experiment, we measure and record pressures, and quantify flow rates and solute transport. The results present a plausible argument that laboratory analogs can characterize groundwater water flow, solute transport, and mass exchange between the conduit and matrix domains in a karst aquifer. The analog validates the predictions of a numerical model and demonstrates the need of laboratory analogs to provide verification of proposed theories and the calibration of mathematical models.

Changes in groundwater quality in a conduit-flow-dominated karst aquifer, following BMP implementation

USGS Publications Warehouse

Currens, J.C.

2002-01-01

Water quality in the Pleasant Grove Spring karst groundwater basin, Logan County, Kentucky, was monitored to determine the effectiveness of best management practices (BMPs) in protecting karst aquifers. Ninety-two percent of the 4,069-ha (10,054-acre) watershed is used for agriculture. Water-quality monitoring began in October 1992 and ended in November 1998. By the fall of 1995 approximately 72% of the watershed was enrolled in BMPs sponsored by the US Department of Agriculture Water Quality Incentive Program (WQIP). Pre-BMP nitrate-nitrogen concentration averaged 4.65 mg/1. The median total suspended solids concentration was 127 mg/1. The median triazine concentration measured by immunosorbent assay was 1.44 ??tg/l. Median bacteria counts were 418 colonies per 100 ml (col/100 ml) for fecal coliform and 540 col/100 ml for fecal streptococci. Post-BMP, the average nitrate-nitrogen concentration was 4.74 mg/1. The median total suspended solids concentration was 47.8 mg/1. The median triazine concentration for the post-BMP period was 1.48 ??g/1. The median fecal coliform count increased to 432 col/100 ml after BMP implementation, but the median fecal streptococci count decreased to 441 col/100 ml. The pre- and post-BMP water quality was statistically evaluated by comparing the annual mass flux, annual descriptive statistics, and population of analyses for the two periods. Nitrate-nitrogen concentration was unchanged. Increases in atrazine-equivalent flux and triazine geometric averages were not statistically significant. Total suspended solids concentration decreased slightly, whereas orthophosphate concentration increased slightly. Fecal streptococci counts were reduced. The BMPs were only partially successful because the types available and the rules for participation resulted in less effective BMPs being chosen. Future BMP programs in karst areas should emphasize buffer strips around sinkholes, excluding livestock from streams and karst windows, and withdrawing

Carbonate aquifers

USGS Publications Warehouse

Cunningham, Kevin J.; Sukop, Michael; Curran, H. Allen

2012-01-01

Only limited hydrogeological research has been conducted using ichnology in carbonate aquifer characterization. Regardless, important applications of ichnology to carbonate aquifer characterization include its use to distinguish and delineate depositional cycles, correlate mappable biogenically altered surfaces, identify zones of preferential groundwater flow and paleogroundwater flow, and better understand the origin of ichnofabric-related karst features. Three case studies, which include Pleistocene carbonate rocks of the Biscayne aquifer in southern Florida and Cretaceous carbonate strata of the Edwards–Trinity aquifer system in central Texas, demonstrate that (1) there can be a strong relation between ichnofabrics and groundwater flow in carbonate aquifers and (2) ichnology can offer a useful methodology for carbonate aquifer characterization. In these examples, zones of extremely permeable, ichnofabric-related macroporosity are mappable stratiform geobodies and as such can be represented in groundwater flow and transport simulations.

Using dye tracing to establish groundwater flow paths in a limestone marble aquifer, University of California, Santa Cruz, California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes, J.; Bertschinger, V.; Aley, T.

1993-04-01

Areas underlain by karst aquifers are characterized by soluble rock with sinkholes, caves, and a complex underground drainage network. Groundwater issues such as flow direction, well pumping impacts, spring recharge areas, and potential contamination transport routes are greatly complicated by the unique structure of karst aquifers. Standard aquifer analysis techniques cannot be applied unless the structure of the karst aquifer is understood. Water soluble fluorescent dyes are a powerful tool for mapping the irregular subsurface connections and flow paths in karst aquifers. Mapping the subsurface connections allows reasonable estimates of the hydrologic behavior of the aquifer. Two different fluorescent dyesmore » were injected at two points in a limestone karst aquifer system beneath the University of California, Santa Cruz campus. Flow paths in the marble were thought to be closely tied to easily recognized geomorphic alignments of sinkholes associated with fault and fracture zones. The dye tests revealed unexpected and highly complex interconnections. These complex flow paths only partially corresponded to previous surface mapping and aerial photo analysis of fracture systems. Several interfingering but hydrologically unconnected flow paths evidently exist within the cavernous aquifer. For example, dye did not appear at some discharge springs close to the dye injection points, but did appear at more distant springs. This study shows how a dye tracing study in a small, well-defined limestone body can shed light on a variety of environmental and hydrological issues, including potential well pumping impact areas, wellhead protection and recharge areas, parking lot runoff injection to aquifers, and drainage routes from hazardous materials storage areas.« less

Groundwater recharge assessment at local and episodic scale in a soil mantled perched karst aquifer in southern Italy

USGS Publications Warehouse

Allocca, V.; De Vita, P.; Manna, F.; Nimmo, John R.

2015-01-01

Depending on the seasonally varying air temperature, evapotranspiration, and precipitation patterns, calculated values of RPR varied between 35% and 97% among the individual episodes. A multiple linear correlation of the RPR with both the average intensity of recharging rainfall events and the antecedent soil water content was calculated. Given the relatively easy measurability of precipitation and soil water content, such an empirical model would have great hydrogeological and practical utility. It would facilitate short-term forecasting of recharge in karst aquifers of the Mediterranean region and other aquifers with similar hydrogeological characteristics. By establishing relationships between the RPR and climate-dependent variables such as average storm intensity, it would facilitate prediction of climate-change effects on groundwater recharge. The EMR methodology could further be applied to other aquifers for evaluating the relationship of recharge to various hydrometeorological and hydrogeological processes.

ERT, GPR, InSAR, and tracer tests to characterize karst aquifer systems under urban areas: The case of Quebec City

NASA Astrophysics Data System (ADS)

Martel, Richard; Castellazzi, Pascal; Gloaguen, Erwan; Trépanier, Luc; Garfias, Jaime

2018-06-01

Urban infrastructures built over karst settings may be at risk of collapse due to hydro-chemical erosion of underlying rock structures. In such settings, mapping cave networks and monitoring ground stability is important to assure civil safety and guide future infrastructure development decisions. However, no technique can directly and comprehensively map these hydrogeological features and monitor their stability. The most reliable method to map a cave network is through speleological exploration, which is not always possible due to restrictions, narrow corridors/passages, or high water levels. Borehole drilling is expensive and is often only performed where the presence of karsts is suggested by other techniques. Numerous indirect and cost-effective methods exist to map a karst flow system, such as geophysics, geodesy, and tracer tests. This paper presents the outcomes from a challenging application in Quebec City, Canada, where a multidisciplinary approach was designed to better understand the groundwater dynamics and cave paths. Two tracer tests in groundwater flowing through the cave system indicated that water flows along an approximately straight path from the sinking stream to the spring. It also suggests the presence of a parallel flow path close to the one already partially mapped. This observation was confirmed by combining Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) techniques, and ultimately by observing voids in several boreholes drilled close to the main cave path. Lowering the water levels at the suspected infiltration zone and inside the karst, the infiltration cracks were identified and the hydraulic link between them was confirmed. In fact, almost no infiltration occurs into the karst system when the water level at the sinking stream drops below a threshold level. Finally, SAR interferometry (InSAR) using RADARSAT-2 images detected movements on few buildings located over a backfilled sinkhole intercepted by the karst

Modern and Unconventional Approaches to Karst Hydrogeology

NASA Astrophysics Data System (ADS)

Sukop, M. C.

2017-12-01

Karst hydrogeology is frequently approached from a hydrograph/statistical perspective where precipitation/recharge inputs are converted to output hydrographs and the conversion process reflects the hydrology of the system. Karst catchments show hydrological response to short-term meteorological events and to long-term variation of large-scale atmospheric circulation. Modern approaches to analysis of these data include, for example, multiresolution wavelet techniques applied to understand relations between karst discharge and climate fields. Much less effort has been directed towards direct simulation of flow fields and transport phenomena in karst settings. This is primarily due to the lack of information on the detailed physical geometry of most karst systems. New mapping, sampling, and modeling techniques are beginning to enable direct simulation of flow and transport. A Conduit Flow Process (CFP) add-on to the USGS ModFlow model became available in 2007. FEFLOW and similar models are able to represent flows in individual conduits. Lattice Boltzmann models have also been applied to flow modeling in karst systems. Regarding quantitative measurement of karst system geometry, at scales to 0.1 m, X-ray computed tomography enables good detection of detailed (sub-millimeter) pore space in karstic rocks. Three-dimensional printing allows reconstruction of fragile high porosity rocks, and surrogate samples generated this way can then be subjected to laboratory testing. Borehole scales can be accessed with high-resolution ( 0.001 m) Digital Optical Borehole Imaging technologies and can provide virtual samples more representative of the true nature of karst aquifers than can obtained from coring. Subsequent extrapolation of such samples can generate three-dimensional models suitable for direct modeling of flow and transport. Finally, new cave mapping techniques are beginning to provide information than can be applied to direct simulation of flow. Due to flow rates and cave

Preliminary conceptual models of the occurrence, fate, and transport of chlorinated solvents in karst regions of Tennessee

USGS Publications Warehouse

Wolfe, W.J.; Haugh, C.J.; Webbers, Ank; Diehl, T.H.

1997-01-01

Published and unpublished reports and data from 22 contaminated sites in Tennessee were reviewed to develop preliminary conceptual models of the behavior of chlorinated solvents in karst aquifers. Chlorinated solvents are widely used in many industrial operations. High density and volatility, low viscosity, and solubilities that are low in absolute terms but high relative to drinkingwater standards make chlorinated solvents mobile and persistent contaminants that are difficult to find or remove when released into the groundwater system. The major obstacle to the downward migration of chlorinated solvents in the subsurface is the capillary pressure of small openings. In karst aquifers, chemical dissolution has enlarged joints, bedding planes, and other openings that transmit water. Because the resulting karst conduits are commonly too large to develop significant capillary pressures, chlorinated solvents can migrate to considerable depth in karst aquifers as dense nonaqueous-phase liquids (DNAPL?s). Once chlorinated DNAPL accumulates in a karst aquifer, it becomes a source for dissolved-phase contamination of ground water. A relatively small amount of chlorinated DNAPL has the potential to contaminate ground water over a significant area for decades or longer. Conceptual models are needed to assist regulators and site managers in characterizing chlorinated-solvent contamination in karst settings and in evaluating clean-up alternatives. Five preliminary conceptual models were developed, emphasizing accumulation sites for chlorinated DNAPL in karst aquifers. The models were developed for the karst regions of Tennessee, but are intended to be transferable to similar karst settings elsewhere. The five models of DNAPL accumulation in karst settings are (1) trapping in regolith, (2) pooling at the top of bedrock, (3) pooling in bedrock diffuse-flow zones, (4) pooling in karst conduits, and (5) pooling in isolation from active ground-water flow. More than one conceptual

Numerical simulation of freshwater/seawater interaction in a dual-permeability karst system with conduits: the development of discrete-continuum VDFST-CFP model

NASA Astrophysics Data System (ADS)

Xu, Zexuan; Hu, Bill

2016-04-01

Dual-permeability karst aquifers of porous media and conduit networks with significant different hydrological characteristics are widely distributed in the world. Discrete-continuum numerical models, such as MODFLOW-CFP and CFPv2, have been verified as appropriate approaches to simulate groundwater flow and solute transport in numerical modeling of karst hydrogeology. On the other hand, seawater intrusion associated with fresh groundwater resources contamination has been observed and investigated in numbers of coastal aquifers, especially under conditions of sea level rise. Density-dependent numerical models including SEAWAT are able to quantitatively evaluate the seawater/freshwater interaction processes. A numerical model of variable-density flow and solute transport - conduit flow process (VDFST-CFP) is developed to provide a better description of seawater intrusion and submarine groundwater discharge in a coastal karst aquifer with conduits. The coupling discrete-continuum VDFST-CFP model applies Darcy-Weisbach equation to simulate non-laminar groundwater flow in the conduit system in which is conceptualized and discretized as pipes, while Darcy equation is still used in continuum porous media. Density-dependent groundwater flow and solute transport equations with appropriate density terms in both conduit and porous media systems are derived and numerically solved using standard finite difference method with an implicit iteration procedure. Synthetic horizontal and vertical benchmarks are created to validate the newly developed VDFST-CFP model by comparing with other numerical models such as variable density SEAWAT, couplings of constant density groundwater flow and solute transport MODFLOW/MT3DMS and discrete-continuum CFPv2/UMT3D models. VDFST-CFP model improves the simulation of density dependent seawater/freshwater mixing processes and exchanges between conduit and matrix. Continuum numerical models greatly overestimated the flow rate under turbulent flow

Numerical modeling of groundwater flow in the coastal aquifer system of Taranto (southern Italy)

NASA Astrophysics Data System (ADS)

De Filippis, Giovanna; Giudici, Mauro; Negri, Sergio; Margiotta, Stefano; Cattaneo, Laura; Vassena, Chiara

2014-05-01

The Mediterranean region is characterized by a strong development of coastal areas with a high concentration of water-demanding human activities, resulting in weakly controlled withdrawals of groundwater which accentuate the saltwater intrusion phenomenon. The worsening of groundwater quality is a huge problem especially for those regions, like Salento (southern Italy), where a karst aquifer system represents the most important water resource because of the deficiency of a well developed superficial water supply. In this frame, the first 2D numerical model describing the groundwater flow in the karst aquifer of Salento peninsula was developed by Giudici et al. [1] at the regional scale and then improved by De Filippis et al. [2]. In particular, the estimate of the saturated thickness of the deep aquifer highlighted that the Taranto area is particularly sensitive to the phenomenon of seawater intrusion, both for the specific hydrostratigraphic configuration and for the presence of highly water-demanding industrial activities. These remarks motivate a research project which is part of the research program RITMARE (The Italian Research for the Sea), within which a subprogram is specifically dedicated to the problem of the protection and preservation of groundwater quality in Italian coastal aquifers and in particular, among the others, in the Taranto area. In this context, the CINFAI operative unit aims at providing a contribution to the characterization of groundwater in the study area. The specific objectives are: a. the reconstruction of the groundwater dynamic (i.e., the preliminary identification of a conceptual model for the aquifer system and the subsequent modeling of groundwater flow in a multilayered system which is very complex from the hydrostratigraphical point of view); b. the characterization of groundwater outflows through submarine and subaerial springs and the water exchanges with the shallow coastal water bodies (e.g. Mar Piccolo) and the off

Long distance seawater intrusion through a karst conduit network in the Woodville Karst Plain, Florida

NASA Astrophysics Data System (ADS)

Xu, Zexuan; Bassett, Seth Willis; Hu, Bill; Dyer, Scott Barrett

2016-08-01

Five periods of increased electrical conductivity have been found in the karst conduits supplying one of the largest first magnitude springs in Florida with water. Numerous well-developed conduit networks are distributed in the Woodville Karst Plain (WKP), Florida and connected to the Gulf of Mexico. A composite analysis of precipitation and electrical conductivity data provides strong evidence that the increases in conductivity are directly tied to seawater intrusion moving inland and traveling 11 miles against the prevailing regional hydraulic gradient from from Spring Creek Spring Complex (SCSC), a group of submarine springs at the Gulf Coast. A geochemical analysis of samples from the spring vent rules out anthropogenic contamination and upwelling regional recharge from the deep aquifer as sources of the rising conductivity. The interpretation is supported by the conceptual model established by prior researchers working to characterize the study area. This paper documents the first and longest case of seawater intrusion in the WKP, and also indicates significant possibility of seawater contamination through subsurface conduit networks in a coastal karst aquifer.

Long distance seawater intrusion through a karst conduit network in the Woodville Karst Plain, Florida.

PubMed

Xu, Zexuan; Bassett, Seth Willis; Hu, Bill; Dyer, Scott Barrett

2016-08-25

Five periods of increased electrical conductivity have been found in the karst conduits supplying one of the largest first magnitude springs in Florida with water. Numerous well-developed conduit networks are distributed in the Woodville Karst Plain (WKP), Florida and connected to the Gulf of Mexico. A composite analysis of precipitation and electrical conductivity data provides strong evidence that the increases in conductivity are directly tied to seawater intrusion moving inland and traveling 11 miles against the prevailing regional hydraulic gradient from from Spring Creek Spring Complex (SCSC), a group of submarine springs at the Gulf Coast. A geochemical analysis of samples from the spring vent rules out anthropogenic contamination and upwelling regional recharge from the deep aquifer as sources of the rising conductivity. The interpretation is supported by the conceptual model established by prior researchers working to characterize the study area. This paper documents the first and longest case of seawater intrusion in the WKP, and also indicates significant possibility of seawater contamination through subsurface conduit networks in a coastal karst aquifer.

Long distance seawater intrusion through a karst conduit network in the Woodville Karst Plain, Florida

PubMed Central

Xu, Zexuan; Bassett, Seth Willis; Hu, Bill; Dyer, Scott Barrett

2016-01-01

Five periods of increased electrical conductivity have been found in the karst conduits supplying one of the largest first magnitude springs in Florida with water. Numerous well-developed conduit networks are distributed in the Woodville Karst Plain (WKP), Florida and connected to the Gulf of Mexico. A composite analysis of precipitation and electrical conductivity data provides strong evidence that the increases in conductivity are directly tied to seawater intrusion moving inland and traveling 11 miles against the prevailing regional hydraulic gradient from from Spring Creek Spring Complex (SCSC), a group of submarine springs at the Gulf Coast. A geochemical analysis of samples from the spring vent rules out anthropogenic contamination and upwelling regional recharge from the deep aquifer as sources of the rising conductivity. The interpretation is supported by the conceptual model established by prior researchers working to characterize the study area. This paper documents the first and longest case of seawater intrusion in the WKP, and also indicates significant possibility of seawater contamination through subsurface conduit networks in a coastal karst aquifer. PMID:27557803

Evaluation of subsidence hazard in mantled karst setting: a case study from Val d'Orléans (France)

NASA Astrophysics Data System (ADS)

Perrin, Jérôme; Cartannaz, Charles; Noury, Gildas; Vanoudheusden, Emilie

2015-04-01

Soil subsidence/collapse is a major geohazard occurring in karst region. It occurs as suffosion or dropout sinkholes developing in the soft cover. Less frequently it corresponds to a breakdown of karst void ceiling (i.e., collapse sinkhole). This hazard can cause significant engineering challenges. Therefore decision-makers require the elaboration of methodologies for reliable predictions of such hazards (e.g., karst subsidence susceptibility and hazards maps, early-warning monitoring systems). A methodological framework was developed to evaluate relevant conditioning factors favouring subsidence (Perrin et al. submitted) and then to combine these factors to produce karst subsidence susceptibility maps. This approach was applied to a mantled karst area south of Paris (Val d'Orléans). Results show the significant roles of the overburden lithology (presence/absence of low-permeability layer) and of the karst aquifer piezometric surface position within the overburden. In parallel, an experimental site has been setup to improve the understanding of key processes leading to subsidence/collapse and includes piezometers for measurements of water levels and physico-chemical parameters in both the alluvial and karst aquifers as well as surface deformation monitoring. Results should help in designing monitoring systems to anticipate occurrence of subsidence/collapse. Perrin J., Cartannaz C., Noury G., Vanoudheusden E. 2015. A multicriteria approach to karst subsidence hazard mapping supported by Weights-of-Evidence analysis. Submitted to Engineering Geology.

Pesticides and biocides in a karst catchment: Identification of contaminant sources and related flow components

NASA Astrophysics Data System (ADS)

Wagner, Thomas; Bollmann, Ulla E.; Bester, Kai; Birk, Steffen

2013-04-01

Karst aquifers are widely used as drinking water resources. However, their high vulnerability to chemical and bacterial contamination due to the heterogeneity in aquifer properties (highly conductive solution conduits embedded in the less conductive fissured rock) is difficult to assess and thus poses major challenges to the management of karst water resources. Contamination of karst springs by organic micro-pollutants has been observed in recent studies. Within this study the water from different springs draining one karst aquifer as well as the main sinking stream replenishing it were analysed before, during and after a storm water event in order to examine the occurrence of different pesticides and biocides. Contaminants from both urban as well as agricultural origin could be detected in the water with concentrations in the low ng/L range (tebuconazole, carbendazim, diuron, isoproturon, terbutryn, atrazine, dichlorobenzamide (BAM), which is a metabolite of dichlobenil). While some compounds could be followed from the sinking stream to the springs (e.g. dichlorobenzamide) some seem to have a source in the autogenic recharge from the karst plateau (Tebuconazole: wood preservative in buildings). These compounds appear to be related to fast flow components with residence times in the order of days, which are known from a number of tracer tests with fluorescent dyes. However, the occurrence of the pesticide atrazine (banned since 1995 in Austria) in the springs, while on the other hand no current input into the karst occurs, shows that some compounds have long residence times in the karst aquifer. These differences in residence times can hardly be attributed to differences in physico-chemical properties of the compounds and must thus be due to the presence of slow and fast flow components. This is in agreement with the duality of karst aquifers due to highly conductive networks of solution conduits embedded in less conductive fissured carbonate rocks.

Comparing and refining karst disturbance index methods through application in an island karst setting

NASA Astrophysics Data System (ADS)

Porter, Brandon L.; North, Leslie A.; Polk, Jason S.

2016-12-01

The interconnected nature of surface and subsurface karst environments allows easy disturbance to their aquifers and specialized ecosystems from anthropogenic impacts. The karst disturbance index is a holistic tool used to measure disturbance to karst environments and has been applied and refined through studies in Florida and Italy, among others. Through these applications, the karst disturbance index has evolved into two commonly used methods of application; yet, the karst disturbance index is still susceptible to evaluation and modification for application in other areas around the world. The geographically isolated and highly vulnerable municipality of Arecibo, Puerto Rico's karst area provides an opportunity to test the usefulness and validity of the karst disturbance index in an island setting and to compare and further refine the application of the original and modified methods. This study found the both methods of karst disturbance index application resulted in high disturbance scores (Original Method 0.54 and Modified Method 0.69, respectively) and uncovered multiple considerations for the improvement of the karst disturbance index. An evaluation of multiple methods together in an island setting also resulted in the need for adding additional indicators, including Mogote Removal and Coastal Karst. Collectively, the results provide a holistic approach to using the karst disturbance index in an island karst setting and suggest a modified method by which scaling and weighting may compensate for the difference between the original and modified method scores and allow interested stakeholders to evaluate disturbance regardless of his or her level of expertise.

Porosity Gradient Development Around Karst Features due to Tidal Pumping in Eastern Yucatan Peninsula

NASA Astrophysics Data System (ADS)

Maqueda, A.; Renard, P.

2016-12-01

Water exchange between karst features and the porous matrix around them has been observed in karst aquifers by previous research. The exchange is driven by hydraulic head gradients caused by stormwater runoff or sea tides and may cause mineral dissolution. The authors of this work proposed a conceptual model of porosity development under tidal variations of hydraulic head is proposed. Simulations of reactive transport and porosity evolution were conducted to explore the porosity gradient development around a karst feature. Simulations account for petrophysical properties of porous media and groundwater geochemical characteristics. Data used in simulations corresponds to an eogenetic karst aquifer found on the eastern coast of Yucatan Peninsula in Mexico. Simulations include both analytical and numerical solutions of porosity increase caused by mineral dissolution. The estimated rate of porosity development and associated wall retreat (3-30 cm/100 yr) are large enough to develop karst cavities on time periods relevant to karst formation in the study area (10K yr). The analytical solution could be used to assess porosity increase in rock samples and can be also applied to model slow reactions in porous media under flow driven by sinusoidal hydraulic boundary conditions. The results show a possible alternative mechanism of karst cavity development in a high conductive limestone rock matrix aquifer.

Quantification of frequency-components contributions to the discharge of a karst spring

NASA Astrophysics Data System (ADS)

Taver, V.; Johannet, A.; Vinches, M.; Borrell, V.; Pistre, S.; Bertin, D.

2013-12-01

Karst aquifers represent important underground resources for water supplies, providing it to 25% of the population. Nevertheless such systems are currently underexploited because of their heterogeneity and complexity, which make work fields and physical measurements expensive, and frequently not representative of the whole aquifer. The systemic paradigm appears thus at a complementary approach to study and model karst aquifers in the framework of non-linear system analysis. Its input and output signals, namely rainfalls and discharge contain information about the function performed by the physical process. Therefore, improvement of knowledge about the karst system can be provided using time series analysis, for example Fourier analysis or orthogonal decomposition [1]. Another level of analysis consists in building non-linear models to identify rainfall/discharge relation, component by component [2]. In this context, this communication proposes to use neural networks to first model the rainfall-runoff relation using frequency components, and second to analyze the models, using the KnoX method [3], in order to quantify the importance of each component. Two different neural models were designed: (i) the recurrent model which implements a non-linear recurrent model fed by rainfalls, ETP and previous estimated discharge, (ii) the feed-forward model which implements a non-linear static model fed by rainfalls, ETP and previous observed discharges. The first model is known to better represent the rainfall-runoff relation; the second one to better predict the discharge based on previous discharge observations. KnoX method is based on a variable selection method, which simply considers values of parameters after the training without taking into account the non-linear behavior of the model during functioning. An amelioration of the KnoX method, is thus proposed in order to overcome this inadequacy. The proposed method, leads thus to both a hierarchization and a quantification

Colonization by aerobic bacteria in karst: Laboratory and in situ experiments

USGS Publications Warehouse

Personne, J.-C.; Poty, F.; Mahler, B.J.; Drogue, C.

2004-01-01

Experiments were carried out to investigate the potential for bacterial colonization of different substrates in karst aquifers and the nature of the colonizing bacteria. Laboratory batch experiments were performed using limestone and PVC as substrates, a natural bacterial isolate and a known laboratory strain (Escherichia coli [E. coli]) as inocula, and karst ground water and a synthetic formula as growth media. In parallel, fragments of limestone and granite were submerged in boreholes penetrating two karst aquifers for more than one year; the boreholes are periodically contaminated by enteric bacteria from waste water. Once a month, rock samples were removed and the colonizing bacteria quantified and identified. The batch experiments demonstrated that the natural isolate and E. coli both readily colonized limestone surfaces using karst ground water as the growth medium. In contrast, bacterial colonization of both the limestone and granite substrates, when submerged in the karst, was less intense. More than 300 bacterial strains were isolated over the period sampled, but no temporal pattern in colonization was seen as far as strain, and colonization by E. coli was notably absent, although strains of Salmonella and Citrobacter were each observed once. Samples suspended in boreholes penetrating highly fractured zones were less densely colonized than those in the borehole penetrating a less fractured zone. The results suggest that contamination of karst aquifers by enteric bacteria is unlikely to be persistent. We hypothesize that this may be a result of the high flow velocities found in karst conduits, and of predation of colonizing bacteria by autochthonous zooplankton.

Hydrogeology and hydrologic conditions of the Ozark Plateaus aquifer system

USGS Publications Warehouse

Hays, Phillip D.; Knierim, Katherine J.; Breaker, Brian K.; Westerman, Drew A.; Clark, Brian R.

2016-11-23

The hydrogeology and hydrologic characteristics of the Ozark Plateaus aquifer system were characterized as part of ongoing U.S. Geological Survey efforts to assess groundwater availability across the Nation. The need for such a study in the Ozark Plateaus physiographic province (Ozark Plateaus) is highlighted by increasing demand on groundwater resources by the 5.3 million people of the Ozark Plateaus, water-level declines in some areas, and potential impacts of climate change on groundwater availability. The subject study integrates knowledge gained through local investigation within a regional perspective to develop a regional conceptual model of groundwater flow in the Ozark Plateaus aquifer system (Ozark system), a key phase of groundwater availability assessment. The Ozark system extends across much of southern Missouri and northwestern and north-central Arkansas and smaller areas of southeastern Kansas and northeastern Oklahoma. The region is one of the major karst landscapes in the United States, and karst aquifers are predominant in the Ozark system. Groundwater flow is ultimately controlled by aquifer and confining unit lithologies and stratigraphic relations, geologic structure, karst development, and the character of surficial lithologies and regolith mantle. The regolith mantle is a defining element of Ozark Plateaus karst, affecting recharge, karst development, and vulnerability to surface-derived contaminants. Karst development is more advanced—as evidenced by larger springs, hydraulic characteristics, and higher well yields—in the Salem Plateau and in the northern part of the Springfield Plateau (generally north of the Arkansas-Missouri border) as compared with the southern part of the Springfield Plateau in Arkansas, largely due to thinner, less extensive regolith and purer carbonate lithology.Precipitation is the ultimate source of all water to the Ozark system, and the hydrologic budget for the Ozark system includes inputs from recharge

Effects of Hydrogeologic Conditions on Groundwater Contamination of CVOCs in the North Coast Karst Aquifer of Puerto Rico

NASA Astrophysics Data System (ADS)

Torres Torres, N. I.; Howard, J.; Padilla, I. Y.; Torres, P.; Cotto, I.; Irizarry, C.

2012-12-01

The karst system of northern Puerto Rico is the most productive aquifer of the island. It serves freshwater to industrial, domestic and agricultural purposes, and contributes to the ecological integrity of the region. The same characteristics that make this a highly productive aquifer, make it vulnerable to contamination of groundwater. Of particular importance is contamination with chlorinated volatile organic compounds (CVOCs), which have been related to preterm birth problems. A great extent of CVOC contamination has been seen in the North Coast of Puerto Rico since the 1970s. The main purposes of this study are (1) to relate the water quality of wells and springs with the hydrogeological conditions in the north coast limestone aquifer of Puerto Rico, and (2) to make a statistical analysis of the historical groundwater contamination in that area. To achieve these objectives, groundwater samples are collected from wells and springs during dry and wet seasons. Results show that trichloroethylene (TCE), tetrachloroethylene (PCE) and chloroform (TCM) are frequently detected in groundwater samples. A greater detection of CVOCs is detected during the wet season than the dry season. This is attributed to a greater capacity to flush stored contaminants during the wet season. Historical analysis of contamination in the north coast of Puerto Rico shows a high capacity of the aquifer to store and release contaminants. Future work will be focused the statistical analysis of the historical groundwater contamination data to understand the behavior of the contaminants in different hydrologic conditions.

Tracking changing X-ray contrast media application to an urban-influenced karst aquifer in the Wadi Shueib, Jordan.

PubMed

Zemann, Moritz; Wolf, Leif; Grimmeisen, Felix; Tiehm, Andreas; Klinger, Jochen; Hötzl, Heinz; Goldscheider, Nico

2015-03-01

Sewage input into a karst aquifer via leaking sewers and cesspits was investigated over five years in an urbanized catchment. Of 66 samples, analyzed for 25 pharmaceuticals, 91% indicated detectable concentrations. The former standard iodinated X-ray contrast medium (ICM) diatrizoic acid was detected most frequently. Remarkably, it was found more frequently in groundwater (79%, median: 54 ng/l) than in wastewater (21%, 120 ng/l), which is supposed to be the only source in this area. In contrast, iopamidol, a possible substitute, spread over the aquifer during the investigation period whereas concentrations were two orders of magnitude higher in wastewater than in groundwater. Knowledge about changing application of pharmaceuticals thus is essential to assess urban impacts on aquifers, especially when applying mass balances. Since correlated concentrations provide conclusive evidence that, for this catchment, nitrate in groundwater rather comes from urban than from rural sources, ICM are considered useful tracers. Copyright © 2015 Elsevier Ltd. All rights reserved.

Evaluation of onsite sewage treatment and disposal systems in shallow karst terrain.

PubMed

Harden, Harmon S; Roeder, Eberhard; Hooks, Mark; Chanton, Jeffrey P

2008-05-01

Two conventional onsite sewage treatment and disposal systems (OSTDSs) at Manatee Springs State Park, Florida, USA, were studied to assess their impact on groundwater quality in a shallow karst environment. Sulfur hexafluoride (SF6) and fluorescein were used as tracers to establish connections between the drainfields and monitoring wells. Elevated nutrients were found in all wells where significant concentrations of both tracers were observed, with the mean of the highest nitrate (NO3) concentration observed at each well being 47.8+/-14.9 (n=11) mg/L NO3-N. The most elevated nutrient concentrations were found directly in the flow path of the effluent. Fecal coliform densities above 10 colony-forming units (cfu)/100 mL were observed in wells with the most rapid connection to the drainfield. The proximity and connectivity of the 0.4-4m thick sandy surficial soils and the underlying karst aquifer allow rapid contaminant transport and limit the ability of conventional OSTDSs to attenuate NO3.

The impact of river water intrusion on trace metal cycling in karst aquifers: an example from the Floridan aquifer system at Madison Blue Spring, Florida

NASA Astrophysics Data System (ADS)

Brown, A. L.; Martin, J. B.; Screaton, E.; Spellman, P.; Gulley, J.

2011-12-01

Springs located adjacent to rivers can serve as recharge points for aquifers when allogenic runoff increases river stage above the hydraulic head of the spring, forcing river water into the spring vent. Depending on relative compositions of the recharged water and groundwater, the recharged river water could be a source of dissolved trace metals to the aquifer, could mobilize solid phases such as metal oxide coatings, or both. Whether metals are mobilized or precipitated should depend on changes in redox and pH conditions as dissolved oxygen and organic carbon react following intrusion of the river water. To assess how river intrusion events affect metal cycling in springs, we monitored a small recharge event in April 2011 into Madison Blue Spring, which discharges to the Withlacoochee River in north-central Florida. Madison Blue Spring is the entrance to a phreatic cave system that includes over 7.8 km of surveyed conduits. During the event, river stage increased over base flow conditions for approximately 25 days by a maximum of 8%. Intrusion of the river water was monitored with conductivity, temperature and depth sensors that were installed within the cave system and adjacent wells. Decreased specific conductivity within the cave system occurred for approximately 20 days, reflecting the length of time that river water was present in the cave system. During this time, grab samples were collected seven times over a period of 34 days for measurements of major ion and trace metal concentrations at the spring vent and at Martz sink, a karst window connected to the conduit system approximately 150 meters from the spring vent. Relative fractions of surface water and groundwater were estimated based on Cl concentrations of the samples, assuming conservative two end-member mixing during the event. This mixing model indicates that maximum river water contribution to the groundwater system was approximately 20%. River water had concentrations of iron, manganese, and other

Bacterial Activity and Geochemical Reactions in Submerged Cave Development -- Impact on Karst Aquifers in Florida

NASA Astrophysics Data System (ADS)

Herman, J. S.; Franklin, R. B.; Mills, A. L.; Giannotti, A. L.; Tysall, T. N.

2008-05-01

Elucidation of coupled mechanisms of sulfide oxidation and biomass generation supports an improved understanding the driving forces behind acid production, calcite dissolution, cave development, and karst aquifers characterization. Wekiwa Springs Cave and DeLeon Springs Cave, located in central Florida, both contain prolific bacterial mats from which sulfur-oxidizing bacteria have been identified. Wekiwa Springs Cave, a submerged cave developed in the Hawthorne Formation and located near Orlando, Florida, has groundwater discharge from the Floridian aquifer system, with some contribution from surficial and intermediate aquifers. The spring is the headwater of the Wekiwa River and releases a total of 170,000 m3 of water per day. The ceiling and walls are heavily covered (10 cm thick) with three morphologically distinct types of microbial mats largely comprising sulfur-oxidizing bacteria. Analysis of nearby groundwater collected from wells confirms sulfide concentrations in the regional groundwater of ~ 1.5 mg/L, though sulfide concentrations for water collected in the cave are below detection. Dissolved oxygen concentration in the water is low (<0.5 mg/L). DeLeon Springs Cave, a submerged cave located in Volusia County, Florida, is a single conduit with an average discharge of ~ 70,000 m3 of water per day, and water chemistry data suggest the presence of a saline seep in the system. Dense microbial mats cover the rock surfaces of the cave; the mats are highly filamentous, with long white streamers that often extend 1-2 feet from the cave wall. Microscopic analysis has confirmed the presence of sulfur granules within these bacterial cells, similar to those observed in the Wekiwa cave organisms. The water chemistry in DeLeon Springs Cave, however, is distinct from that of Wekiwa Springs Cave. Though DO, Fetotal, and HS- values are similar for the two sites, the concentration of ions such as Cl-, Na+, and SO42- are considerably higher at DeLeon. A similar contrast

Hydrograph monitoring and analysis for sustainable karst water management in Nyadeng Spring, East Borneo

NASA Astrophysics Data System (ADS)

Widyastuti, M.; Fatchurohman, H.; Fathoni, W. A.; Hakim, A. A.; Haryono, E.

2018-04-01

Karst aquifer stores abundant water resources within its matrix, conduits, and intergranular pores. Karst aquifer plays an important role in providing water supply, especially in the areas nearby that commonly dry and lack of surface water resources. Karst spring hydrograph analysis is very fundamental step to–assess and determines the condition of the catchment area in karst terrain. Recession curve is believed to be the most stable part in single flood hydrograph that represents the aquifer characteristics. Nyadeng is one of the most significant karst springs that located in Merabu Karst Area, East Borneo. Villagers in Merabu highly depend on Nyadeng Spring for fulfilled their freshwater need. Hydrograph monitoring has been initiated for one year in Nyadeng Spring as a preliminary action for karst water management in Merabu. Water level data series obtained using automatic water level data logger and then correlated with manual discharge measurement to generate stage-discharge rating curve. The stage-discharge rating curve formula for Nyadeng Spring calculated as y = 0,0102e5,8547x with r2 value = 0.8759. From the combination of several single flood events, Master Recession Curve (MRC) was generated to determine flow regime as the main consideration for karstification degree calculation. From the MRC result, flow regimes formula determined as Qt = 3.2-0.001t + 1.2(1-0.012t)+1.6(1-0.035t) indicated that one sub-regime with laminar flow and two sub-regimes with turbulent flow existed. From the MRC formula, the degree of karstification in Nyadeng Spring classified at seventh scale (developed karstification of the aquifer) based on Malik’s karstification degree (2012). The degree of karstification in Nyadeng Spring indicates that the aquifer formed by large conduit channels, fissures, and macro fissures which are able to provide significant water sources that can be utilized for multi purposes. Therefore, it is concluded that spring hydrograph monitoring provide

Analysis of TCE Fate and Transport in Karst Groundwater Systems Using Statistical Mixed Models

NASA Astrophysics Data System (ADS)

Anaya, A. A.; Padilla, I. Y.

2012-12-01

Karst groundwater systems are highly productive and provide an important fresh water resource for human development and ecological integrity. Their high productivity is often associated with conduit flow and high matrix permeability. The same characteristics that make these aquifers productive also make them highly vulnerable to contamination and a likely for contaminant exposure. Of particular interest are trichloroethylene, (TCE) and Di-(2-Ethylhexyl) phthalate (DEHP). These chemicals have been identified as potential precursors of pre-term birth, a leading cause of neonatal complications with a significant health and societal cost. Both of these contaminants have been found in the karst groundwater formations in this area of the island. The general objectives of this work are to: (1) develop fundamental knowledge and determine the processes controlling the release, mobility, persistence, and possible pathways of contaminants in karst groundwater systems, and (2) characterize transport processes in conduit and diffusion-dominated flow under base flow and storm flow conditions. The work presented herein focuses on the use of geo-hydro statistical tools to characterize flow and transport processes under different flow regimes, and their application in the analysis of fate and transport of TCE. Multidimensional, laboratory-scale Geo-Hydrobed models (GHM) were used for this purpose. The models consist of stainless-steel tanks containing karstified limestone blocks collected from the karst aquifer formation of northern Puerto Rico. The models integrates a network of sampling wells to monitor flow, pressure, and solute concentrations temporally and spatially. Experimental work entails injecting dissolved CaCl2 tracers and TCE in the upstream boundary of the GHM while monitoring TCE and tracer concentrations spatially and temporally in the limestone under different groundwater flow regimes. Analysis of the temporal and spatial concentration distributions of solutes

[Characteristic of ammonia nitrogen adsorption on karst underground river sediments].

PubMed

Guo, Fang; Chen, Kun-Kun; Jiang, Guang-Hui

2011-02-01

Karst aquifers are one of the most important aquifers in Southwestern China. One of the characteristics of karst aquifers is the enhanced permeability permits high flow velocities are capable of transporting suspended and bedload sediments. Mobile sediment in karst may act as a vector for the transport of contaminates. 14 sediment samples were collected from two underground rivers in two typical karst areas in Liuzhou city, Guangxi Autonomous Region, China. According to simulated experiment methods, characteristic of adsorption of ammonia nitrogen on sediment was studied. The results of ammonia nitrogen adsorption dynamics on sediments showed that the maximum adsorption velocity was less than 2 h. The adsorption balance quantity in 5 h accounted for 71% - 98% of the maximum adsorption quantity. The maximum adsorption quantity of ammonia nitrogen was 385.5 mg/kg, which was sediment from a cave in the middle areas of Guancun underground river system. The study of isotherm adsorption indicated adsorption quantity of NH4+ increase followed by incremental balance concentration of NH4+ in the aquatic phase. Adsorption quantity of ammonia nitrogen in sediments has a relative linear relationship with adsorption balance concentrations. Adsorption-desorption balance concentrations were all low, indicating sediments from underground rivers have great adsorption potential. Under the condition of low and high concentrations of ammonia nitrogen in overlying water, Langmuir and Tempkin couldn't simulate or simulate results couldn't reach remarkable level, whilst Linear and Freundlich models could simulate well. Research on different type sediments, sampling times and depths from two underground rivers shows characteristic of ammonia nitrogen adsorption on karst underground river sediments doesn't have good correspondence with the type of sediments. One of the reasons is there is no big difference between sediments in the development of climate, geology, hydrological conditions

Development, description, and application of a geographic information system data base for water resources in karst terrane in Greene County, Missouri

USGS Publications Warehouse

Waite, L.A.; Thomson, Kenneth C.

1993-01-01

A geographic information system data base was developed for Greene County, Missouri, to provide data for use in the protection of water resources. The geographic information system data base contains the following map layers: geology, cave entrances and passages, county and quadrangle boundary, dye traces, faults, geographic names, hypsography, hydrography, lineaments, Ozark aquifer potentio- metric surface, public land survey system, sink- holes, soils, springs, and transportation. Several serious incidents of ground-water contamination have been reported in the karst terrane developed in soluble carbonate rocks in Greene County. Karst terranes are environmentally sensitive because any contaminant carried by surface runoff has the potential for rapid transport through solution enlarged fractures to the ground-water system. In the karst terrane in Greene County, about 2,500 sinkholes have been located; these sinkholes are potential access points for contamination to the ground-water system. Recent examples of ground-water contamination by sewage, fertilizers, and hydrocarbon chemicals have demonstrated the sensitivity of ground water in the Greene County karst terrane to degradation. The ground-water system is a major source of drinking water for Greene County. The population in Greene County, which includes Springfield, the third largest city in Missouri, is rapidly increasing and the protection of the water resources of Greene County is an increasing concern.

Karst groundwater: a challenge for new resources

NASA Astrophysics Data System (ADS)

Bakalowicz, Michel

2005-03-01

Karst aquifers have complex and original characteristics which make them very different from other aquifers: high heterogeneity created and organised by groundwater flow; large voids, high flow velocities up to several hundreds of m/h, high flow rate springs up to some tens of m3/s. Different conceptual models, known from the literature, attempt to take into account all these particularities. The study methods used in classical hydrogeology—bore hole, pumping test and distributed models—are generally invalid and unsuccessful in karst aquifers, because the results cannot be extended to the whole aquifer nor to some parts, as is done in non-karst aquifers. Presently, karst hydrogeologists use a specific investigation methodology (described here), which is comparable to that used in surface hydrology. Important points remain unsolved. Some of them are related to fundamental aspects suc h as the void structure - only a conduit network, or a conduit network plus a porous matrix -, the functioning - threshold effects and non-linearities -, the modeling of the functioning - double or triple porosity, or viscous flow in conduits - and of karst genesis. Some other points deal with practical aspects, such as the assessment of aquifer storage capacity or vulnerability, or the prediction of the location of highly productive zones. Los acuíferos kársticos tienen características originales y complejas que los hacen muy diferentes de otros acuíferos: alta heterogeneidad creada y organizada por el flujo de agua subterránea, espacios grandes, velocidades altas de flujo de hasta varios cientos de m/h, manantiales con ritmo alto de flujo de hasta algunas decenas de m3/s. Diferentes modelos conceptuales que se conocen en la literatura tratan de tomar en cuenta todas estas particularidades. Los métodos de estudio usados en hidrogeología clásica- pozos, pruebas de bombeo y modelos distribuidos- son generalmente inválidos y no exitosos en acu

Turbulent and Laminar Flow in Karst Conduits Under Unsteady Flow Conditions: Interpretation of Pumping Tests by Discrete Conduit-Continuum Modeling

NASA Astrophysics Data System (ADS)

Giese, M.; Reimann, T.; Bailly-Comte, V.; Maréchal, J.-C.; Sauter, M.; Geyer, T.

2018-03-01

Due to the duality in terms of (1) the groundwater flow field and (2) the discharge conditions, flow patterns of karst aquifer systems are complex. Estimated aquifer parameters may differ by several orders of magnitude from local (borehole) to regional (catchment) scale because of the large contrast in hydraulic parameters between matrix and conduit, their heterogeneity and anisotropy. One approach to deal with the scale effect problem in the estimation of hydraulic parameters of karst aquifers is the application of large-scale experiments such as long-term high-abstraction conduit pumping tests, stimulating measurable groundwater drawdown in both, the karst conduit system as well as the fractured matrix. The numerical discrete conduit-continuum modeling approach MODFLOW-2005 Conduit Flow Process Mode 1 (CFPM1) is employed to simulate laminar and nonlaminar conduit flow, induced by large-scale experiments, in combination with Darcian matrix flow. Effects of large-scale experiments were simulated for idealized settings. Subsequently, diagnostic plots and analyses of different fluxes are applied to interpret differences in the simulated conduit drawdown and general flow patterns. The main focus is set on the question to which extent different conduit flow regimes will affect the drawdown in conduit and matrix depending on the hydraulic properties of the conduit system, i.e., conduit diameter and relative roughness. In this context, CFPM1 is applied to investigate the importance of considering turbulent conditions for the simulation of karst conduit flow. This work quantifies the relative error that results from assuming laminar conduit flow for the interpretation of a synthetic large-scale pumping test in karst.

Contamination, Transport, and Exposure Mapping and Assessment of Karst Groundwater Systems in Northern Puerto Rico Using GIS

NASA Astrophysics Data System (ADS)

Howard, J.; Schifman, L. A.; Irrizary, C.; Torres, P.; Padilla, I. Y.

2011-12-01

Ground waters from karst aquifer systems are one of the most important sources of freshwater worldwide and are highly vulnerable to both natural and anthropogenic contamination. Contaminants released into karst groundwater systems move through complex pathways from their sources to discharge areas of potential exposure. Points of exposure can include wells, springs, and surface waters that serve as drinking water sources. In Puerto Rico, the North Coast Limestone Aquifer System, which extends 90 miles across the north coast with an area of nearly 700 sq. miles, provides more than 50% of the potable water demand for industrial and drinking purposes. Historical reports from the 1980s revealed that volatile organic compounds, phthalates, and metals were close to or exceeded maximum contaminant levels. Exposure to such contaminants has been reported to cause reproductive and developmental issues, such as preterm birth. Since there is minimal understanding of the extent of contamination it is important to identify areas of potential concern. Preliminary analysis of 20 groundwater/springs and 20 tap water sites within the North Coast suggest that contamination is still a major concern. In addition, mixed effects models analyses suggest that >60% of pre-term birth rates may be explained by the presence of sites contaminated with volatile organic compounds, phthalates, and metals within the North Coast region. This presentation will focus primarily on how GIS was used as a tool for developing sampling strategies for collecting groundwater and tap water sources within the North Coast Limestone Aquifer System of Puerto Rico. In addition, the linkage of contamination, transport, and exposure to volatile organic compounds and phthalates will be addressed.

Large-scale assessment of present day and future groundwater recharge and its sensitivity to climate variability in Europe's karst regions

NASA Astrophysics Data System (ADS)

Hartmann, A. J.; Gleeson, T. P.; Wagener, T.; Wada, Y.

2016-12-01

Karst aquifers in Europe are an important source of fresh water contributing up to half of the total drinking water supply in some countries. Karstic groundwater recharge is one of the most important components of the water balance of karst systems as it feeds the karst aquifers. Presently available large-scale hydrological models do not consider karst heterogeneity adequately. Projections of current and potential future groundwater recharge of Europe's karst aquifers are therefore unclear. In this study we compare simulations of present (1991-2010) and future (2080-2099) recharge using two different models to simulate groundwater recharge processes. One model includes karst processes (subsurface heterogeneity, lateral flow and concentrated recharge), while the other is based on the conceptual understanding of common hydrological systems (homogeneous subsurface, saturation excess overland flow). Both models are driven by the bias-corrected 5 GCMs of the ISI-MIP project (RCP8.5). To further assess sensitivity of groundwater recharge to climate variability, we calculate the elasticity of recharge rates to annual precipitation, temperature and average intensity of rainfall events, which is the median change of recharge that corresponds to the median change of these climate variables within the present and future time period, respectively. Our model comparison shows that karst regions over Europe have enhanced recharge rates with greater inter-annual variability compared to those with more homogenous subsurface properties. Furthermore, the heterogeneous representation shows stronger elasticity concerning climate variability than the homogeneous subsurface representation. This difference tends to increase towards the future. Our results suggest that water management in regions with heterogeneous subsurface can expect a higher water availability than estimated by most of the current large-scale simulations, while measures should be taken to prepare for increasingly

Groundwater vulnerability mapping of Qatar aquifers

NASA Astrophysics Data System (ADS)

Baalousha, Husam Musa

2016-12-01

Qatar is one of the most arid countries in the world with limited water resources. With little rainfall and no surface water, groundwater is the only natural source of fresh water in the country. Whilst the country relies mainly on desalination of seawater to secure water supply, groundwater has extensively been used for irrigation over the last three decades, which caused adverse environmental impact. Vulnerability assessment is a widely used tool for groundwater protection and land-use management. Aquifers in Qatar are carbonate with lots of fractures, depressions and cavities. Karst aquifers are generally more vulnerable to contamination than other aquifers as any anthropogenic-sourced contaminant, especially above a highly fractured zone, can infiltrate quickly into the aquifer and spread over a wide area. The vulnerability assessment method presented in this study is based on two approaches: DRASTIC and EPIK, within the framework of Geographical Information System (GIS). Results of this study show that DRASTIC vulnerability method suits Qatar hydrogeological settings more than EPIK. The produced vulnerability map using DRASTIC shows coastal and karst areas have the highest vulnerability class. The southern part of the country is located in the low vulnerability class due to occurrence of shale formation within aquifer media, which averts downward movement of contaminants.

Intensive exploitation of a karst aquifer leads to Cryptosporidium water supply contamination.

PubMed

Khaldi, S; Ratajczak, M; Gargala, G; Fournier, M; Berthe, T; Favennec, L; Dupont, J P

2011-04-01

Groundwater from karst aquifers is an important source of drinking water worldwide. Outbreaks of cryptosporidiosis linked to surface water and treated public water are regularly reported. Cryptosporidium oocysts are resistant to conventional drinking water disinfectants and are a major concern for the water industry. Here, we examined conditions associated with oocyst transport along a karstic hydrosystem, and the impact of intensive exploitation on Cryptosporidium oocyst contamination of the water supply. We studied a well-characterized karstic hydrosystem composed of a sinkhole, a spring and a wellbore. Thirty-six surface water and groundwater samples were analyzed for suspended particulate matter, turbidity, electrical conductivity, and Cryptosporidium and Giardia (oo)cyst concentrations. (Oo)cysts were identified and counted by means of solid-phase cytometry (ChemScan RDI(®)), a highly sensitive method. Cryptosporidium oocysts were detected in 78% of both surface water and groundwater samples, while Giardia cysts were found in respectively 22% and 8% of surface water and groundwater samples. Mean Cryptosporidium oocyst concentrations were 29, 13 and 4/100 L at the sinkhole, spring and wellbore, respectively. Cryptosporidium oocysts were transported from the sinkhole to the spring and the wellbore, with respective release rates of 45% and 14%, suggesting that oocysts are subject to storage and remobilization in karst conduits. Principal components analysis showed that Cryptosporidium oocyst concentrations depended on variations in hydrological forcing factors. All water samples collected during intensive exploitation contained oocysts. Control of Cryptosporidium oocyst contamination during intensive exploitation is therefore necessary to ensure drinking water quality. Copyright © 2011. Published by Elsevier Ltd.

Spatiotemporal changes of CVOC concentrations in karst aquifers: analysis of three decades of data from Puerto Rico

PubMed Central

Yu, Xue; Ghasemizadeh, Reza; Padilla, Ingrid; Irizarry, Celys; Kaeli, David; Alshawabkeh, Akram

2014-01-01

We studied the spatial and temporal distribution patterns of Chlorinated Volatile Organic Compounds (CVOCs) in the karst aquifers in northern Puerto Rico (1982-2013). Seventeen CVOCs were widely detected across the study area, with the most detected and persistent contaminated CVOCs including trichloroethylene (TCE), tetrachloroethylene (PCE), carbon tetrachloride (CT), chloroform (TCM), and methylene chloride (DCM). Historically, 471 (76%) and 319 (52%) of the 615 sampling sites have CVOC concentrations above the detection limit and maximum contamination level (MCL), respectively. The spatiotemporal patterns of the CVOC concentrations showed two clusters of contaminated areas, one near the Superfund site “Upjohn” and another near “Vega Alta Public Supply Wells.” Despite a decreasing trend in concentrations, there is a general northward movement and spreading of contaminants even beyond the extent of known sources of the Superfund and landfill sites. Our analyses suggest that, besides the source conditions, karst characteristics (high heterogeneity, complex hydraulic and biochemical environment) are linked to the long-term spatiotemporal patterns of CVOCs in groundwater. PMID:25522355

Factors affecting ground-water exchange and catchment size for Florida lakes in mantled karst terrain

USGS Publications Warehouse

Lee, Terrie Mackin

2002-01-01

In the mantled karst terrain of Florida, the size of the catchment delivering ground-water inflow to lakes is often considerably smaller than the topographically defined drainage basin. The size is determined by a balance of factors that act individually to enhance or diminish the hydraulic connection between the lake and the adjacent surficial aquifer, as well as the hydraulic connection between the surficial aquifer and the deeper limestone aquifer. Factors affecting ground-water exchange and the size of the ground-water catchment for lakes in mantled karst terrain were examined by: (1) reviewing the physical and hydrogeological characteristics of 14 Florida lake basins with available ground-water inflow estimates, and (2) simulating ground-water flow in hypothetical lake basins. Variably-saturated flow modeling was used to simulate a range of physical and hydrogeologic factors observed at the 14 lake basins. These factors included: recharge rate to the surficial aquifer, thickness of the unsaturated zone, size of the topographically defined basin, depth of the lake, thickness of the surficial aquifer, hydraulic conductivity of the geologic units, the location and size of karst subsidence features beneath and onshore of the lake, and the head in the Upper Floridan aquifer. Catchment size and the magnitude of ground-water inflow increased with increases in recharge rate to the surficial aquifer, the size of the topographically defined basin, hydraulic conductivity in the surficial aquifer, the degree of confinement of the deeper Upper Floridan aquifer, and the head in the Upper Floridan aquifer. The catchment size and magnitude of ground-water inflow increased with decreases in the number and size of karst subsidence features in the basin, and the thickness of the unsaturated zone near the lake. Model results, although qualitative, provided insights into: (1) the types of lake basins in mantled karst terrain that have the potential to generate small and large

Estimating exposure to groundwater contaminants in karst areas

NASA Astrophysics Data System (ADS)

Butscher, C.

2012-12-01

Large multidisciplinary projects investigate health effects and environmental impacts of contamination. Such multidisciplinary projects challenge groundwater hydrologist because they demand estimations of human or environmental exposure to groundwater contaminants. But especially in karst regions, groundwater quality is subject to rapid changes resulting from highly dynamic flow systems with rapid groundwater recharge and contaminant transport in karst conduits. There is a strong need for tools that allow the quantification of the risk of contaminant exposure via the karst groundwater and its temporal variation depending on rainfall events and overall hydrological conditions. A fact that makes the assessment of contaminant exposure even more difficult is that many contaminants behave differently in the subsurface than the groundwater, because they do not dissolve and exist as a separate phase. Important examples are particulate contaminants, such as bacteria, and non-aqueous phase liquids (NAPLs), such as many organic compounds. Both are ubiquitous in the environment and have large potential for health impacts. It is known from bacterial contamination of karst springs that such contamination is strongly related to flow conditions. Bacteria, which are present at the land surface, in the soil, rock matrix or the conduit system, are immobile during base flow conditions. During storm events however, they become mobilized and are rapidly transported through the conduit flow system from sources to areas of potential exposure. As a result, bacteria concentrations that most times are low at a spring can show a high peak during storm flow. Conceptual models exist that suggest that the transport of NAPLs in karst aquifers is, just like bacterial contamination, related to flow conditions. Light NAPLs that reach the saturated zone float and accumulate on the water table; and dense NAPLs sink downward in the aquifer until they are trapped in pores, fractures and conduits where

Process-based monitoring and modeling of Karst springs - Linking intrinsic to specific vulnerability.

PubMed

Epting, Jannis; Page, Rebecca M; Auckenthaler, Adrian; Huggenberger, Peter

2018-06-01

The presented work illustrates to what extent field investigations as well as monitoring and modeling approaches are necessary to understand the high discharge dynamics and vulnerability of Karst springs. In complex settings the application of 3D geological models is essential for evaluating the vulnerability of Karst systems. They allow deriving information on catchment characteristics, as the geometry of aquifers and aquitards as well as their displacements along faults. A series of Karst springs in northwestern Switzerland were compared and Karst system dynamics with respect to qualitative and quantitative issues were evaluated. The main objective of the studies was to combine information of catchment characteristics and data from novel monitoring systems (physicochemical and microbiological parameters) to assess the intrinsic vulnerability of Karst springs to microbiological contamination with simulated spring discharges derived from numerical modeling (linear storage models). The numerically derived relation of fast and slow groundwater flow components enabled us to relate different sources of groundwater recharge and to characterize the dynamics of the Karst springs. Our study illustrates that comparably simple model-setups were able to reproduce the overall dynamic intrinsic vulnerability of several Karst systems and that one of the most important processes involved was the temporal variation of groundwater recharge (precipitation, evapotranspiration and snow melt). Furthermore, we make a first attempt on how to link intrinsic to specific vulnerability of Karst springs, which involves activities within the catchment area as human impacts from agriculture and settlements. Likewise, by a more detailed representation of system dynamics the influence of surface water, which is impacted by release events from storm sewers, infiltrating into the Karst system, could be considered. Overall, we demonstrate that our approach can be the basis for a more flexible and

Field observations of extended seawater intrusion through subsurface karst conduit networks at Wakulla Spring in the Woodville Karst Plain, Florida

NASA Astrophysics Data System (ADS)

Xu, Z.; Bassett, S.; Hu, B. X.; Dyer, S.

2016-12-01

Five periods of increased electrical conductivity have been found in the karst conduits supplying one of the largest first magnitude springs in Florida with water. Numerous well-developed conduit networks are distributed in the Woodville Karst Plain (WKP), Florida and connected to the Gulf of Mexico. A composite analysis of precipitation and electric conductivity data provides strong evidence that the increases in conductivity are directly tied to seawater intrusion moving inland and traveling 14 miles against the prevailing regional hydraulic gradient from from Spring Creek Spring Complex (SCSC), a group of submarine springs at the Gulf Coast. A geochemical analysis of samples from the spring vent rules out anthropogenic contamination and upwelling regional recharge from the deep aquifer as sources of the rising conductivity. The interpretation is supported by the conceptual model established by prior researchers working to characterize the study area. This abstract documented the first and longest case of seawater intrusion in the WKP, and also indicates significant possibility of seawater contamination through subsurface conduit networks in a coastal karst aquifer.

A large-scale integrated karst-vegetation recharge model to understand the impact of climate and land cover change

NASA Astrophysics Data System (ADS)

Sarrazin, Fanny; Hartmann, Andreas; Pianosi, Francesca; Wagener, Thorsten

2017-04-01

Karst aquifers are an important source of drinking water in many regions of the world, but their resources are likely to be affected by changes in climate and land cover. Karst areas are highly permeable and produce large amounts of groundwater recharge, while surface runoff is typically negligible. As a result, recharge in karst systems may be particularly sensitive to environmental changes compared to other less permeable systems. However, current large-scale hydrological models poorly represent karst specificities. They tend to provide an erroneous water balance and to underestimate groundwater recharge over karst areas. A better understanding of karst hydrology and estimating karst groundwater resources at a large-scale is therefore needed for guiding water management in a changing world. The first objective of the present study is to introduce explicit vegetation processes into a previously developed karst recharge model (VarKarst) to better estimate evapotranspiration losses depending on the land cover characteristics. The novelty of the approach for large-scale modelling lies in the assessment of model output uncertainty, and parameter sensitivity to avoid over-parameterisation. We find that the model so modified is able to produce simulations consistent with observations of evapotranspiration and soil moisture at Fluxnet sites located in carbonate rock areas. Secondly, we aim to determine the model sensitivities to climate and land cover characteristics, and to assess the relative influence of changes in climate and land cover on aquifer recharge. We perform virtual experiments using synthetic climate inputs, and varying the value of land cover parameters. In this way, we can control for variations in climate input characteristics (e.g. precipitation intensity, precipitation frequency) and vegetation characteristics (e.g. canopy water storage capacity, rooting depth), and we can isolate the effect that each of these quantities has on recharge. Our results

Tracing coastal and estuarine groundwater discharge sources in a complex faulted and fractured karst aquifer system

NASA Astrophysics Data System (ADS)

Lagomasino, D.; Price, R. M.

2013-05-01

Groundwater discharge can be an important input of water, nutrients and other constituents to coastal wetlands and adjacent marine areas, particularly in karst regions with little to no surface water flow. A combination of natural processes (e.g., sea-level rise and climate change) and anthropogenic pressures (e.g., urban growth and development) can alter the subterranean water flow to the coastline. For water management practices and environmental preservation to be better suited for the natural and human environment, a better understanding is needed of the hydrogeologic connectivity between the areas of fresh groundwater recharge and the coastal zone. The Yucatan peninsula has a unique tectonic and geologic history consisting of a Cretaceous impact crater, Miocene and Eocene tectonic plate movements, and multiple sea-level stands. These events have shaped many complex geologic formations and structures. The Sian Káan Biosphere Reserve (SKBR), a UNESCO World Heritage Site located along the Atlantic Ocean, overlaps two distinct hydrogeologic regions: the evaporate region to the south and south west, and the Holbox Fracture Zone to the north. These two regions create a complex network of layered, perched and fractured aquifers and an extensive groundwater cave network. The two regions are distinguished by bedrock mineralogical differences that can be used to trace shallow subsurface water from interior portions of the peninsula to the Bahia de la Ascension in the SKBR. The objective of this research was to use naturally occurring geochemical tracers (eg., Cl-, SO42-, HCO3-, K+, Mg2+, Na+, Ca2+ and stable isotopes of oxygen and hydrogen) to decipher the sources of groundwater flow through the coastal wetlands of the SKBR and into the Bahia de la Ascension. Surface water and groundwater samples were collected during two field campaigns in 2010 and 2012 within the coastal and estuarine waters of the SKBR. Additional water samples were collected at select cenotes along

Hydrologic connections and dynamics of water movement in the classical Karst (Kras) Aquifer: evidence from frequent chemical and stable isotope sampling

USGS Publications Warehouse

Doctor, Daniel H.

2008-01-01

A review of past research on the hydrogeology of the Classical Karst (Kras) region and new information obtained from a two- year study using environmental tracers are presented in this paper. The main problems addressed are 1) the sources of water to the Kras aquifer resurgence zone-including the famous Timavo springs-under changing flow regimes; 2) a quantification of the storage volumes of the karst massif corresponding to flow regimes defined by hydrograph recessions of the Timavo springs; and 3) changing dynamics between deep phreatic conduit flow and shallow phreatic and epiphreatic storage within the aquifer resurgence zone as determined through changes in chemical and isotopic composition at springs and wells. Particular focus was placed on addressing the long-standing question of the influence of the Soca River on the ground waters of the aquifer resurgence zone. The results indicate that the alluvial aquifer supplied by the sinking of the Soca River on the northwestern edge of the massif contributes approximately 75% of the mean annual outflow to the smaller springs of the aquifer resurgence zone, and as much as 53% to the mean annual outflow of the Timavo springs. As a whole, the Soca River is estimated to contribute 56% of the average outflow of the Kras aquifer resurgence. The proportions of Soca River water increase under drier conditions, and decrease under wetter conditions. Time series analysis of oxygen stable isotope records indicate that the transit time of Soca River water to the Timavo springs, Sardos spring, and well B-4 is on the order of 1-2 months, depending on hydrological conditions. The total baseflow storage of the Timavo springs is estimated to be 518 million m3, and represents 88.5% of the storage capacity estimated for all flow regimes of the springs. The ratio of baseflow storage volume to the average annual volume discharged at the Timavo springs is 0.54. The Reka River sinking in Slovenia supplies substantial allogenic recharge to

FATE AND TRANSPORT OF PETROLEUM RELEASED FROM UNDERGROUND STORAGE TANKS in Areas of Karst Topography

EPA Science Inventory

The study determines the transport and ultimate fate of petroleum products within a region of karst geomorphology. The paper entails a complete literature review, including references that pertain to contaminant transport within karst aquifers

Classification of Thermal Patterns at Karst Springs and Cave Streams

USGS Publications Warehouse

Luhmann, A.J.; Covington, M.D.; Peters, Albert J.; Alexander, S.C.; Anger, C.T.; Green, J.A.; Runkel, Anthony C.; Alexander, E.C.

2011-01-01

Thermal patterns of karst springs and cave streams provide potentially useful information concerning aquifer geometry and recharge. Temperature monitoring at 25 springs and cave streams in southeastern Minnesota has shown four distinct thermal patterns. These patterns can be divided into two types: those produced by flow paths with ineffective heat exchange, such as conduits, and those produced by flow paths with effective heat exchange, such as small fractures and pore space. Thermally ineffective patterns result when water flows through the aquifer before it can equilibrate to the rock temperature. Thermally ineffective patterns can be either event-scale, as produced by rainfall or snowmelt events, or seasonal scale, as produced by input from a perennial surface stream. Thermally effective patterns result when water equilibrates to rock temperature, and the patterns displayed depend on whether the aquifer temperature is changing over time. Shallow aquifers with seasonally varying temperatures display a phase-shifted seasonal signal, whereas deeper aquifers with constant temperatures display a stable temperature pattern. An individual aquifer may display more than one of these patterns. Since karst aquifers typically contain both thermally effective and ineffective routes, we argue that the thermal response is strongly influenced by recharge mode. ?? 2010 The Author(s). Journal compilation ?? 2010 National Ground Water Association.

Hydrogeological controls of variable microbial water quality in a complex subtropical karst system in Northern Vietnam

NASA Astrophysics Data System (ADS)

Ender, Anna; Goeppert, Nadine; Goldscheider, Nico

2018-05-01

Karst aquifers are particularly vulnerable to bacterial contamination. Especially in developing countries, poor microbial water quality poses a threat to human health. In order to develop effective groundwater protection strategies, a profound understanding of the hydrogeological setting is crucial. The goal of this study was to elucidate the relationships between high spatio-temporal variability in microbial contamination and the hydrogeological conditions. Based on extensive field studies, including mapping, tracer tests and hydrochemical analyses, a conceptual hydrogeological model was developed for a remote and geologically complex karst area in Northern Vietnam called Dong Van. Four different physicochemical water types were identified; the most important ones correspond to the karstified Bac Son and the fractured Na Quan aquifer. Alongside comprehensive investigation of the local hydrogeology, water quality was evaluated by analysis for three types of fecal indicator bacteria (FIB): Escherichia coli, enterococci and thermotolerant coliforms. The major findings are: (1) Springs from the Bac Son formation displayed the highest microbial contamination, while (2) springs that are involved in a polje series with connections to sinking streams were distinctly more contaminated than springs with a catchment area characterized by a more diffuse infiltration. (3) FIB concentrations are dependent on the season, with higher values under wet season conditions. Furthermore, (4) the type of spring capture also affects the water quality. Nevertheless, all studied springs were faecally impacted, along with several shallow wells within the confined karst aquifer. Based on these findings, effective protection strategies can be developed to improve groundwater quality.

Determination of the sources of nitrate contamination in karst springs using isotopic and chemical indicators

USGS Publications Warehouse

Panno, S.V.; Hackley, Keith C.; Hwang, H.-H.; Kelly, W.R.

2001-01-01

The sources of nitrate (NO-3) in groundwater of the shallow karst aquifer in southwestern Illinois' sinkhole plain were investigated using chemical and isotopic techniques. The groundwater in this aquifer is an important source of potable water for about half of the residents of the sinkhole plain area. Previous work has shown that groundwater from approximately 18% of the wells in the sinkhole plain has NO-3 concentrations in excess of the USEPA's drinking water standard of 10 mg N/1. Relative to background levels, the NO-3 concentrations in water from 52% of the wells, and probably all of the springs in the study area, are anomalously high, suggesting that sources other than naturally occurring soil organic matter have contributed additional NO-3 to groundwater in the shallow karst aquifer. This information, and the dominance of agriculture in the study area, suggest that agrichemical contributions may be significant. To test this hypothesis, water samples from 10 relatively large karst springs were collected during four different seasons and analyzed for inorganic constituents, dissolved organic carbon, atrazine, and ??15N and ??18O of the NO-3 ions. The isotopic data were most definitive and suggested that the sources of NO-3 in spring water are dominated by N-fertilizer with some possible influence of atmospheric NO-3 and, to a much lesser extent, human and/or animal waste. Differences in the isotopic composition of NO-3 and some of the chemical characteristics were observed during the four consecutive seasons in which spring water samples were collected. Isotopic values for ??15N and ??18O of the NO-3 ranged from 3.2??? to 19.1??? and from 7.2??? to 18.7???, respectively. The trend of ??15N and ??18O data for NO-3 also indicated that a significant degree of denitrification is occurring in the shallow karst hydrologic system (within the soil zone, the epikarst and the shallow karst aquifer) prior to discharging to springs. ?? 2001 Elsevier Science B.V. All

On the use of multiple-point statistics to improve groundwater flow modeling in karst aquifers: A case study from the Hydrogeological Experimental Site of Poitiers, France

NASA Astrophysics Data System (ADS)

Le Coz, Mathieu; Bodin, Jacques; Renard, Philippe

2017-02-01

Limestone aquifers often exhibit complex groundwater flow behaviors resulting from depositional heterogeneities and post-lithification fracturing and karstification. In this study, multiple-point statistics (MPS) was applied to reproduce karst features and to improve groundwater flow modeling. For this purpose, MPS realizations were used in a numerical flow model to simulate the responses to pumping test experiments observed at the Hydrogeological Experimental Site of Poitiers, France. The main flow behaviors evident in the field data were simulated, particularly (i) the early-time inflection of the drawdown signal at certain observation wells and (ii) the convex behavior of the drawdown curves at intermediate times. In addition, it was shown that the spatial structure of the karst features at various scales is critical with regard to the propagation of the depletion wave induced by pumping. Indeed, (i) the spatial shape of the cone of depression is significantly affected by the karst proportion in the vicinity of the pumping well, and (ii) early-time inflection of the drawdown signal occurs only at observation wells crossing locally well-developed karst features.

Transport of environmental tracers through a karst system with a thick unsaturated zone

NASA Astrophysics Data System (ADS)

Geyer, Tobias; Sültenfuss, Jürgen; Eichinger, Florian; Sauter, Martin

2010-05-01

is about 15 years with a travel time of water through the unsaturated zone of 10 years (Geyer 2008). This result reflects the variation of estimated ages for different tracers sampled at the Gallusquelle spring. Additionally, we demonstrate that depending on boundary conditions, the unsaturated zone of a karst system may provide a large water storage since the porous matrix can be expected to be close to saturation and the volume fraction of fissures and conduits is small. Literature Cornaton, F., Perrochet, P. (2006): Ground-water age, life expectancy and transit time distributions in advective-dispersive systems: 1. Generalized reservoir theory. - Advances in Water Resources 29 (9): 1267-1291. Geyer, T. (2008): Characterisation of flow and transport in karst aquifers at catchment scale, Ph.D. diss., Georg-August-Universität Göttingen, 103 pp.

Integration of models of various types of aquifers for water quality management in the transboundary area of the Soča/Isonzo river basin (Slovenia/Italy).

PubMed

Vižintin, Goran; Ravbar, Nataša; Janež, Jože; Koren, Eva; Janež, Naško; Zini, Luca; Treu, Francesco; Petrič, Metka

2018-04-01

Due to intrinsic characteristics of aquifers groundwater frequently passes between various types of aquifers without hindrance. The complex connection of underground water paths enables flow regardless of administrative boundaries. This can cause problems in water resources management. Numerical modelling is an important tool for the understanding, interpretation and management of aquifers. Useful and reliable methods of numerical modelling differ with regard to the type of aquifer, but their connections in a single hydrodynamic model are rare. The purpose of this study was to connect different models into an integrated system that enables determination of water travel time from the point of contamination to water sources. The worst-case scenario is considered. The system was applied in the Soča/Isonzo basin, a transboundary river in Slovenia and Italy, where there is a complex contact of karst and intergranular aquifers and surface flows over bedrock with low permeability. Time cell models were first elaborated separately for individual hydrogeological units. These were the result of numerical hydrological modelling (intergranular aquifer and surface flow) or complex GIS analysis taking into account the vulnerability map and tracer tests results (karst aquifer). The obtained cellular models present the basis of a contamination early-warning system, since it allows an estimation when contaminants can be expected to appear, and in which water sources. The system proves that the contaminants spread rapidly through karst aquifers and via surface flows, and more slowly through intergranular aquifers. For this reason, karst water sources are more at risk from one-off contamination incidents, while water sources in intergranular aquifers are more at risk in cases of long-term contamination. The system that has been developed is the basis for a single system of protection, action and quality monitoring in the areas of complex aquifer systems within or on the borders of

Assessing the vulnerability of a municipal well field to contamination in a karst aquifer

USGS Publications Warehouse

Renken, R.A.; Cunningham, K.J.; Zygnerski, M.R.; Wacker, M.A.; Shapiro, A.M.; Harvey, R.W.; Metge, D.W.; Osborn, C.L.; Ryan, J.N.

2005-01-01

Proposed expansion of extractive lime-rock mines near the Miami-Dade County Northwest well field and Everglades wetland areas has garnered intense scrutiny by government, public, environmental stakeholders, and the media because of concern that mining will increase the risk of pathogen contamination. Rock mines are excavated to the same depth as the well field's primary producing zone. The underlying karst Biscayne aquifer is a triple-porosity system characterized by (1) a matrix of interparticle porosity and separate vug porosity; (2) touching-vug porosity that forms preferred, stratiform passageways; and, less commonly, (3) conduit porosity formed by thin solution pipes, bedding-plane vugs, and cavernous vugs. Existing ground-water flow and particle tracking models do not provide adequate information regarding the ability the aquifer to limit the advective movement of pathogens and other contaminants. Chemical transport and colloidal mobility properties have been delineated using conservative and microsphere-surrogate tracers for Cryptosporidium parvum. Forced-gradient tests were executed by introducing conservative tracers into injection wells located 100 m (328 ft) from a municipal-supply well. Apparent mean advective velocity between the wells is one to two orders of magnitude greater than previously measured. Touching-vug, stratiform flow zones are efficient pathways for tracer movement at the well field. The effective porosity for a continuum model between the point of injection and tracer recovery ranges from 2 to 4 percent and is an order of magnitude smaller than previously assumed. Existing well-field protection zones were established using porosity estimates based on specific yield. The effective, or kinematic, porosity of a Biscayne aquifer continuum model is lower than the total porosity, because high velocities occur along preferential flow paths that result in faster times of travel than can be represented with the ground-water flow equation. Tracer

Determination of groundwater travel time in a karst aquifer by stable water isotopes, Tanour and Rasoun spring (Jordan)

NASA Astrophysics Data System (ADS)

Hamdan, Ibraheem; Wiegand, Bettina; Sauter, Martin; Ptak, Thomas

2016-04-01

Key words: karst aquifers, stable isotopes, water travel time, Jordan. Tanour and Rasoun karst springs are located about 75 kilometers northwest of the city of Amman in Jordan. The aquifer is composed of Upper Cretaceous limestone that exhibits a moderate to high degree of karstification. The two springs represent the main drinking water resources for the surrounding villages. The yearly water production is about 1,135,000 m3/yr for Tanour spring and 125,350 m3/yr for Rasoun spring (MWI 2015). Due to contamination from microbiological pollution (leakage of wastewater from septic tanks) or infiltration of wastewater from local olive presses, drinking water supply from the two springs is frequently interrupted. From November 2014 through March 2015, spring water samples were collected from Tanour and Rasoun spring for the analysis of stable hydrogen and oxygen isotopes to investigate spring response to precipitation and snowmelt events. Both Tanour and Rasoun spring show a fast response to precipitation and snowmelt events, implying short water travel times. Based on the variation of δ 18O and δ 2H in spring discharge, the average maximum water travel time is in the order of 8 days for Tanour spring and 6 days for Rasoun spring. Due to fast water travel times, Tanour and Rasoun spring can be considered as highly vulnerable to pollutants. δ 18O and δ 2H values of Tanour and Rasoun springs parallel other monitored parameter like water temperature, turbidity, electrical conductivity and spring discharge. In addition, a high turbidity peak was monitored in Tanour spring during a pollution event from olive mills wastewater (Hamdan et al., 2016; Hamdan, in prep.). The fast response in both Tanour and Rasoun springs to precipitation events requires monitoring potential sources of pollution within the catchment area. References: MWI (Ministry of Water and Irrigation) (2015) Monthly Production values for Tanour and Rasoun Springs for the time period between 1996 and 2014

Techniques to better understand complex epikarst hydrogeology and contaminant transport in telogenetic karst settings

USDA-ARS?s Scientific Manuscript database

The movement of autogenic recharge through the shallow epikarstic zone in soil-mantled karst aquifers is important in understanding recharge areas and rates, groundwater storage, and contaminant transport processes. The groundwater flow in agricultural karst areas, such as Kentucky’s Pennyroyal Plat...

Management Can Reduce Mobility of Escherichia coli compared to traditional groundwater tracers within karst terrains

USDA-ARS?s Scientific Manuscript database

An understanding of fundamental processes controlling pathogen movement is necessary to protect water resources across the globe. Limited filtration and turbulent flow make karst aquifers susceptible to microbial contamination. Groundwater tracers typically used in karst terrains include fluorescent...

Negative grouting consequences on karst environment

NASA Astrophysics Data System (ADS)

Bonacci, O.; Roje-Bonacci, T.; Gottstein, S.

2009-04-01

Grouting is a procedure by means of which grout is injected into different kinds of karst spaces (cracks, fissures, conduits and caves). It has a wide application in modern civil engineering, especially in karst terrains. It started nearly 200 years ago. In most cases the ingredients for the preparation of mortars and grouting suspensions are: cement, bentonite, clay and fillers, additives for stability and water. In practice the composition of grouting suspension is not standardized. A suspension injected under pressure will circulate in the karst spaces like a more or less viscous fluid until some of the larger suspended particles are blocked where the karst voids get narrower than the size of injected grains. The injection of materials into karst groundwater, i.e. the construction of grouting curtains, definitely could be the cause of unpredictable negative consequences on karst groundwater environments. The building of dams in karst areas always go along the construction of grouting curtains. During the construction of most dams in karst all over the world millions tons of injection mass have been injected in karst underground. It may impact water quantity in vadose zone and in karstic aquifer causing water table lowering and spring desiccation. In such cases the negative impact on local karst environment could be very dangerous. Physically as well as chemically this mass voraciously and quickly destroyed underground habitats and killed an enormous number of endangered and endemic species. Very often this is extremely expensive procedure and in many cases not very successful from the engineering point of view. From the ecological point of view it could causes catastrophic consequences. The greatest problem is that until now neither engineers nor ecologists took care of these great and massive negative influences on underground karst environments. In this paper few examples of different consequences of grouting on the hydrogeological as well as ecological regime

Hydrologic Conditions that Influence Streamflow Losses in a Karst Region of the Upper Peace River, Polk County, Florida

USGS Publications Warehouse

Metz, P.A.; Lewelling, B.R.

2009-01-01

The upper Peace River from Bartow to Fort Meade, Florida, is described as a groundwater recharge area, reflecting a reversal from historical groundwater discharge patterns that existed prior to the 1950s. The upper Peace River channel and floodplain are characterized by extensive karst development, with numerous fractures, crevasses, and sinks that have been eroded in the near-surface and underlying carbonate bedrock. With the reversal in groundwater head gradients, river water is lost to the underlying groundwater system through these karst features. An investigation was conducted to evaluate the hydrologic conditions that influence streamflow losses in the karst region of the upper Peace River. The upper Peace River is located in a basin that has been altered substantially by phosphate mining and increases in groundwater use. These alterations have changed groundwater flow patterns and caused streamflow declines through time. Hydrologic factors that have had the greatest influence on streamflow declines in the upper Peace River include the lowering of the potentiometric surfaces of the intermediate aquifer system and Upper Floridan aquifer beneath the riverbed elevation due to below-average rainfall (droughts), increases in groundwater use, and the presence of numerous karst features in the low-water channel and floodplain that enhance the loss of streamflow. Seepage runs conducted along the upper Peace River, from Bartow to Fort Meade, indicate that the greatest streamflow losses occurred along an approximate 2-mile section of the river beginning about 1 mile south of the Peace River at Bartow gaging station. Along the low-water and floodplain channel of this 2-mile section, there are about 10 prominent karst features that influence streamflow losses. Losses from the individual karst features ranged from 0.22 to 16 cubic feet per second based on measurements made between 2002 and 2007. The largest measured flow loss for all the karst features was about 50 cubic

Ratosa playa lake in southern Spain. Karst pan or compound sink?

PubMed

Rodríguez-Rodríguez, Miguel; Martos-Rosillo, Sergio; Pedrera, Antonio; Benavente-Herrera, José

2015-04-01

In Andalusia (Spain), there are more than 45 semiarid playa lakes protected as natural reserves and related to karstic outcrops. Some of them are located over regional karstic aquifers and have internal drainage networks with sporadic surface outlets, such as sinkholes (compound sinks), but the majority of such playas have no internal drainage systems, so the only water output is evaporation (karst pans). Karst pans are perched and disconnected from the groundwater system. The fact that the Ratosa playa lake is partially located over a karstic Sierra, as well as other hydromorphological observations, it is suggested that the system could be of a compound type, but a detailed hydrogeological analysis showed that the playa is disconnected from the aquifer, so it is in fact a karst pan. Once the hydrological functioning had been established, a monthly water balance for a 10-year period (1998-2008), enabled us to reproduce the evolution of the water level of the playa lake. Estimations of runoff were carried out by a soil water estimate for a water holding capacity in the soil of 191 mm. Results show a good correlation (>90%) after calibration with the time series of water level in the lake for the same period confirming geological observations. Our results highlight that this water body is extremely vulnerable to hydrological alterations of its watershed caused by human activities, particularly those related to land-use change for agriculture. For this reason, we propose a new protection zone, based on hydrological knowledge, instead of the present Peripheral Area of Protection.

Spatial distribution of nitrogen on grazed karst landscapes.

PubMed

Boyer, D G; Alloush, G A

2001-11-27

The impact on water quality by agricultural activity in karst terrain is an important consideration for resource management within the Appalachian region. Karst areas comprise about 18% of the region"s land area. An estimated one-third of the region"s farms, cattle, and agricultural market value are located on karst terrain. Mean nitrate concentrations in several karst springs in southeastern West Virginia exhibit a strong linear relationship with the percentage of agriculture land cover. Development of best management practices for efficient nitrogen (N) use and reduction of outflow of N to water from karst areas requires knowledge about N dynamics on those landscapes. Water extractable NO3-N and NH4-N were measured along transects at four soil depths in two grazed sinkholes and one wooded sinkhole. Distribution of soil NO3-N and NH4-N were related to frequency of animal presence and to topographic and hydrologic redistribution of soil and fecal matter in the grazed sinkholes. Karst pastures are characterized by under drainage and funneling of water and contaminants to the shallow aquifer. Control of NO3-N leaching from karst pasture may depend on management strategies that change livestock grazing behavior in sinkholes and reduce the opportunity for water and contaminants to quickly reach sinkhole drains.

Spring distribution in Winona County, Minnesota, USA and the relationship with geologic strata in a karst landscape

USGS Publications Warehouse

Vondracek, Bruce C.; Williams, Mary A.

2010-01-01

Karst aquifers are important groundwater resources, but are vulnerable to contamination due to relatively rapid subsurface transport. Springs, points where the landscape and water table intersect and cold groundwater discharges, link aquifer systems with land surfaces and water bodies. As such, in many regions, they are critical to the viability of lakes, streams and cold-water fish communities. An understanding of where springs are located is important to watershed, fishery and environmental management efforts in karst regions. To better understand spatial distribution of springs and as a potential method for identifying variables that characterize locations of springs for improved land and watershed management, a nearest-neighbor analysis and a discriminant function analysis (DFA) of springs were conducted in Winona County, Minnesota, USA, a karst landscape. Nearest-neighbor analysis examined the spatial spring distribution. Twenty-two variables describing the locations of springs were analyzed to ascertain their ability to discriminate correct aquifer unit or bedrock unit classification for each spring. Springs were clumped with the highest densities in the lowest elevations. Springs were correctly assigned to aquifer units and bedrock units with eight and 11 landscape variables, respectively. Forest land cover was the only land cover type contributing to spring discrimination. Consideration of upland human activities, particularly in forested areas, on spring discharge along with a better understanding of characteristics describing spring locations could lead to better management activities that locate and protect springs and their important contributions to regional ecohydrology.

Climatic and geologic controls on the piezometry of the Querença-Silves karst aquifer, Algarve (Portugal)

NASA Astrophysics Data System (ADS)

Neves, Maria C.; Costa, Luis; Monteiro, José P.

2016-06-01

Karst aquifers in semi-arid regions, like Querença-Silves (Portugal), are particularly vulnerable to climate variability. For the first time in this region, the temporal structure of a groundwater-level time series (1985-2010) was explored using the continuous wavelet transform. The investigation focused on a set of four piezometers, two at each side of the S. Marcos-Quarteira fault, to demonstrate how each of the two sectors of the aquifer respond to climate-induced patterns. Singular spectral analysis applied to an extended set of piezometers enabled identification of several quasi-periodic modes of variability, with periods of 6.5, 4.3, 3.2 and 2.6 years, which can be explained by low-frequency climate patterns. The geologic forcing accounts for ~15 % of the differential variability between the eastern and western sectors of the aquifer. The western sector displays spatially homogenous piezometric variations, large memory effects and low-pass filtering characteristics, which are consistent with relatively large and uniform values of water storage capacity and transmissivity properties. In this sector, the 6.5-year mode of variability accounts for ~70 % of the total variance of the groundwater levels. The eastern sector shows larger spatial and temporal heterogeneity, is more reactive to short-term variations, and is less influenced by the low-frequency components related to climate patterns.

Retrieving hydrological connectivity from empirical causality in karst systems

NASA Astrophysics Data System (ADS)

Delforge, Damien; Vanclooster, Marnik; Van Camp, Michel; Poulain, Amaël; Watlet, Arnaud; Hallet, Vincent; Kaufmann, Olivier; Francis, Olivier

2017-04-01

Because of their complexity, karst systems exhibit nonlinear dynamics. Moreover, if one attempts to model a karst, the hidden behavior complicates the choice of the most suitable model. Therefore, both intense investigation methods and nonlinear data analysis are needed to reveal the underlying hydrological connectivity as a prior for a consistent physically based modelling approach. Convergent Cross Mapping (CCM), a recent method, promises to identify causal relationships between time series belonging to the same dynamical systems. The method is based on phase space reconstruction and is suitable for nonlinear dynamics. As an empirical causation detection method, it could be used to highlight the hidden complexity of a karst system by revealing its inner hydrological and dynamical connectivity. Hence, if one can link causal relationships to physical processes, the method should show great potential to support physically based model structure selection. We present the results of numerical experiments using karst model blocks combined in different structures to generate time series from actual rainfall series. CCM is applied between the time series to investigate if the empirical causation detection is consistent with the hydrological connectivity suggested by the karst model.

Karst Lands: The dissolution of carbonate rock produces unique landscapes and poses significant hydrological and environmental concerns

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, W.B.; Culver, D.C.; Herman, J.S.

1995-09-01

Karst lands are produced by the action of water on soluble rocks, a process among the most dynamic of all erosive forces that counterbalance the uplifting forces of tectonics. The dissolution of carbonate rock, primarily limestone and dolomite, produces unique landscapes and poses significant hydrological and environmental concerns. The major topic areas discussed in this article include the following: processes that form karst; karst drainage basins; discharge from karst aquifers; caves as paleoclimatic recorders; caves as ecosystems; water issues in karst regions; and sinkholes, soil piping and subsidence. 20 refs., 9 figs.

Advanced karst hydrological and contaminant monitoring techniques for real-time and high resolution applications

USDA-ARS?s Scientific Manuscript database

In telogenetic and soil-mantled karst aquifers, the movement of autogenic recharge through the epikarstic zone and into the regional aquifer can be a complex process and have implications for flooding, groundwater contamination, and other difficult to capture processes. Recent advances in instrument...

Review: Characterization, evolution, and environmental issues of karst water systems in Northern China

NASA Astrophysics Data System (ADS)

Liang, Yongping; Gao, Xubo; Zhao, Chunhong; Tang, Chunlei; Shen, Haoyong; Wang, Zhiheng; Wang, Yanxin

2018-05-01

In Northern China, karst systems in widely distributed carbonate rocks are one of the most important water supplies for local inhabitants. Constrained by the specific geological and geomorphological conditions, most karst water in this region is discharged as individual or groups of springs. This paper summarizes the characteristics, chemistry, and environmental quality of these karst systems in Northern China. Five structural models of karst water systems were identified based on the relationships between the karst geological strata and karst groundwater flow fields. These specific structural models may closely relate to the attendant environmental geological issues and consistent risks from pollution. Over the past 40 years, the karst water systems in Northern China have suffered from various environmental problems, including deteriorating water quality, the drying up of springs, a continuous decline in the level of karst water, and so on. Based on the field investigation and previous data, a preliminary summary is provided of the environmental problems related to the development and evolutionary trends of karst water in this region. The results highlight the significant challenges associated with karst water, and it is essential that all segments of society be made aware of the situation in order to demand change. In addition, the study provides a scientific basis for the management, protection, and sustainable utilization of karst water resources.

Groundwater Quality: Analysis of Its Temporal and Spatial Variability in a Karst Aquifer.

PubMed

Pacheco Castro, Roger; Pacheco Ávila, Julia; Ye, Ming; Cabrera Sansores, Armando

2018-01-01

This study develops an approach based on hierarchical cluster analysis for investigating the spatial and temporal variation of water quality governing processes. The water quality data used in this study were collected in the karst aquifer of Yucatan, Mexico, the only source of drinking water for a population of nearly two million people. Hierarchical cluster analysis was applied to the quality data of all the sampling periods lumped together. This was motivated by the observation that, if water quality does not vary significantly in time, two samples from the same sampling site will belong to the same cluster. The resulting distribution maps of clusters and box-plots of the major chemical components reveal the spatial and temporal variability of groundwater quality. Principal component analysis was used to verify the results of cluster analysis and to derive the variables that explained most of the variation of the groundwater quality data. Results of this work increase the knowledge about how precipitation and human contamination impact groundwater quality in Yucatan. Spatial variability of groundwater quality in the study area is caused by: a) seawater intrusion and groundwater rich in sulfates at the west and in the coast, b) water rock interactions and the average annual precipitation at the middle and east zones respectively, and c) human contamination present in two localized zones. Changes in the amount and distribution of precipitation cause temporal variation by diluting groundwater in the aquifer. This approach allows to analyze the variation of groundwater quality controlling processes efficiently and simultaneously. © 2017, National Ground Water Association.

Hydraulics of epiphreatic flow of a karst aquifer

NASA Astrophysics Data System (ADS)

Gabrovšek, Franci; Peric, Borut; Kaufmann, Georg

2018-05-01

The nature of epiphreatic flow remains an important research challenge in karst hydrology. This study focuses on the flood propagation along the epiphreatic system of Reka-Timavo system (Kras/Carso Plateau, Slovenia/Italy). It is based on long-term monitoring of basic physical parameters (pressure/level, temperature, specific electric conductivity) of ground water in six active caves belonging to the flow system. The system vigorously responds to flood events, with stage rising >100 m in some of the caves. Besides presenting the response of the system to flood events of different scales, the work focuses on the interpretation of recorded hydrographs in view of the known distribution and size of conduits and basic hydraulic relations. Furthermore, the hydrographs were used to infer the unknown geometry between the observation points. This way, the main flow restrictors, overflow passages and large epiphreatic storages were identified. The assumptions were tested with a hydraulic model, where the inversion procedure was used for an additional parameter optimisation. Time series of temperature and specific electric conductivity were used to assess the apparent velocities of flow between consecutive points.

Spring distributions and relationships with land cover and hydrogeologic strata in a karst landscape in Winona County, Minnesota, USA

USGS Publications Warehouse

Williams, M.A.; Vondracek, B.

2010-01-01

Karst aquifers are important groundwater resources, but are vulnerable to contamination due to relatively rapid subsurface transport. Springs, points where the landscape and water table intersect and cold groundwater discharges, link aquifer systems with land surfaces and water bodies. As such, in many regions, they are critical to the viability of lakes, streams and cold-water fish communities. An understanding of where springs are located is important to watershed, fishery and environmental management efforts in karst regions. To better understand spatial distribution of springs and as a potential method for identifying variables that characterize locations of springs for improved land and watershed management, a nearest-neighbor analysis and a discriminant function analysis (DFA) of springs were conducted in Winona County, Minnesota USA, a karst landscape. Nearestneighbor analysis examined the spatial spring distribution. Twenty-two variables describing the locations of springs were analyzed to ascertain their ability to discriminate correct aquifer unit or bedrock unit classification for each spring. Springs were clumped with the highest densities in the lowest elevations. Springs were correctly assigned to aquifer units and bedrock units with eight and 11 landscape variables, respectively. Forest land cover was the only land cover type contributing to spring discrimination. Consideration of upland human activities, particularly in forested areas, on spring discharge along with a better understanding of characteristics describing spring locations could lead to better management activities that locate and protect springs and their important contributions to regional ecohydrology. ?? 2010 Springer-Verlag.

The effects of monsoons and climate teleconnections on the Niangziguan Karst Spring discharge in North China

NASA Astrophysics Data System (ADS)

Zhang, Juan; Hao, Yonghong; Hu, Bill X.; Huo, Xueli; Hao, Pengmei; Liu, Zhongfang

2017-01-01

Karst aquifers supply drinking water for 25 % of the world's population, and they are, however, vulnerable to climate change. This study is aimed to investigate the effects of various monsoons and teleconnection patterns on Niangziguan Karst Spring (NKS) discharge in North China for sustainable exploration of the karst groundwater resources. The monsoons studied include the Indian Summer Monsoon, the West North Pacific Monsoon and the East Asian Summer Monsoon. The climate teleconnection patterns explored include the Indian Ocean Dipole, E1 Niño Southern Oscillation, and the Pacific Decadal Oscillation. The wavelet transform and wavelet coherence methods are used to analyze the karst hydrological processes in the NKS Basin, and reveal the relations between the climate indices with precipitation and the spring discharge. The study results indicate that both the monsoons and the climate teleconnections significantly affect precipitation in the NKS Basin. The time scales that the monsoons resonate with precipitation are strongly concentrated on the time scales of 0.5-, 1-, 2.5- and 3.5-year, and that climate teleconnections resonate with precipitation are relatively weak and diverged from 0.5-, 1-, 2-, 2.5-, to 8-year time scales, respectively. Because the climate signals have to overcome the resistance of heterogeneous aquifers before reaching spring discharge, with high energy, the strong climate signals (e.g. monsoons) are able to penetrate through aquifers and act on spring discharge. So the spring discharge is more strongly affected by monsoons than the climate teleconnections. During the groundwater flow process, the precipitation signals will be attenuated, delayed, merged, and changed by karst aquifers. Therefore, the coherence coefficients between the spring discharge and climate indices are smaller than those between precipitation and climate indices. Further, the fluctuation of the spring discharge is not coincident with that of precipitation in most

Hysteresis, regime shifts, and non-stationarity in aquifer recharge-storage-discharge systems

NASA Astrophysics Data System (ADS)

Klammler, Harald; Jawitz, James; Annable, Michael; Hatfield, Kirk; Rao, Suresh

2016-04-01

Based on physical principles and geological information we develop a parsimonious aquifer model for Silver Springs, one of the largest karst springs in Florida. The model structure is linear and time-invariant with recharge, aquifer head (storage) and spring discharge as dynamic variables at the springshed (landscape) scale. Aquifer recharge is the hydrological driver with trends over a range of time scales from seasonal to multi-decadal. The freshwater-saltwater interaction is considered as a dynamic storage mechanism. Model results and observed time series show that aquifer storage causes significant rate-dependent hysteretic behavior between aquifer recharge and discharge. This leads to variable discharge per unit recharge over time scales up to decades, which may be interpreted as a gradual and cyclic regime shift in the aquifer drainage behavior. Based on field observations, we further amend the aquifer model by assuming vegetation growth in the spring run to be inversely proportional to stream velocity and to hinder stream flow. This simple modification introduces non-linearity into the dynamic system, for which we investigate the occurrence of rate-independent hysteresis and of different possible steady states with respective regime shifts between them. Results may contribute towards explaining observed non-stationary behavior potentially due to hydrological regime shifts (e.g., triggered by gradual, long-term changes in recharge or single extreme events) or long-term hysteresis (e.g., caused by aquifer storage). This improved understanding of the springshed hydrologic response dynamics is fundamental for managing the ecological, economic and social aspects at the landscape scale.

Hydrological response of karst systems to large-scale climate variability for different catchments of the French karst observatory network INSU/CNRS SNO KARST

NASA Astrophysics Data System (ADS)

Massei, Nicolas; Labat, David; Jourde, Hervé; Lecoq, Nicolas; Mazzilli, Naomi

2017-04-01

The french karst observatory network SNO KARST is a national initiative from the National Institute for Earth Sciences and Astronomy (INSU) of the National Center for Scientific Research (CNRS). It is also part of the new french research infrastructure for the observation of the critical zone OZCAR. SNO KARST is composed by several karst sites distributed over conterminous France which are located in different physiographic and climatic contexts (Mediterranean, Pyrenean, Jura mountain, western and northwestern shore near the Atlantic or the English Channel). This allows the scientific community to develop advanced research and experiments dedicated to improve understanding of the hydrological functioning of karst catchments. Here we used several sites of SNO KARST in order to assess the hydrological response of karst catchments to long-term variation of large-scale atmospheric circulation. Using NCEP reanalysis products and karst discharge, we analyzed the links between large-scale circulation and karst water resources variability. As karst hydrosystems are highly heterogeneous media, they behave differently across different time-scales : we explore the large-scale/local-scale relationships according to time-scales using a wavelet multiresolution approach of both karst hydrological variables and large-scale climate fields such as sea level pressure (SLP). The different wavelet components of karst discharge in response to the corresponding wavelet component of climate fields are either 1) compared to physico-chemical/geochemical responses at karst springs, or 2) interpreted in terms of hydrological functioning by comparing discharge wavelet components to internal components obtained from precipitation/discharge models using the KARSTMOD conceptual modeling platform of SNO KARST.

Characterizing the interaction of groundwater and surface water in the karst aquifer of Fangshan, Beijing (China)

NASA Astrophysics Data System (ADS)

Chu, Haibo; Wei, Jiahua; Wang, Rong; Xin, Baodong

2017-03-01

Correct understanding of groundwater/surface-water (GW-SW) interaction in karst systems is of greatest importance for managing the water resources. A typical karst region, Fangshan in northern China, was selected as a case study. Groundwater levels and hydrochemistry analyses, together with isotope data based on hydrogeological field investigations, were used to assess the GW-SW interaction. Chemistry data reveal that water type and the concentration of cations in the groundwater are consistent with those of the surface water. Stable isotope ratios of all samples are close to the local meteoric water line, and the 3H concentrations of surface water and groundwater samples are close to that of rainfall, so isotopes also confirm that karst groundwater is recharged by rainfall. Cross-correlation analysis reveals that rainfall leads to a rise in groundwater level with a lag time of 2 months and groundwater exploitation leads to a fall within 1 month. Spectral analysis also reveals that groundwater level, groundwater exploitation and rainfall have significantly similar response periods, indicating their possible inter-relationship. Furthermore, a multiple nonlinear regression model indicates that groundwater level can be negatively correlated with groundwater exploitation, and positively correlated with rainfall. The overall results revealed that groundwater level has a close correlation with groundwater exploitation and rainfall, and they are indicative of a close hydraulic connection and interaction between surface water and groundwater in this karst system.

Eikonal-Based Inversion of GPR Data from the Vaucluse Karst Aquifer

NASA Astrophysics Data System (ADS)

Yedlin, M. J.; van Vorst, D.; Guglielmi, Y.; Cappa, F.; Gaffet, S.

2009-12-01

In this paper, we present an easy-to-implement eikonal-based travel time inversion algorithm and apply it to borehole GPR measurement data obtained from a karst aquifer located in the Vaucluse in Provence. The boreholes are situated with a fault zone deep inside the aquifer, in the Laboratoire Souterrain à Bas Bruit (LSBB). The measurements were made using 250 MHz MALA RAMAC borehole GPR antennas. The inversion formulation is unique in its application of a fast-sweeping eikonal solver (Zhao [1]) to the minimization of an objective functional that is composed of a travel time misfit and a model-based regularization [2]. The solver is robust in the presence of large velocity contrasts, efficient, easy to implement, and does not require the use of a sorting algorithm. The computation of sensitivities, which are required for the inversion process, is achieved by tracing rays backward from receiver to source following the gradient of the travel time field [2]. A user wishing to implement this algorithm can opt to avoid the ray tracing step and simply perturb the model to obtain the required sensitivities. Despite the obvious computational inefficiency of such an approach, it is acceptable for 2D problems. The relationship between travel time and the velocity profile is non-linear, requiring an iterative approach to be used. At each iteration, a set of matrix equations is solved to determine the model update. As the inversion continues, the weighting of the regularization parameter is adjusted until an appropriate data misfit is obtained. The inversion results, shown in the attached image, are consistent with previously obtained geological structure. Future work will look at improving inversion resolution and incorporating other measurement methodologies, with the goal of providing useful data for groundwater analysis. References: [1] H. Zhao, “A fast sweeping method for Eikonal equations,” Mathematics of Computation, vol. 74, no. 250, pp. 603-627, 2004. [2] D

Occurrence, distribution and sources of organochlorine pesticides (OCPs) in surface sediments from the Lijiang River, a typical karst river of southwestern China.

PubMed

Zhang, Dan; Wang, Yinghui; Yu, Kefu; Li, Pingyang; Zhang, Ruijie; Xu, Yiyin

2014-11-01

The Lijiang River is a typical karst river of southwestern China. Karst-aquifer systems are more vulnerable to contamination compared to other types of aquifers. The occurrence and distribution of organochlorine pesticides (OCPs) in surface sediments from the Lijiang River were investigated to evaluate their potential ecological risks. The total concentrations of them in sediments ranged from 0.80 to 18.73 ng/g dry weight (dw) (mean 6.83 ng/g dw). The residue levels of OCPs varied in the order of HCB > HCHs > DDTs. Compositional analyses of OCPs showed that HCHs and DDTs were mainly from historical usage. The ecological risk assessment suggested that HCHs and DDTs in Lijiang River sediments may cause adverse ecological risks, particularly at sites near agricultural areas.

Assessing flow paths in a karst aquifer based on multiple dye tracing tests using stochastic simulation and the MODFLOW-CFP code

NASA Astrophysics Data System (ADS)

Assari, Amin; Mohammadi, Zargham

2017-09-01

Karst systems show high spatial variability of hydraulic parameters over small distances and this makes their modeling a difficult task with several uncertainties. Interconnections of fractures have a major role on the transport of groundwater, but many of the stochastic methods in use do not have the capability to reproduce these complex structures. A methodology is presented for the quantification of tortuosity using the single normal equation simulation (SNESIM) algorithm and a groundwater flow model. A training image was produced based on the statistical parameters of fractures and then used in the simulation process. The SNESIM algorithm was used to generate 75 realizations of the four classes of fractures in a karst aquifer in Iran. The results from six dye tracing tests were used to assign hydraulic conductivity values to each class of fractures. In the next step, the MODFLOW-CFP and MODPATH codes were consecutively implemented to compute the groundwater flow paths. The 9,000 flow paths obtained from the MODPATH code were further analyzed to calculate the tortuosity factor. Finally, the hydraulic conductivity values calculated from the dye tracing experiments were refined using the actual flow paths of groundwater. The key outcomes of this research are: (1) a methodology for the quantification of tortuosity; (2) hydraulic conductivities, that are incorrectly estimated (biased low) with empirical equations that assume Darcian (laminar) flow with parallel rather than tortuous streamlines; and (3) an understanding of the scale-dependence and non-normal distributions of tortuosity.

Variations of the spatiotemporal patterns of CVOCs concentrations in northern karst of Puerto Rico

NASA Astrophysics Data System (ADS)

Yu, X.; Ghasemizadeh, R.; Padilla, I. Y.; Irizarry, C.; Yegen, C.; Kaeli, D.; Alshawabkeh, A. N.

2013-12-01

The northern Puerto Rico is characterized as karst topography, where the groundwater is a major source of water use to the island. Various types of Chlorinated Volatile Organic Compounds (CVOCs), which are due to improper disposal of industrial waste, are detected in these karst aquifers. It is important to study the spatiotemporal distribution patterns of the CVOCs in this region, which are posing a serious threat to both the ecological and human health. In this study, various historical CVOCs data from 264 wells across the northern karst region from January 1982 to December 2000 were collected from a number of reports and studies. We found that 38% (99 out of 264) of the sites had at least one sample with CVOC concentration above the standards established to protect human health over the study period. We found that the distribution of the CVOCs spatially varied with areas containing clusters of sites contaminated by different organic compound. The response of CVOC concentrations were occasionally retarded even though they were depleted significantly in the source zones. The study confirmed that the measured CVOC concentrations decreased during the study period at most of the sites. The source origin (toxics release locations and quantities) and the intrinsic characteristics of the karst (high heterogeneity and complex hydraulic behavior) are most likely related with the spatial and temporal distribution patterns of CVOCs. The study of the spatiotemporal patterns of CVOCs concentrations in the northern karst aquifers has important implications on the public water use, especially when it coincides with the recent population growth in this region. Locations of Puerto Rico, the northern karst region of Puerto Rico and 264 sampling sites in the karst region.

Modelling Contributions of the Local and Regional Groundwater Flow of Managed Aquifer Recharge Activities at Querença-Silves Aquifer System.

NASA Astrophysics Data System (ADS)

Costa, Luís; Monteiro, José Paulo; Oliveira, Manuel; Mota, Rogério; Lobo-Ferreira, João Paulo; Martins de Carvalho, José; Martins de Carvalho, Tiago; Agostinho, Rui; Hugman, Rui

2015-04-01

The Querença-Silves (QS) aquifer system is one of the most important natural groundwater reservoirs in the Algarve region of southern Portugal. With a surface area of 324 km2, this karst aquifer system is the main source of supply for irrigation as well as an important source of water for the urban supply. Due to the importance given to QS aquifer system by both governmental actors and end users, ongoing research during the last two decades at the University of Algarve has attempted to provide a better understanding of the hydrogeology and hydraulic behavior, which has resulted in the development of regional scale numerical models. The most recent hydrogeological data has been acquired during the ongoing MARSOL project (MARSOL-GA-2013-619120) which aims to demonstrate that Managed Aquifer Recharge (MAR) is a sound, safe and sustainable strategy that can be applied with great confidence in finding solutions to water scarcity in Southern Europe. Within the scope of the project large diameter well injection tests (with and without tracers) as well as geophysical surveys have been carried out in order to determine the infiltration capacity and aquifer properties. The results of which allowed the use of analytical methods to determine local scale values of hydraulic parameters (e.g. hydraulic conductivity and storage coefficient). These values will be compared with results from pre-existing numerical flow and transport models in order to obtain complementary solutions to the problem at local and regional scales. This analysis will contribute to the selection of the most appropriate methods to interpret, reproduce and model the impacts of MAR activities planned within the scope of the MARSOL project. Subsequent to the planned injection tests and, with the support of modelling efforts, the capacity of infiltration of rejected water from water treatment plants or surface storage dams in the large diameter well will be assessed.

Estimating Preferential Flow in Karstic Aquifers Using Statistical Mixed Models

PubMed Central

Anaya, Angel A.; Padilla, Ingrid; Macchiavelli, Raul; Vesper, Dorothy J.; Meeker, John D.; Alshawabkeh, Akram N.

2013-01-01

Karst aquifers are highly productive groundwater systems often associated with conduit flow. These systems can be highly vulnerable to contamination, resulting in a high potential for contaminant exposure to humans and ecosystems. This work develops statistical models to spatially characterize flow and transport patterns in karstified limestone and determines the effect of aquifer flow rates on these patterns. A laboratory-scale Geo-HydroBed model is used to simulate flow and transport processes in a karstic limestone unit. The model consists of stainless-steel tanks containing a karstified limestone block collected from a karst aquifer formation in northern Puerto Rico. Experimental work involves making a series of flow and tracer injections, while monitoring hydraulic and tracer response spatially and temporally. Statistical mixed models are applied to hydraulic data to determine likely pathways of preferential flow in the limestone units. The models indicate a highly heterogeneous system with dominant, flow-dependent preferential flow regions. Results indicate that regions of preferential flow tend to expand at higher groundwater flow rates, suggesting a greater volume of the system being flushed by flowing water at higher rates. Spatial and temporal distribution of tracer concentrations indicates the presence of conduit-like and diffuse flow transport in the system, supporting the notion of both combined transport mechanisms in the limestone unit. The temporal response of tracer concentrations at different locations in the model coincide with, and confirms the preferential flow distribution generated with the statistical mixed models used in the study. PMID:23802921

Spring hydrograph simulation of karstic aquifers: Impacts of variable recharge area, intermediate storage and memory effects

NASA Astrophysics Data System (ADS)

Hosseini, Seiyed Mossa; Ataie-Ashtiani, Behzad; Simmons, Craig T.

2017-09-01

A simple conceptual rainfall-runoff model is proposed for the estimation of groundwater balance components in complex karst aquifers. In the proposed model the effects of memory length of different karst flow systems of base-flow, intermediate-flow, and quick-flow and also time variation of recharge area (RA) during a hydrological year were investigated. The model consists of three sub-models: soil moisture balance (SMB), epikarst balance (EPB), and groundwater balance (GWB) to simulate the daily spring discharge. The SMB and EPB sub-models utilize the mass conservation equation to compute the variation of moisture storages in the soil cover and epikarst, respectively. The GWB sub-model computes the spring discharge hydrograph through three parallel linear reservoirs for base-flow, intermediate-flow, and quick-flow. Three antecedent recharge indices are defined and embedded in the model structure to deal with the memory effect of three karst flow systems to antecedent recharge flow. The Sasan Karst aquifer located in the semi-arid region of south-west Iran with a continuous long-term (21-years) daily meteorological and discharge data are considered to describe model calibration and validation procedures. The effects of temporal variations of RA of karst formations during the hydrological year namely invariant RA, two RA (winter and summer), four RA (seasonal), and twelve RA (monthly) are assessed to determine their impact on the model efficiency. Results indicated that the proposed model with monthly-variant RA is able to reproduce acceptable simulation results based on modified Kling-Gupta efficiency (KGE = -0.83). The results of density-based global sensitivity analysis for dry (June to September) and a wet (October to May) period reveal the dominant influence of RA (with sensitivity indices equal to 0.89 and 0.93, respectively) in spring discharge simulation. The sensitivity of simulated spring discharge to memory effect of different karst formations during the

Eogenetic karst hydrology: Insights from the 2004 hurricanes, peninsular Florida

USGS Publications Warehouse

Florea, L.J.; Vacher, H. Leonard

2007-01-01

Eogenetic karst lies geographically and temporally close to the depositional environment of limestone in warm marine water at low latitude, in areas marked by midafternoon thunderstorms during a summer rainy season. Spring hydrographs from such an environment in north-central Florida are characterized by smooth, months-long, seasonal maxima. The passage of Hurricanes Frances and Jeanne in September 2004 over three field locations shows how the eogenetic karst of the Upper Floridan Aquifer responds to unequivocal recharge events. Hydrographs at wells in the High Springs area, Rainbow Springs, and at Morris, Briar, and Bat Caves all responded promptly with a similar drawn-out rise to a maximum that extended long into the winter dry season. The timing indicates that the typical hydrograph of eogenetic karst is not the short-term fluctuations of springs in epigenic, telogenetic karst, or the smoothed response to all the summer thunderstorms, but rather the protracted response of the system to rainfall that exceeds a threshold. The similarity of cave and noncave hydrographs indicates distributed autogenic recharge and a free communication between secondary porosity and permeable matrix - both of which differ from the hydrology of epigenic, telogenetic karst. At Briar Cave, drip rates lagged behind the water table rise, suggesting that recharge was delivered by fractures, which control the cave's morphology. At High Springs, hydrographs at the Santa Fe River and a submerged conduit apparently connected to it show sharp maxima after the storms, unlike the other cave hydrographs. Our interpretation is that the caves, in general, are discontinuous. ?? 2007 National Ground Water Association.

Eogenetic karst hydrology: insights from the 2004 hurricanes, peninsular Florida.

PubMed

Florea, Lee J; Vacher, H L

2007-01-01

Eogenetic karst lies geographically and temporally close to the depositional environment of limestone in warm marine water at low latitude, in areas marked by midafternoon thunderstorms during a summer rainy season. Spring hydrographs from such an environment in north-central Florida are characterized by smooth, months-long, seasonal maxima. The passage of Hurricanes Frances and Jeanne in September 2004 over three field locations shows how the eogenetic karst of the Upper Floridan Aquifer responds to unequivocal recharge events. Hydrographs at wells in the High Springs area, Rainbow Springs, and at Morris, Briar, and Bat Caves all responded promptly with a similar drawn-out rise to a maximum that extended long into the winter dry season. The timing indicates that the typical hydrograph of eogenetic karst is not the short-term fluctuations of springs in epigenic, telogenetic karst, or the smoothed response to all the summer thunderstorms, but rather the protracted response of the system to rainfall that exceeds a threshold. The similarity of cave and noncave hydrographs indicates distributed autogenic recharge and a free communication between secondary porosity and permeable matrix-both of which differ from the hydrology of epigenic, telogenetic karst. At Briar Cave, drip rates lagged behind the water table rise, suggesting that recharge was delivered by fractures, which control the cave's morphology. At High Springs, hydrographs at the Santa Fe River and a submerged conduit apparently connected to it show sharp maxima after the storms, unlike the other cave hydrographs. Our interpretation is that the caves, in general, are discontinuous.

Assessing vulnerability mapping and protection zones of karst spring waters and validating by the joint use of natural and artificial tracers. The case of Auta Spring (Southern Spain)

NASA Astrophysics Data System (ADS)

Marín, Ana Isabel; Mudarra, Matías; Andreo, Bartolomé

2016-04-01

effective procedure for validating vulnerability mapping of karst systems and springs used for water supply. This procedure is meant to implement and to complement protection zone mapping, particularly in countries lacking guidelines for protecting the water resources of karst aquifers.

Multi-scale hydrogeological and hydrogeophysical approach to monitor vadose zone hydrodynamics of a karst system

NASA Astrophysics Data System (ADS)

Watlet, Arnaud; Poulain, Amaël; Van Camp, Michel; Francis, Olivier; Triantafyllou, Antoine; Rochez, Gaëtan; Hallet, Vincent; Kaufmann, Olivier

2016-04-01

The vadose zone of karst systems plays an important role on the water dynamics. In particular, temporary perched aquifers can appear in the subsurface due to changes of weather conditions, reduced evapotranspiration and the vertical gradients of porosity and permeability. Although many difficulties are usually encountered when studying karst environments due to their heterogeneities, cave systems offer an outstanding opportunity to investigate vadose zone from the inside. We present a multi-scale study covering two years of hydrogeological and geophysical monitoring of the Lomme Karst System (LKS) located in the Variscan fold-and-thrust belt (Belgium), a region (~ 3000 ha) that shows many karstic networks within Devonian limestone units. Hydrogeological data cover the whole LKS and involve e.g. flows and levels monitoring or tracer tests performed in both vadose and saturated zones. Such data bring valuable information on the hydrological context of the studied area at the catchment scale. Combining those results with geophysical measurements allows validating and imaging them at a smaller scale, with more integrative techniques. Hydrogeophysical measurements are focused on only one cave system of the LKS, at the Rochefort site (~ 40 ha), taking benefit of the Rochefort Cave Laboratory (RCL) infrastructures. In this study, a microgravimetric monitoring and an Electrical Resistivity Tomography (ERT) monitoring are involved. The microgravimetric monitoring consists in a superconducting gravimeter continuously measuring gravity changes at the surface of the RCL and an additional relative gravimeter installed in the underlying cave located 35 meters below the surface. While gravimeters are sensible to changes that occur in both the vadose zone and the saturated zone of the whole cave system, combining their recorded signals allows enhancing vadose zone's gravity changes. Finally, the surface ERT monitoring provide valuable information at the (sub)-meter scale on the

Summary of the hydrology of the Floridan aquifer system in Florida and in parts of Georgia, South Carolina, and Alabama

USGS Publications Warehouse

Johnston, Richard H.; Bush, Peter W.

1988-01-01

The Floridan aquifer system is one of the major sources of ground-water supplies in the United States. This highly productive aquifer system underlies all of Florida, southern Georgia, and small parts of adjoining Alabama and South Carolina, for a total area of about 100,000 square miles. About 3 billion gallons of water per day is withdrawn from the aquifer for all uses, and, in many areas, the Floridan is the sole source of freshwater. The aquifer system is a sequence of hydraulically connected carbonate rocks (principally limestone and some dolomite) that generally range in age from Late Paleocene to Early Miocene. The rocks vary in thickness from a featheredge where they crop out to more than 3,500 ft where the aquifer is deeply buried. The aquifer system generally consists of an upper aquifer and a lower aquifer, separated by a less permeable confining unit of highly variable properties. In parts of north Florida and southwest Georgia, there is little permeability contrast within the aquifer system. Thus in these areas the Floridan is effectively one continuous aquifer. The upper and lower aquifers are defined on the basis of permeability, and their boundaries locally do not coincide with those for either time-stratigraphic or rock-stratigraphic units. Low-permeability clastic rocks overlie much of the Floridan aquifer system. The lithology, thickness, and integrity of these low-permeability rocks have a controlling effect on the development of permeability and ground-water flow in the Floridan locally. The Floridan aquifer system derives its permeability from openings that vary from fossil hashes and networks of many solution-widened joints to large cavernous openings in karst areas. Diffuse flow pre-dominates where the small openings occur, whereas conduit flow may occur where there are large cavernous openings. For the Upper Floridan aquifer, transmissivities are highest (greater than 1,000,000 ft squared per day) in the unconfined karst areas of central

New insights into nitrate dynamics in a karst groundwater system gained from in situ high-frequency optical sensor measurements

USGS Publications Warehouse

Opsahl, Stephen P.; Musgrove, MaryLynn; Slattery, Richard N.

2017-01-01

Understanding nitrate dynamics in groundwater systems as a function of climatic conditions, especially during contrasting patterns of drought and wet cycles, is limited by a lack of temporal and spatial data. Nitrate sensors have the capability for making accurate, high-frequency measurements of nitrate in situ, but have not yet been evaluated for long-term use in groundwater wells. We measured in situ nitrate continuously in two groundwater monitoring wells —one rural and one urban—located in the recharge zone of a productive karst aquifer in central Texas in order to resolve changes that occur over both short-term (hourly to daily) and long-term (monthly to yearly) periods. Nitrate concentrations, measured as nitrate-nitrogen in milligrams per liter (mg/L), during drought conditions showed little or no temporal change as groundwater levels declined. During aquifer recharge, extremely rapid changes in concentration occurred at both wells as documented by hourly data. At both sites, nitrate concentrations were affected by recharging surface water as evidenced by nitrate concentrations in groundwater recharge (0.8–1.3 mg/L) that were similar to previously reported values for regional recharging streams. Groundwater nitrate concentrations responded differently at urban and rural sites during groundwater recharge. Concentrations at the rural well (approximately 1.0 mg/L) increased as a result of higher nitrate concentrations in groundwater recharge relative to ambient nitrate concentrations in groundwater, whereas concentrations at the urban well (approximately 2.7 mg/L) decreased as a result of the dilution of higher ambient nitrate concentrations relative to those in groundwater recharge. Notably, nitrate concentrations decreased to as low as 0.8 mg/L at the urban site during recharge but postrecharge concentrations exceeded 3.0 mg/L. A return to higher nitrate concentrations postrecharge indicates mobilization of a localized source of elevated nitrate

Field Investigation and Modeling Development for Hydrological and Carbon Cycles in Southwest Karst Region of China

NASA Astrophysics Data System (ADS)

Hu, X. B.

2017-12-01

It is required to understanding water cycle and carbon cycle processes for water resource management and pollution prevention and global warming influence in southwest karst region of China. Lijiang river basin is selected as our study region. Interdisciplinary field and laboratory experiments with various technologies are conducted to characterize the karst aquifers in detail. Key processes in the karst water cycle and carbon cycle are determined. Based on the MODFLOW-CFP model, new watershed flow and carbon cycle models are developed coupled subsurface and surface water flow models. Our study focus on the karst springshed in Mao village, the mechanisms coupling carbon cycle and water cycle are explored. This study provides basic theory and simulation method for water resource management and groundwater pollution prevention in China karst region.

Aquifers of Arkansas: protection, management, and hydrologic and geochemical characteristics of groundwater resources in Arkansas

USGS Publications Warehouse

Kresse, Timothy M.; Hays, Phillip D.; Merriman, Katherine R.; Gillip, Jonathan A.; Fugitt, D. Todd; Spellman, Jane L.; Nottmeier, Anna M.; Westerman, Drew A.; Blackstock, Joshua M.; Battreal, James L.

2014-01-01

individual flow paths. Dominant changes in geochemistry for the Ouachita Mountains aquifer and the Western Interior Plains confining system are attributed to rock/water interaction and changes in redox zonation along the flow path. In these areas, groundwater evolves along flow paths from a calcium- to a sodium-bicarbonate water type with increasing reducing conditions resulting in denitrification, elevated iron and manganese concentrations, and production of methane in the more geochemically evolved and strongest reducing conditions. In the Ozark and Springfield Plateau aquifers, rapid influx of surface-derived contaminants, especially nitrogen, coupled with few to no attenuation processes was attributed to the karst landscape developed on Mississippian- and Ordovician-age carbonate rocks of the Ozark Plateaus. Increasing nitrate concentrations are related to increasing agricultural land use, and areas of mature karst development result in higher nitrate concentrations than areas with less karst features.

Lattice Boltzmann methods applied to large-scale three-dimensional virtual cores constructed from digital optical borehole images of the karst carbonate Biscayne aquifer in southeastern Florida

USGS Publications Warehouse

Michael Sukop,; Cunningham, Kevin J.

2014-01-01

Digital optical borehole images at approximately 2 mm vertical resolution and borehole caliper data were used to create three-dimensional renderings of the distribution of (1) matrix porosity and (2) vuggy megaporosity for the karst carbonate Biscayne aquifer in southeastern Florida. The renderings based on the borehole data were used as input into Lattice Boltzmann methods to obtain intrinsic permeability estimates for this extremely transmissive aquifer, where traditional aquifer test methods may fail due to very small drawdowns and non-Darcian flow that can reduce apparent hydraulic conductivity. Variogram analysis of the borehole data suggests a nearly isotropic rock structure at lag lengths up to the nominal borehole diameter. A strong correlation between the diameter of the borehole and the presence of vuggy megaporosity in the data set led to a bias in the variogram where the computed horizontal spatial autocorrelation is strong at lag distances greater than the nominal borehole size. Lattice Boltzmann simulation of flow across a 0.4 × 0.4 × 17 m (2.72 m3 volume) parallel-walled column of rendered matrix and vuggy megaporosity indicates a high hydraulic conductivity of 53 m s−1. This value is similar to previous Lattice Boltzmann calculations of hydraulic conductivity in smaller limestone samples of the Biscayne aquifer. The development of simulation methods that reproduce dual-porosity systems with higher resolution and fidelity and that consider flow through horizontally longer renderings could provide improved estimates of the hydraulic conductivity and help to address questions about the importance of scale.

Lattice Boltzmann methods applied to large-scale three-dimensional virtual cores constructed from digital optical borehole images of the karst carbonate Biscayne aquifer in southeastern Florida

NASA Astrophysics Data System (ADS)

Sukop, Michael C.; Cunningham, Kevin J.

2014-11-01

Digital optical borehole images at approximately 2 mm vertical resolution and borehole caliper data were used to create three-dimensional renderings of the distribution of (1) matrix porosity and (2) vuggy megaporosity for the karst carbonate Biscayne aquifer in southeastern Florida. The renderings based on the borehole data were used as input into Lattice Boltzmann methods to obtain intrinsic permeability estimates for this extremely transmissive aquifer, where traditional aquifer test methods may fail due to very small drawdowns and non-Darcian flow that can reduce apparent hydraulic conductivity. Variogram analysis of the borehole data suggests a nearly isotropic rock structure at lag lengths up to the nominal borehole diameter. A strong correlation between the diameter of the borehole and the presence of vuggy megaporosity in the data set led to a bias in the variogram where the computed horizontal spatial autocorrelation is strong at lag distances greater than the nominal borehole size. Lattice Boltzmann simulation of flow across a 0.4 × 0.4 × 17 m (2.72 m3 volume) parallel-walled column of rendered matrix and vuggy megaporosity indicates a high hydraulic conductivity of 53 m s-1. This value is similar to previous Lattice Boltzmann calculations of hydraulic conductivity in smaller limestone samples of the Biscayne aquifer. The development of simulation methods that reproduce dual-porosity systems with higher resolution and fidelity and that consider flow through horizontally longer renderings could provide improved estimates of the hydraulic conductivity and help to address questions about the importance of scale.

Enhanced recharge and karst, Edwards aquifer, south central Texas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hammond, W.W. Jr.

1993-02-01

Enhanced recharge is a water management strategy which can add significant quantities of ground water to the available water resources of the San Antonio region by utilizing the immense storage capacity of the unconfined zone of the Edwards aquifer. The Edwards aquifer presently is the sole source of water for a population of over 1,200,000, meeting public supply, industrial, and irrigation demands over a wide area of south central Texas. Valdina Farms Sinkhole is located adjacent to Seco Creek in Medina County and is in the recharge zone of the aquifer. Initial studies indicated that the sinkholes was capable ofmore » taking flood flows from Seco Creek and functioning as a recharge structure. Stream channels in the cavern system associated with Valdina Farms Sinkhole were incised into cave deposits and flood debris was present in the caverns at some distance from the sinkhole. Chemical analyses of samples of water from the cave and from nearby wells showed nitrate concentrations that decreased with distance from the cavern. Gradient of the potentiometric surface in the vicinity of the cave was very low, indicating high values of hydraulic conductivity for the aquifer. Based on evidence from these field studies a dam was constructed in 1982 on Seco Creek and a flood diversion channel was excavated to the sinkhole. Reservoir capacity is 2 acre-feet and design recharge rate is 3.8-6.7 m[sup 3]/sec. Annual recharge at the sinkhole has varied from 0 during periods of low runoff to 12,915 acre-feet.« less

Hydrograph separation for karst watersheds using a two-domain rainfall-discharge model

USGS Publications Warehouse

Long, Andrew J.

2009-01-01

Highly parameterized, physically based models may be no more effective at simulating the relations between rainfall and outflow from karst watersheds than are simpler models. Here an antecedent rainfall and convolution model was used to separate a karst watershed hydrograph into two outflow components: one originating from focused recharge in conduits and one originating from slow flow in a porous annex system. In convolution, parameters of a complex system are lumped together in the impulse-response function (IRF), which describes the response of the system to an impulse of effective precipitation. Two parametric functions in superposition approximate the two-domain IRF. The outflow hydrograph can be separated into flow components by forward modeling with isolated IRF components, which provides an objective criterion for separation. As an example, the model was applied to a karst watershed in the Madison aquifer, South Dakota, USA. Simulation results indicate that this watershed is characterized by a flashy response to storms, with a peak response time of 1 day, but that 89% of the flow results from the slow-flow domain, with a peak response time of more than 1 year. This long response time may be the result of perched areas that store water above the main water table. Simulation results indicated that some aspects of the system are stationary but that nonlinearities also exist.

Spatial resolution of transport parameters in a subtropical karst conduit system during dry and wet seasons

NASA Astrophysics Data System (ADS)

Ender, Anna; Goeppert, Nadine; Goldscheider, Nico

2018-04-01

Karst aquifers are characterized by a high degree of hydrologic variability and spatial heterogeneity of transport parameters. Tracer tests allow the quantification of these parameters, but conventional point-to-point experiments fail to capture spatiotemporal variations of flow and transport. The goal of this study was to elucidate the spatial distribution of transport parameters in a karst conduit system at different flow conditions. Therefore, six tracer tests were conducted in an active and accessible cave system in Vietnam during dry and wet seasons. Injections and monitoring were done at five sites along the flow system: a swallow hole, two sites inside the cave, and two springs draining the system. Breakthrough curves (BTCs) were modeled with CXTFIT software using the one-dimensional advection-dispersion model and the two-region nonequilibrium model. In order to obtain transport parameters in the individual sections of the system, a multi-pulse injection approach was used, which was realized by using the BTCs from one section as input functions for the next section. Major findings include: (1) In the entire system, mean flow velocities increase from 183 to 1,043 m/h with increasing discharge, while (2) the proportion of immobile fluid regions decrease; (3) the lowest dispersivity was found at intermediate discharge; (4) in the individual cave sections, flow velocities decrease along the flow direction, related to decreasing gradients, while (5) dispersivity is highest in the middle section of the cave. The obtained results provide a valuable basis for the development of an adapted water management strategy for a projected water-supply system.

Estimating preferential flow in karstic aquifers using statistical mixed models.

PubMed

Anaya, Angel A; Padilla, Ingrid; Macchiavelli, Raul; Vesper, Dorothy J; Meeker, John D; Alshawabkeh, Akram N

2014-01-01

Karst aquifers are highly productive groundwater systems often associated with conduit flow. These systems can be highly vulnerable to contamination, resulting in a high potential for contaminant exposure to humans and ecosystems. This work develops statistical models to spatially characterize flow and transport patterns in karstified limestone and determines the effect of aquifer flow rates on these patterns. A laboratory-scale Geo-HydroBed model is used to simulate flow and transport processes in a karstic limestone unit. The model consists of stainless steel tanks containing a karstified limestone block collected from a karst aquifer formation in northern Puerto Rico. Experimental work involves making a series of flow and tracer injections, while monitoring hydraulic and tracer response spatially and temporally. Statistical mixed models (SMMs) are applied to hydraulic data to determine likely pathways of preferential flow in the limestone units. The models indicate a highly heterogeneous system with dominant, flow-dependent preferential flow regions. Results indicate that regions of preferential flow tend to expand at higher groundwater flow rates, suggesting a greater volume of the system being flushed by flowing water at higher rates. Spatial and temporal distribution of tracer concentrations indicates the presence of conduit-like and diffuse flow transport in the system, supporting the notion of both combined transport mechanisms in the limestone unit. The temporal response of tracer concentrations at different locations in the model coincide with, and confirms the preferential flow distribution generated with the SMMs used in the study. © 2013, National Ground Water Association.

Fate of effluent-borne contaminants beneath septic tank drainfields overlying a Karst aquifer.

PubMed

Katz, Brian G; Griffin, Dale W; McMahon, Peter B; Harden, Harmon S; Wade, Edgar; Hicks, Richard W; Chanton, Jeffrey P

2010-01-01

Groundwater quality effects from septic tanks were investigated in the Woodville Karst Plain, an area that contains numerous sinkholes and a thin veneer of sands and clays overlying the Upper Floridan aquifer (UFA). Concerns have emerged about elevated nitrate concentrations in the UFA, which is the source of water supply in this area of northern Florida. At three sites during dry and wet periods in 2007-2008, water samples were collected from the septic tank, shallow and deep lysimeters, and drainfield and background wells in the UFA and analyzed for multiple chemical indicators including nutrients, nitrate isotopes, organic wastewater compounds (OWCs), pharmaceutical compounds, and microbiological indicators (bacteria and viruses). Median NO3-N concentration in groundwater beneath the septic tank drainfields was 20 mg L(-1) (8.0-26 mg L(-1)). After adjusting for dilution, about 25 to 40% N loss (from denitrification, ammonium sorption, and ammonia volatilization) occurs as septic tank effluent moves through the unsaturated zone to the water table. Nitrogen loading rates to groundwater were highly variable at each site (3.9-12 kg N yr(-1)), as were N and chloride depth profiles in the unsaturated zone. Most OWCs and pharmaceutical compounds were highly attenuated beneath the drainfields; however, five Cs (caffeine, 1,7-dimethylxanthine, phenol, galaxolide, and tris(dichloroisotopropyl)phosphate) and two pharmaceutical compounds (acetaminophen and sulfamethoxazole) were detected in groundwater samples. Indicator bacteria and human enteric viruses were detected in septic tank effluent samples but only intermittently in soil water and groundwater. Contaminant movement to groundwater beneath each septic tank system also was related to water use and differences in lithology at each site.

Hydrochemical constraints between the karst Tabular Middle Atlas Causses and the Saïs basin (Morocco): implications of groundwater circulation

NASA Astrophysics Data System (ADS)

Miche, Hélène; Saracco, Ginette; Mayer, Adriano; Qarqori, Khaoula; Rouai, Mohamed; Dekayir, Abdelilah; Chalikakis, Konstantinos; Emblanch, Christophe

2018-02-01

The karst Tabular Middle Atlas Causses reservoir is the main drinking-water supply of Fez-Meknes region (Saïs Basin) in Morocco. Recent analyses showed a decline in associated groundwater chemical quality and increased turbidity. To understand this hydrosystem, four surveys were undertaken during fall and spring, 2009-2011. Hydrogeochemical studies coupled with isotopic analyses (δ18O, δD and 222Rn) showed that the aquifers between the causses (mountains) and the Saïs Basin are of Liassic origin and at the southern extremities are of Triassic origin. Five recharge zones of different altitudes have been defined, including two main mixing zones in the south. Deuterium excess results suggest local recharge, while a plot of δ18O versus δD characterizes a confined aquifer in the eastern sector. 222Rn results reveal areas of rapid exchanges with an upwelling time of less than 2 weeks. A schematic conceptual model is presented to explain the groundwater circulation system and the behavior of this karst system.

Stable sulfur and oxygen isotopes as geochemical tracers of sulfate in karst waters

NASA Astrophysics Data System (ADS)

Sun, Jing; Kobayashi, Tatsuaki; Strosnider, William H. J.; Wu, Pan

2017-08-01

Karst water resources, which are extremely sensitive to mining activities, are critical for the support of human societies and ecological systems in many regions worldwide. In order to determine the sources and fate of dissolved sulfate in low-pH karst waters, hydrochemical variations of karst waters with and without acid mine drainage (AMD) impacts were investigated along with stable isotope dynamics. As expected, hydrochemical characteristics and isotopic compositions of the AMD and AMD-downstream water (ADW) were dramatically different from that of the non-AMD-impacted water (NAW). The sources of sulfur isotopes in sulfate were predominantly pyrite oxidation for the AMD and ADW, and atmospheric deposition for the NAW. Based on the general isotope-balance model, the relative proportions of sulfate oxygen derived from water and air were calculated. The mean proportion of sulfate oxygen derived from water in ADW was roughly double that of AMD. This suggests that the sulfate associated with AMD is predominantly influenced by aerobic pyrite oxidation, while that of ADW is likely affected by the dissolution of pyrite under anaerobic conditions in reservoir sediment. This observation was coincident with the noted variations of hydrochemical characteristics and was supported by principal component analysis. These results provide a better understanding of how stable isotopes of sulfate and water can be used to track mining contamination in karst aquifers, which could benefit remediation planning for these distinctive systems.

Application of major and trace elements as well as boron isotopes for tracing hydrochemical processes: the case of Trifilia coastal karst aquifer, Greece

NASA Astrophysics Data System (ADS)

Panagopoulos, G.

2009-09-01

The Trifilia karst aquifer presents a complex hydrochemical character due to the intricate geochemical processes that take place in the area. Their discernment was achieved by using the chemical analyses of major, trace elements and boron isotopes. Major ion composition indicates mixing between seawater and freshwater is occurring. Five hydrochemical zones corresponding to five respective groundwater types were distinguished, in which the chemical composition of groundwater is influenced mainly due to the different salinization grade of the aquifer. The relatively increased temperature of the aquifer indicates the presence of hydrothermal waters. Boron isotopes and trace elements indicate that the intruding seawater has been hydrothermally altered, as it is shown by the δ11B depleted signature and the increased concentrations of Li and Sr. Trace elements analyses showed that the groundwater is enriched in various metallic elements, which derive from the solid hydrocarbons (bitumens), contained in the carbonate sediments of the Tripolis zone. The concentration of these trace elements depends on the redox environment. Thus, in reductive conditions As, Mn, Co and NH4 concentrations are high, in oxidized conditions the V, Se, Mo, Tl and U concentration increases while Ni is not redox sensitive and present high concentration in both environments.

Effectiveness of airborne multispectral thermal data for karst groundwater resources recognition in coastal areas

NASA Astrophysics Data System (ADS)

Pignatti, Stefano; Fusilli, Lorenzo; Palombo, Angelo; Santini, Federico; Pascucci, Simone

2013-04-01

and the retrieving of accurate sea surface temperatures (SST) allowed us to detect and identify thermal anomalies related to coastal and submarine karst springs. In particular, the preprocessing for both MIVIS and TASI-600 sensors was carried out as follows: (a) radiometric calibration of the raw data by using the RADCORR software provided by ITRES (Canada) and the application of a new correction tool for blinking pixel correction, developed by CNR (Italy); (b) atmospheric compensation of the TIR data by applying the ISAC (In-Scene Atmospheric Compensation) algorithm [7]; (c) calibration to temperature by separating temperature and emissivity according to the methods described by [8]. This study points out that considerable water resources are dispersed into the sea, through karst springs and such water resources could be effectively protected in artificial way against the salting sea water influence and exploited for human local uses. The obtained preliminary results are encouraging, even though suitable integration approaches also with the classical geophysical investigation techniques have to be improved for rapid and cost-effective karst groundwater resources detection and monitoring. Table 1. Characteristics of sensors used for this study. Spectral Region Bands Spectral Resolution Spectral Range IFOV Spatial Resolution MIVISVNIR-SWIR LWIR 92 10 90-500 nm 340-540 nm 0.4÷12.7 μm 8.2÷12.7 μm 2.0 mrad3 m TASI LWIR 32 100 nm 8.0÷11.5 μm 1.2 mrad1 m References Jemcov, I. 2007. Water supply potential and optimal exploitation capacity of karst aquifer systems. Environm. Geol., vol. 51, 767-773. Bakalowicz, M. 2005. Karst groundwater: a challenge for new resources. Hydrogeology Journal, vol. 13, pp. 148-160. Milanovic, S. 2007. Hydrogeological characteristics of some deep siphonal springs in Serbia and Montenegro karst. Environmental Geology, vol 51, p.p. 755-759. Avanzi, G., Palombo, A., Pignatti, S. 2006. MIVIS image geocoding experience on merging position

Transport of free and particulate-associated bacteria in karst

USGS Publications Warehouse

Mahler, B.J.; Personne, J.-C.; Lods, G.F.; Drogue, C.

2000-01-01

Karst aquifers, because of their unique hydrogeologic characteristics, are extremely susceptible to contamination by pathogens. Here we present the results of an investigation of contamination of a karst aquifer by fecal indicator bacteria. Two wells intercepting zones with contrasting effective hydraulic conductivities, as determined by pump test, were monitored both during the dry season and in response to a rain event. Samples were also collected from the adjacent ephemeral surface Stream, which is known to be impacted by an upstream wastewater treatment plant after rainfall. Whole water and suspended sediment samples were analyzed for fecal coliforms and enterococci. During the dry season, pumping over a 2-day period resulted in increases in concentrations of fecal coliforms to greater than 10,000 CFU/100 ml in the high-conductivity well; enterococci and total suspended solids also increased, to a lesser degree. Toward the end of the pumping period, as much as 50% of the fecal coliforms were associated with suspended sediment. Irrigation of an up-gradient pine plantation with primary-treated wastewater is the probable source of the bacterial contamination. Sampling after a rain event revealed the strong influence of water quality of the adjacent Terrieu Creek on the ground water. Bacterial concentrations in the wells showed a rapid response to increased concentrations in the surface water, with fecal coliform concentrations in ground water ultimately reaching 60,000 CFU/100 ml. Up to 100% of the bacteria in the ground water was associated with suspended sediment at various times. The results of this investigation are evidence of the strong influence of surface water on ground water in karst terrain, including that of irrigation water. The large proportion of bacteria associated with particulates in the ground Water has important implications for public health, as bacteria associated with particulates may be more persistent and more difficult to inactivate. The

The Qtracer2 Program for Tracer-Breakthrough Curve Analysis for Tracer Tests in Karstic Aquifers and Other Hydrologic Systems (2002)

EPA Science Inventory

Tracer testing is generally regarded as the most reliable and efficient method of gathering surface and subsurface hydraulic information. This is especially true for karstic and fractured-rock aquifers. Qualitative tracing tests have been conventionally employed in most karst s...

Transport of free and particulate-associated bacteria in karst

NASA Astrophysics Data System (ADS)

Mahler, B. J.; Personné, J.-C.; Lods, G. F.; Drogue, C.

2000-12-01

Karst aquifers, because of their unique hydrogeologic characteristics, are extremely susceptible to contamination by pathogens. Here we present the results of an investigation of contamination of a karst aquifer by fecal indicator bacteria. Two wells intercepting zones with contrasting effective hydraulic conductivities, as determined by pump test, were monitored both during the dry season and in response to a rain event. Samples were also collected from the adjacent ephemeral surface stream, which is known to be impacted by an upstream wastewater treatment plant after rainfall. Whole water and suspended sediment samples were analyzed for fecal coliforms and enterococci. During the dry season, pumping over a 2-day period resulted in increases in concentrations of fecal coliforms to greater than 10,000 CFU/100 ml in the high-conductivity well; enterococci and total suspended solids also increased, to a lesser degree. Toward the end of the pumping period, as much as 50% of the fecal coliforms were associated with suspended sediment. Irrigation of an up-gradient pine plantation with primary-treated wastewater is the probable source of the bacterial contamination. Sampling after a rain event revealed the strong influence of water quality of the adjacent Terrieu Creek on the ground water. Bacterial concentrations in the wells showed a rapid response to increased concentrations in the surface water, with fecal coliform concentrations in ground water ultimately reaching 60,000 CFU/100 ml. Up to 100% of the bacteria in the ground water was associated with suspended sediment at various times. The results of this investigation are evidence of the strong influence of surface water on ground water in karst terrain, including that of irrigation water. The large proportion of bacteria associated with particulates in the ground water has important implications for public health, as bacteria associated with particulates may be more persistent and more difficult to inactivate. The

Distribution of effluent injected into the Boulder Zone of the Floridan aquifer system at the North District Wastewater Treatment Plant, southeastern Florida, 1997–2011

USGS Publications Warehouse

King, Jeffrey N.; Decker, Jeremy D.

2018-02-09

Nonhazardous, secondarily treated, domestic wastewater (effluent) has been injected about 1 kilometer below land surface into the Boulder Zone of the Floridan aquifer system at the North District Wastewater Treatment Plant in southeastern Florida. The Boulder Zone contains saline, nonpotable water. Effluent transport out of the injection zone is a risk of underground effluent injection. At the North District Wastewater Treatment Plant, injected effluent was detected outside the Boulder Zone. The U.S. Geological Survey, in cooperation with Miami-Dade Water and Sewer Department, investigated effluent transport from the Boulder Zone to overlying permeable zones in the Floridan aquifer system.One conceptual model is presented to explain the presence of effluent outside of the injection zone in which effluent injected into the Boulder Zone was transported to the Avon Park permeable zone, forced by buoyancy and injection pressure. In this conceptual model, effluent injected primarily into the Boulder Zone reaches a naturally occurring feature (a karst-collapse structure) near an injection well, through which the effluent is transported vertically upward to the uppermost major permeable zone of the Lower Floridan aquifer. The effluent is then transported laterally through the uppermost major permeable zone of the Lower Floridan aquifer to another naturally occurring feature northwest of the North District Wastewater Treatment Plant, through which it is then transported vertically upward into the Avon Park permeable zone. In addition, a leak within a monitoring well, between monitoring zones, allowed interflow between the Avon Park permeable zone and the Upper Floridan aquifer. A groundwater flow and effluent transport simulation of the hydrogeologic system at the North District Wastewater Treatment Plant, based on the hypothesized and non-unique conceptualization of the subsurface hydrogeology and flow system, generally replicated measured effluent constituent

Use of chemical and isotopic tracers to characterize the interactions between ground water and surface water in mantled karst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katz, B.G.; Davis, J.H.; Coplen, T.B.

1997-11-01

In the mantled karst terrane of northern Florida, the water quality of the Upper Floridan aquifer is influenced by the degree of connectivity between the aquifer and the surface. Chemical and isotopic analyses [{sup 18}O/{sup 16}O ({delta}{sup 18}O), {sup 2}H/{sup 1}H ({delta}D), {sup 13}C/{sup 12}C ({delta}{sup 13}C), tritium ({sup 3}H), and strontium-87/strontium-86 ({sup 87}Sr/{sup 86}Sr)] along with geochemical mass-balance modeling were used to identify the dominant hydrochemical processes that control the composition of ground water as it evolves downgradient in two systems. In one system, surface water enters the Upper Florida aquifer through a sinkhole located in the Northern Highlandsmore » physiographic unit. In the other system, surface water enters the aquifer through a sinkhole lake (Lake Bradford) in the Woodville Karst Plain. Differences in the composition of water isotopes ({delta}{sup 18}O and {delta}D) in rainfall, ground water, and surface water were used to develop mixing models of surface water (leakage of water to the Upper Floridan aquifer from a sinkhole lake and a sinkhole) and ground water. Using mass-balance calculations, based on differences in {delta}{sup 18}O and {delta}D, the proportion of lake water that mixed with meteoric water ranged from 7 to 86% in water from wells located in close proximity to lake Bradford. In deeper parts of the Upper Floridan aquifer, water enriched in {sup 18}O and D from five of 12 samples municipal wells indicated that recharge from a sinkhole (1 to 24%) and surface water with an evaporated isotopic signature (2 to 32%) was mixing with ground water. The solute isotopes, {delta}{sup 13}C and {sup 87}Sr/{sup 86}Sr, were used to test the sensitivity of binary and ternary mixing models, and to estimate the amount of mass transfer of carbon and other dissolved species in geochemical reactions.« less

Nitrate reduction mechanisms and rates in an unconfined eogenetic karst aquifer in two sites with different redox potential

NASA Astrophysics Data System (ADS)

Henson, W. R.; Huang, L.; Graham, W. D.; Ogram, A.

2017-05-01

This study integrates push-pull tracer tests (PPTT) with microbial characterization of extracted water via quantitative polymerase chain reaction (qPCR) and reverse transcriptase qPCR (RT-qPCR) of selected functional N transformation genes to quantify nitrate reduction mechanisms and rates in sites with different redox potential in a karst aquifer. PPTT treatments with nitrate (AN) and nitrate-fumarate (ANC) were executed in two wells representing anoxic and oxic geochemical end-members. Oxic aquifer zero-order nitrate loss rates (mmol L-1 h-1) were similar for AN and ANC treatment, ranging from 0.03 ± 0.01 to 0.05 ± 0.01. Anoxic aquifer zero-order nitrate loss rates ranged from 0.03 ± 0.02 (AN) to 0.13 ± 0.02 (ANC). Microbial characterization indicates mechanisms influencing these rates were dissimilatory nitrate reduction to ammonium (DNRA) at the anoxic site with AN treatment, assimilatory reduction of nitrate to ammonium (ANRA) with ANC treatment in the water column at both sites, and additional documented nitrate reduction that occurred in unsampled biofilms. With carbon treatment, total numbers of microbes (16S rRNA genes) significantly increased (fourteenfold to thirtyfold), supporting stimulated growth with resulting ANRA. Decreased DNRA gene concentrations (nrfA DNA) and increased DNRA activity ratio (nrfA-cDNA/DNA) supported the assertion that DNRA occurred in the anoxic zone with AN and ANC treatment. Furthermore, decreased DNRA gene copy numbers at the anoxic site with ANC treatment suggests that DNRA microbes in the anoxic site are chemolithoautotrophic. Increased RT-qPCR denitrification gene expression (nirK and nirS) was not observed in water samples, supporting that any observed NO3-N loss due to denitrification may be occurring in unsampled microbial biofilms.

Nitrate reduction mechanisms and rates in an unconfined eogenetic karst aquifer in two sites with different redox potential

USGS Publications Warehouse

Henson, Wesley; Huang, Laibin; Graham, Wendy D.; Ogram, Andrew

2017-01-01

This study integrates push-pull tracer tests (PPTT) with microbial characterization of extracted water via quantitative polymerase chain reaction (qPCR) and reverse transcriptase qPCR (RT-qPCR) of selected functional N transformation genes to quantify nitrate reduction mechanisms and rates in sites with different redox potential in a karst aquifer. PPTT treatments with nitrate (AN) and nitrate-fumarate (ANC) were executed in two wells representing anoxic and oxic geochemical end-members. Oxic aquifer zero-order nitrate loss rates (mmol L−1 h−1) were similar for AN and ANC treatment, ranging from 0.03 ± 0.01 to 0.05 ± 0.01. Anoxic aquifer zero-order nitrate loss rates ranged from 0.03 ± 0.02 (AN) to 0.13 ± 0.02 (ANC). Microbial characterization indicates mechanisms influencing these rates were dissimilatory nitrate reduction to ammonium (DNRA) at the anoxic site with AN treatment, assimilatory reduction of nitrate to ammonium (ANRA) with ANC treatment in the water column at both sites, and additional documented nitrate reduction that occurred in unsampled biofilms. With carbon treatment, total numbers of microbes (16S rRNA genes) significantly increased (fourteenfold to thirtyfold), supporting stimulated growth with resulting ANRA. Decreased DNRA gene concentrations (nrfA DNA) and increased DNRA activity ratio (nrfA-cDNA/DNA) supported the assertion that DNRA occurred in the anoxic zone with AN and ANC treatment. Furthermore, decreased DNRA gene copy numbers at the anoxic site with ANC treatment suggests that DNRA microbes in the anoxic site are chemolithoautotrophic. Increased RT-qPCR denitrification gene expression (nirK and nirS) was not observed in water samples, supporting that any observed NO3-N loss due to denitrification may be occurring in unsampled microbial biofilms.

Near-surface, marine seismic-reflection data defines potential hydrogeologic confinement bypass in a tertiary carbonate aquifer, southeastern Florida

USGS Publications Warehouse

Cunningham, Kevin J.; Walker, Cameron; Westcott, Richard L.

2012-01-01

Approximately 210 km of near-surface, high-frequency, marine seismic-reflection data were acquired on the southeastern part of the Florida Platform between 2007 and 2011. Many high-resolution, seismic-reflection profiles, interpretable to a depth of about 730 m, were collected on the shallow-marine shelf of southeastern Florida in water as shallow as 1 m. Landward of the present-day shelf-margin slope, these data image middle Eocene to Pleistocene strata and Paleocene to Pleistocene strata on the Miami Terrace. This high-resolution data set provides an opportunity to evaluate geologic structures that cut across confining units of the Paleocene to Oligocene-age carbonate rocks that form the Floridan aquifer system.Seismic profiles image two structural systems, tectonic faults and karst collapse structures, which breach confining beds in the Floridan aquifer system. Both structural systems may serve as pathways for vertical groundwater flow across relatively low-permeability carbonate strata that separate zones of regionally extensive high-permeability rocks in the Floridan aquifer system. The tectonic faults occur as normal and reverse faults, and collapse-related faults have normal throw. The most common fault occurrence delineated on the reflection profiles is associated with karst collapse structures. These high-frequency seismic data are providing high quality structural analogs to unprecedented depths on the southeastern Florida Platform. The analogs can be used for assessment of confinement of other carbonate aquifers and the sealing potential of deeper carbonate rocks associated with reservoirs around the world.

Opening the black box of spring water microbiology from alpine karst aquifers to support proactive drinking water resource management

PubMed Central

Savio, Domenico; Stadler, Philipp; Reischer, Georg H.; Kirschner, Alexander K.T.; Demeter, Katalin; Linke, Rita; Blaschke, Alfred P.; Sommer, Regina; Szewzyk, Ulrich; Wilhartitz, Inés C.; Mach, Robert L.; Stadler, Hermann

2018-01-01

Over the past 15 years, pioneering interdisciplinary research has been performed on the microbiology of hydrogeologically well‐defined alpine karst springs located in the Northern Calcareous Alps (NCA) of Austria. This article gives an overview on these activities and links them to other relevant research. Results from the NCA springs and comparable sites revealed that spring water harbors abundant natural microbial communities even in aquifers with high water residence times and the absence of immediate surface influence. Apparently, hydrogeology has a strong impact on the concentration and size of the observed microbes, and total cell counts (TCC) were suggested as a useful means for spring type classification. Measurement of microbial activities at the NCA springs revealed extremely low microbial growth rates in the base flow component of the studied spring waters and indicated the importance of biofilm‐associated microbial activities in sediments and on rock surfaces. Based on genetic analysis, the autochthonous microbial endokarst community (AMEC) versus transient microbial endokarst community (TMEC) concept was proposed for the NCA springs, and further details within this overview article are given to prompt its future evaluation. In this regard, it is well known that during high‐discharge situations, surface‐associated microbes and nutrients such as from soil habitats or human settlements—potentially containing fecal‐associated pathogens as the most critical water‐quality hazard—may be rapidly flushed into vulnerable karst aquifers. In this context, a framework for the comprehensive analysis of microbial pollution has been proposed for the NCA springs to support the sustainable management of drinking water safety in accordance with recent World Health Organization guidelines. Near‐real‐time online water quality monitoring, microbial source tracking (MST) and MST‐guided quantitative microbial‐risk assessment (QMRA) are examples of

Opening the black box of spring water microbiology from alpine karst aquifers to support proactive drinking water resource management.

PubMed

Savio, Domenico; Stadler, Philipp; Reischer, Georg H; Kirschner, Alexander K T; Demeter, Katalin; Linke, Rita; Blaschke, Alfred P; Sommer, Regina; Szewzyk, Ulrich; Wilhartitz, Inés C; Mach, Robert L; Stadler, Hermann; Farnleitner, Andreas H

2018-01-01

Over the past 15 years, pioneering interdisciplinary research has been performed on the microbiology of hydrogeologically well-defined alpine karst springs located in the Northern Calcareous Alps (NCA) of Austria. This article gives an overview on these activities and links them to other relevant research. Results from the NCA springs and comparable sites revealed that spring water harbors abundant natural microbial communities even in aquifers with high water residence times and the absence of immediate surface influence. Apparently, hydrogeology has a strong impact on the concentration and size of the observed microbes, and total cell counts (TCC) were suggested as a useful means for spring type classification. Measurement of microbial activities at the NCA springs revealed extremely low microbial growth rates in the base flow component of the studied spring waters and indicated the importance of biofilm-associated microbial activities in sediments and on rock surfaces. Based on genetic analysis, the autochthonous microbial endokarst community (AMEC) versus transient microbial endokarst community (TMEC) concept was proposed for the NCA springs, and further details within this overview article are given to prompt its future evaluation. In this regard, it is well known that during high-discharge situations, surface-associated microbes and nutrients such as from soil habitats or human settlements-potentially containing fecal-associated pathogens as the most critical water-quality hazard-may be rapidly flushed into vulnerable karst aquifers. In this context, a framework for the comprehensive analysis of microbial pollution has been proposed for the NCA springs to support the sustainable management of drinking water safety in accordance with recent World Health Organization guidelines. Near-real-time online water quality monitoring, microbial source tracking (MST) and MST-guided quantitative microbial-risk assessment (QMRA) are examples of the proposed analytical

Integrated monitoring technologies for the management of a Soil-Aquifer-Treatment (SAT) system.

NASA Astrophysics Data System (ADS)

Papadopoulos, Alexandros; Kallioras, Andreas; Kofakis, Petros; Bumberger, Jan; Schmidt, Felix; Athanasiou, Georgios; Uzunoglou, Nikolaos; Amditis, Angelos; Dietrich, Peter

2016-04-01

flow effects of the TDR/FDR sensors and (ii) monitoring of the water table within the shallow karst aquifer layer. The above technique will offer continuous monitoring of infiltration rates and identify possible mechanical or biological clogging effects. The monitoring system will be connected to an ad-hoc wireless network for continuous data transfer within the SAT facilities. It is envisaged that the development and combined application of all the above technologies will provide an integrated monitoring platform for the evaluation of SAT system performance.

Characterisation of the heterogeneity of karst using electrical geophysics - applications in SW China

NASA Astrophysics Data System (ADS)

Binley, A. M.; Cheng, Q.; Tao, M.; Chen, X.

2017-12-01

The southwest China karst region is one of the largest globally continuous karst areas. The great (structural, hydrological and geochemical) complexity of karstic environments and their rapidly evolving nature make them extremely vulnerable to natural and anthropogenic processes/activities. Characterising the location and properties of structures within the karst critical zone, and understanding how the landform is evolving is essential for the mitigation and adaption to locally- and globally-driven changes. Because of the specific nature of karst geology and geomorphology in the humid tropics and subtropics, spatial heterogeneity is high, evidenced by specific landforms features. Such heterogeneity leads to a high dynamic variability of hydrological processes in space and time, along with a complex exchange of surface water and groundwater. Investigating karst hydrogeological features is extremely challenging because of the three-dimensional nature of the system. Observations from boreholes can vary significantly over several metres, making conventional aquifer investigative methods limited. Geophysical methods have emerged as potentially powerful tools for hydrogeological investigations. Geophysical surveys can help to obtain more insight into the complex conduit networks and depth of weathering, both of which can provide quantitative information about the hydrological and hydrochemical dynamics of the system, in addition to providing a better understanding of how critical zone structures have been established and how the landscape is evolving. We present here results from recent geophysical field campaigns in SW China. We illustrate the effectiveness of electrical methods for mapping soil infil in epikarst and report results from field-based investigations along hillslope and valley transects. Our results reveal distinct zones of relatively high electrical conductivity to depths of tens of metres, which we attribute to localised increased fracture density. We

Fate of Organic Matters in a Soil Erosion Context : Qualitative and Quantitative Monitoring in a Karst Hydrosystem

NASA Astrophysics Data System (ADS)

Quiers, M.; Gateuille, D.; Perrette, Y.; Naffrechoux, E.; David, B.; Malet, E.

2017-12-01

Soils are a key compartments of hydrosystems, especially in karst aquifers which are characterized by fast hydrologic responses to rainfalls. In steady state, soils are efficient filters preventing karst water from pollutions. But agricultural or forestry land uses can alter or even reverse the role of soils. Thus , soils can act as pollution sources rather than pollution filters. In order to manage water quality together with man activities in karst environment, the development of new tools and procedures designed to monitor the fate of soil organic matter are needed. This study reports two complementary methods applied in a moutain karst system impacted by anthropic activities and environmental stresses. A continuous monitoring of water fluorescence coupled with punctual sampling was analyzed by chemiometric methods and allowed to discriminate the type of organic matter transferred through the karst system along the year (winter / summer) and hydrological stages. As a main result, the modelisation of organic carbone fluxes is dominated by a colloidal or particulate part during highwaters, and a main part dissolved in solution during low water, demonstrating the change of organic carbone source. To confirm this result, a second method was used based on the observation of Polycyclic Aromatic Hydrocarbons (PAH) profiles. Two previous studies (Perrette et al 2013, Schwarz et al 2011) led to opposite conclusions about the fate of PAH from soil to groundwaters. This opposition leads to a potential use of PAH profiles (low molecular weight less hydrophobic ones versus high molecular weight more hydrophobic ones) as an indicator of soil erosion. We validate that use by the anaylsis of these PAH profiles for low and high waters (floods). These results demonstrate if needed the high vulnerability of karst system to soil erosion, and propose a new proxy to record soils erosion in groundwaters and in natural archives as stalagmites or sediments.

Vulnerability of karst aquifers to agricultural contaminants: A case study in the Pennyroyal Plateau of Kentucky

USDA-ARS?s Scientific Manuscript database

Karst landscapes are common in many agricultural regions in the US. Well-developed karst landscapes are characterized by shallow soils, sinkholes, sinking streams, underground conduits, and springs. In these landscapes surface runoff is minimal and most recharge enters the subsurface relatively quic...

Seismic-sequence stratigraphy and geologic structure of the Floridan aquifer system near "Boulder Zone" deep wells in Miami-Dade County, Florida

USGS Publications Warehouse

Cunningham, Kevin J.

2015-01-01

In addition to the preceding seismic-reflection analysis, interpretation of geophysical well log data from four effluent injection wells at the North District “Boulder Zone” Well Field delineated a narrow karst collapse structure beneath the injection facility that extends upward about 900 ft from the top of the Boulder Zone to about 125 ft above the top of the uppermost major permeable zone of the Lower Floridan aquifer. No karst collapse structures were identified in the seismic-reflection profiles acquired near the North District “Boulder Zone” Well Field. However, karst collapse structures at the level of the lowermost major permeable zone of the Lower Floridan aquifer at the South District “Boulder Zone” Well Field are present at three locations, as indicated by seismic-reflection data acquired in the C–1 Canal bordering the south side of the injection facility. Results from the North District “Boulder Zone” Well Field well data indicate that a plausible hydraulic connection between faults and stratiform permeability zones may contribute to the upward transport of effluent, terminating above the base of the deepest U.S. Environmental Protection Agency designated underground source of drinking water at the North District “Boulder Zone” Well Field.

Speleogenesis in Dinaric karst area

NASA Astrophysics Data System (ADS)

Garasic, Mladen; Garasic, Davor

2015-04-01

remarkable variety in types of caves. It is estimated that the Dinaric Karst has at least 100,000 caves, only a fifth of which have been explored and suitably documented so far. Karst caves are truly unique by a variety of their types (dry caves, water caves, cave systems, shafts, spring caves, etc.), by their dimensions (the longest cave systems can reach over 100 km, the deepest ones are more than 1,430 metres deep), and by their great spatial frequency. In the Classical Karst, in area around the town Sežana and Fernetti/Fernetiči there are up to 60 caves/km2 - the number which is unprecedented. The great numbers of cave channels covered in dripstone, types of dripstone and its forms (stalactites, stalagmite, curtains, cave pearls, etc.) only contribute to this abundance. One should not forget the significance of cave sediments for scientific explorations. Their dating was used to determine the age of caves and scientifically explain the dynamics of karst evolution. Another important set of karst features are numerous submarine springs. This is the area where the science of karstology and speleology started to develop, where the basic ideas about the karstification processes (corrosion) and karst hydrology were born. The international term karst and the scientific investigation of karst originate in this region as well as many other international professional terms. Many words, describing karst features, originate from the Dinaric Karst Area, and belong to internationally accepted karst terminology (karst, dolina, polje, vrtača, ponikva, vrulja etc.). The word "karst" was first mentioned in Charter of Juraj Pariježić in 1230 in which "kras" locality near Dobrinj on the Island Krk in Croatia was subject of donation. The first written note that mentions the Italian word "Carso" dates back to the year 1292. In an Austrian document term "Karst" was cited for the first time in 1423. From the etymological point of view the word "Karst" is expression of Indo

Turbidity forecasting at a karst spring using combined machine learning and wavelet multiresolution analysis.

NASA Astrophysics Data System (ADS)

Savary, M.; Massei, N.; Johannet, A.; Dupont, J. P.; Hauchard, E.

2016-12-01

25% of the world populations drink water extracted from karst aquifer. The comprehension and the protection of these aquifers appear as crucial due to an increase of drinking water needs. In Normandie(North-West of France), the principal exploited aquifer is the chalk aquifer. The chalk aquifer highly karstified is an important water resource, regionally speaking. Connections between surface and underground waters thanks to karstification imply turbidity that decreases water quality. Both numerous parameters and phenomenons, and the non-linearity of the rainfall/turbidity relation influence the turbidity causing difficulties to model and forecast turbidity peaks. In this context, the Yport pumping well provides half of Le Havreconurbation drinking water supply (236 000 inhabitants). The aim of this work is thus to perform prediction of the turbidity peaks in order to help pumping well managers to decrease the impact of turbidity on water treatment. Database consists in hourly rainfalls coming from six rain gauges located on the alimentation basin since 2009 and hourly turbidity since 1993. Because of the lack of accurate physical description of the karst system and its surface basin, the systemic paradigm is chosen and a black box model: a neural network model is chosen. In a first step, correlation analyses are used to design the original model architecture by identifying the relation between output and input. The following optimization phases bring us four different architectures. These models were experimented to forecast 12h ahead turbidity and threshold surpassing. The first model is a simple multilayer perceptron. The second is a two-branches model designed to better represent the fast (rainfall) and low (evapotranspiration) dynamics. Each kind of model is developed using both a recurrent and feed-forward architecture. This work highlights that feed-forward multilayer perceptron is better to predict turbidity peaks when feed-forward two-branches model is

Regional aquifer systems

NASA Astrophysics Data System (ADS)

The fifth in the American Water Resources Association (AWRA) Monograph series “Regional Aquifer Systems of the United States” has just been published as Monograph Series No. 13, “Aquifers of the Midwestern Area,” edited by L. A. Swain and A. Ivan Johnson. The 238-page publication is available for $18 to AWRA members and $21 for nonmembers.Each AWRA Annual Conference since 1985 has sponsored special seminars describing hydrologic, geochemical, and geologic characteristics of the Regional Aquifer System Analysis (RASA) studies carried out by the U.S. Geological Survey

Hydrogeology of northern Sierra de Chiapas, Mexico: a conceptual model based on a geochemical characterization of sulfide-rich karst brackish springs

NASA Astrophysics Data System (ADS)

Rosales Lagarde, Laura; Boston, Penelope J.; Campbell, Andrew R.; Hose, Louise D.; Axen, Gary; Stafford, Kevin W.

2014-09-01

Conspicuous sulfide-rich karst springs flow from Cretaceous carbonates in northern Sierra de Chiapas, Mexico. This is a geologically complex, tropical karst area. The physical, geologic, hydrologic and chemical attributes of these springs were determined and integrated into a conceptual hydrogeologic model. A meteoric source and a recharge elevation below 1,500 m are estimated from the spring-water isotopic signature regardless of their chemical composition. Brackish spring water flows at a maximum depth of 2,000 m, as inferred from similar chemical attributes to the produced water from a nearby oil well. Oil reservoirs may be found at depths below 2,000 m. Three subsurface environments or aquifers are identified based on the B, Li+, K+ and SiO2 concentrations, spring water temperatures, and CO2 pressures. There is mixing between these aquifers. The aquifer designated Local is shallow and contains potable water vulnerable to pollution. The aquifer named Northern receives some brackish produced water. The composition of the Southern aquifer is influenced by halite dissolution enhanced at fault detachment surfaces. Epigenic speleogenesis is associated with the Local springs. In contrast, hypogenic speleogenesis is associated with the brackish sulfidic springs from the Northern and the Southern environments.

Karst medium characterization and simulation of groundwater flow in Lijiang Riversed, China

NASA Astrophysics Data System (ADS)

Hu, B. X.

2015-12-01

It is important to study water and carbon cycle processes for water resource management, pollution prevention and global warming influence on southwest karst region of China. Lijiang river basin is selected as our study region. Interdisciplinary field and laboratory experiments with various technologies are conducted to characterize the karst aquifers in detail. Key processes in the karst water cycle and carbon cycle are determined. Based on the MODFLOW-CFP model, new watershed flow and carbon cycle models are developed coupled subsurface and surface water flow models, flow and chemical/biological models. Our study is focused on the karst springshed in Mao village. The mechanisms coupling carbon cycle and water cycle are explored. Parallel computing technology is used to construct the numerical model for the carbon cycle and water cycle in the small scale watershed, which are calibrated and verified by field observations. The developed coupling model for the small scale watershed is extended to a large scale watershed considering the scale effect of model parameters and proper model structure simplification. The large scale watershed model is used to study water cycle and carbon cycle in Lijiang rivershed, and to calculate the carbon flux and carbon sinks in the Lijiang river basin. The study results provide scientific methods for water resources management and environmental protection in southwest karst region corresponding to global climate change. This study could provide basic theory and simulation method for geological carbon sequestration in China karst region.

Seasonal changes of organic matter quality and quantity at the outlet of a forested karst system (La Roche Saint Alban, French Alps)

NASA Astrophysics Data System (ADS)

Tissier, Grégory; Perrette, Yves; Dzikowski, Marc; Poulenard, Jérome; Hobléa, Fabien; Malet, Emmanuel; Fanget, Bernard

2013-03-01

SummaryBecause of its impact on water quality, organic matter (OM) in karst groundwater has been widely studied. The present article describes a method for monitoring OM in karst aquifers characterized by quick responses to rainfall. This method combines weekly manual sampling and continuous monitoring to provide, qualitative and quantitative information about OM flow. Weekly samples were analyzed for Total Organic Carbon (TOC) content and spectrofluorescence, while continuous monitoring was carried out at the main spring, using a field fluorimeter (310/400-700 nm and 280/300-600 nm) to quantify chromophoric organic matter (COM). The type and quantity of COM were defined by decomposing Excitation Emission Matrices (EEMs) and by applying a 2D fluorescence decomposition method. Continuous monitoring data showed that the dominant COM was humic-like (HL). We found three types of relationship between HL and discharge and between HL and TOC, showing that caution must be exercised when using field fluorimeter measurements to quantify TOC. Each relationship was characterized by global differences in OM content and by the presence of different percentages of non-chromophoric organic matter. These three relationships are associated with changes in hydrology and microorganism activity during the year. We used these relationships to estimate the annual OM flow (about 15 kg/ha/year) and thereby quantify OM flow during the year. Our results show the importance of the non-chromophoric organic matter in such estimation. That work illustrates the need to couple qualitative and quantitative monitoring of OM in karst spring to improve the global comprehension of karst system and of the sources implies in the OM flow.

Karst system vadose zone hydrodynamics highlighted by an integrative geophysical and hydrogeological monitoring

NASA Astrophysics Data System (ADS)

Watlet, A.; Van Camp, M. J.; Francis, O.; Poulain, A.; Hallet, V.; Rochez, G.; Kaufmann, O.

2015-12-01

The vadose zone of karst systems plays an important role on the water dynamics. In particular, temporary perched aquifers can appear in the subsurface due to changes of climate conditions, diminished evapotranspiration and differences of porosity relative to deeper layers. It is therefore crucial, but challenging, to separate the hydrological signature of the vadose zone from the one of the saturated zone for understanding hydrological processes that occur in the vadose zone. Although many difficulties are usually encountered when studying karst environments due to their heterogeneities, cave systems offer an outstanding opportunity to investigate vadose zone from the inside with various techniques. We present results covering two years of hydrogeological and geophysical monitoring at the Rochefort Cave Laboratory (RCL), located in the Variscan fold-and-thrust belt (Belgium), a region that shows many karstic networks within Devonian limestone units. Hydrogeological data such as flows and levels monitoring or tracer tests performed in both vadose and saturated zones bring valuable information on the hydrological context of the studied area. Combining those results with geophysical measurements allows validating and imaging them with more integrative techniques. A microgravimetric monitoring involves a superconducting gravimeter continuously measuring at the surface of the RCL. Early in 2015, a second relative gravimeter was installed in the underlying cave system located 35 meters below the surface. This set up allows highlighting vadose gravity changes. These relative measurements are calibrated using an absolute gravimeter. 12 additional stations (7 at the surface, 5 in the cave) are monitored on a monthly basis by a spring gravimeter. To complete these gravimetric measurements, the site has been equipped with a permanent Electrical Resistivity Tomography (ERT) monitoring system comprising an uncommon array of surface, borehole and cave electrodes. Although such

U-isotopes and (226)Ra as tracers of hydrogeochemical processes in carbonated karst aquifers from arid areas.

PubMed

Guerrero, José Luis; Vallejos, Ángela; Cerón, Juan Carlos; Sánchez-Martos, Francisco; Pulido-Bosch, Antonio; Bolívar, Juan Pedro

2016-07-01

Sierra de Gádor is a karst macrosystem with a highly complex geometry, located in southeastern Spain. In this arid environment, the main economic activities, agriculture and tourism, are supported by water resources from the Sierra de Gádor aquifer system. The aim of this work was to study the levels and behaviour of some of the most significant natural radionuclides in order to improve the knowledge of the hydrogeochemical processes involved in this groundwater system. For this study, 28 groundwater and 7 surface water samples were collected, and the activity concentrations of the natural U-isotopes ((238)U, (235)U and (234)U) and (226)Ra by alpha spectrometry were determined. The activity concentration of (238)U presented a large variation from around 1.1 to 65 mBq L(-1). Elevated groundwater U concentrations were the result of oxidising conditions that likely promoted U dissolution. The PHREEQC modelling code showed that dissolved U mainly existed as uranyl carbonate complexes. The (234)U/(238)U activity ratios were higher than unity for all samples (1.1-3.8). Additionally, these ratios were in greater disequilibrium in groundwater than surface water samples, the likely result of greater water-rock contact time. (226)Ra presented a wide range of activity concentrations, (0.8 up to about 4 × 10(2) mBq L(-1)); greatest concentrations were detected in the thermal area of Alhama. Most of the samples showed (226)Ra/(234)U activity ratios lower than unity (median = 0.3), likely the result of the greater mobility of U than Ra in the aquifer system. The natural U-isotopes concentrations were strongly correlated with dissolution of sulphate evaporites (mainly gypsum). (226)Ra had a more complex behaviour, showing a strong correlation with water salinity, which was particularly evident in locations where thermal anomalies were detected. The most saline samples showed the lowest (234)U/(238)U activity ratios, probably due to fast uniform bulk mineral dissolution

CO2 outgassing in a combined fracture and conduit karst aquifer near lititz spring, Pennsylvania

USGS Publications Warehouse

Toran, L.; Roman, E.

2006-01-01

Lititz Spring in southeastern Pennsylvania and a nearby domestic well were sampled for 9 months. Although both locations are connected to conduits (as evidenced by a tracer test), most of the year they were saturated with respect to calcite, which is more typical of matrix flow. Geochemical modeling (PHREEQC) was used to explain this apparent paradox and to infer changes in matrix and conduit contribution to flow. The saturation index varied from 0.5 to 0 most of the year, with a few samples in springtime dropping below saturation. The log PCO2 value varied from -2.5 to -1.7. Lower log PCO2 values (closer to the atmospheric value of -3.5) were observed when the solutions were at or above saturation with respect to calcite. In contrast, samples collected in the springtime had high PCO2, low saturation indices, and high water levels. Geochemical modeling showed that when outgassing occurs from a water with initially high PCO2, the saturation index of calcite increases. In the Lititz Spring area, the recharge water travels through the soil zone, where it picks up CO2 from soil gas, and excess CO 2 subsequently is outgassed when this recharge water reaches the conduit. At times of high water level (pipe full), recharge with excess CO 2 enters the system but the outgassing does not occur. Instead the recharge causes dilution, reducing the calcite saturation index. Understanding the temporal and spatial variation in matrix and conduit flow in karst aquifers benefited here by geochemical modeling and calculation of PCO2 values. ?? 2006 Geological Society of America.

Karst flash floods: an example from the Dinaric karst (Croatia)

NASA Astrophysics Data System (ADS)

Bonacci, O.; Ljubenkov, I.; Roje-Bonacci, T.

2006-03-01

Flash floods constitute one of the deadliest and costliest natural disasters worldwide. This paper explains the karst flash flood phenomenon, which represents a special kind of flash flood. As the majority of flash floods karst flash floods are caused by intensive short-term precipitation in an area whose surface rarely exceeds a few square kilometres. The characteristics of all flash floods are their short duration, small areal extent, high flood peaks and rapid flows, and heavy loss of life and property. Karst flash floods have specific characteristics due to special conditions for water circulation, which exist in karst terrains. During karst flash floods a sudden rise of groundwater levels occurs, which causes the appearance of numerous, unexpected, abundant and temporary karst springs. This paper presents in detail an example of a karst flash flood in the Marina bay (Dinaric karst region of Croatia), which occurred in December 2004.

Using stable isotopes and multi-spatial variable parameters in characterising the karstic aquifer of the Ajloun area, NW-Jordan - A case study of the Tanour and Rasoun springs

NASA Astrophysics Data System (ADS)

Hamdan, Ibraheem; Wiegand, Bettina; Ptak, Thomas; Licha, Tobias; Toll, Mathias; Margane, Armin; Sauter, Martin

2015-04-01

Key words: Karst systems, Groundwater vulnerability, Stable isotopes, Jordan. Water resources are extremely scarce in Jordan, which is considered as one of the poorest countries in the world with respect to water resources availability (UNDP 2014), with more than 90% of the country receiving less than 200 mm/year of rainfall (Al Kharadsheh et al. 2012). The most important aquifer for drinking-water purposes in Jordan is the upper Cretaceous limestone aquifer. The karstic springs of Tanour and Rasoun, located in the Ajloun governorate around 75 kilometres northwest of the capital of Amman, have been selected for this study. These springs are the main source for the local domestic water supply, with an average discharge between the years 2000 and 2012 of 200 m3/h and 60 m3/h, respectively (MWI, 2013). During the past few years, the water supply from these two springs had to be discontinued due to high contamination of the groundwater either by microbiological contaminants or by wastewater from local olive oil presses. This wastewater is locally called 'Zeebar'. Understanding of the karst aquifer system, the pathways and movement within the epikarst, and estimation of the travel and residence time within the aquifer is important for managing and evaluating the pollution risk, which affects the usability of groundwater for drinking purposes. For a better understanding of the karstic system and its behaviour, different methods are applied: 1. Analysis of the stable isotope composition of δ2H and δ18O during the winter season for both (a) Tanour and Rasoun groundwater, and (b) rainfall samples collected from several locations at different elevations within the catchment. 2. Analysis of major ion concentrations in groundwater of the Tanour and Rasoun springs. 3. Long-term measurements of different physico-chemical parameters from the Tanour and Rasoun springs (temperature, conductivity, turbidity, TOC, etc.) using multiparameter probes with telemetric data transfer. 4

Modeling daily discharge responses of a large karstic aquifer using soft computing methods: Artificial neural network and neuro-fuzzy

NASA Astrophysics Data System (ADS)

Kurtulus, Bedri; Razack, Moumtaz

2010-02-01

SummaryThis paper compares two methods for modeling karst aquifers, which are heterogeneous, highly non-linear, and hierarchical systems. There is a clear need to model these systems given the crucial role they play in water supply in many countries. In recent years, the main components of soft computing (fuzzy logic (FL), and Artificial Neural Networks, (ANNs)) have come to prevail in the modeling of complex non-linear systems in different scientific and technologic disciplines. In this study, Artificial Neural Networks and Adaptive Neuro-Fuzzy Interface System (ANFIS) methods were used for the prediction of daily discharge of karstic aquifers and their capability was compared. The approach was applied to 7 years of daily data of La Rochefoucauld karst system in south-western France. In order to predict the karst daily discharges, single-input (rainfall, piezometric level) vs. multiple-input (rainfall and piezometric level) series were used. In addition to these inputs, all models used measured or simulated discharges from the previous days with a specified delay. The models were designed in a Matlab™ environment. An automatic procedure was used to select the best calibrated models. Daily discharge predictions were then performed using the calibrated models. Comparing predicted and observed hydrographs indicates that both models (ANN and ANFIS) provide close predictions of the karst daily discharges. The summary statistics of both series (observed and predicted daily discharges) are comparable. The performance of both models is improved when the number of inputs is increased from one to two. The root mean square error between the observed and predicted series reaches a minimum for two-input models. However, the ANFIS model demonstrates a better performance than the ANN model to predict peak flow. The ANFIS approach demonstrates a better generalization capability and slightly higher performance than the ANN, especially for peak discharges.

Analysis of the maximum discharge of karst springs

NASA Astrophysics Data System (ADS)

Bonacci, Ognjen

2001-07-01

Analyses are presented of the conditions that limit the discharge of some karst springs. The large number of springs studied show that, under conditions of extremely intense precipitation, a maximum value exists for the discharge of the main springs in a catchment, independent of catchment size and the amount of precipitation. Outflow modelling of karst-spring discharge is not easily generalized and schematized due to numerous specific characteristics of karst-flow systems. A detailed examination of the published data on four karst springs identified the possible reasons for the limitation on the maximum flow rate: (1) limited size of the karst conduit; (2) pressure flow; (3) intercatchment overflow; (4) overflow from the main spring-flow system to intermittent springs within the same catchment; (5) water storage in the zone above the karst aquifer or epikarstic zone of the catchment; and (6) factors such as climate, soil and vegetation cover, and altitude and geology of the catchment area. The phenomenon of limited maximum-discharge capacity of karst springs is not included in rainfall-runoff process modelling, which is probably one of the main reasons for the present poor quality of karst hydrological modelling. Résumé. Les conditions qui limitent le débit de certaines sources karstiques sont présentées. Un grand nombre de sources étudiées montrent que, sous certaines conditions de précipitations extrêmement intenses, il existe une valeur maximale pour le débit des sources principales d'un bassin, indépendante des dimensions de ce bassin et de la hauteur de précipitation. La modélisation des débits d'exhaure d'une source karstique n'est pas facilement généralisable, ni schématisable, à cause des nombreuses caractéristiques spécifiques des écoulements souterrains karstiques. Un examen détaillé des données publiées concernant quatre sources karstiques permet d'identifier les raisons possibles de la limitation de l'écoulement maximal: (1

Karst geomorphology and hydrology of the Shenandoah Valley near Harrisonburg, Virginia

USGS Publications Warehouse

Doctor, Daniel H.; Orndorff, Wil; Maynard, Joel; Heller, Matthew J.; Casile, Gerolamo C.

2014-01-01

The karst of the central Shenandoah Valley has characteristics of both shallow and deep phreatic formation. This field guide focuses on the region around Harrisonburg, Virginia, where a number of these karst features and their associated geologic context can be examined. Ancient, widespread alluvial deposits cover much of the carbonate bedrock on the western side of the valley, where shallow karstification has resulted in classical fluviokarst development. However, in upland exposures of carbonate rock, isolated caves exist atop hills not affected by surface processes other than exposure during denudation. The upland caves contain phreatic deposits of calcite and fine-grained sediments. They lack any evidence of having been invaded by surface streams. Recent geologic mapping and LIDAR (light detection and ranging) elevation data have enabled interpretive association between bedrock structure, igneous intrusions, silicification and brecciation of host carbonate bedrock, and the location of several caves and karst springs. Geochemistry, water quality, and water temperature data support the broad categorization of springs into those affected primarily by shallow near-surface recharge, and those sourced deeper in the karst aquifer. The deep-seated karst formation occurred in the distant past where subvertical fracture and fault zones intersect thrust faults and/or cross-strike faults, enabling upwelling of deep-circulating meteoric groundwater. Most caves formed in such settings have been overprinted by later circulation of shallow groundwater, thus removing evidence of the history of earliest inception; however, several caves do preserve evidence of an earlier formation.

Assessing Spatio-temporal Variability of Karst Water Storage over Southwest China from GRACE and Reservoir Storage

NASA Astrophysics Data System (ADS)

Yao, C.; Luo, Z.; Lo, M. H.; Li, Q.

2016-12-01

This study assesses spatio-temporal variability of terrestrial water storage (TWS) over the world's largest karst aquifer with continuous coverage in Southwest China (SWC) from Gravity Recovery and Climate Experiment (GRACE), along with hydrological model outputs, precipitation and reservoir water level data. GRACE shows karst water increases for the period 2003/01-2014/06 with a total volume ranging from 29.0 to 49.1 km3, and observes an extremely wet condition in 2008/2009 caused by the increase in precipitation and Longtan Reservoir (LTR) storage. The subsequent two droughts in 2009/2010 and 2011 have resulted in significant aquifer water depletion, with abnormal karst water losses of 180.2±43.3 km3 and 269.8±34.6 km3 respectively. In particular, the sustained reduction in peaks of the LTR storage is associated with the long-term dry condition over the upper Pearl River. Nonseasonal karst TWS variations are considerably impacted by LTR impoundment in the post-dam period, especially for the impounding episode of autumn and the dry season of winter, with correlations of 0.71 and 0.93 between TWS and reservoir volume variations respectively. Additionally, the nonseasonal GRACE TWS deficit provides an alternative and valuable drought indicator for the study karst region since large differences exist in modeled soil moisture and drought indices. This study demonstrates that the combination of GRACE and other hydrological variables could be beneficial for studying karst hydrologic dynamics. Acknowledgments: This work was supported by the National Natural Science Foundation of China (Grant Nos. 41174020, 41131067, 41174021), the National Basic Research Program of China (973 Program) (Grant No. 2013CB733302), the Fundamental Research Funds for the Central Universities (Grant No. 2014214020203), the open fund of Key Laboratory of Geospace Environment and Geodesy, Ministry of Education (Grant No. 14-02-011), the open fund of Guangxi Key Laboratory of Spatial Information

Sequence stratigraphy, seismic stratigraphy, and seismic structures of the lower intermediate confining unit and most of the Floridan aquifer system, Broward County, Florida

USGS Publications Warehouse

Cunningham, Kevin J.; Kluesner, Jared W.; Westcott, Richard L.; Robinson, Edward; Walker, Cameron; Khan, Shakira A.

2017-12-08

��an approach never before applied to this area. Notably, the 3D geomodeling provided 3D visualizations and geocellular models of the depositional sequences, hydrostratigraphy, and structural features. The geocellular data could be used to update the hydrogeologic structure inherent to groundwater flow simulations that are designed to address the sustainability of the water resources of the Floridan aquifer system.Two kinds of pathways that could enable upward cross-formational flow of injected treated wastewater from the Boulder Zone have been identified in the 80 miles of high-resolution seismic data collected for this study: a near-vertical reverse fault and karst collapse structures. The single reverse fault, inferred to be of tectonic origin, is in extreme northeastern Broward County and has an offset of about 19 feet at the level of the Arcadia Formation. Most of the 17 karst collapse structures identified manifest as columniform, vertically stacked sagging seismic reflections that span early Eocene to Miocene age rocks equivalent to much of the Floridan aquifer system and the lower part of the overlying intermediate confining unit. In some cases, the seismic-sag structures extend upward into strata of Pliocene age. The seismic-sag structures are interpreted to have a semicircular shape in plan view on the basis of comparison to (1) other seismic-sag structures in southeastern Florida mapped with two 2D seismic cross lines or 3D data, (2) comparison to these structures located in other carbonate provinces, and (3) plausible extensional ring faults detected with multi-attribute analysis. The seismic-sag structures in the study area have heights as great as 2,500 vertical feet, though importantly, one spans about 7,800 feet. Both multi-attribute analysis and visual detection of offset of seismic reflections within the seismic-sag structures indicate faults and fractures are associated with many of the structures. Multi-attribute analysis highlighting chimney fluid pathways

Delineation and description of the regional aquifer systems of Tennessee; Cumberland Plateau aquifer system

USGS Publications Warehouse

Brahana, J.V.; Macy, J.A.; Mulderink, Dolores; Zemo, Dawn

1986-01-01

The Cumberland Plateau aquifer system consists of Pennsylvanian sandstones, conglomerates, shales, and coals which underlie the Cumberland Plateau in Tennessee. Major water-bearing zones occur within the sandstones and conglomerates in interconnected fractures. The water-bearing formations are separated by shale and siltstone that retard the vertical circulation of ground water, The Pennington Formation serves as the base of this aquifer system and is an effective confining unit, The Cumberland Plateau aquifer system is an important water source for the Cumberland Plateau, wells and springs from the aquifer system supply most of the rural domestic and public drinking-water supplies, water from wells drilled into the Cumberland Plateau aquifer system is generally of good to excellent quality. Of the 32 water-quality analyses on file from this aquifer. only 2 had dissolved-solids concentrations greater than 500 milligrams per liter, and about three-fourths had less than 200 milligrams per liter dissolved solids, However, no samples from depths greater than 300 feet below land surface have been recorded. Ground water from locations where the sandstones are buried deeply, such as the Wartburg basin, may contain dissolved-solids concentrations greater than 1,000 milligrams per liter.

Karst development in central Butler County, Kansas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bain, B.A.

1993-02-01

Research was conducted to study the geology and hydrology of sinkholes, springs, and caves formed in Lower Permian, Fort Riley Limestone, located in central Butler County, Kansas. The goal was to better understand the controlling factors of these karst features and the processes that produce them in a portion of Kansas that is undergoing rapid population growth and increased groundwater usage. Research was accomplished in seven phases: literature search, locating karst features, measuring bedrock fracture joint trends, surveying major caves, estimating discharge of springs, dye tracing, and water chemistry analysis. Recognizable karst landforms within the study area were plotted ontomore » a base map to demonstrate their geographic, geologic, and hydrologic relationships. Karst features identified were 125 sinkholes, a major cave system composed of at least three enterable cave segments, and one large spring. The karst terrain found within the study area is clearly a system of interrelated features and processes. Long-term solution of the bedrock allows karst features to form, joints and bedding planes to enlarge, and creates an efficient network of subsurface drainage. Factors that control karst development in the study area are lithology, thickness, and dip of the bedrock; presence of well defined joints and bedding planes; relatively level topography; nearby entrenched river valleys; lack of thick surficial cover; and climate. Of these influences, solutional activity at joints plays a major role in the formation of sinkholes and cave passages; however, a complex combination of all the controlling factors is responsible for the present, unique, and dynamic karst system.« less

Assessing lateral flows and solute transport during floods in a conduit-flow-dominated karst system using the inverse problem for the advection-diffusion equation

NASA Astrophysics Data System (ADS)

Cholet, Cybèle; Charlier, Jean-Baptiste; Moussa, Roger; Steinmann, Marc; Denimal, Sophie

2017-07-01

. From our results we build the functional scheme of the karst system. It demonstrates the impact of the saturated zone on matrix-conduit exchanges in this shallow phreatic aquifer and highlights the important role of the unsaturated zone on storage and transfer functions of the system.

Megaporosity and permeability of Thalassinoides-dominated ichnofabrics in the Cretaceous karst-carbonate Edwards-Trinity aquifer system, Texas

USGS Publications Warehouse

Cunningham, Kevin J.; Sukop, Michael C.

2012-01-01

Current research has demonstrated that trace fossils and their related ichnofabrics can have a critical impact on the fluid-flow properties of hydrocarbon reservoirs and groundwater aquifers. Most petroleum-associated research has used ichnofabrics to support the definition of depositional environments and reservoir quality, and has concentrated on siliciclastic reservoir characterization and, to a lesser degree, carbonate reservoir characterization (for example, Gerard and Bromley, 2008; Knaust, 2009). The use of ichnology in aquifer characterization has almost entirely been overlooked by the hydrologic community because the dynamic reservoir-characterization approach has not caught on with hydrologists and so hydrology is lagging behind reservoir engineering in this area (de Marsily and others, 2005). The objective of this research is to show that (1) ichnofabric analysis can offer a productive methodology for purposes of carbonate aquifer characterization, and (2) a clear relation can exist between ichnofabrics and groundwater flow in carbonate aquifers.

Spatial heterogeneities and variability of karst hydro-system : insights from geophysics

NASA Astrophysics Data System (ADS)

Champollion, C.; Fores, B.; Lesparre, N.; Frederic, N.

2017-12-01

Heterogeneous systems such as karsts or fractured hydro-systems are challenging for both scientist and groundwater resources management. Karsts heterogeneities prevent the comparison and moreover the combination of data representative of different scales: borehole water level can generally not be used directly to interpret spring flow dynamic for example. The spatial heterogeneity has also an impact on the temporal variability of groundwater transfer and storage. Karst hydro-systems have characteristic non linear relation between precipitation amount and discharge at the outlets with threshold effects and a large variability of groundwater transit times In the presentation, geophysical field experiments conducted in karst hydro-system in the south of France are used to investigate groundwater transfer and storage variability at a scale of a few hundred meters. We focus on the added value of both geophysical time-lapse gravity experiments and 2D ERT imaging of the subsurface heterogeneities. Both gravity and ERT results can only be interpreted with large ambiguity or some strong a priori: the relation between resistivity and water content is not unique; almost no information about the processes can be inferred from the groundwater stock variations. The present study demonstrate how the ERT and gravity field experiments can be interpreted together in a coherent scheme with less ambiguity. First the geological and hydro-meteorological context is presented. Then the ERT field experiment including the processing and the results are detailed in the section about geophysical imaging of the heterogeneities. The gravity double difference (S2D) time-lapse experiment is described in the section about geophysical monitoring of the temporal variability. The following discussion demonstrate the impact of both experiments on the interpretation in terms of processes and heterogeneities.

Characterization of the hydrogeology of the sacred Gihon Spring, Jerusalem: a deteriorating urban karst spring

NASA Astrophysics Data System (ADS)

Amiel, Ronit Benami; Grodek, Tamir; Frumkin, Amos

2010-09-01

The Gihon Spring, Jerusalem, is important for the major monotheistic religions. Its hydrogeology and hydrochemistry is studied here in order to understand urbanization effects on karst groundwater resources, and promote better water management. High-resolution monitoring of the spring discharge, temperature and electrical conductivity, was performed, together with chemical and bacterial analysis. All these 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, Na+ and K+ values (2.0 mS/cm, 130 and 50 mg/l respectively) are very high compared to other nearby springs located at the town margins (0.6 mS/cm, 15 and <1 mg/l respectively), indicating considerable urban pollution in the Gihon area. The previously cited pulsating nature of the spring was not detected during the present high-resolution monitoring. This phenomenon may have ceased due to additional water sources from urban leakage and irrigation feeding the spring. The urbanization of the recharge catchment thus affects the spring water dramatically, both chemically and hydrologically. Appropriate measures should therefore be undertaken to protect the Gihon Spring and other karst aquifers threatened by rapid urbanization.

Hydrogeologic and water-quality characteristics of the Upper Carbonate aquifer, Southeast Minnesota

USGS Publications Warehouse

Ruhl, J.F.; Wolf, R.J.

1983-01-01

The quality of water in the Upper Carbonate aquifer is suitable for most uses. However, the water is susceptible to contamination in karst areas because sinkholes and disappearing streams provide direct passageways for entry of contaminants into the aquifer. Calcium magnesium bicarbonate type waters are most common. Concentrations of dissolved solids and some major ions, specifically magnesium, sodium, bicarbonate, and sulfate, are generally highest in the southwestern part of the study area.

[Variation Characteristics and Sources of Heavy Metals in an Urban Karst Groundwater System during Rainfall Event].

PubMed

Ren, Kun; Yang, Ping-heng; Jiang, Ze-li; Wang, Zun-bo; Shi, Yang; Wang, Feng-kang; Li, Xiao-chun

2015-04-01

The groundwater discharge and heavy metal concentrations (Mn, Pb, Cu and As) at the outlet of Nanshan Laolongdong karst subterranean river, located at the urban region in Chongqing, were observed during the rainfall events. Analysis of flow and concentrations curves was employed to study their responses to the rainfall events and explore the internal structure of karst hydrological system. Principal component analysis (PCA) and measurements were used to identify the sources of heavy metals during rainfall. The result showed that the discharge and concentrations of the heavy metals responded promptly to the rainfall event. The variation characteristics of flow indicated that Laolongdong subterranean river system belonged to a karst hydrological system including fractures together with conduits. Urban surface runoff containing large amounts of Mn, Pb and Cu went directly to subterranean river via sinkholes, shafts and karst windows. As a result, the peak concentrations of contaminants (Mn, Pb and Cu) flowed faster than those of discharge. The major sources of water pollution were derived from urban surface runoff, soil and water loss. Cave dripwater and rainwater could also bring a certain amount of Mn, Pb and As into the subterranean river. Urban construction in karst areas needs scientific and rational design, perfect facilities and well-educated population to prevent groundwater pollution from the source.

Multiple technologies applied to characterization of the porosity and permeability of the Biscayne aquifer, Florida

USGS Publications Warehouse

Cunningham, K.J.; Sukop, M.C.

2011-01-01

Research is needed to determine how seepage-control actions planned by the Comprehensive Everglades Restoration Plan (CERP) will affect recharge, groundwater flow, and discharge within the dual-porosity karstic Biscayne aquifer where it extends eastward from the Everglades to Biscayne Bay. A key issue is whether the plan can be accomplished without causing urban flooding in adjacent populated areas and diminishing coastal freshwater flow needed in the restoration of the ecologic systems. Predictive simulation of groundwater flow is a prudent approach to understanding hydrologic change and potential ecologic impacts. A fundamental problem to simulation of karst groundwater flow is how best to represent aquifer heterogeneity. Currently, U.S. Geological Survey (USGS) researchers and academic partners are applying multiple innovative technologies to characterize the spatial distribution of porosity and permeability within the Biscayne aquifer.

Seismic Signals Recorded During Artificial and Natural Karst Recharge Events

NASA Astrophysics Data System (ADS)

Bilek, S. L.; Luhmann, A. J.; Diniakos, R. S.; Morton, E.; Rinehart, A. J.; Alexander, E. C., Jr.; Alexander, S. C.; Larsen, M.; Green, J. A.

2016-12-01

Seismology has recently been used to explore a variety of surficial processes, including tracking landslides, glaciers, and river flow. The seismic data collected can provide useful information about these flow processes, particularly in areas where other flow-related observations are difficult to make. Underground flow through karst aquifers is an area of significant interest, where most of the flow occurs through preferential flow conduits whose locations are largely unknown. We investigate seismic signals generated by both controlled and natural recharge into a karst aquifer system located near Bear Spring, near Eyota, MN, USA. The controlled recharge experiments involved injecting a pool full of water ( 13,000 L) into a dry overflow spring, which then flowed underground until it was discharged at Bear Spring. The natural recharge fortuitously involved a large rainstorm that supplied over 2 inches of rain in a few hour period, which caused the overflow spring to start flowing and total discharge to increase from a background of 100 L/s to 300 L/s. These events were recorded by 12 seismometers (11 short period and 1 broadband with 500 Hz sampling rate) all placed within the 4500 m2 area containing the dry overflow spring and predicted underground flow path. Spectrograms for the artificial and natural recharge events show significant seismic energy over a broad frequency range (few to nearly 220 Hz) during the periods of artificial recharge, largely contained during the period of water injection. Stations closest to Bear Spring see peak seismic energy in the 20-30 Hz range during these tests, likely related to changes in the underground water flow. During the natural recharge event, we find much longer duration of seismic energy over the broad frequency range. We compare these seismic results with discharge measurements conducted during all tests at Bear Spring, as well as with rainfall measurements recorded for the natural recharge event.

Hydrogeologic and geospatial data for the assesment of focused recharge to the Carbonate-Rock Aquifer in Genesee County, New York

USGS Publications Warehouse

Reddy, James E.; Kappel, William M.

2010-01-01

Existing hydrogeologic and geospatial data useful for the assessment of focused recharge to the carbonate-rock aquifer in the central part of Genesee County, NY, were compiled from numerous local, State, and Federal agency sources. Data sources utilized in this pilot study include available geospatial datasets from Federal and State agencies, interviews with local highway departments and the Genesee County Soil and Water Conservation District, and an initial assessment of karst features through the analysis of ortho-photographs, with minimal field verification. The compiled information is presented in a series of county-wide and quadrangle maps. The county-wide maps present generalized hydrogeologic conditions including distribution of geologic units, major faults, and karst features, and bedrock-surface and water-table configurations. Ten sets of quadrangle maps of the area that overlies the carbonate-rock aquifer present more detailed and additional information including distribution of bedrock outcrops, thin and (or) permeable soils, and karst features such as sinkholes and swallets. Water-resource managers can utilize the information summarized in this report as a guide to their assessment of focused recharge to, and the potential for surface contaminants to reach the carbonate-rock aquifer.

Characterization of aquifer heterogeneity using Cyclostratigraphy and geophysical methods in the upper part of the Karstic Biscayne Aquifer, Southeastern Florida

USGS Publications Warehouse

Cunningham, Kevin J.; Carlson, Janine L.; Wingard, G. Lynn; Robinson, Edward; Wacker, Michael A.

2004-01-01

This report identifies and characterizes candidate ground-water flow zones in the upper part of the shallow, eogenetic karst limestone of the Biscayne aquifer in the Lake Belt area of north-central Miami-Dade County using cyclostratigraphy, ground-penetrating radar (GPR), borehole geophysical logs, and continuously drilled cores. About 60 miles of GPR profiles were used to calculate depths to shallow geologic contacts and hydrogeologic units, image karst features, and produce qualitative views of the porosity distribution. Descriptions of the lithology, rock fabrics, and cyclostratigraphy, and interpretation of depositional environments of 50 test coreholes were linked to the geophysical interpretations to provide an accurate hydrogeologic framework. Molluscan and benthic foraminiferal paleontologic constraints guided interpretation of depositional environments represented by rockfabric facies. Digital borehole images were used to characterize and quantify large-scale vuggy porosity. Preliminary heat-pulse flowmeter data were coupled with the digital borehole image data to identify candidate ground-water flow zones. Combined results show that the porosity and permeability of the karst limestone of the Biscayne aquifer have a highly heterogeneous and anisotropic distribution that is mostly related to secondary porosity overprinting vertical stacking of rock-fabric facies within high-frequency cycles (HFCs). This distribution of porosity produces a dual-porosity system consisting of diffuse-carbonate and conduit flow zones. The nonuniform ground-water flow in the upper part of the Biscayne aquifer is mostly localized through secondary permeability, the result of solution-enlarged carbonate grains, depositional textures, bedding planes, cracks, root molds, and paleokarst surfaces. Many of the resulting pore types are classified as touching vugs. GPR, borehole geophysical logs, and whole-core analyses show that there is an empirical relation between formation porosity

A mathematical model for simulating spring discharge and estimating sinkhole porosity in a karst watershed

NASA Astrophysics Data System (ADS)

Li, Guangquan; Field, Malcolm S.

2014-03-01

Documenting and understanding water balances in a karst watershed in which groundwater and surface water resources are strongly interconnected are important aspects for managing regional water resources. Assessing water balances in karst watersheds can be difficult, however, because karst watersheds are so very strongly affected by groundwater flows through solution conduits that are often connected to one or more sinkholes. In this paper we develop a mathematical model to approximate sinkhole porosity from discharge at a downstream spring. The model represents a combination of a traditional linear reservoir model with turbulent hydrodynamics in the solution conduit connecting the downstream spring with the upstream sinkhole, which allows for the simulation of spring discharges and estimation of sinkhole porosity. Noting that spring discharge is an integral of all aspects of water storage and flow, it is mainly dependent on the behavior of the karst aquifer as a whole and can be adequately simulated using the analytical model described in this paper. The model is advantageous in that it obviates the need for a sophisticated numerical model that is much more costly to calibrate and operate. The model is demonstrated using the St. Marks River Watershed in northwestern Florida.

Agriculture and Karst in Kentucky

USDA-ARS?s Scientific Manuscript database

This publication describes the unique hydrologic and environmental issues found in karst environments. The publication describes karst landscapes, the importance of karst, different types of karst features, and how water moves through karst landscapes. The publication includes details on methods for...

Insights on surface-water/groundwater exchange in the upper Floridan aquifer, north-central Florida (USA), from streamflow data and numerical modeling

NASA Astrophysics Data System (ADS)

Sutton, James E.; Screaton, Elizabeth J.; Martin, Jonathan B.

2015-03-01

Surface-water/groundwater exchange impacts water quality and budgets. In karst aquifers, these exchanges also play an important role in dissolution. Five years of river discharge data were analyzed and a transient groundwater flow model was developed to evaluate large-scale temporal and spatial variations of exchange between an 80-km stretch of the Suwannee River in north-central Florida (USA) and the karstic upper Floridan aquifer. The one-layer transient groundwater flow model was calibrated using groundwater levels from 59 monitoring wells, and fluxes were compared to the exchange calculated from discharge data. Both the numerical modeling and the discharge analysis suggest that the Suwannee River loses water under both low- and high-stage conditions. River losses appear greatest at the inside of a large meander, and the former river water may continue across the meander within the aquifer rather than return to the river. In addition, the numerical model calibration reveals that aquifer transmissivity is elevated within this large meander, which is consistent with enhanced dissolution due to river losses. The results show the importance of temporal and spatial variations in head gradients to exchange between streams and karst aquifers and dissolution of the aquifers.

Geologic and climatic controls on streamflow generation processes in a complex eogenetic karst basin

NASA Astrophysics Data System (ADS)

Vibhava, F.; Graham, W. D.; Maxwell, R. M.

2012-12-01

Streamflow at any given location and time is representative of surface and subsurface contributions from various sources. The ability to fully identify the factors controlling these contributions is key to successfully understanding the transport of contaminants through the system. In this study we developed a fully integrated 3D surface water-groundwater-land surface model, PARFLOW, to evaluate geologic and climatic controls on streamflow generation processes in a complex eogenetic karst basin in North Central Florida. In addition to traditional model evaluation criterion, such as comparing field observations to model simulated streamflow and groundwater elevations, we quantitatively evaluated the model's predictions of surface-groundwater interactions over space and time using a suite of binary end-member mixing models that were developed using observed specific conductivity differences among surface and groundwater sources throughout the domain. Analysis of model predictions showed that geologic heterogeneity exerts a strong control on both streamflow generation processes and land atmospheric fluxes in this watershed. In the upper basin, where the karst aquifer is overlain by a thick confining layer, approximately 92% of streamflow is "young" event flow, produced by near stream rainfall. Throughout the upper basin the confining layer produces a persistent high surficial water table which results in high evapotranspiration, low groundwater recharge and thus negligible "inter-event" streamflow. In the lower basin, where the karst aquifer is unconfined, deeper water tables result in less evapotranspiration. Thus, over 80% of the streamflow is "old" subsurface flow produced by diffuse infiltration through the epikarst throughout the lower basin, and all surface contributions to streamflow originate in the upper confined basin. Climatic variability provides a secondary control on surface-subsurface and land-atmosphere fluxes, producing significant seasonal and

Use of sinkhole and specific capacity distributions to assess vertical gradients in a karst aquifer

USGS Publications Warehouse

McCoy, K.J.; Kozar, M.D.

2008-01-01

The carbonate-rock aquifer in the Great Valley, West Virginia, USA, was evaluated using a database of 687 sinkholes and 350 specific capacity tests to assess structural, lithologic, and topographic influences on the groundwater flow system. The enhanced permeability of the aquifer is characterized in part by the many sinkholes, springs, and solutionally enlarged fractures throughout the valley. Yet, vertical components of subsurface flow in this highly heterogeneous aquifer are currently not well understood. To address this problem, this study examines the apparent relation between geologic features of the aquifer and two spatial indices of enhanced permeability attributed to aquifer karstification: (1) the distribution of sinkholes and (2) the occurrence of wells with relatively high specific capacity. Statistical results indicate that sinkholes (funnel and collapse) occur primarily along cleavage and bedding planes parallel to subparallel to strike where lateral or downward vertical gradients are highest. Conversely, high specific capacity values are common along prominent joints perpendicular or oblique to strike. The similarity of the latter distribution to that of springs suggests these fractures are areas of upward-convergent flow. These differences between sinkhole and high specific capacity distributions suggest vertical flow components are primarily controlled by the orientation of geologic structure and associated subsurface fracturing. ?? 2007 Springer-Verlag.

Multi-tracer investigation of groundwater residence time in a karstic aquifer: Bitter Lakes National Wildlife Refuge, New Mexico, USA

NASA Astrophysics Data System (ADS)

Land, Lewis; Huff, G. F.

2010-03-01

Several natural and anthropogenic tracers have been used to evaluate groundwater residence time within a karstic limestone aquifer in southeastern New Mexico, USA. Natural groundwater discharge occurs in the lower Pecos Valley from a region of karst springs, wetlands and sinkhole lakes at Bitter Lakes National Wildlife Refuge, on the northeast margin of the Roswell Artesian Basin. The springs and sinkholes are formed in gypsum bedrock that serves as a leaky confining unit for an artesian aquifer in the underlying San Andres limestone. Because wetlands on the Refuge provide habitat for threatened and endangered species, there is concern about the potential for contamination by anthropogenic activity in the aquifer recharge area. Estimates of the time required for groundwater to travel through the artesian aquifer vary widely because of uncertainties regarding karst conduit flow. A better understanding of groundwater residence time is required to make informed decisions about management of water resources and wildlife habitat at Bitter Lakes. Results indicate that the artesian aquifer contains a significant component of water recharged within the last 10-50 years, combined with pre-modern groundwater originating from deeper underlying aquifers, some of which may be indirectly sourced from the high Sacramento Mountains to the west.

Multi-Tracer Investigation of Groundwater Residence Time in a Karstic Aquifer: Bitter Lakes National Wildlife Refuge, New Mexico, USA

NASA Astrophysics Data System (ADS)

Land, L. A.; Huff, R.

2009-12-01

Several natural and anthropogenic tracers are used to evaluate groundwater residence time within the karstic limestone aquifer of the Roswell Artesian Basin, southeastern New Mexico, USA. Natural groundwater discharge occurs in the lower Pecos Valley from a region of karst springs, wetlands and sinkhole lakes at Bitter Lakes National Wildlife Refuge. The springs and sinkholes are formed in gypsum bedrock that serves as a leaky confining unit for an artesian aquifer in the underlying San Andres limestone. Because wetlands on the Refuge provide habitat for a number of threatened and endangered species, Refuge managers have expressed concern about the potential for contamination by anthropogenic activity in the aquifer recharge area. Estimates of the time required for groundwater to travel through the artesian aquifer vary widely because of uncertainties regarding the role of karst conduit flow. A better understanding of groundwater residence time is thus required to make informed decisions about management of water resources and wildlife habitat at Bitter Lakes. Results of tracer investigations indicate that the artesian aquifer contains a significant component of water recharged within the last 10 to 50 years, combined with pre-modern groundwater originating from deeper underlying aquifers, some of which may be indirectly sourced from the high Sacramento Mountains to the west.

Organic micro-pollutants in a karst system during low and high flow periods, results of a two-year study

NASA Astrophysics Data System (ADS)

Reh, Roland; Licha, Tobias; Geyer, Tobias; Nödler, Karsten; Sauter, Martin

2013-04-01

and desethylatrazine, indicates limited aquifer connections and demonstrates a residence time of several years for vertical transport into the deep aquifer. Phenazone originates also from a disused waste disposal and is showing a persistency for more than three decades under the observed redox conditions. References Nödler K, Licha T, Bester K, Sauter M. Development of a multi-residue analytical method, based on liquid chromatography-tandem mass spectrometry, for the simultaneous determination of 46 micro-contaminants in aqueous samples. Journal of Chromatography A 2010;1217(42), 6511-6521. Reh R, Licha T, Geyer T, Nödler, K.,Sauter M. Occurrence and spatial distribution of organic micro-pollutants in a complex hydrogeological karst system during low flow and high flow periods, results of a two-year study. Science of The Total Environment 2013, 443,438-445, 10.1016/j.scitotenv.2012.11.005.

Charaterising water-rock interaction in a mixed carbonate-evaporite karstified aquifer system, Qatar

NASA Astrophysics Data System (ADS)

Thirathititham, R.; Whitaker, F.

2017-12-01

Qatar is an arid country, most of the rainfall (80 mm/yr) occurring during intense storms. Surface runoff is endorheic and recharge is facilitated by karst features developed over an extended (c.30 Ma) period of exposure of the carbonate bedrock. In December 2016, we sampled a rare intense rainfall event (41 mm over 3 days), after which waters ponded within low-relief terminal depressions prior to infiltration. We compare the chemistry of these recharge waters with that of ground waters from 76 wells distributed across Qatar to understand the nature and spatial distribution of water-rock interaction. Using Cl- as a conservative tracer for seawater mixing, we calculate concentrations of rock-derived Ca2+, Mg2+ and SO42-. During surface detention, rain chemistry is modified by evaporation and interaction with clays and the surface bedrock over days to weeks. However, groundwater chemistry is dominated by subsurface interaction between recharge waters and the karstified Tertiary aquifers. These include the largely dolomitic Paleocene to Lower Eocene Umm er Radhuma (UER) and overlying Lower Eocene Rus, with the Middle Eocene Abarug limestone forming a locally important aquifer in the south west. Away from coastal areas which show clear evidence of salinisation, TDS of groundwaters in the interior of the peninsula increases from north to south. All groundwaters are significantly enriched in SO42-, but this enrichment is marked greater in the south. This likely reflects the presence of a unit of middle Rus gypsum that in the south of the country confines the Lower Rus and UER aquifers, whilst in the north either gypsum was not deposited or has been dissolved. Waters in the Abarug limestone show limited sulfate enrichment and a 1:1 molar ratio of rock-derived SO42-: Ca2+, but across much of the country both SO42- enrichment and SO42-: Ca2+ molar ratio are significantly higher, the latter reaching 2:1 and suggesting an additional sink for Ca2+. The dolomite aquifer waters

Geohydrologic systems in Kansas, geohydrology of the upper aquifer unit in the western interior plains aquifer system

USGS Publications Warehouse

Kenny, J.F.; Wolf, R.J.; Hansen, Cristi V.

1993-01-01

The purpose of the investigation is to provide a description of the principal geohydrologic systems in Upper Cambrian through Lower Cretaceous rocks in Kansas. This investigation was made as part of the Central Midwest Regional Aquifer-System Analysis (CMRASA). The CMRASA is one of several major investigations by the U.S. Geological Survey of regional aquifer systems in the United States. These regional investigations are designed to increase knowledge of the flow regime and hydrologic properties of major aquifer systems and to provide quantitative information for the assessment, development, and management of water supplies. The CMRASA study area includes all or parts of 10 Central Midwestern States (Jorgensen and Signor, 1981), as shown of the envelope cover,This Hydrologic Investigations Atlas, which consists of a series of chapters, presents a description of the physical framework and geohydrology of principal aquifers and confining systems in Kansas. Chapter H presents the geohydrology of the upper aquifer unit in the Western Interior Plains aquifer system. The physical framework of the aquifer system in relation to other systems is described by maps and sections showing areal extent and the thickness of rocks that compose the unit. The physical framework of the upper aquifer unit is described in detail in chapter D of the atlas (Hansen and others, in press). The hydrology of the system in relation to that of other systems is described in this chapter by maps showing the altitude of fluid levels and the direction of water movement within the unit. The chemical composition of water in the system is described by maps that show the distribution of dissolved-solids concentrations and the differences in water types on the basis of principal chemical constituents. Chapter A of this atlas series (Wolf and others, 1990) describes the relation of principal geohydrologic systems in Kansas and presents a more detailed discussion of the methods and data used to prepare

Geohydrologic Framework of the Edwards and Trinity Aquifers, South-Central Texas

USGS Publications Warehouse

Blome, Charles D.; Faith, Jason R.; Ozuna, George B.

2007-01-01

This five-year USGS project, funded by the National Cooperative Geologic Mapping Program, is using multidisciplinary approaches to reveal the surface and subsurface geologic architecture of two important Texas aquifers: (1) the Edwards aquifer that extends from south of Austin to west of San Antonio and (2) the southern part of the Trinity aquifer in the Texas Hill Country west and south of Austin. The project's principal areas of research include: Geologic Mapping, Geophysical Surveys, Geochronology, Three-dimensional Modeling, and Noble Gas Geochemistry. The Edwards aquifer is one of the most productive carbonate aquifers in the United States. It also has been designated a sole source aquifer by the U.S. Environmental Protection Agency and is the primary source of water for San Antonio, America's eighth largest city. The Trinity aquifer forms the catchment area for the Edwards aquifer and it intercepts some surface flow above the Edwards recharge zone. The Trinity may also contribute to the Edwards water budget by subsurface flow across formation boundaries at considerable depths. Dissolution, karst development, and faulting and fracturing in both aquifers directly control aquifer geometry by compartmentalizing the aquifer and creating unique ground-water flow paths.

Hydrological deformation signals in karst systems: new evidence from the European Alps

NASA Astrophysics Data System (ADS)

Serpelloni, E.; Pintori, F.; Gualandi, A.; Scoccimarro, E.; Cavaliere, A.; Anderlini, L.; Belardinelli, M. E.; Todesco, M.

2017-12-01

The influence of rainfall on crustal deformation has been described at local scales, using tilt and strain meters, in several tectonic settings. However, the literature on the spatial extent of rainfall-induced deformation is still scarce. We analyzed 10 years of displacement time-series from 150 continuous GPS stations operating across the broad zone of deformation accommodating the N-S Adria-Eurasia convergence and the E-ward escape of the Eastern Alps toward the Pannonian basin. We applied a blind-source-separation algorithm based on a variational Bayesian Independent Component Analysis method to the de-trended time-series, being able to characterize the temporal and spatial features of several deformation signals. The most important ones are a common mode annual signal, with spatially uniform response in the vertical and horizontal components and a time-variable, non-cyclic, signal characterized by a spatially variable response in the horizontal components, with stations moving (up to 8 mm) in the opposite directions, reversing the sense of movement in time. This implies a succession of extensional/compressional strains, with variable amplitudes through time, oriented normal to rock fractures in karst areas. While seasonal displacements in the vertical component (with an average amplitude of 4 mm over the study area) are satisfactorily reproduced by surface hydrological loading, estimated from global assimilation models, the non seasonal signal is associated with groundwater flow in karst systems, and is mainly influencing the horizontal component. The temporal evolution of this deformation signal is correlated with cumulated precipitation values over periods of 200-300 days. This horizontal deformation can be explained by pressure changes associated with variable water levels within vertical fractures in the vadose zones of karst systems, and the water level changes required to open or close these fractures are consistent with the fluctuations of precipitation

Geohydrologic systems in Kansas physical framework of the upper aquifer unit in the western interior plains aquifer system

USGS Publications Warehouse

Hansen, Cristi V.; Spinazola, Joseph M.; Underwood, E.J.; Wolf, R.J.

1992-01-01

The purpose of this Hydrologic Investigations Atlas is to provide a description of the principal geohydrologic systems in Upper Cambrian through Lower Cretaceous rocks in Kansas. This investigation was made as part of the Central Midwest Regional Aquifer-System Analysis (CMRASA). The CMRASA is one of several major investigations by the U.S. Geological Survey of regional aquifer systems in the United States. These regional investigations are designed to increase knowledge of the flow regime and hydrologic properties of major aquifer systems and to provide quantitative information for the assessment, development, and management water supplies. The CMRASA study area includes all or parts of 10 Central Midwestern States (Jorgensen and Signor, 1981), as shown on the envelope cover.This Hydrologic Investigations Atlas, which consists of a series of nine chapters, presents a description of the physical framework and the geohydrology of principal aquifers and confining systems in Kansas. Chapter D presents maps that show the areal extent, altitude and configuration of the top, and thickness of Mississippian rocks that compose the upper aquifer unit of the Western Interior Plains aquifer system in Kansas, The chapter is limited to the presentation of the physical framework of the upper aquifer unit. The interpretation of the physical framework of the upper aquifer unit is based on selected geophysical and lithologic logs and published maps of stratigraphically equivalent units. Maps indicating the thickness and the altitude and configuration of the top of the upper aquifer unit in the Western Interior Plains aquifer system have been prepared as part of a series of interrelated maps that describe the stratigraphic interval from the Precambrian basement through Lower Cretaceous rocks. A concerted effort was made to ensure that maps of each geohydrologic unit are consistent with the maps of underlying and overlying units. Chapter A of this atlas series (Wolf and others, 1990

Determination of anisotropic karst features in the Biscayne Aquifer using multi electrical resistivity imaging techniques

NASA Astrophysics Data System (ADS)

Yeboah-Forson, A.; Whitman, D.

2012-12-01

The Biscayne Aquifer of Southeast Florida is characterized by limestone cavities and solution hole features that are often beneath the surface and are difficult to detect and quantify accurately. Electrical resistivity imaging (ERI) is often used to image the subsurface for detection of cavities and other karst features. A recent regional study of electrical anisotropy derived from rotated square array measurements measured coefficients of anisotropy of 1.12 or less. At one particular site however, the coefficient of anisotropy was found to be as high as 1.36 with the average minimum resistivity direction trending 105°. The highest values of anisotropy are found at squares array sizes equivalent to effective depths of 4-9m. The cause of this higher anisotropy and its associated orientation was investigated using a combination of azimuthal 2-D profiles and a 3-D tomography survey using a mixed dipole gradient array. Results indicate a low resistivity zone at a depth of 5-10 m in the saturated zone (10-40Ωm) trending 109° in the 2-D profiles and the presence of low resistivity zone (14-43Ωm) trending 90-105° in the 3-D model. This observed lower resistivity zone is at least 50% lower than the surrounding resistivity. Although further geophysical studies are planned at the site, the primary analysis from these three contrasting ERI techniques indicates that the cause of higher anisotropy might be due to the presence of a solution cavity oriented in the E-SE direction.

U.S. Geological Survey Karst Interest Group Proceedings, Fayetteville, Arkansas, April 26-29, 2011

USGS Publications Warehouse

Kuniansky, Eve L.

2011-01-01

This fifth workshop is a joint workshop of the USGS Karst Interest Group and University of Arkansas HydroDays workshop, sponsored by the USGS, the Department of Geosciences at the University of Arkansas in Fayetteville. Additional sponsors are: the National Cave and Karst Research Institute, the Edwards Aquifer Authority, San Antonio, Texas, and Beaver Water District, northwest Arkansas. The majority of funding for the proceedings preparation and workshop was provided by the USGS Groundwater Resources Program, National Cooperative Mapping Program, and the Regional Executives of the Northeast, Southeast, Midwest, South Central and Rocky Mountain Areas. The University of Arkansas provided the rooms and facilities for the technical and poster presentations of the workshop, vans for the field trips, and sponsored the HydroDays banquet at the Savoy Experimental Watershed on Wednesday after the technical sessions.

Geophysical imaging of karst features in Missouri

NASA Astrophysics Data System (ADS)

Obi, Jeremiah Chukwunonso

Automated electrical resistivity tomography (ERT) supported with multichannel analysis of surface waves (MASW) and boring data were used to map karst related features in Missouri in order to understand karst processes better in Missouri. Previous works on karst in Missouri were mostly surficial mapping of bedrock outcrops and joints, which are not enough to define the internal structure of karst system, since most critical processes in karst occur underground. To understand these processes better, the density, placement and pattern of karst related features like solution-widened joints and voids, as well as top of bedrock were mapped. In the course of the study, six study sites were visited in Missouri. The sites were in Nixa, Gasconade River Bridge in Lebanon, Battlefield, Aurora, Protem and Richland. The case studies reflect to a large extent some of the problems inherent in karst terrain, ranging from environmental problems to structural problems especially sinkhole collapses. The result of the study showed that karst in Missouri is mostly formed as a result of piping of sediments through solution-widened joints, with a pattern showing that the joints/fractures are mostly filled with moist clay-sized materials of low resistivity values. The highest density of mapped solution-widened joints was one in every one hundred and fifty feet, and these areas are where intense dissolution is taking place, and bedrock pervasively fractured. The study also showed that interpreted solution-widened joints trend in different directions, and often times conform with known structural lineaments in the area. About 40% of sinkhole collapses in the study areas are anthropogenic. Karst in Missouri varies, and can be classified as a combination of kI (juvenile), kIII (mature) and kIV (complex) karsts.

Hydrogeology of an alpine rockfall aquifer system and its role in flood attenuation and maintaining baseflow

NASA Astrophysics Data System (ADS)

Lauber, U.; Kotyla, P.; Morche, D.; Goldscheider, N.

2014-06-01

The frequency and intensity of extreme hydrological events in alpine regions is projected to increase with climate change. The goal of this study was to better understand the functioning of aquifers composed of complex alluvial and rockfall deposits in alpine valleys and to quantify the role of these natural storage spaces in flood attenuation and baseflow maintenance. Geomorphological and hydrogeological mapping, tracer tests, and continuous flow measurements were conducted in the Reintal valley (German Alps), where runoff from a karst spring infiltrates into a series of postglacial alluvial/rockfall aquifers. During high-flow conditions, groundwater velocities of 30 m h-1 were determined along 500 m; hydrograph analyses revealed short lag times (5 h) between discharge peaks upstream and downstream from the aquifer series; the maximum discharge ratio downstream (22) and the peak recession coefficient (0.196 d-1) are low compared with other alpine catchments. During low-flow conditions, the underground flow path length increased to 2 km and groundwater velocities decreased to 13 m h-1. Downstream hydrographs revealed a delayed discharge response after 101 h and peaks dampened by a factor of 1.5. These results indicate that alluvial/rockfall aquifers might play an important role in the flow regime and attenuation of floods in alpine regions.

Hydrogeology of an Alpine rockfall aquifer system and its role in flood attenuation and maintaining baseflow

NASA Astrophysics Data System (ADS)

Lauber, U.; Kotyla, P.; Morche, D.; Goldscheider, N.

2014-11-01

The frequency and intensity of extreme hydrological events in Alpine regions is projected to increase with climate change. The goal of this study is to better understand the functioning of aquifers composed of complex alluvial and rockfall deposits in Alpine valleys and to quantify the role of these natural storage spaces in flood attenuation and baseflow maintenance. Geomorphological and hydrogeological mapping, tracer tests, and continuous flow measurements were conducted in the Reintal (German Alps), where runoff from a karst spring infiltrates a series of postglacial alluvial/rockfall aquifers. During high-flow conditions, groundwater velocities of 30 m h-1 were determined along 500 m; hydrograph analyses revealed short lag times (5 h) between discharge peaks upstream and downstream from the aquifer series; the maximum discharge ratio downstream (22) and the peak recession coefficient (0.196 d-1) are low compared with other Alpine catchments. During low-flow conditions, the underground flow path length increased to 2 km and groundwater velocities decreased to 13 m h-1. Downstream hydrographs revealed a delayed discharge response after 101 h and peaks damped by a factor of 1.5. These results indicate that alluvial/rockfall aquifers might play an important role in the flow regime and attenuation of floods in Alpine regions.

Conceptualization of Karstic Aquifer with Multiple Outlets Using a Dual Porosity Model.

PubMed

Hosseini, Seiyed Mossa; Ataie-Ashtiani, Behzad

2017-07-01

In this study, two conceptual models, the classic reservoir (CR) model and exchange reservoirs model embedded by dual porosity approach (DPR) are developed for simulation of karst aquifer functioning drained by multiple outlets. The performances of two developed models are demonstrated at a less developed karstic aquifer with three spring outlets located in Zagros Mountain in the south-west of Iran using 22-years of daily data. During the surface recharge, a production function based on water mass balance is implemented for computing the time series of surface recharge to the karst formations. The efficiency of both models has been assessed for simulation of daily spring discharge during the recession and also surface recharge periods. Results indicate that both CR and DPR models are capable of simulating the ordinates of spring hydrographs which drainage less developed karstic aquifer. However, the goodness of fit criteria indicates outperformance of DPR model for simulation of total hydrograph ordinates. In addition, the DPR model is capable of quantifying hydraulic properties of two hydrologically connected overlapping continua conduits network and fissure matrix which lays important foundations for the mining operation and water resource management whereas homogeneous model representations of the karstic subsurface (e.g., the CR) do not work accurately in the karstic environment. © 2017, National Ground Water Association.

Recharge estimation in semi-arid karst catchments: Central West Bank, Palestine

NASA Astrophysics Data System (ADS)

Jebreen, Hassan; Wohnlich, Stefan; Wisotzky, Frank; Banning, Andre; Niedermayr, Andrea; Ghanem, Marwan

2018-03-01

Knowledge of groundwater recharge constitutes a valuable tool for sustainable management in karst systems. In this respect, a quantitative evaluation of groundwater recharge can be considered a pre-requisite for the optimal operation of groundwater resources systems, particular for semi-arid areas. This paper demonstrates the processes affecting recharge in Palestine aquifers. The Central Western Catchment is one of the main water supply sources in the West Bank. Quantification of potential recharge rates are estimated using chloride mass balance (CMB) and empirical recharge equations over the catchment. The results showing the spatialized recharge rate, which ranges from 111-216 mm/year, representing 19-37% of the long-term mean annual rainfall. Using Water Balance models and climatological data (e. g. solar radiation, monthly temperature, average monthly relative humidity and precipitation), actual evapotranspiration (AET) is estimated. The mean annual actual evapotranspiration was about 66-70% of precipitation.

Use of chemical and isotopic tracers to characterize the interactions between ground water and surface water in mantled karst

USGS Publications Warehouse

Katz, B.G.; Coplen, T.B.; Bullen, T.D.; Hal, Davis J.

1997-01-01

In the mantled karst terrane of northern Florida, the water quality of the Upper Floridan aquifer is influenced by the degree of connectivity between the aquifer and the surface. Chemical and isotopic analyses [18O/16O (??18O), 2H/1H (??D), 13C/12C (??13C), tritium(3H), and strontium-87/strontium-86(87Sr/86Sr)]along with geochemical mass-balance modeling were used to identify the dominant hydrochemical processes that control the composition of ground water as it evolves downgradient in two systems. In one system, surface water enters the Upper Floridan aquifer through a sinkhole located in the Northern Highlands physiographic unit. In the other system, surface water enters the aquifer through a sinkhole lake (Lake Bradford) in the Woodville Karst Plain. Differences in the composition of water isotopes (??18O and ??D) in rainfall, ground water, and surface water were used to develop mixing models of surface water (leakage of water to the Upper Floridan aquifer from a sinkhole lake and a sinkhole) and ground water. Using mass-balance calculations, based on differences in ??18O and ??D, the proportion of lake water that mixed with meteoric water ranged from 7 to 86% in water from wells located in close proximity to Lake Bradford. In deeper parts of the Upper Floridan aquifer, water enriched in 18O and D from five of 12 sampled municipal wells indicated that recharge from a sinkhole (1 to 24%) and surface water with an evaporated isotopic signature (2 to 32%) was mixing with ground water. The solute isotopes, ??13C and 87Sr/86Sr, were used to test the sensitivity of binary and ternary mixing models, and to estimate the amount of mass transfer of carbon and other dissolved species in geochemical reactions. In ground water downgradient from Lake Bradford, the dominant processes controlling carbon cycling in ground water were dissolution of carbonate minerals, aerobic degradation of organic matter, and hydrolysis of silicate minerals. In the deeper parts of the Upper

NMR imaging of fluid exchange between macropores and matrix in eogenetic karst

USGS Publications Warehouse

Florea, L.J.; Cunningham, K.J.; Altobelli, S.

2009-01-01

Sequential time-step images acquired using nuclear magnetic resonance (NMR) show the displacement of deuterated water (D2O) by fresh water within two limestone samples characterized by a porous and permeable limestone matrix of peloids and ooids. These samples were selected because they have a macropore system representative of some parts of the eogenetic karst limestone of the Biscayne Aquifer in southeastern Florida. The macroporosity, created by the trace fossil Ophiomorpha, is principally well connected and of centimeter scale. These macropores occur in broadly continuous stratiform zones that create preferential flow layers within the hydrogeologic units of the Biscayne. This arrangement of porosity is important because in coastal areas, it could produce a preferential pathway for salt water intrusion. Two experiments were conducted in which samples saturated with D2O were placed in acrylic chambers filled with fresh water and examined with NMR. Results reveal a substantial flux of fresh water into the matrix porosity with a simultaneous loss of D 2O. Specifically, we measured rates upward of 0.001 mL/h/g of sample in static conditions, and perhaps as great as 0.07 mL/h/g of sample when fresh water continuously flows past a sample at velocities less than those found within stressed areas of the Biscayne. These experiments illustrate how fresh water and D2O, with different chemical properties, migrate within one type of matrix porosity found in the Biscayne. Furthermore, these experiments are a comparative exercise in the displacement of sea water by fresh water in the matrix of a coastal, karst aquifer since D2O has a greater density than fresh water. ?? 2008 National Ground Water Association.

Flow Dependence Assessment for Fate and Transport of DNAPL in Karst Media

NASA Astrophysics Data System (ADS)

Carmona, M.; Padilla, I. Y.

2017-12-01

DNAPLs are a group of organic compounds, which exhibit high fluid density, relatively aqueous solubility, and a high level of toxicity. It is also very persistent and remains in the environment long after been released. Massive production of these compounds, their constant use and poor disposal methods have increased the occurrence of these contaminants in groundwater systems. The physico-chemical properties of DNAPL, combined with the high variation of groundwater flow causes contaminants to behave unpredictably in such aquifer. This research focuses on fate and transport of trichloroethylene (which is one of the most frequent DNAPL found) in a karstified limestone physical model (KLPM) at two different flow rates. The KLPM represents a real case of a saturated confined karst aquifer consisting of a porous limestone block enclosed in a stainless-steel tank with fifteen horizontal sampling ports. After injection of pure TCE solvent into a steady groundwater flow field, samples are taken spatially and temporally and analyzed volumetrically and analytically with HPLC. Data show pure TCE volumes are collected at the beginnings of the experiment in sampling ports located near the injection port. Results from the constructed temporal distributions curves at different spatial locations show spatial variations related to the limestone block heterogeneity. Rapid response to TCE concentrations is associated with preferential flow paths. Slow response with long tailing is indicative of diffusive transport in the rock matrix and mass transport rates limitations. Although, high flow rates show greater mass removal of TCE by dissolving its NAPL, pure TCE accumulates at all flow rates studied. Overall, results show that karstified limestone has a high capacity to rapidly transport, as well as store and slowly release TCE pure and dissolved phase for long periods of time. They also show that fate and transport of contaminants in karst environments is significantly flow dependent.

Characterization of TCE DNAPL and Dissolved Phase Transport in Karst Media

NASA Astrophysics Data System (ADS)

Carmona, M.; Padilla, I. Y.

2015-12-01

Trichloroethylene (TCE) contaminated sites are a threat to the environment and human health. Of particular concerns is the contamination of karst groundwater systems (KGWSs). Their heterogeneous character, rapid flow through conduits, high permeability zones, and strong storage capacity in the rock porous-matrix pose a high risk of exposure over large areas and temporal scales. To achieve effective remedial actions for TCE removal, it is important to understand and quantify the fate and transport process of trichloroethylene in these systems. This research studies the fate, transport, and distribution of TCE Non-Aqueous Phase Liquids (NAPLs) and associated dissolved species in KGWSs. Experiments are conducted in a karstified limestone physical model, a limestone rock mimicking a saturated confined karst aquifer. After injecting TCE solvent into a steady groundwater flow field, samples are taken spatially and temporally and analyzed for TCE NAPL and dissolved phases. Data analysis shows the rapid detection of TCE NAPL and high aqueous concentrations along preferential pathway, even at distances far away from the injection point. Temporal distribution curves exhibit spatial variations related to the limestone rock heterogeneity. Rapid response to TCE concentrations is associated with preferential flow paths. Slow response with long tailing indicates rate-limited diffusive transport in the rock matrix. Overall, results indicate that karstified limestone has a high capacity to rapidly transport pure and dissolved TCE along preferential flow paths, and to store and slowly release TCE over long periods of time.

Recent Trends in Karst Geomorphology.

ERIC Educational Resources Information Center

Palmer, Arthur N.

1984-01-01

Recent trends related to the karst processes and the evolution of karst landscapes are discussed. The hydrochemical processes responsible for the origin of karst are expanded on to illustrate the present scope of karst studies. These geomorphological studies are combined with concepts and techniques from hydraulics, chemistry, and mathematics. (JN)

Ground-water flow in the shallow aquifer system at the Naval Weapons Station Yorktown, Virginia

USGS Publications Warehouse

Smith, Barry S.

2001-01-01

The Environmental Directorate of the Naval Weapons Station Yorktown, Virginia, is concerned about possible contamination of ground water at the Station. Ground water at the Station flows through a shallow system of layered aquifers and leaky confining units. The units of the shallow aquifer system are the Columbia aquifer, the Cornwallis Cave confining unit, the Cornwallis Cave aquifer, the Yorktown confining unit, and the Yorktown-Eastover aquifer. The Eastover-Calvert confining unit separates the shallow aquifer system from deeper confined aquifers beneath the Station. A three-dimensional, finite-difference, ground-water flow model was used to simulate steady-state ground-water flow of the shallow aquifer system in and around the Station. The model simulated ground-water flow from the peninsular drainage divide that runs across the Lackey Plain near the southern end of the Station north to King Creek and the York River and south to Skiffes Creek and the James River. The model was calibrated by minimizing the root mean square error between 4 7 measured and corresponding simulated water levels. The calibrated model was used to determine the ground-water budget and general directions of ground-water flow. A particle-tracking routine was used with the calibrated model to estimate groundwater flow paths, flow rates, and traveltimes from selected sites at the Station. Simulated ground-water flow velocities of the Station-area model were small beneath the interstream areas of the Lackey Plain and Croaker Flat, but increased outward toward the streams and rivers where the hydraulic gradients are larger. If contaminants from the land surface entered the water table at or near the interstream areas of the Station, where hydraulic gradients are smaller, they would migrate more slowly than if they entered closer to the streams or the shores of the rivers where gradients commonly are larger. The ground-water flow simulations indicate that some ground water leaks downward from

Peculiarity and vulnerability of karst settings, analyzed through a review of available environmental indices

NASA Astrophysics Data System (ADS)

Parise, Mario; Mazzei, Marianna

2016-04-01

Karst is a unique environment on Earth, characterized by a variety of peculiar geological and hydrological features, that are expressed by typical landforms at the surface (doline, ponor, polje, etc.) and underground (single cave, sinkhole, complex hypogean systems consisting of sequences of pits and galleries, etc.). Among the main characters of karst, the direct connection between the surface and the underground is at the origin of the fragility of karst settings, and the related high vulnerability. Many different types of natural geological hazards (or geo-hazards) may potentially affect karst lands, with sinkholes and flash floods being the most frequent and typical. In addition, karst is exposed to a variety of anthropogenic disturbances as well, including loss of natural landscapes, destruction of caves and speleothems, and contamination and pollution problems. At this latter regard, it has to be reminded that karst aquifers host high quality groundwaters, that are used as source of drinking water worldwide, with estimates indicating that the supply of drinking water from karst is going to have a significant increase in the next decades, From all of this, the importance in fully defining the karst setting, and in a detail examination of all the natural and anthropogenic events that may cause negative effects on it, comes out. Uniqueness of karst has been acknowledged since a long time, but only in recent years efforts have been made to develop approaches and methods specifically dedicated to this peculiar environment. Such approaches represent definitely a mandatory step in the correct management of karst terranes, providing useful elements to stakeholders, land managers and people living in karst lands about their fragility, and the need to safeguard them and the natural resources therein contained. Starting from these considerations, in this contribution we review the main environmental indices dedicated to karst that have been recently proposed in the

Sediment carbon fate in phreatic karst (Part 1): Conceptual model development

NASA Astrophysics Data System (ADS)

Husic, A.; Fox, J.; Agouridis, C.; Currens, J.; Ford, W.; Taylor, C.

2017-06-01

Recent research has paid increased attention to quantifying the fate of carbon pools within fluvial networks, but few, if any, studies consider the fate of sediment organic carbon in fluviokarst systems despite that karst landscapes cover 12% of the earth's land surface. The authors develop a conceptual model of sediment carbon fate in karst terrain with specific emphasis upon phreatic karst conduits, i.e., those located below the groundwater table that have the potential to trap surface-derived sediment and turnover carbon. To assist with their conceptual model development, the authors study a phreatic system and apply a mixture of methods traditional and novel to karst studies, including electrical resistivity imaging, well drilling, instantaneous velocimetry, dye tracing, stage recording, discrete and continuous sediment and water quality sampling, and elemental and stable carbon isotope fingerprinting. Results show that the sediment transport carrying capacity of the phreatic karst water is orders of magnitude less than surface streams during storm-activated periods promoting deposition of fine sediments in the phreatic karst. However, the sediment transport carrying capacity is sustained long after the hydrologic event has ended leading to sediment resuspension and prolonged transport. The surficial fine grained laminae occurs in the subsurface karst system; but unlike surface streams, the light-limited conditions of the subsurface karst promotes constant heterotrophy leading to carbon turnover. The coupling of the hydrological processes leads to a conceptual model that frames phreatic karst as a biologically active conveyor of sediment carbon that recharges degraded organic carbon back to surface streams. For example, fluvial sediment is estimated to lose 30% of its organic carbon by mass during a one year temporary residence within the phreatic karst. It is recommended that scientists consider karst pathways when attempting to estimate organic matter stocks

Preliminary delineation and description of the regional aquifers of Tennessee : Cumberland Plateau aquifer system

USGS Publications Warehouse

Brahana, J.V.; Macy, Jo Ann; Mulderink, Dolores; Zemo, Dawn

1986-01-01

The Cumberland Plateau aquifer system consists of Pennsylvanian sandstones, conglomerates, shales, and coals which underlie the Cumberland Plateau in Tennessee. Major water-bearing zones occur within the sandstones and conglomerates in interconnected fractures. The water-bearing formations are separated by shale and siltstone that retard the vertical circulation of ground water. The Pennington Formation serves as the base of this aquifer system and is an effective confining unit. The Cumberland Plateau aquifer system is an important water source for the Cumberland Plateau. Wells and springs from the aquifer system supply most of the rural domestic and public drinking-water supplies. Water from wells drilled into the Cumberland Plateau aquifer system is generally of good to excellent quality. Of the 32 water-quality analyses on file from this aquifer, only 2 had dissolved-solids concentrations greater than 500 milligrams per liter, and about three-fourths had less than 200 milligrams per liter dissolved solids. However, no samples from depths greater than 300 feet below land surface have been recorded. Ground water from locations where the sandstones are buried deeply, such as the Wartburg basin, may contain dissolved-solids concentrations greater than 1,000 milligrams per liter.

Hydrologic and geochemical dynamics of vadose zone recharge in a mantled karst aquifer: Results of monitoring drip waters in Mystery Cave, Minnesota

USGS Publications Warehouse

Doctor, Daniel H.; Alexander, E. Calvin; Jameson, Roy A.; Alexander, Scott C.

2015-01-01

Caves provide direct access to flows through the vadose zone that recharge karst aquifers. Although many recent studies have documented the highly dynamic processes associated with vadose zone flows in karst settings, few have been conducted in mantled karst settings, such as that of southeastern Minnesota. Here we present some results of a long-term program of cave drip monitoring conducted within Mystery Cave, Minnesota. In this study, two perennial ceiling drip sites were monitored between 1997 and 2001. The sites were located about 90 m (300 ft) apart along the same cave passage approximately 18 m (60 ft) below the surface; 7 to 9 m (20 to 30 ft) of loess and 12 m (40 ft) of flat-lying carbonate bedrock strata overlie the cave. Records of drip rate, electrical conductivity, and water temperature were obtained at 15 minute intervals, and supplemented with periodic sampling for major ion chemistry and water stable isotopes. Patterns in flow and geochemistry emerged at each of the two drip sites that were repeated year after year. Although one site responded relatively quickly (within 2-7 hours) to surface recharge events while the other responded more slowly (within 2-5 days), thresholds of antecedent moisture needed to be overcome in order to produce a discharge response at both sites. The greatest amount of flow was observed at both sites during the spring snowmelt period. Rainfall events less than 10 mm (0.4 in) during the summer months generally did not produce a drip discharge response, yet rapid drip responses were observed following intense storm events after periods of prolonged rainfall. The chemical data from both sites indicate that reservoirs of vadose zone water with distinct chemical signatures mixed during recharge events, and drip chemistry returned to a baseline composition during low flow periods. A reservoir with elevated chloride and sulfate concentrations impacts the slow-response drip site with each recharge event, but does not similarly

Characterization of the spatial distribution of porosity in the eogenetic karst Miami Limestone using ground penetrating radar

NASA Astrophysics Data System (ADS)

Mount, G. J.; Comas, X.; Wright, W. J.; McClellan, M. D.

2014-12-01

Hydrogeologic characterization of karst limestone aquifers is difficult due to the variability in the spatial distribution of porosity and dissolution features. Typical methods for aquifer investigation, such as drilling and pump testing, are limited by the scale or spatial extent of the measurement. Hydrogeophysical techniques such as ground penetrating radar (GPR) can provide indirect measurements of aquifer properties and be expanded spatially beyond typical point measures. This investigation used a multiscale approach to identify and quantify porosity distribution in the Miami Limestone, the lithostratigraphic unit that composes the uppermost portions of the Biscayne Aquifer in Miami Dade County, Florida. At the meter scale, laboratory measures of porosity and dielectric permittivity were made on blocks of Miami Limestone using zero offset GPR, laboratory and digital image techniques. Results show good correspondence between GPR and analytical porosity estimates and show variability between 22 and 66 %. GPR measurements at the field scale 10-1000 m investigated the bulk porosity of the limestone based on the assumption that a directly measured water table would remain at a consistent depth in the GPR reflection record. Porosity variability determined from the changes in the depth to water table resulted in porosity values that ranged from 33 to 61 %, with the greatest porosity variability being attributed to the presence of dissolution features. At the larger field scales, 100 - 1000 m, fitting of hyperbolic diffractions in GPR common offsets determined the vertical and horizontal variability of porosity in the saturated subsurface. Results indicate that porosity can vary between 23 and 41 %, and delineate potential areas of enhanced recharge or groundwater / surface water interactions. This study shows porosity variability in the Miami Limestone can range from 22 to 66 % within 1.5 m distances, with areas of high macroporosity or karst dissolution features

New Electrical Resistivity Tomography approach for karst cave characterization: Castello di Lepre karst cave (Marsico Nuovo, Southern Italy).

NASA Astrophysics Data System (ADS)

Guerriero, Merilisa; Capozzoli, Luigi; De Martino, Gregory; Perciante, Felice; Gueguen, Erwan; Rizzo, Enzo

2017-04-01

Geophysical methods are commonly applied to characterize karst cave. Several geophysical method are used such as electrical resistivity tomography (ERT), gravimetric prospecting (G), ground penetrating radar (GPR) and seismic methods (S), in order to provide information on cave geometry and subsurface geological structure. In detail, in some complex karst systems, each geophysical method can only give partial information if used in normal way due to a low resolution for deep target. In order to reduce uncertainty and avoid misinterpretations based on a normal use of the electrical resistivity tomography method, a new ERT approach has been applied in karst cave Castello di Lepre (Marsico Nuovo, Basilicata region, Italy) located in the Mezo-Cenozoic carbonate substratum of the Monti della Maddalena ridge (Southern Appenines). In detail, a cross-ERT acquisition system was applied in order to improve the resolution on the electrical resistivity distribution on the surrounding geological structure of a karst cave. The cross-ERT system provides a more uniform model resolution vertically, increasing the resolution of the surface resistivity imaging. The usual cross-ERT is made by electrode setting in two or more borehole in order to acquire the resistivity data distribution. In this work the cross-ERT was made between the electrodes located on surface and along a karst cave, in order to obtain an high resolution of the electrical resistivity distributed between the cave and the surface topography. Finally, the acquired cross-ERT is potentially well-suited for imaging fracture zones since electrical current flow in fractured rock is primarily electrolytic via the secondary porosity associated with the fractures.

Hydrological connectivity in the karst critical zone: an integrated approach

NASA Astrophysics Data System (ADS)

Chen, X.; Zhang, Z.; Soulsby, C.; Cheng, Q.; Binley, A. M.; Tao, M.

2017-12-01

Spatial heterogeneity in the subsurface is high, evidenced by specific landform features (sinkholes, caves etc.) and resulting in high variability of hydrological processes in space and time. This includes complex exchange of various flow sources (e.g. hillslope springs and depression aquifers) and fast conduit flow and slow fracture flow. In this paper we integrate various "state-of-the-art" methods to understand the structure and function of this understudied critical zone environment. Geophysical, hydrometric and hydrogeochemical tools are used to characterize the hydrological connectivity of the cockpit karst critical zone in a small catchment of Chenqi, Guizhou province, China. Geophysical surveys, using electrical resistivity tomography (ERT), identified the complex conduit networks that link flows between hillslopes and depressions. Statistical time series analysis of water tables and discharge responses at hillslope springs and in depression wells and underground channels showed different threshold responses of hillslope and depression flows. This reflected the differing relative contribution of fast and slow flow paths during rainfall events of varying magnitude in the hillslope epikarst and depression aquifer in dry and wet periods. This showed that the hillslope epikarst receives a high proportion of rainfall recharge and is thus a main water resource in the catchment during the drought period. In contrast, the depression aquifer receives fast, concentrated hillslope flows during large rainfall events during the wet period, resulting in the filling of depression conduits and frequent flooding. Hydrological tracer studies using water temperatures and stable water isotopes (δD and δ18O) corroborated this and provided quantitative information of the mixing proportions of various flow sources and insights into water travel times. This revealed how higher contributions of event "new" water (from hillslope springs and depression conduits displaces "old" pre

Flow of ground water through fractured carbonate rocks in the Prairie du Chien-Jordan Aquifer, southeastern Minnesota

USGS Publications Warehouse

Ruhl, J.F.

1989-01-01

Contamination of groundwater from point and nonpoint sources (such as landfills, feedlots, agricultural chemicals applied to fields, and septic systems) is a recognized problem in the karst area of southeastern Minnesota. The US Geological Survey, in cooperation with the Minnesota Department of Natural Resources and the Legislative Commission on Minnesota Resources, Began a study in October 1987 to improve the understanding of local groundwater flow through karst terrain in southeastern Minnesota. The objectives of the study are to: (1) describe the orientations of systematic rock fractures and solution channels of the Prairie du Chien Group of Ordovician-age carbonate rocks in southeastern Minnesota, and, if possible, to define the principal and minor axes of these orientations; and (2) evaluate the effect of fractures and solution channels in the Prairie du Chien Group on the local flow of groundwater. Groundwater in the Upper Carbonate aquifer regionally flows toward the periphery of the aquifer and locally flows into streams and bedrock valleys. The hydraulic gradient in this aquifer generally is greatest near areas of groundwater seepage to streams. Regional groundwater flow in the Prairie du Chien-Jordan aquifer generally is to the south and east in much of Fillmore and Houston Counties and in the southern parts of Olmsted and Winona Counties. Groundwater seepage to selected streams was evaluated by current-meter measurements of downstream gains or losses of streamflow and by an experimental approach based on radon activity in streams. The activity of radon in groundwater ranges from two to four orders of magnitude greater than the activity in surface water; therefore, groundwater seepage to streams generally increases the in-stream radon activity.

Karst database development in Minnesota: Design and data assembly

USGS Publications Warehouse

Gao, Y.; Alexander, E.C.; Tipping, R.G.

2005-01-01

The Karst Feature Database (KFD) of Minnesota is a relational GIS-based Database Management System (DBMS). Previous karst feature datasets used inconsistent attributes to describe karst features in different areas of Minnesota. Existing metadata were modified and standardized to represent a comprehensive metadata for all the karst features in Minnesota. Microsoft Access 2000 and ArcView 3.2 were used to develop this working database. Existing county and sub-county karst feature datasets have been assembled into the KFD, which is capable of visualizing and analyzing the entire data set. By November 17 2002, 11,682 karst features were stored in the KFD of Minnesota. Data tables are stored in a Microsoft Access 2000 DBMS and linked to corresponding ArcView applications. The current KFD of Minnesota has been moved from a Windows NT server to a Windows 2000 Citrix server accessible to researchers and planners through networked interfaces. ?? Springer-Verlag 2005.

On the optimal selection of interpolation methods for groundwater contouring: An example of propagation of uncertainty regarding inter-aquifer exchange

NASA Astrophysics Data System (ADS)

Ohmer, Marc; Liesch, Tanja; Goeppert, Nadine; Goldscheider, Nico

2017-11-01

The selection of the best possible method to interpolate a continuous groundwater surface from point data of groundwater levels is a controversial issue. In the present study four deterministic and five geostatistical interpolation methods (global polynomial interpolation, local polynomial interpolation, inverse distance weighting, radial basis function, simple-, ordinary-, universal-, empirical Bayesian and co-Kriging) and six error statistics (ME, MAE, MAPE, RMSE, RMSSE, Pearson R) were examined for a Jurassic karst aquifer and a Quaternary alluvial aquifer. We investigated the possible propagation of uncertainty of the chosen interpolation method on the calculation of the estimated vertical groundwater exchange between the aquifers. Furthermore, we validated the results with eco-hydrogeological data including the comparison between calculated groundwater depths and geographic locations of karst springs, wetlands and surface waters. These results show, that calculated inter-aquifer exchange rates based on different interpolations of groundwater potentials may vary greatly depending on the chosen interpolation method (by factor >10). Therefore, the choice of an interpolation method should be made with care, taking different error measures as well as additional data for plausibility control into account. The most accurate results have been obtained with co-Kriging incorporating secondary data (e.g. topography, river levels).

Dynamic Vulnerability of Karst Systems: a Concept to understand qualitative and quantitative Aspects of Karst springs due to Changes in Groundwater Recharge

NASA Astrophysics Data System (ADS)

Huggenberger, P.; Butscher, C.; Epting, J.; Auckenthaler, A.

2015-12-01

Karst groundwater resources represent valuable water resources, which may be affected by different types of pollution and changes of groundwater recharge by climate change. In many parts of Europe, it has been predicted that record-breaking heat waves, such as the one experienced in 2003 and 2015, will become more frequent. At the same time, even as summers become drier, the incidence of severe precipitation events could increase. What is the influence such changes to the quantitative and qualitative aspects of Karst groundwater systems? A factor to be considered in conjunction with groundwater quality is the vulnerability of the resource, which is defined as the sensitivity of a groundwater system to pollution. Intrinsic vulnerability refers to the sensitivity to pollution when considering only natural, geogenic conditions without the effects of human activities such as contaminant release. Intrinsic vulnerability depends on the recharge conditions, which are dependent on the surface and subsurface structure and on precipitation and evaporation patterns. The latter are highly time dependent. Therefore, our groundwater vulnerability concept also includes dynamic aspects of the system, the variations of spatial and temporal components. We present results of combined monitoring and modelling experiments of several types of Karst systems in the Tabular and the Folded Jura of NW Switzerland. The recharge, conduit flow, diffuse flow(RCD) rainfall-discharge model "RCD-seasonal" was used to simulate the discharge and substance concentration of several spring. This lumped parameter model include: the recharge system (soil and epikarst system), the conduit flow system, and the diffuse flow system. The numerically derived Dynamic Vulnerability Index (DVI) can indicate qualitative changes of spring water with sufficient accuracy to be used for drinking water management. In addition, the results obtained from the test sites indicate a decrease in short-lived contaminants in

Soil gas screening for chlorinated solvents at three contaminated karst sites in Tennessee

USGS Publications Warehouse

Wolfe, W.J.; Williams, S.D.

2002-01-01

Soil gas was sampled using active sampling techniques and passive collectors at three sites in Tennessee to evaluate the effectiveness of these techniques for locating chlorinated solvent sources and flowpaths in karst aquifers. Actively collected soil gas samples were analyzed in the field with a portable gas chromatograph, and the passive soil gas collectors were analyzed in the lab with gas chromatography/mass spectrometry. Results of the sampling indicate that the effectiveness of both techniques is highly dependent on the distribution of the contaminants in the subsurface, the geomorphic and hydrogeologic characteristics of the site, and, in one case, on seasonal conditions. Both active and passive techniques identified areas of elevated subsurface chlorinated solvent concentrations at a landfill site where contamination remains concentrated in the regolith. Neither technique detected chlorinated solvents known to be moving in the bedrock at a manufacturing site characterized by thick regolith and an absence of surficial karst features. Passive soil gas sampling had varied success detecting flowpaths for chloroform in the bedrock at a train derailment site characterized by shallow regolith and abundant surficial karst features. At the train derailment site, delineation of the contaminant flowpath through passive soil gas sampling was stronger and more detailed under Winter conditions than summer.

Karst map of Puerto Rico

USGS Publications Warehouse

Alemán González, Wilma B.

2010-01-01

This map is a digital compilation, combining the mapping of earlier geologists. Their work, cited on the map, contains more detailed descriptions of karst areas and landforms in Puerto Rico. This map is the basis for the Puerto Rico part of a new national karst map currently being compiled by the U.S. Geological Survey. In addition, this product is a standalone, citable source of digital karst data for Puerto Rico. Nearly 25 percent of the United States is underlain by karst terrain, and a large part of that area is undergoing urban and industrial development. Accurate delineations of karstic rocks are needed at scales suitable for national, State, and local maps. The data on this map contribute to a better understanding of subsidence hazards, groundwater contamination potential, and cave resources as well as serve as a guide to topical research on karst. Because the karst data were digitized from maps having a different scale and projection from those on the base map used for this publication, some karst features may not coincide perfectly with physiographic features portrayed on the base map.

An Integrated Hydrogeologic and Geophysical Investigation to Characterize the Hydrostratigraphy of the Edwards Aquifer in an Area of Northeastern Bexar County, Texas

USGS Publications Warehouse

Shah, Sachin D.; Smith, Bruce D.; Clark, Allan K.; Payne, Jason

2008-01-01

In August 2007, the U.S. Geological Survey, in cooperation with the San Antonio Water System, did a hydrogeologic and geophysical investigation to characterize the hydrostratigraphy (hydrostratigraphic zones) and also the hydrogeologic features (karst features such as sinkholes and caves) of the Edwards aquifer in a 16-square-kilometer area of northeastern Bexar County, Texas, undergoing urban development. Existing hydrostratigraphic information, enhanced by local-scale geologic mapping in the area, and surface geophysics were used to associate ranges of electrical resistivities obtained from capacitively coupled (CC) resistivity surveys, frequency-domain electromagnetic (FDEM) surveys, time-domain electromagnetic (TDEM) soundings, and two-dimensional direct-current (2D-DC) resistivity surveys with each of seven hydrostratigraphic zones (equivalent to members of the Kainer and Person Formations) of the Edwards aquifer. The principal finding of this investigation is the relation between electrical resistivity and the contacts between the hydrostratigraphic zones of the Edwards aquifer and the underlying Trinity aquifer in the area. In general, the TDEM data indicate a two-layer model in which an electrical conductor underlies an electrical resistor, which is consistent with the Trinity aquifer (conductor) underlying the Edwards aquifer (resistor). TDEM data also show the plane of Bat Cave fault, a well-known fault in the area, to be associated with a local, nearly vertical zone of low resistivity that provides evidence, although not definitive, for Bat Cave fault functioning as a flow barrier, at least locally. In general, the CC resistivity, FDEM survey, and 2D-DC resistivity survey data show a sharp electrical contrast from north to south, changing from high resistivity to low resistivity across Bat Cave fault as well as possible karst features in the study area. Interpreted karst features that show relatively low resistivity within a relatively high

Effect of Short-Circuit Pathways on Water Quality in Selected Confined Aquifers (Invited)

NASA Astrophysics Data System (ADS)

McMahon, P. B.

2010-12-01

Confined aquifers in the United States generally contain fewer anthropogenic contaminants than unconfined aquifers because confined aquifers often contain water recharged prior to substantial human development and redox conditions are more reducing, which favors degradation of common contaminants like nitrate and chlorinated solvents. Groundwater in a confined part of the High Plains aquifer near York, Nebraska had an adjusted radiocarbon age of about 2,000 years, and groundwater in a confined part of the Floridan aquifer near Tampa, Florida had apparent ages greater than 60 years on the basis of tritium measurements. Yet compounds introduced more recently into the environment (anthropogenic nitrate and volatile organic compounds) were detected in selected public-supply wells completed in both aquifers. Depth-dependent measurements of flow and chemistry in the pumping supply wells, groundwater age dating, numerical modeling of groundwater flow, and other monitoring data indicated that the confined aquifers sampled by the supply wells were connected to contaminated unconfined aquifers by short-circuit pathways. In the High Plains aquifer, the primary pathways appeared to be inactive irrigation wells screened in both the unconfined and confined aquifers. In the Floridan aquifer, the primary pathways were karst sinkholes and conduits. Heavy pumping in both confined systems exacerbated the problem by reducing the potentiometric surface and increasing groundwater velocities, thus enhancing downward gradients and reducing reaction times for processes like denitrification. From a broader perspective, several confined aquifers in the U.S. have experienced large declines in their potentiometric surfaces because of groundwater pumping and this could increase the potential for contamination in those aquifers, particularly where short-circuit pathways connect them to shallower, contaminated sources of water, such as was observed in York and Tampa.

Towards sustainable groundwater management in Karst aquifers in semi-arid environments: Central West Bank, Palestine

NASA Astrophysics Data System (ADS)

Jebreen, H.; Banning, A.; Wohnlich, S.

2017-12-01

The Central West Bank (CWB) is characterized by karstified carbonate aquifers in the semiarid climate zone, where groundwater resources are frequently threatened by overexploitation and pollution. Despite often limited system knowledge, quantitative and qualitative factors such as groundwater recharge rate, aquifer parameters, flow and transport dynamics, anthropogenic impacts, and groundwater vulnerability need to be assessed. Therefore, sustainable groundwater use in the CWB is of critical importance. In the present study, we explore the scale of the groundwater problems in CWB as well as the possibility of sustainable management through different scenarios: 1) Managed aquifer recharge using a water balance model, stable isotopes (2H & 18O) and chloride mass balance, 2) Geochemical evolution and renewability of groundwater, and 3) Anthropogenic impacts. A total of 20 spring water samples were collected and analyzed for pH, electrical conductivity, total dissolved solids (TDS), hardness, major-ion chemistry (Cl-, HCO3-, SO42-, Na+, K+, Ca2+ and Mg2+), trace elements (Li, Be, Al, Ba, Tl, Pb, Bi, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Mo, Ag and Cd), microbiological data (total and fecal coliforms bacteria), and stable isotopes (2H & 18O). The results show a spatialized recharge rate, which ranges from 111-211 mm/year, representing 17-33 % of the long-term mean annual rainfall. The mean annual actual evapotranspiration was about 19-37 % of precipitation. The chemical composition of groundwater of the study area is strongly influenced by rock-water interaction, dissolution and deposition of carbonate and silicate minerals. Stable isotopes show that precipitation is the source of recharge to the groundwater system. All analyzed spring waters are suitable for irrigation but not for drinking purposes. This studýs results can serve as a basis for decision makers, and will lead to an increased understanding of the sustainable management of the Central West Bank

Hydrologic controls of methane dynamics in a karst subterranean estuary

NASA Astrophysics Data System (ADS)

Brankovits, D.; Pohlman, J.; Ganju, N. K.; Lowell, N. S.; Roth, E.; Lapham, L.

2017-12-01

Subterranean estuaries extend into carbonate landmasses where abundant cave networks influence the hydrology and biogeochemistry of the coastal aquifer environment. Enhanced density stratification between meteoric freshwater and saline groundwater facilitates the development of sharp salinity and redox gradients associated with the production and consumption of methane, a potent greenhouse gas. These processes impact methane-dynamics in the coastal zone and provide nutritive resources for the cave-adapted estuarine food web in this oligotrophic habitat. These observations were based on sampling in discrete time periods, leaving questions about the effects of temporally dynamic hydrology on the production, consumption and transport of methane. In this study, we evaluated hydro-biogeochemical controls of methane dynamics in a subterranean estuary to quantify the magnitude of the methane sink in the coastal karst platform of the Yucatan Peninsula, Mexico. We deployed osmotically-driven sampling devices (OsmoSamplers) in flooded cave passages to document temporal variability in methane concentrations and δ13C values, as well as major ions in the groundwater. Water level, current velocities, water and air temperatures, and precipitation were also monitored. Using these records, we built an integrated model to provide a first-order calculation on methane consumption rates for the coastal aquifer. The year-long water chemistry record reveals higher source concentrations of methane in the dry season (5849 ± 1198 nM) than in the wet season (4265 ± 778 nM) with depleted δ13C values (-65.4 ± 2.1 ‰) throughout the year. Our analyses suggest the methane sink potential and ecosystem function are significantly affected by precipitation induced hydrological changes within the tropical subterranean karst estuary.

Modeling Raw Sewage Leakage and Transport in the Unsaturated Zone of Carbonate Aquifer Using Carbamazepine as an Indicator

NASA Astrophysics Data System (ADS)

Yakirevich, A.; Kuznetsov, M.; Livshitz, Y.; Gasser, G.; Pankratov, I.; Lev, O.; Adar, E.; Dvory, N. Z.

2016-12-01

Fast contamination of groundwater in karstic aquifers can be caused due to leaky sewers, for example, or overflow from sewer networks. When flowing through a karst system, wastewater has the potential to reach the aquifer in a relatively short time. The Western Mountain Aquifer (Yarkon-Taninim) of Israel is one of the country's major water resources. During late winter 2013, maintenance actions were performed on a central sewage pipe that caused raw sewage to leak into the creek located in the study area. The subsequent infiltration of sewage through the thick ( 100 m) fractured/karst unsaturated zone led to a sharp increase in contaminant concentrations in the groundwater, which was monitored in a well located 29 meters from the center of the creek. Carbamazepine (CBZ) was used as an indicator for the presence of untreated raw sewage and its quantification in groundwater. The ultimate research goal was to develop a mathematical model for quantifying flow and contaminant transport processes in the fractured-porous unsaturated zone and karstified groundwater system. A quasi-3D dual permeability numerical model, representing the 'vadose zone - aquifer' system, was developed by a series of 1D equations solved in variably-saturated zone and by 3D-saturated flow and transport equation in groundwater. The 1D and 3D equations were coupled at the moving phreatic surface. The model was calibrated and applied to a simulated water flow scenario and CBZ transport during and after the observed sewage leakage event. The results of simulation showed that after the leakage stopped, significant amounts of CBZ were retained in the porous matrix of the unsaturated zone below the creek. Water redistribution and slow recharge during the dry summer season contributed to elevated CBZ concentrations in the groundwater in the vicinity of the creek and tens of meters downstream. The resumption of autumn rains enhanced flushing of CBZ from the unsaturated zone and led to an increase in

Hydrogeology of the surficial aquifer system, Dade County, Florida

USGS Publications Warehouse

Fish, J.E.; Stewart, M.T.

1991-01-01

An investigation of the surficial aquifer system in Dade County, begun in 1983, is part of a regional study of the aquifer system in southeastern Florida. Test drilling for lithologic samples, flow measurements during drilling, aquifer testing, and analyses of earlier data permitted delineation of the hydraulic conductivity distribution (on hydrogeologic sections), the aquifers in the system, the generalized transmissivity distribution, and interpretation of the ground-water flow system. The surficial aquifer system, in which an unconfined ground-water flow system exists, is composed of the sediments from land surface downward to the top of a regionally extensive zone of sediments of low permeability called the intermediate confining unit. The aquifer system units, which vary in composition from clay-size sediments to cavernous limestone, are hydro stratigraphically divided into the Biscayne aquifer at the top; an intervening semiconfining unit that consists principally of clayey sand; a predominantly gray limestone aquifer in the Tamiami Formation in western and west-central Dade County; and sand or clayey sand near the base of the surficial aquifer system. The base of the surficial aquifer system ranges from a depth of about 175 to 210 feet below land surface in westernmost Dade County to greater than 270 feet in northeastern Dade County. Test drilling and aquifer-test data indicate a complex hydraulic conductivity distribution. Hydraulic conductivities of the very highly permeable zone of the Biscayne aquifer commonly exceed 10,000 feet per day; in the gray limestone aquifer, they range from 210 to 780 feet per day. Transmissivities of the surficial aquifer system vary locally but have a recognizable areal trend. Estimated values generally are about 300,000 feet squared per day or greater in nearly all of central and eastern Dade County. Transmissivity is lower to the west, decreasing to less than 75,000 feet squared per day in western Dade County. High

Potentiometric surface of the Upper Floridan aquifer in the Ichetucknee springshed and vicinity, northern Florida, September 2003

USGS Publications Warehouse

Sepulveda, A. Alejandro; Katz, Brian G.; Mahon, Gary L.

2006-01-01

The Upper Floridan aquifer is a highly permeable unit of carbonate rock extending beneath most of Florida and parts of southern Alabama, Georgia, and South Carolina. The high permeability is due in a large part to the widening of fractures that developed over time and the formation of conduits within the aquifer through dissolution of the limestone. This process has also produced numerous karst features such as springs, sinking streams, and sinkholes in northern Florida. These dissolution features, whether expressed at the surface or not, greatly influence the direction of ground-water flow in the Ichetucknee springshed adjacent to the Ichetucknee River. Ground water generally flows southwestward in the springshed and discharges to the Ichetucknee or Santa Fe Rivers, or to the springs along those rivers. This map depicts the September 9-10, 2003, potentiometric surface of the Upper Floridan aquifer based on 94 water-level measurements made by the Suwannee River Water Management District. Ground-water levels in this watershed fluctuate in response to precipitation and due to the high degree of interconnection between the surface-water system and the aquifer.

Hypogenic contribution to speleogenesis in a predominant epigenic karst system: A case study from the Venetian Alps, Italy

NASA Astrophysics Data System (ADS)

Tisato, Nicola; Sauro, Francesco; Bernasconi, Stefano M.; Bruijn, Rolf H. C.; De Waele, Jo

2012-05-01

Buso della Rana and Buso della Pisatela are two karstic caves located in north-east Italy. They are part of the same karst system and are developed in the Castelgomberto calcarenitic marine sediments, which were deposited in a shallow Caribbean-type sea during the Eocene. The Buso della Rana-Pisatela system developed mostly at the contact between the Castelgomberto calcarenite and underlying volcanic rocks. The system of caves is ~ 37 km long and has only three entrances, two of which are semi-artificial. The overlying karst plateau is not directly connected to the Buso della Rana-Pisatela system and, with the exception of one deep abyss, exhibits a rather poorly developed karst. This is unexpected considering the presence at depth of such a large and long cave. Gypsum (CaSO4·2H2O) has locally been observed on the walls of the Buso della Pisatela cave. Energy dispersive X-ray spectroscopy (EDS), performed with a scanning electron microscope (SEM), reveals the presence of sulfur-bearing minerals within the host rock. Gypsum was formed by oxidation of these minerals as indicated by negative δ34S values. The oxidation of sulfide minerals forms a sulfuric-acid solution that dissolves the Castelgomberto calcarenite and, once it is oversaturated in calcium, precipitates as gypsum. The lack of well-developed karst on top of the plateau and the analyses suggest that the formation mechanisms for the Buso della Rana-Pisatela system differ from classical epigenic speleogenesis. The "pyrite-effect" has been recognized in other caves and described in literature. In our case pyrite is responsible of two hypo-speleogenetic processes: i) the dissolution of a portion of the host rock and ii) the enlargement of the karst voids as a consequence of the haloclastic effect.

A General Solution for Groundwater Flow in Estuarine Leaky Aquifer System with Considering Aquifer Anisotropy

NASA Astrophysics Data System (ADS)

Chen, Po-Chia; Chuang, Mo-Hsiung; Tan, Yih-Chi

2014-05-01

In recent years the urban and industrial developments near the coastal area are rapid and therefore the associated population grows dramatically. More and more water demand for human activities, agriculture irrigation, and aquaculture relies on heavy pumping in coastal area. The decline of groundwater table may result in the problems of seawater intrusion and/or land subsidence. Since the 1950s, numerous studies focused on the effect of tidal fluctuation on the groundwater flow in the coastal area. Many studies concentrated on the developments of one-dimensional (1D) and two-dimensional (2D) analytical solutions describing the tide-induced head fluctuations. For example, Jacob (1950) derived an analytical solution of 1D groundwater flow in a confined aquifer with a boundary condition subject to sinusoidal oscillation. Jiao and Tang (1999) derived a 1D analytical solution of a leaky confined aquifer by considered a constant groundwater head in the overlying unconfined aquifer. Jeng et al. (2002) studied the tidal propagation in a coupled unconfined and confined costal aquifer system. Sun (1997) presented a 2D solution for groundwater response to tidal loading in an estuary. Tang and Jiao (2001) derived a 2D analytical solution in a leaky confined aquifer system near open tidal water. This study aims at developing a general analytical solution describing the head fluctuations in a 2D estuarine aquifer system consisted of an unconfined aquifer, a confined aquifer, and an aquitard between them. Both the confined and unconfined aquifers are considered to be anisotropic. The predicted head fluctuations from this solution will compare with the simulation results from the MODFLOW program. In addition, the solutions mentioned above will be shown to be special cases of the present solution. Some hypothetical cases regarding the head fluctuation in costal aquifers will be made to investigate the dynamic effects of water table fluctuation, hydrogeological conditions, and

Sustainable Capture: Concepts for Managing Stream-Aquifer Systems.

PubMed

Davids, Jeffrey C; Mehl, Steffen W

2015-01-01

Most surface water bodies (i.e., streams, lakes, etc.) are connected to the groundwater system to some degree so that changes to surface water bodies (either diversions or importations) can change flows in aquifer systems, and pumping from an aquifer can reduce discharge to, or induce additional recharge from streams, springs, and lakes. The timescales of these interactions are often very long (decades), making sustainable management of these systems difficult if relying only on observations of system responses. Instead, management scenarios are often analyzed based on numerical modeling. In this paper we propose a framework and metrics that can be used to relate the Theis concepts of capture to sustainable measures of stream-aquifer systems. We introduce four concepts: Sustainable Capture Fractions, Sustainable Capture Thresholds, Capture Efficiency, and Sustainable Groundwater Storage that can be used as the basis for developing metrics for sustainable management of stream-aquifer systems. We demonstrate their utility on a hypothetical stream-aquifer system where pumping captures both streamflow and discharge to phreatophytes at different amounts based on pumping location. In particular, Capture Efficiency (CE) can be easily understood by both scientists and non-scientist alike, and readily identifies vulnerabilities to sustainable stream-aquifer management when its value exceeds 100%. © 2014, National Ground Water Association.

Geochemical and isotopic characterization of groundwater origins in a Mediterranean karst system (southern France)

NASA Astrophysics Data System (ADS)

Seidel, J. L.; Ladouche, B.; Batiot-Guilhe, C.

2013-12-01

sources of the mineralization increase. However, the Lez spring REE profiles, despite a close Cretaceous end-member signature, exhibit an evolution between the Bajocian and the highly depleted Triassic signature. A better characterization of the regional deep basement end-member and a multi-isotopic approach (d7Li, d11B, d18O, D and 87Sr/86Sr) have been undertaken for a conclusive identification of the Lez spring water type. This study could be generalized to the coastal karstic systems of the Mediterranean region. Caetano Bicalho C., Batiot-Guilhe C., Seidel J. L., Van Exter S. and Jourde H. (2012). Geochemical evidence of water source characterization and hydrodynamic responses in a karst aquifer. J. Hydrol., 450-451, 206-218. Joseph, C., Rodier, C., Soulte, M., Sinegre, F., Baylet, R., Deltour, P., 1988. Approche des transferts de pollution bactérienne dans une crue karstique par l'étude des paramètres physico-chimiques. Rev. Sci. l'eau 1-2, 73-106. Marjolet, G., Salado, J., 1976. Contribution à l'étude de l'aquifère karstique de la source du Lez (Hérault). Etude du chimisme des eaux de la source du Lez et de son bassin Tome IX - FASC II., Université des Sciences et Techniques du Languedoc (Montpellier 2), Montpellier 101 pp.

Taking the mystery out of mathematical model applications to karst aquifers—A primer

USGS Publications Warehouse

Kuniansky, Eve L.

2014-01-01

Advances in mathematical model applications toward the understanding of the complex flow, characterization, and water-supply management issues for karst aquifers have occurred in recent years. Different types of mathematical models can be applied successfully if appropriate information is available and the problems are adequately identified. The mathematical approaches discussed in this paper are divided into three major categories: 1) distributed parameter models, 2) lumped parameter models, and 3) fitting models. The modeling approaches are described conceptually with examples (but without equations) to help non-mathematicians understand the applications.

Use of isotopically-tagged isolates of E. coli for tracking bacterial movement in karst environments

NASA Astrophysics Data System (ADS)

Bandy, A.; Fryar, A. E.; Macko, S. A.; Cook, K.

2014-12-01

Because of limited filtration and turbulent flow, karst aquifers are more susceptible to microbial contamination than clastic aquifers. Assessment of microbial transport in groundwater is complicated by the need to identify tracers that have a low detection limit, have minimal background concentrations, behave like the organisms of interest, and are non-pathogenic. We are assessing transport of two non-pathogenic isolates of Escherichia coli (E. coli) compared to traditional groundwater tracers in epikarst above Cave Springs Cavern near Bowling Green, KY, and in a karst conduit that emerges at Royal Spring in Georgetown, KY. The E. coli isolate exhibiting higher attachment efficiency in saturated granular columns contains the iha gene, while the isolate exhibiting lower attachment efficiency contains the kps gene. For the field experiments, bacteria are being grown on media enriched in 13C or 15N. Isotopically-tagged bacteria will be injected with rhodamine WT as a solute tracer and fluorescent microspheres as an abiotic particulate tracer. We will monitor breakthrough of the tracers in the cave and at the spring; based on a previous field test, we anticipate that particulate tracers may be remobilized during subsequent storm events. E. coli will be quantified by molecular methods (qPCR) and dual isotope analysis. Preliminary findings suggest that these two methods may be complementary, with each method having detection limitations.

Potentiometric surface of the intermediate aquifer system, west- central Florida, May 1987

USGS Publications Warehouse

Lewelling, B.R.

1988-01-01

The intermediate aquifer system within the Southwest Florida Water Management District underlies a 5,000 sq mi area of De Soto, Sarasota, Hardee, Manatee, and parts of Charlotte, Hillsborough, Highlands, and Polk Counties. The intermediate aquifer system occurs between the overlying surficial aquifer system and the underlying Floridan aquifer system, and consists of layers of sand, shell, clay, marl, limestone, and dolom of the Tamiami, Hawthorn, and Tampa Formations of late Tertiary age. The intermediate aquifer system contains one or more water-bearing units separated by discontinuous confining units. This aquifer system is the principal source of potable water in the southwestern part of the study area and is widely used as a source of water in other parts where wells are open to the intermediate aquifer system or to both the intermediate and Floridan aquifer systems. Yields of individual wells open to the intermediate aquifer system range from a few gallons to several hundred gallons per minute. The volume of water withdrawn from the intermediate aquifer system is considerably less than that withdrawn from the Floridan aquifer system in the study area. The surface was mapped by determining the altitude of water levels in a network of wells and is represented on maps by contours that connect points of equal altitude. The compos potentiometric surface of all water-bearing units within the intermediate aquifer system is shown. In areas where multiple aquifers exist, wells open to all aquifers were selected for water level measurements whenever possible. In the southwestern and lower coastal region of the study area, two aquifers and confining units are described for the intermediate aquifer system: the Tamiami-upper Hawthorn aquifer and the underlying lower Hawthorn-upper Tampa aquifer. The potentiometric surface of the Tamiami-upper Hawthorn aquifer is also shown. Water levels are from wells drilled and open exclusively to that aquifer. The exact boundary for the

Gypsum-karst problems in constructing dams in the USA

USGS Publications Warehouse

Johnson, K.S.

2008-01-01

Gypsum is a highly soluble rock and is dissolved readily to form caves, sinkholes, disappearing streams, and other karst features that typically are also present in limestones and dolomites. Gypsum karst is widespread in the USA and has caused problems at several sites where dams were built, or where dam construction was considered. Gypsum karst is present (at least locally) in most areas where gypsum crops out, or is less than 30-60 m below the land surface. These karst features can compromise on the ability of a dam to hold water in a reservoir, and can even cause collapse of a dam. Gypsum karst in the abutments or foundation of a dam can allow water to pass through, around, or under a dam, and solution channels can enlarge quickly, once water starts flowing through such a karst system. The common procedure for controlling gypsum karst beneath the dam is a deep cut-off trench, backfilled with impermeable material, or a close-spaced grout curtain that hopefully will fill all cavities. In Oklahoma, the proposed Upper Mangum Dam was abandoned before construction, because of extensive gypsum karst in the abutments and impoundment area. Catastrophic failure of the Quail Creek Dike in southwest Utah in 1989 was due to flow of water through an undetected karstified gypsum unit beneath the earth-fill embankment. The dike was rebuilt, at a cost of US $12 million, with construction of a cut-off trench 600 m long and 25 m deep. Other dams in the USA with severe gypsum-karst leakage problems in recent years are Horsetooth and Carter Lake Dams, in Colorado, and Anchor Dam, in Wyoming. ?? 2007 Springer-Verlag.

Extending GIS Technology to Study Karst Features of Southeastern Minnesota

NASA Astrophysics Data System (ADS)

Gao, Y.; Tipping, R. G.; Alexander, E. C.; Alexander, S. C.

2001-12-01

This paper summarizes ongoing research on karst feature distribution of southeastern Minnesota. The main goals of this interdisciplinary research are: 1) to look for large-scale patterns in the rate and distribution of sinkhole development; 2) to conduct statistical tests of hypotheses about the formation of sinkholes; 3) to create management tools for land-use managers and planners; and 4) to deliver geomorphic and hydrogeologic criteria for making scientifically valid land-use policies and ethical decisions in karst areas of southeastern Minnesota. Existing county and sub-county karst feature datasets of southeastern Minnesota have been assembled into a large GIS-based database capable of analyzing the entire data set. The central database management system (DBMS) is a relational GIS-based system interacting with three modules: GIS, statistical and hydrogeologic modules. ArcInfo and ArcView were used to generate a series of 2D and 3D maps depicting karst feature distributions in southeastern Minnesota. IRIS ExplorerTM was used to produce satisfying 3D maps and animations using data exported from GIS-based database. Nearest-neighbor analysis has been used to test sinkhole distributions in different topographic and geologic settings. All current nearest-neighbor analyses testify that sinkholes in southeastern Minnesota are not evenly distributed in this area (i.e., they tend to be clustered). More detailed statistical methods such as cluster analysis, histograms, probability estimation, correlation and regression have been used to study the spatial distributions of some mapped karst features of southeastern Minnesota. A sinkhole probability map for Goodhue County has been constructed based on sinkhole distribution, bedrock geology, depth to bedrock, GIS buffer analysis and nearest-neighbor analysis. A series of karst features for Winona County including sinkholes, springs, seeps, stream sinks and outcrop has been mapped and entered into the Karst Feature Database

Transient well flow in leaky multiple-aquifer systems

NASA Astrophysics Data System (ADS)

Hemker, C. J.

1985-10-01

A previously developed eigenvalue analysis approach to groundwater flow in leaky multiple aquifers is used to derive exact solutions for transient well flow problems in leaky and confined systems comprising any number of aquifers. Equations are presented for the drawdown distribution in systems of infinite extent, caused by wells penetrating one or more of the aquifers completely and discharging each layer at a constant rate. Since the solution obtained may be regarded as a combined analytical-numerical technique, a type of one-dimensional modelling can be applied to find approximate solutions for several complicating conditions. Numerical evaluations are presented as time-drawdown curves and include effects of storage in the aquitard, unconfined conditions, partially penetrating wells and stratified aquifers. The outcome of calculations for relatively simple systems compares very well with published corresponding results. The proposed multilayer solution can be a valuable tool in aquifer test evaluation, as it provides the analytical expression required to enable the application of existing computer methods to the determination of aquifer characteristics.

Integrating seismic-reflection and sequence-stratigraphic methods to characterize the hydrogeology of the Floridan aquifer system in southeast Florida

USGS Publications Warehouse

Cunningham, Kevin J.

2013-01-01

The Floridan aquifer system (FAS) is receiving increased attention as a result of regulatory restrictions on water-supply withdrawals and treated wastewater management practices. The South Florida Water Management District’s Regional Water Availability Rule, adopted in 2007, restricts urban withdrawals from the shallower Biscayne aquifer to pre-April 2006 levels throughout southeast Florida. Legislation adopted by the State of Florida requires elimination of ocean outfalls of treated wastewater by 2025. These restrictions have necessitated the use of the more deeply buried FAS as an alternate water resource to meet projected water-supply shortfalls, and as a repository for the disposal of wastewater via Class I deep injection wells and injection of reclaimed water. Some resource managers in Broward County have expressed concern regarding the viability of the FAS as an alternative water supply due to a lack of technical data and information regarding its long-term sustainability. Sustainable development and management of the FAS for water supply is uncertain because of the potential risk posed by structural geologic anomalies (faults, fractures, and karst collapse structures) and knowledge gaps in the stratigraphy of the system. The integration of seismic-reflection and borehole data into an improved geologic and hydrogeologic framework will provide a better understanding of the structural and stratigraphic features that influence groundwater flow and contaminant transport.

Potentiometric surfaces of the intermediate aquifer system, west-central Florida, September 2000

USGS Publications Warehouse

Duerr, A.D.

2001-01-01

The intermediate aquifer system underlies a 5,000-square-mile area within the Southwest Florida Water Management District including De Soto, Sarasota, Hardee, Manatee, and parts of Charlotte, Hillsborough, Highlands, Polk, and Lee Counties.  The intermediate aquifer system is overlain by the surficial aquifer system and is underlain by the Floridan aquifer system.  The intermediate aquifer system consists of layers of sand, shell, clay, calcareous clay, limestone, and dolomite of the Tamiami Formation and Hawthorn Group of Oligocene to Pleistocene age (Wingard and others, 1995).  The intermediate aquifer system contains one or more water-bearing units separated by discontinuous confining units.  The intermediate aquifer system is the principal source of potable water in the southwestern part of the study area and is widely used as a source of water where wells are open to the intermediate aquifer system or to both the intermediate and Floridan aquifer systems.  Yields of individual wells open to the intermediate aquifer system vary from a few gallons to several hundred gallons per minute.  The volume of water withdrawn from the intermediate aquifer system is considerably less than that withdrawn from the Floridan aquifer system in the study area (Duerr and others, 1988).

Hydrogeologic framework of the North Carolina Coastal Plain aquifer system

USGS Publications Warehouse

Winner, M.D.; Coble, R.W.

1989-01-01

The hydrogeologic framework of the North Carolina Coastal Plain aquifer system consists of ten aquifers separated by nine confining units. From top to bottom the aquifers are: the surficial aquifer, Yorktown aquifer, Pungo River aquifer, Castle Hayne aquifer, Beaufort aquifer, Peedee aquifer, Black Creek aquifer, upper Cape Fear aquifer, lower Cape Fear aquifer, and the Lower Cretaceous aquifer. The uppermost aquifer (the surficial aquifer in most places) is a water-table aquifer and the bottom of the system is underlain by crystalline bedrock. The sedimentary deposits forming the aquifers are of Holocene to Cretaceous age and are composed mostly of sand with lesser amounts of gravel and limestone. Confining units between aquifers are composed primarily of clay and silt. The thickness of the aquifers ranges from zero along the Fall Line to more than 10,000 feet at Cape Hatteras. Prominent structural features are the increasing easterly homoclinal dip of the sediments and the Cape Fear arch, the axis of which trends in a southeast direction. The stratigraphic continuity is determined from correlations of 161 geophysical logs along with data from drillers' and geologists' logs. Aquifers were defined by means of these logs plus water-level and water-quality data and evidence of the continuity of pumping effects. Eighteen hydrogeologic sections depict the correlation of these aquifers throughout the Coastal Plain.

Geomorphic interaction among climate, sea levels and karst groundwater: the Taranto area (South of Italy)

NASA Astrophysics Data System (ADS)

Spilotro, Giuseppe; Fidelibus, Maria Dolores; Argentiero, Ilenia; Pellicani, Roberta; Parisi, Alessandro; Di Modugno, Antonella

2017-04-01

The area of Taranto (Apulia region, Italy) has an extraordinary environmental and landscape value, which derives from its specific geological, geomorphological and hydrogeological conditions: they represent the effect of a complex mechanism of interaction in the geological time among the sea, its level variations and stands driven by climate changes, karst groundwater and the geo lithological frame. The knowledge of this interaction spans over two very different time duration: the first is subsequent to the sedimentary pleistocenic deposition and diagenesis and lasts until the late Holocene; the second spans over a more limited time durations, from the LIA until today, and its knowledge is mainly based on hystorical topographic records and reports. The general geological and stratigraphical setting is represented by marine deposits, which fill the Bradanic Trough, shaped in the upper part as marine terraces bordering the W and SW side of the Murgian carbonate platform (Apulia, South of Italy) as well. This latter constitutes an important karst hydro-structure, fed by precipitation, bordered on the opposite side of the Bradanic Trough by the Adriatic Sea. Fresh groundwater hosted in the huge coastal aquifer freely flows towards the Adriatic coast, while on the opposite W-NW side, the continuous confinement by the impermeable filling of the trough, forces the underground drainage of the aquifer towards the Ionian Sea just in the Taranto area. The overall flow rate of the groundwater through submarine and subaerial coastal springs, according to the current sea level, is significant and currently estimated in about 18 m3/sec. Climate changes have forced over geological time, but also in shorter periods, sea level changes and stands, consequently correlated to groundwater levels. This allowed genesis of selected karst levels, of regional extension, both at the surface or underground, which arise as typical forms, namely polje and karst plane inland, terraces on the sea

GIS thematic layers for assessing karst hazard in Murgia region (Italy)

NASA Astrophysics Data System (ADS)

Canora, Filomena; D'Angella, Annachiara; Fidelibus, Dolores; Lella, Angela; Pellicani, Roberta; Spilotro, Giuseppe

2013-04-01

The assessment of karst hazard in a carbonate area may be somewhat complex for the multiplicity of involved factors (geological, hydrological, morphological, anthropogenic, etc.), their history and the slow rate of evolution of the processes. In coastal areas, moreover, the long term sea level variations and the short term oscillations generally influence the generation and evolution of the karst process. Another peculiarity of the karst hazard assessment consists in the difficulty for identifying the location of subsurface forms, which may develop over very large areas without any kind of surface signal. The karst processes and landforms often require specific methods of investigation and mitigation, due to the unique and highly variable characters of karst environments. In addition, the hidden character of the karst processes, often accelerated by human activity, is an issue with significant economic impact, affecting many regions of the world. The assessment of karst hazard in the Murgia plateau (in central-west of Apulia region) is the main goal of this research. For this aim, the typologies of karst phenomena, able to produce hazard in the study area, were individuated and collected in a specific database. The hazard was evaluated on the basis of the probability of occurrence of a phenomenon of instability, active (produced by human activities) or passive (natural evolution of karst process), in relation to the presence, evolution or generation of karst forms on surface or at critical distance from the surface. The critical distance from the surface is defined as the distance at which the local or general destructive evolution of a karst process can produce a variation of the usability of the area or of the value of elements involved in the instability. The thematic layers relative to the factors influencing karst processes and landforms (doline, sinkholes, polje, lame, gravine, caves) were elaborated and managed in a GIS system. The archives of the main karst

A LEXICON OF CAVE AND KARST TERMINOLOGY WITH SPECIAL REFERENCE TO ENVIRONMENTAL KARST HYDROLOGY (2002 EDITION)

EPA Science Inventory

Several attempts to classify karst terminology in an organized manner have been attempted in the past. The last few glossaries of karst terminology were organized in the late 1960s and published in the early 1970s. Since that time, many new terms related to karst in general hav...

Stochastic modeling of a lava-flow aquifer system

USGS Publications Warehouse

Cronkite-Ratcliff, Collin; Phelps, Geoffrey A.

2014-01-01

This report describes preliminary three-dimensional geostatistical modeling of a lava-flow aquifer system using a multiple-point geostatistical model. The purpose of this study is to provide a proof-of-concept for this modeling approach. An example of the method is demonstrated using a subset of borehole geologic data and aquifer test data from a portion of the Calico Hills Formation, a lava-flow aquifer system that partially underlies Pahute Mesa, Nevada. Groundwater movement in this aquifer system is assumed to be controlled by the spatial distribution of two geologic units—rhyolite lava flows and zeolitized tuffs. The configuration of subsurface lava flows and tuffs is largely unknown because of limited data. The spatial configuration of the lava flows and tuffs is modeled by using a multiple-point geostatistical simulation algorithm that generates a large number of alternative realizations, each honoring the available geologic data and drawn from a geologic conceptual model of the lava-flow aquifer system as represented by a training image. In order to demonstrate how results from the geostatistical model could be analyzed in terms of available hydrologic data, a numerical simulation of part of an aquifer test was applied to the realizations of the geostatistical model.

Development and implementation of a Bayesian-based aquifer vulnerability assessment in Florida

USGS Publications Warehouse

Arthur, J.D.; Wood, H.A.R.; Baker, A.E.; Cichon, J.R.; Raines, G.L.

2007-01-01

The Florida Aquifer Vulnerability Assessment (FAVA) was designed to provide a tool for environmental, regulatory, resource management, and planning professionals to facilitate protection of groundwater resources from surface sources of contamination. The FAVA project implements weights-of-evidence (WofE), a data-driven, Bayesian-probabilistic model to generate a series of maps reflecting relative aquifer vulnerability of Florida's principal aquifer systems. The vulnerability assessment process, from project design to map implementation is described herein in reference to the Floridan aquifer system (FAS). The WofE model calculates weighted relationships between hydrogeologic data layers that influence aquifer vulnerability and ambient groundwater parameters in wells that reflect relative degrees of vulnerability. Statewide model input data layers (evidential themes) include soil hydraulic conductivity, density of karst features, thickness of aquifer confinement, and hydraulic head difference between the FAS and the watertable. Wells with median dissolved nitrogen concentrations exceeding statistically established thresholds serve as training points in the WofE model. The resulting vulnerability map (response theme) reflects classified posterior probabilities based on spatial relationships between the evidential themes and training points. The response theme is subjected to extensive sensitivity and validation testing. Among the model validation techniques is calculation of a response theme based on a different water-quality indicator of relative recharge or vulnerability: dissolved oxygen. Successful implementation of the FAVA maps was facilitated by the overall project design, which included a needs assessment and iterative technical advisory committee input and review. Ongoing programs to protect Florida's springsheds have led to development of larger-scale WofE-based vulnerability assessments. Additional applications of the maps include land-use planning

Hydraulics of Reka-Timavo system, Classical Karst (Carso), Slovenia-Italy

NASA Astrophysics Data System (ADS)

Gabrovsek, Franci; Kaufmann, Georg; Peric, Borut

2016-04-01

In tectonically active areas, karst systems continuously adapt to the relatively rapid changes of the structural and boundary conditions. The flow pathways in such systems are characterised by high variability of channel cross-sections and breakdowns, which restrict the flow and cause high fluctuations of groundwater level, particularly if the recharge variations are high. One of the world's most prominent karst systems with such characteristics is the Kras/Carso plateau (Classical Karst), which extends between SW Slovenia and NE Italy. The ground water dynamics is mainly influenced by the allogenic input of Reka river which sinks at the Škocjanske jame (Škocjan caves) and emerges about 40 km north-west at the coast of Adria near Duino in springs of Timavo. The ratio between highest and lowest flow of Reka reaches 1700 with the maximum measured discharge 305 m3/s, and minimum 0.18 m3/s. This work is based on the long-term continuous monitoring of basic physical parameters of underground flow within six active caves of the Reka-Timavo system. Using stage, temperature and specific electric conductivity hydrographs, following questions were addressed: How do different signals (flood pulse, temperature, SEP) propagate through the system? How does the known geometry relate to the recorded hydrographs in caves? Can we infer on the structure of unknown parts of the system from the recorded hydrographs ? Where are the restrictions causing floods in different parts of the system? The data analysis includes heuristic and statistical analysis of the hydrographs and optimisation based hydraulic modelling. The response to recharge events is vigorous; high flow variability causes extreme stage variations along the whole observed system, with more than 100 m difference between the base and highest water levels at rising and recession rates reaching almost 10 m/h. By analysing large recharge events, we show that high floods in the two most upstream caves (Škocjanske jame and Ka

How to Recharge a Confined Alluvial Aquifer System

NASA Astrophysics Data System (ADS)

Maples, S.; Fogg, G. E.; Liu, Y.

2016-12-01

Greater water storage capacity is needed to offset future decreases in snowpack-water storage in California. Managed aquifer recharge (MAR) in California's Central Valley aquifer system is a promising alternative to new surface reservoir storage because it has the potential to both reduce overdraft conditions observed in many Central Valley groundwater basins and offset continued decreases in snowpack storage. MAR to the Central Valley's productive confined-aquifer system remains a challenge because, like most alluvial aquifer systems, it is composed mostly of silt and clay sediments that form nearly ubiquitous, multiple confining layers that inhibit direct recharge of the interconnected sand and gravel body networks. Several studies have mapped surficial soil types in the Central Valley that are conducive to MAR, but few studies have evaluated how subsurface geologic heterogeneity controls recharge to the confined aquifer system. Here, we use a transition probability Markov-chain geostatistical model conditioned with 1200 well logs to create a physically-realistic representation of the subsurface geologic heterogeneity in the American and Cosumnes River watersheds on the east side of the Sacramento Valley, CA, where studies have shown the presence of massive, interconnected, highly-permeable gravel deposits that are potentially conducive to considerably higher rates of regional recharge than would be possible over the rest of the landscape. Such localized stratigraphic features to support accelerated recharge occur throughout the Central Valley, but are mostly still undiscovered. A variably-saturated, fully-integrated, groundwater/surface-water code, ParFlow, was used to simulate MAR dynamics in this system. Results show the potential for (1) accelerated, high-volume recharge through interconnected gravels where they outcrop at land surface, and (2) regional repressurization of the deeper confined aquifer system. These findings provide insight into the critical

A preliminary study on the feedback of heat transfer on groundwater flow in a Karst geothermal field

NASA Astrophysics Data System (ADS)

Kong, Y.; Pang, Z.; Hu, S.; Pang, J.; Shao, H.; Kolditz, O.

2014-12-01

In deep sedimentary basins, groundwater movement can significantly alter the heat flow pattern. At the same time, heat flux induced temperature change can reversely determine the flow regime through density dependent convection process. In Karst aquifers, the heterogeneity in the carbonate rocks makes the identification of this feedback much more complex. In this work, a preliminary study has been made on this feedback in Xiongxian geothermal field. The Karst aquifer in our site has an average thickness of about 1000 m, and is overlaid by over 400 m of quaternary clay, and subsequently 600 m of Neogene sandstone. Geothermal energy has been exploited in the site for space heating. During the heating period from Nov 15th to Mar 15th every year, hot water was extracted from the aquifer and re-injected after the heat extraction. A detailed temperature logging has been carried out in the field, both before and after the heating period, with the consideration that temperature distribution will be affected by the re-injection of cold water. The vertical distribution of temperature in the cap rock shows a constant positive gradient over depth. The heat flux at different locations has been calculated respectively. It is found to decline from southwest to northeast, with the highest value of 113.9 mW/m2 to the lowest of 80.6 mW/m2. This pattern can be well explained by the tectonic features. More interestingly, two inflection points appear on the temperature profile of the Karst layer, revealing strong influence from the cold re-injection water. Also, a 3℃ temperature difference was observed in the June and October measurement, which is related to the reservoir recovery. Currently, a 3D numerical model is being constructed, using the open-source software OpenGeoSys. Heat transport process is coupled with density dependent flow in a monolithic approach, to simulate both heat conduction and groundwater convection. This model will help to quantify the feedback from heat

Regional scale hydrologic modeling of a karst-dominant geomorphology: The case study of the Island of Crete

NASA Astrophysics Data System (ADS)

Malagò, Anna; Efstathiou, Dionissios; Bouraoui, Fayçal; Nikolaidis, Nikolaos P.; Franchini, Marco; Bidoglio, Giovanni; Kritsotakis, Marinos

2016-09-01

Crete Island (Greece) is a karst dominated region that faces limited water supply and increased seasonal demand, especially during summer for agricultural and touristic uses. In addition, due to the mountainous terrain, interbasin water transfer is very limited. The resulting water imbalance requires a correct quantification of available water resources in view of developing appropriate management plans to face the problem of water shortage. The aim of this work is the development of a methodology using the SWAT model and a karst-flow model (KSWAT, Karst SWAT model) for the quantification of a spatially and temporally explicit hydrologic water balance of karst-dominated geomorphology in order to assess the sustainability of the actual water use. The application was conducted in the Island of Crete using both hard (long time series of streamflow and spring monitoring stations) and soft data (i.e. literature information of individual processes). The KSWAT model estimated the water balance under normal hydrological condition as follows: 6400 Mm3/y of precipitation, of which 40% (2500 Mm3/y) was lost through evapotranspiration, 5% was surface runoff and 55% percolated into the soil contributing to lateral flow (2%), and recharging the shallow (9%) and deep aquifer (44%). The water yield was estimated as 22% of precipitation, of which about half was the contribution from spring discharges (9% of precipitation). The application of the KSWAT model increased our knowledge about water resources availability and distribution in Crete under different hydrologic conditions. The model was able to capture the hydrology of the karst areas allowing a better management and planning of water resources under scarcity.

A generalized genetic framework for the development of sinkholes and Karst in Florida, U.S.A.

NASA Astrophysics Data System (ADS)

Beck, Barry F.

1986-03-01

Karst topography in Florida is developed on the Tertiary limestones of the Floridan aquifer Post-depositional diagenesis and solution have made these limestones highly permeable, T=ca. 50,000 m2/d. Zones of megaporosity have formed at unconformities, and dissolution has enlarged joints and fractures Erosion of the overlying clastic Miocene Hawthorn group strata on one flank of a structural arch has exposed the limestone The elevated edge of the Hawthorn cover forms the Cody scarp Ubiquitous solution pipes have previously formed at joint intersections and are now filled Downwashing of the fill deeper into solution cavities in the limestone and subsidence of the overlying unconsolidated sediments causes surface collapse a subsidence doline or sinkhole This process may penetrate up to 60 m of the semi-consolidated Hawthorn cover, as occurred when the Winter Park sinkhole developed Dense clusters of solution pipes may have formed cenotes which are now found on the exposed limestone terrain Groundwater moves laterally as diffuse flow except where input or outflow is concentrated. At sinking streams, vertical shafts, and springs, karst caves have formed, but only the major sinking streams form through-flowing conduit systems Shaft recharge dissipates diffusely. Spring discharge is concentrated from diffuse flow In both cases, conduits taper and merge into a zone of megaporosity

Observation of a Distinct Transition in Transport Response to Injection Stress in the Floridan Aquifer System, Southeastern Florida, U.S.A

NASA Astrophysics Data System (ADS)

King, J. N.; Cunningham, K. J.; Foster, A. L.

2011-12-01

The Miami-Dade Water and Sewer Department (MDWASD) injects effluent approximately one km below land surface into the Boulder Zone (BZ) at the North District Wastewater Treatment Plant (NDWWTP). The BZ is highly conductive and composed of fractured dolomite. MDWASD monitors upward effluent migration 450 m below land surface in the Avon Park Permeable Zone (APPZ). The BZ and APPZ---units within the Floridan aquifer system---are separated by a series of inter-bedded aquifers and leaky confining units with hydraulic conductivities that are orders of magnitude smaller than the BZ. MDWASD injected effluent at the NDWWTP during two distinct periods: (1) July 1997 to September 1999, and (2) August 2004 to January 2011. No effluent was injected between October 1999 and July 2004. A few months after the July 1997 injection, MDWASD observed effluent constituents in the APPZ (Figure 1). Some confinement bypass feature permits effluent constituents to be transported from the BZ to the APPZ. Bypass features may include poorly-cased wells, or natural conduits such as fractures, faults, or karst collapse systems. It is possible to describe confinement bypass features with conductance KA/L, where K is hydraulic conductivity, A is cross-sectional area, and L is length. MDWASD observed a distinct transition in the transport response to injection stress of total dissolved solids (TDS) concentration in the APPZ. The conductance required to describe early system response (1997-1999) is one order-of-magnitude larger than the conductance required to describe late system response (2004-2011). Hypotheses to explain transient conductance include clogging of bypass features by some geochemical or biological process that results from the mixing of effluent with groundwater; dissolution or precipitation; or changes in bypass-feature geometry forced by cyclical changes in aquifer-fluid pressure associated with injection. Hypotheses may be tested with geochemical analyses, tracer tests, hydraulic

Hydraulic Evolution of Karst Microfracture

NASA Astrophysics Data System (ADS)

Windom, L. M.; Dragila, M. I.; Weisbrod, N.

2017-12-01

Karst terrain comprises an astounding 25% of our planet's potable water resources, yet the evolution of these systems from micro-fracture to open channel is poorly understood. Focusing on the unsaturated portion of an evolving karst system, we present a conceptual model for the hydraulic evolution of micro-fractures into larger conduits. Tensional micro-fractures (< 1mm thick) under unsaturated conditions may be eroded by water flowing either as seepage films or as capillary rivulets. In addition to general erosion, the narrow width of capillary rivulets may etch the beginning of preferential paths within the tensional micro-fractures that will lead to tubular channels. Both fluid mechanisms, seepage and rivulets, were tested in the laboratory, and data of the resulting geochemical erosion rates are presented in the form of calcium dissolution rates measured by inductively coupled plasma atomic emission spectroscopy (ICP-OES).

Effects of different boundary conditions on the simulation of groundwater flow in a multi-layered coastal aquifer system (Taranto Gulf, southern Italy)

NASA Astrophysics Data System (ADS)

De Filippis, Giovanna; Foglia, Laura; Giudici, Mauro; Mehl, Steffen; Margiotta, Stefano; Negri, Sergio L.

2017-11-01

The evaluation of the accuracy or reasonableness of numerical models of groundwater flow is a complex task, due to the uncertainties in hydrodynamic properties and boundary conditions and the scarcity of good-quality field data. To assess model reliability, different calibration techniques are joined to evaluate the effects of different kinds of boundary conditions on the groundwater flow in a coastal multi-layered aquifer in southern Italy. In particular, both direct and indirect approaches for inverse modeling were joined through the calibration of one of the most uncertain parameters, namely the hydraulic conductivity of the karst deep hydrostratigraphic unit. The methodology proposed here, and applied to a real case study, confirmed that the selection of boundary conditions is among the most critical and difficult aspects of the characterization of a groundwater system for conceptual analysis or numerical simulation. The practical tests conducted in this study show that incorrect specification of boundary conditions prevents an acceptable match between the model response to the hydraulic stresses and the behavior of the natural system. Such effects have a negative impact on the applicability of numerical modeling to simulate groundwater dynamics in complex hydrogeological situations. This is particularly important for management of the aquifer system investigated in this work, which represents the only available freshwater resource of the study area, and is threatened by overexploitation and saltwater intrusion.

Experimental study of solute transport in pool-pipe system and its significance on karst hydrogeology

NASA Astrophysics Data System (ADS)

Zhao, X.; Chang, Y.; Peng, F.; Wu, J.

2016-12-01

Study of solute transport in karst conduit is of great significance for prediction and prevention of groundwater pollution in southwest karst region. Solute transport in karst conduit is strongly influenced by pools which often develop along karst conduit. In order to investigate the effect of transient storage within pools on solute transport in the conduit, a pool-pipe system was built in the laboratory and some tracer tests were performed in various flow conditions to characterize the solute transport in different pool-pipe structures. The Qtracer2 program was used to obtain solute transport parameters. We used retardation coefficient R to characterize the difference between the 1-D analytical solution of the classical advection-dispersion equation and experimental results. The experimental results reveal that the concentration peak decreases with the number of pools whereas the dispersion coefficient and dispersivity increase gradually. Adding transient storage increases retardation as tailing of the breakthrough curve(BTC) is growing with the number of pools. This demonstrates that transient storage within pools is transformed to retardation. The symmetrical pool has longer tails compared to the asymmetrical pool. The concentration peak lag behind significantly due to the asymmetrical pool. A decrease in dispersivity and tailing of the BTC is observed in all pipes with the increase of flow velocities. The 1-D analytical solution of the classical advection-dispersion equation is well fitted to BTC of a single pipe in maximum flow velocity but is poorly fitted to other BTCs with appreciable tails. Therefore, it requires an appropriate model to explain tailing of the BTC. The conclusion has important significance for understanding of solute transport process in karst conduit. Future work will focus on using the appropriate model to explain tailing of the BTC.

Modeling a network of turloughs in lowland karst

NASA Astrophysics Data System (ADS)

Gill, L. W.; Naughton, O.; Johnston, P. M.

2013-06-01

In lowland karst areas of Ireland topographic depressions which get intermittently flooded on an annual cycle via groundwater sources are termed turloughs. These are sites of high ecological interest as they have communities and substrate characteristic of wetlands. The flooding in many turlough basins is due to insufficient capacity of the underground karst system to take increased flows following excessive precipitation events, causing the conduit-type network to surcharge. Continuous water level measurements have been taken in five linked turloughs in the lowland karst area of south Galway over a 3 year period. These water level fluctuations, in conjunction with river inputs and precipitation, were then used to elucidate the hydrogeological controls forming the hydraulic system beneath the ground. A model of the karst network has been developed using a pipe network model with the turloughs represented as ponds. The contribution to the karst network from diffuse flow through the epikarst via the matrix and fracture flow has also been modeled using a combination of an infiltration module and network of permeable pipes. The final model was calibrated against two separate hydrological years and in general provided a good simulation for all of the turloughs water levels particularly for the year with one main filling event. The model also accurately picked up the tidal response observed in these turloughs at shallow depths. The model has been used to predict the groundwater discharge to the coast via the main spring which had not heretofore been possible to measure, being below the sea level.

Karst hydrogeology and hydrochemistry of the Cave Springs basin near Chattanooga, Tennessee

USGS Publications Warehouse

Pavlicek, D.J.

1996-01-01

The Cave Springs ground-water basin, located near Chattanooga, Tennessee, was chosen as one of the Valley and Ridge physiographic province type area studies for the Appalachian Valley-Piedmont Regional Aquifer-System Analysis study in 1990. Karstic Paleozoic carbonate rocks, residual clay-rich regolith, and coarse alluvium form the aquifer framework. Recharge from rainfall dispersed over the basin enters the karst aquifer through the thick regolith. The area supplying recharge to the Cave Springs Basin is approximately 7 square miles. Recharge from North Chickamauga Creek may contribute recharge to the Cave Springs Basin along losing reaches. The flow medium consists of mixed dolomite and limestone with cavernous and fracture porosity. Flow type as determined by the coefficient of variation of long-term continuous specific conductance (18 and 15 percent) from two wells completed in cavernous intervals about 150 feet northeast of Cave Springs, indicates an aquifer with conduit flow. Flow type, based on the ratio (6:1) of spring flood-flow discharge to spring base-flow discharge, indicates an aquifer with diffuse flow. Conduit flow probably dominates the aquifer system west of Cave Springs Ridge from the highly transmissive, unconfined, alluvium capped aquifer and along losing reaches of North Chickamauga Creek. Diffuse flow probably predominates in the areas along and east of Cave Springs Ridge covered with the thick, clay-rich regolith that forms a leaky confining layer. Based on average annual long-term precipitation and runoff records, the amount of water available for recharge to Cave Springs is 11.8 cubic feet per second. The mean annual long-term discharge of Cave Springs is 16.4 cubic feet per second which leaves 4.6 cubic feet per second of recharge unaccounted for. As determined by low-flow stream discharge measurements, recharge along losing reaches of North Chickamauga Creek may be an important source of unaccounted-for-recharge to the Cave Springs Basin

Geologic framework and hydrogeologic characteristics of the Edwards Aquifer outcrop, Medina County, Texas

USGS Publications Warehouse

Small, Ted A.; Clark, Allan K.

2000-01-01

The hydrogeologic subdivisions of the Edwards aquifer outcrop in Medina County generally are porous and permeable. The most porous and permeable appear to be hydrogeologic subdivision VI, the Kirschberg evaporite member of the Kainer Formation; and hydrogeologic subdivision III, the leached and collapsed members, undivided, of the Person Formation. The most porous and permeable rocks of the Devils River Formation in Medina County appear to be in the top layer. The upper member of the Glen Rose Limestone, the lower confining unit, has much less porosity and permeability than that observed in the Edwards aquifer.The Edwards aquifer has relatively large porosity and permeability resulting, in part, from the development or redistribution of secondary porosity. Lithology, stratigraphy, diagenesis, and karstification account for the effective porosity and permeability in the Edwards aquifer outcrop. Karst features that can greatly enhance effective porosity and permeability in the Edwards aquifer outcrop include sinkholes, dolines, and caves. The Edwards aquifer rocks in Medina County change from the eight-member Edwards Group to the essentially indivisible Devils River Formation. The facies change occurs along a line extending northwestward from just south of Medina Lake.

Application of the Risk-Based Early Warning Method in a Fracture-Karst Water Source, North China.

PubMed

Guo, Yongli; Wu, Qing; Li, Changsuo; Zhao, Zhenhua; Sun, Bin; He, Shiyi; Jiang, Guanghui; Zhai, Yuanzheng; Guo, Fang

2018-03-01

  The paper proposes a risk-based early warning considering characteristics of fracture-karst aquifer in North China and applied it in a super-large fracture-karst water source. Groundwater vulnerability, types of land use, water abundance, transmissivity and spatial temporal variation of groundwater quality were chosen as indexes of the method. Weights of factors were obtained by using AHP method based on relative importance of factors, maps of factors were zoned by GIS, early warning map was conducted based on extension theory with the help of GIS, ENVI+IDL. The early warning map fused five factors very well, serious and tremendous warning areas are mainly located in northwest and east with high or relatively high transmissivity and groundwater pollutant loading, and obviously deteriorated or deteriorated trend of petroleum. The early warning map warns people where more attention should be paid, and the paper guides decision making to take appropriate protection actions in different warning levels areas.

Dye tracing techniques used to determine ground-water flow in a carbonate aquifer system near Elizabethtown, Kentucky

USGS Publications Warehouse

Mull, D.S.; Smoot, J.L.; Liebermann, T.D.

1988-01-01

Because of the vulnerability of karst aquifers to contamination and the need for water managers to know recharge areas and groundwater flow characteristics for springs and wells used for public water supply, qualitative and quantitative dye tracing techniques were used during a groundwater investigation in the Elizabethtown area, Hardin County, in north-central Kentucky. The principal aquifer in the Elizabethtown area is thick, nearly horizontal beds of limestone, and thin beds of shale of Mississippi age. As much as 65% of all water pumped for the city water supply is obtained from two springs and two wells that obtain water from these rocks. Sinkholes were classified according to their ability to funnel runoff directly into the groundwater flow system, based primarily on the nature of the swallet draining the sinkhole. The presence of bedrock in the sinkhole nearly always ensured a well defined swallet leading to the subsurface. Qualitative and quantitative dye tracing techniques and equipment are discussed in detail. Qualitative dye tracing with fluorescein dye and passive dye detectors, consisting of activated coconut charcoal identified point to point connection between representative sinkholes, sinking streams, and karst windows and the city springs and wells. Qualitative tracing confirmed the presence of infiltrated surface water from a perennial stream, Valley Creek, in water from city wells and generally confirmed the direction of groundwater flow as shown by a water level contour map. Quantitative dye tracing with rhodamin WT, automatic samplers, discharge measurements, and fluorometric analyses were used to determine flow characteristics such as traveltime for arrival of the leading edge, peak concentration, trailing edge, and persistence of the dye cloud at the spring resurgence. Analyses of the dye recovery curves for quantitative dye traces completed between the same sinkholes and a city spring, and during different flow conditions showed that the

Hydrogeology of the surficial and intermediate aquifer systems in Sarasota and adjacent counties, Florida

USGS Publications Warehouse

Barr, G.L.

1996-01-01

From 1991 to 1995, the hydrogeology of the surficial aquifer system and the major permeable zones and confining units of the intermediate aquifer system in southwest Florida was studied. The study area is a 1,400-square-mile area that includes Sarasota County and parts of Manatee, De Soto, Charlotte, and Lee Counties. Lithologic, geophysical, hydraulic property, and water-level data were used to correlate the hydrogeology and map the extent of the aquifer systems. Water chemistry was evaluated in southwest Sarasota County to determine salinity of the surficial and intermediate aquifer systems. The surficial aquifer is an unconfined aquifer system that overlies the intermediate aquifer system and ranges from a few feet to over 60 feet in thickness in the study area. Hydraulic properties of the surficial aquifer system determined from aquifer and laboratory tests, and model simulations vary considerably across the study area. The intermediate aquifer system, a confined aquifer system that lies between the surficial and the Upper Floridan aquifers, is composed of alternating confining units and permeable zones. The intermediate aquifer system has three major permeable zones that exhibit a wide range of hydraulic properties. Horizontal flow in the intermediate aquifer system is northeast to southwest. Most of the study area is in a discharge area of the intermediate aquifer system. Water ranges naturally from fresh in the surficial aquifer system and upper permeable zones of the intermediate aquifer system to moderately saline in the lower permeable zone. Water-quality data collected in coastal southwest Sarasota County indicate that ground-water withdrawals from major pumping centers have resulted in lateral seawater intrusion and upconing into the surficial and intermediate aquifer systems.

Source to sink characterization of dissolved organic matter in a tropical karst system

NASA Astrophysics Data System (ADS)

Lechleitner, Franziska; Lang, Susan Q.; McIntyre, Cameron; Baldini, James U. L.; Dittmar, Thorsten; Eglinton, Timothy I.

2016-04-01

Karst systems are widespread surface features present on all continents. They are characterized by complex hydrology with a multitude of possible flow regimes, from diffuse seepage through the host rock to fracture flow in larger conduits. As stalagmite proxy records are important indicators of past terrestrial climate conditions, detailed understanding of the biogeochemistry of cave systems and their relationships to the overlying karst network is crucial. Microbial communities that drive the carbon cycle in caves are nourished by dissolved organic matter (DOM) carried with water into the cave system. Water samples from the Yok Balum cave in Belize were collected for DOM analysis, including soil waters, drip waters and pool waters from inside the cave. Additionally, DOM extracts from a stalagmite from the same cave were analysed to examine DOM signatures and test their applicability for reconstruction of environmental conditions. Ultrahigh-resolution mass spectrometry (via the ESI-FT-ICR-MS technique) yielded detailed molecular fingerprints on DOM from these samples. Several thousand molecular formulae of DOM compounds were identified. In addition, radiocarbon analyses were performed on the DOM samples to gain information on karst turnover times. A principal component analysis of the molecular data revealed a clear gradient between soil waters and cave waters, as soil waters were enriched in highly unsaturated oxygen-rich compounds (typical for vascular plants), which were much less abundant in drip waters. Conversely, peptides, which can originate from bacterial processes, were present only in the drip waters. Our data clearly show connectivity between the cave and overlaying soils, and reworking of DOM by the cave bacterial community. Furthermore, we found molecular evidence for the selective removal of vascular plant-derived DOM in the caves, possibly due to abiotic interactions with minerals.

Hydrochemical processes and evolution of karst groundwater in the northeastern Huaibei Plain, China

NASA Astrophysics Data System (ADS)

Qian, Jiazhong; Peng, Yinxue; Zhao, Weidong; Ma, Lei; He, Xiaorui; Lu, YueHan

2018-06-01

Major ion geochemistry reveals that the hydrochemical evolutionary process of karst groundwater in the northeastern Huaibei Plain, China, consists of three sub-processes: the dissolution of dolomite, gypsum dissolution with dedolomitization, and mixing with overlying pore water. Understanding hydrochemical evolution has been an important topic in understanding the history, status, and dynamics of the groundwater flow system. The presented study found a hydrochemical boundary roughly corresponding to the thickness of overlying strata equating to 50 m depth, indicating two flow compartments participating in different hydrological cycles—a local shallow rapidly replenished compartment showing lower and more stable main ion concentrations, and a regional deep-flow compartment showing higher and sporadic concentrations of Na+, K+, Ca2+, Mg2+, Cl- and SO4 2-, as well as high total dissolved solids (TDS), total hardness, and sodium adsorption ratio (SAR). In areas with aquifers with low water transmitting ability, groundwater samples show a high chloride ratio and elevated TDS values, indicating salinization of groundwater due to stagnant water flows. Analyses of the data on the saturation indexes and mineral solutions, in tandem with trilinear diagram analysis and petrological observations, indicate that dedolomitization is the dominant process controlling the chemical characteristics of karst groundwater in the study area. Groundwater and pore-water mixing was also observed at the later evolutionary stage of groundwater flow, demonstrating frequent groundwater/pore-water interactions where groundwater is recharged by pore water due to lower groundwater level in the study area.

Sanitary protection zoning based on time-dependent vulnerability assessment model - case examples at two different type of aquifers

NASA Astrophysics Data System (ADS)

Živanović, Vladimir; Jemcov, Igor; Dragišić, Veselin; Atanacković, Nebojša

2017-04-01

Delineation of sanitary protection zones of groundwater source is a comprehensive and multidisciplinary task. Uniform methodology for protection zoning for various type of aquifers is not established. Currently applied methods mostly rely on horizontal groundwater travel time toward the tapping structure. On the other hand, groundwater vulnerability assessment methods evaluate the protective function of unsaturated zone as an important part of groundwater source protection. In some particular cases surface flow might also be important, because of rapid transfer of contaminants toward the zones with intense infiltration. For delineation of sanitary protection zones three major components should be analysed: vertical travel time through unsaturated zone, horizontal travel time through saturated zone and surface water travel time toward intense infiltration zones. Integrating the aforementioned components into one time-dependent model represents a basis of presented method for delineation of groundwater source protection zones in rocks and sediments of different porosity. The proposed model comprises of travel time components of surface water, as well as groundwater (horizontal and vertical component). The results obtained using the model, represent the groundwater vulnerability as the sum of the surface and groundwater travel time and corresponds to the travel time of potential contaminants from the ground surface to the tapping structure. This vulnerability assessment approach do not consider contaminant properties (intrinsic vulnerability) although it can be easily improved for evaluating the specific groundwater vulnerability. This concept of the sanitary protection zones was applied at two different type of aquifers: karstic aquifer of catchment area of Blederija springs and "Beli Timok" source of intergranular shallow aquifer. The first one represents a typical karst hydrogeological system with part of the catchment with allogenic recharge, and the second one

Prediction and assessment of the disturbances of the coal mining in Kailuan to karst groundwater system

NASA Astrophysics Data System (ADS)

Sun, Wenjie; Wu, Qiang; Liu, Honglei; Jiao, Jian

Coal resources and water resources play an essential and strategic role in the development of China's social and economic development, being the priority for China's medium and long technological development. As the mining of the coal extraction is increasingly deep, the mine water inrush of high-pressure confined karst water becomes much more a problem. This paper carried out research on the hundred-year old Kailuan coal mine's karst groundwater system. With the help of advanced Visual Modflow software and numerical simulation method, the paper assessed the flow field of karst water area under large-scale exploitation. It also predicted the evolution ofgroundwaterflow field under different mining schemes of Kailuan Corp. The result shows that two cones of depression are formed in the karst flow field of Zhaogezhuang mining area and Tangshan mining area, and the water levels in two cone centers are -270 m and -31 m respectively, and the groundwater generally flows from the northeast to the southwest. Given some potential closed mines in the future, the mine discharge will decrease and the water level of Ordovician limestone will increase slightly. Conversely, given increase of coal yield, the mine drainage will increase, falling depression cone of Ordovician limestone flow field will enlarge. And in Tangshan's urban district, central water level of the depression cone will move slightly towards north due to pumping of a few mines in the north.

Plan of study for the northern Midwest regional aquifer-system analysis

USGS Publications Warehouse

Steinhilber, W.L.; Young, H.L.

1979-01-01

Sedimentary rocks of Cambrian and Ordovician age form a major aquifer system in most of Wisconsin and Iowa, northern Illinois, northwestern Indiana, southeastern Minnesota, and northern Missouri. Many metropolitan areas depend on the aquifer for all or part of their water supplies. Declines in potentiometric head have been large in the most heavily pumped areas, most notably Chicago, Milwaukee-Waukesha, Minneapolis-St. Paul, and Des Moines. A thorough understanding of the aquifer system is needed for sound management decisions. Thus, a 4-year study of the aquifer, beginning in October 1978, is included in the U.S. Geological Survey 's program of Regional Aquifer-System Analysis. The study will evaluate the aquifer 's water-supply potential, describe its water quality, and, through computer models of the ground-water flow system, provide the means to evaluate regional aquifer response to different patterns of ground-water development. This report describes the objectives, work plan, and organization of this study. (Woodard-USGS)

Dissolved oxygen fluctuations in karst spring flow and implications for endemic species: Barton Springs, Edwards aquifer, Texas, USA

USGS Publications Warehouse

Mahler, Barbara J.; Bourgeais, Renan

2013-01-01

Karst aquifers and springs provide the dissolved oxygen critical for survival of endemic stygophiles worldwide, but little is known about fluctuations of dissolved oxygen concentrations (DO) and factors that control those concentrations. We investigated temporal variation in DO at Barton Springs, Austin, Texas, USA. During 2006–2012, DO fluctuated by as much as a factor of 2, and at some periods decreased to concentrations that adversely affect the Barton Springs salamander (Eurycea sorosum) (≤4.4 mg/L), a federally listed endangered species endemic to Barton Springs. DO was lowest (≤4.4 mg/L) when discharge was low (≤1 m3/s) and spring water temperature was >21 °C, although not at a maximum; the minimum DO recorded was 4.0 mg/L. Relatively low DO (3/s) and maximum T (22.2 °C). A four-segment linear regression model with daily data for discharge and spring water temperature as explanatory variables provided an excellent fit for mean daily DO (Nash–Sutcliffe coefficient for the validation period of 0.90). DO also fluctuated at short-term timescales in response to storms, and DO measured at 15-min intervals could be simulated with a combination of discharge, spring temperature, and specific conductance as explanatory variables. On the basis of the daily-data regression model, we hypothesize that more frequent low DO corresponding to salamander mortality could result from (i) lower discharge from Barton Springs resulting from increased groundwater withdrawals or decreased recharge as a result of climate change, and (or) (ii) higher groundwater temperature as a result of climate change.

Nitrate in aquifers beneath agricultural systems

USGS Publications Warehouse

Burkart, M.R.; Stoner, J.D.; ,

2007-01-01

Research from several regions of the world provides spatially anecdotal evidence to hypothesize which hydrologic and agricultural factors contribute to groundwater vulnerability to nitrate contamination. Analysis of nationally consistent measurements from the U.S. Geological Survey's NAWQA program confirms these hypotheses for a substantial range of agricultural systems. Shallow unconfined aquifers are most susceptible to nitrate contamination associated with agricultural systems. Alluvial and other unconsolidated aquifers are the most vulnerable and also shallow carbonate aquifers that provide a substantial but smaller contamination risk. Where any of these aquifers are overlain by permeable soils the risk of contamination is larger. Irrigated systems can compound this vulnerability by increasing leaching facilitated by additional recharge and additional nutrient applications. The system of corn, soybean, and hogs produced significantly larger concentrations of groundwater nitrate than all other agricultural systems because this system imports the largest amount of N-fertilizer per unit production area. Mean nitrate under dairy, poultry, horticulture, and cattle and grains systems were similar. If trends in the relation between increased fertilizer use and groundwater nitrate in the United States are repeated in other regions of the world, Asia may experience increasing problems because of recent increases in fertilizer use. Groundwater monitoring in Western and Eastern Europe as well as Russia over the next decade may provide data to determine if the trend in increased nitrate contamination can be reversed. If the concentrated livestock trend in the United States is global, it may be accompanied by increasing nitrogen contamination in groundwater. Concentrated livestock provide both point sources in the confinement area and intense non-point sources as fields close to facilities are used for manure disposal. Regions where irrigated cropland is expanding, such as

Regional Aquifer-System Analysis Program of the US Geological Survey; bibliography, 1978-86

USGS Publications Warehouse

Weeks, J.B.; Sun, Ren Jen

1987-01-01

The Regional Aquifer-System Analysis Program of the U.S. Geological Survey was initiated in 1978. The purpose of this program is to define the regional geohydrology and establish a framework of background information on geology, hydrology, and geochemistry of the Nation 's important aquifer systems. This information is needed to develop an understanding of the Nation 's major groundwater flow systems and to support better groundwater resources management. As of 1986, investigations of 28 regional aquifer systems were planned, investigations of 9 regional aquifer systems were completed, and 11 regional aquifer systems were being studied. This report is a bibliography of reports completed under the Regional Aquifer-System Analysis Program from 1978 through 1986. The reports resulting from each regional aquifer-system study are listed after an introduction to the study. During 1978-86, 488 reports were completed under the Regional Aquifer-System Analysis Program, and 168 reports which were partially funded by the Regional Aquifer-System Analysis Program were completed under the National Research Program. (Author 's abstract)

Puerto Rican Karst-A Vital Resource

Treesearch

Ariel E. Lugo; Leopoldo Miranda Castro; Abel Vale; Tania del Mar López; Enrique Hernández Prieto; Andrés García Martinó; Alberto R. Puente Rolón; Adrianne G. Tossas; Donald A. McFarlane; Tom Miller; Armando Rodríguez; Joyce Lundberg; John Thomlinson; José Colón; Johannes H. Schellekens; Olga Ramos; Eileen Helmer

2001-01-01

The limestone region of Puerto Rico covers about 27.5 percent of the island’s surface and is subdivided into the northern, southern, and dispersed limestone areas. All limestone areas have karst features. The karst belt is that part of the northern limestone with the most spectacular surficial karst landforms. It covers 142,544 ha or 65 percent of the northern...

Summary of ground-water hydrology of the Cambrian-Ordovician aquifer system in the northern Midwest, United States: A in Regional aquifer system analysis

USGS Publications Warehouse

Young, H.L.

1992-01-01

Development of the aquifer system began in various parts of the northern Midwest in the 1860's and 1870's with the drilling of deep, generally flowing artesian wells near Lake Michigan in eastern Wisconsin and northeastern Illinois and along the valleys of the Mississippi River and its tributaries. Initial heads of 186 and 130 feet above Lake Michigan at Milwaukee and Chicago, respectively, have been reported. Large-scale pumping has produced cones of depression in these two areas, with respective head declines of as much as 375 and 900 feet. Other major pumping centers generally have had much smaller declines. The largest withdrawals from the aquifer system were about 180 million gallons per day in each of the major metropolitan areas of Chicago and Minneapolis-St. Paul (Twin Cities). However, the total decline in head in the St. Peter-Prairie du Chien-Jordan aquifer in the Twin Cities by 1980 was only 90 feet because the aquifer is unconfined. Most of the eastern two-thirds of Iowa, where the aquifer system is tightly confined, is characterized by more than 50 feet of head decline, with 200 feet or more at Mason City and the Quad Cities. Pumpage from the Cambrian-Ordovician aquifer system throughout the study area averaged 683 million gallons per day for the period 1976-80. Results of a transient-model simulation show that recharge increased over predevelopment recharge by 447 million gallons per day. Natural discharge decreased by 99 million gallons per day, and 137 million gallons per day was released from aquifer storage. Mineralization of ground water in the aquifer system increases from slightly mineralized calcium magnesium bicarbonate water in the northern recharge areas, through more mineralized, mixed water types with increased sodium and sulfate, to highly mineralized sodium chloride brines in the deeper parts of the structural basins.

The Effect of Hydraulic Gradient and Pattern of Conduit Systems on Tracing Tests: Bench-Scale Modeling.

PubMed

Mohammadi, Zargham; Gharaat, Mohammad Javad; Field, Malcolm

2018-03-13

Tracer breakthrough curves provide valuable information about the traced media, especially in inherently heterogeneous karst aquifers. In order to study the effect of variations in hydraulic gradient and conduit systems on breakthrough curves, a bench scale karst model was constructed. The bench scale karst model contains both matrix and a conduit. Eight tracing tests were conducted under a wide range of hydraulic gradients from 1 to greater than 5 for branchwork and network-conduit systems. Sampling points at varying distances from the injection point were utilized. Results demonstrate that mean tracer velocities, tracer mass recovery and linear rising slope of the breakthrough curves were directly controlled by hydraulic gradient. As hydraulic gradient increased, both one half the time for peak concentration and one fifth the time for peak concentration decreased. The results demonstrate the variations in one half the time for peak concentration and one fifth the time for peak concentration of the descending limb for different sampling points under differing hydraulic gradients are mainly controlled by the interactions of advection with dispersion. The results are discussed from three perspectives: different conduit systems, different hydraulic-gradient conditions, and different sampling points. The research confirmed the undeniable role of hydrogeological setting (i.e., hydraulic gradient and conduit system) on the shape of the breakthrough curve. The extracted parameters (mobile-fluid velocity, tracer-mass recovery, linear rising limb, one half the time for peak concentration, and one fifth the time for peak concentration) allow for differentiating hydrogeological settings and enhance interpretations the tracing tests in karst aquifers. © 2018, National Ground Water Association.

Detection and quality of previously undetermined Floridan aquifer system discharge to the St. Johns River, Jacksonville, to Green Cove Springs, northeastern Florida

USGS Publications Warehouse

Spechler, R.M.

1996-01-01

Potentiometric surface maps of the Upper Floridan aquifer show two depressions around the St. Johns River frm the city of Jacksonville south toward Green Cove Springs. These depressions, depending on their locations, are the result of withdrawals from agricultural, industrial, domestic and public-supply wells, diffuse upward leakage, and discharge from springs. Submerged springs that discharge into the St. Johns River between Jacksonville and Green Cove Springs have been thought to exist, but locating and evaluating these springs had not been attempted before this investigation. Thermal infrared imagery, seismic reflection, and numerous interviews with local residents were used to locate springs. An airborne thermal infrared survey was conducted along a section of the St. Johns River in northeastern Florida during February 1992 to detect possible sources of ground-water discharge to the river. An infrared image displayed one thermal anomaly in the St. Johns River which is associated with a previously unknown spring discharge from the Floridan aquifer system. Thermal anomalies also were observed at six locations where municipal facilities discharge treated wastewater to the river. Results of seismic reflection surveys indicate the presence of collapse and other karst features underlying the St. Johns River. These features indicate that the surficial deposits and the Hawthorn Formation that underlie the river probably do not consist of continuous beds. The collapse or deformation of the Hawthorn Formation or the presence of permeable sediment of localized extent could create zones of relatively high vertical leakance. This could provide a more direct hydraulic connection between the Upper Floridan aquifer and the river. Water samples collected from the only submerged spring in the St. Johns River within the Jacksonville-Green Cove Springs reach indicate that the source of the water is the Floridan aquifer system. Chloride and sulfate concentrations were 12 and 340

Destruction of dolines: the examples from Slovene karst

NASA Astrophysics Data System (ADS)

Kovacic, G.; Ravbar, N.

2012-04-01

Due to the absence of soil and flat agricultural land, in karst regions, the cultivation of doline bottoms and the clearing of stones on fields and meadows were traditional methods of adapting farming practices to the landscape with limited agricultural potential. In recent years, a variety of activities resulting from comprehensive economic and urban development have increased pressure on karst landscapes. In some areas the surface and the underground are increasingly threatened by industrial activities, uncontrolled settlement and spread of infrastructure, the development of tourism, and intensive agrarian land use. Unsupervised human encroachment on karst landscapes is causing the increasingly more frequent and more widespread degradation of karst relief forms. The intensive reshaping of the landscape has expanded beyond control largely as a result of technological development and mechanization. The excessive modern filling of dolines, as one of the most distinctive karst surface features, has become a major encroachment on the environment for leveling purposes. Such kind of human influence affects the shape of karst features and the appearance of the landscape as well as the intensity of karst processes such as corrosion. Many dolines are filled with general and construction waste, which threatens the existence of unique habitats and quality of groundwater and consequently water supply. This contribution presents some cases of inappropriate management of karst landscape in Slovenia and examines the national legislative framework on spatial planning in karst regions. Unfortunately, in the current legislation, the standards and conditions for the protection of karst landscape characteristics (e.g. dolines) are loose and not fully elaborated. Principally, there are no uniform mechanisms to protect specific relief forms or for the adequate protection of karst. To a large extent, the preservation of the characteristic karst landscape is left to local communities

Simulation of dispersion in layered coastal aquifer systems

USGS Publications Warehouse

Reilly, T.E.

1990-01-01

A density-dependent solute-transport formulation is used to examine ground-water flow in layered coastal aquifers. The numerical experiments indicate that although the transition zone may be thought of as an impermeable 'sharp' interface with freshwater flow parallel to the transition zone in homogeneous aquifers, this is not the case for layered systems. Freshwater can discharge through the transition zone in the confining units. Further, for the best simulation of layered coastal aquifer systems, either a flow-direction-dependent dispersion formulation is required, or the dispersivities must change spatially to reflect the tight thin confining unit. ?? 1990.

Relations between the structure of storage and the transport of chemical compounds in karstic aquifers

NASA Astrophysics Data System (ADS)

Vaute, L.; Drogue, C.; Garrelly, L.; Ghelfenstein, M.

1997-12-01

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 flow 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 karst 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

Going Underground: A Field Investigation and Lab Activity on Karst Topography and Water Systems

ERIC Educational Resources Information Center

O'Dell, Gary; Gonzalez-Espada, Wilson

2011-01-01

Students learn science best with activities that mirror the way scientists work. This article describes how geologists investigate groundwater flow systems in areas of karst topography--geologic formations shaped by dissolving bedrock--and provides a way for students to replicate this research. Students also use electric current to model water…

Ground-water quality of the surficial aquifer system and the upper Floridan Aquifer, Ocala National Forest and Lake County, Florida, 1990-99

USGS Publications Warehouse

Adamski, J.C.; Knowles, Leel

2001-01-01

Data from 217 ground-water samples were statistically analyzed to assess the water quality of the surficial aquifer system and Upper Floridan aquifer in the Ocala National Forest and Lake County, Florida. Samples were collected from 49 wells tapping the surficial aquifer system, 141 wells tapping the Upper Floridan aquifer, and from 27 springs that discharge water from the Upper Floridan aquifer. A total of 136 samples was collected by the U.S. Geological Survey from 1995 through 1999. These data were supplemented with 81 samples collected by the St. Johns River Water Management District and Lake County Water Resources Management from 1990 through 1998. In general, the surficial aquifer system has low concentrations of total dissolved solids (median was 41 milligrams per liter) and major ions. Water quality of the surficial aquifer system, however, is not homogeneous throughout the study area. Concentrations of total dissolved solids, many major ions, and nutrients are greater in samples from Lake County outside the Ocala National Forest than in samples from within the Forest. These results indicate that the surficial aquifer system in Lake County outside the Ocala National Forest probably is being affected by agricultural and (or) urban land-use practices. High concentrations of dissolved oxygen (less than 0.1 to 8.2 milligrams per liter) in the surficial aquifer system underlying the Ocala National Forest indicate that the aquifer is readily recharged by precipitation and is susceptible to surface contamination. Concentrations of total dissolved solids were significantly greater in the Upper Floridan aquifer (median was 182 milligrams per liter) than in the surficial aquifer system. In general, water quality of the Upper Floridan aquifer was homogeneous, primarily being a calcium or calciummagnesium- bicarbonate water type. Near the St. Johns River, the water type of the Upper Floridan aquifer is sodium-chloride, corresponding to an increase in total dissolved

Nitrate in aquifers beneath agricultural systems

USGS Publications Warehouse

Burkart, M.R.; Stoner, J.D.

2002-01-01

Research from several regions of the world provides spatially anecdotal evidence to hypothesize which hydrologic and agricultural factors contribute to groundwater vulnerability to nitrate contamination. Analysis of nationally consistent measurements from the U.S. Geological Survey's NAWOA program confirms these hypotheses for a substantial range of agricultural systems. Shallow unconfined aquifers are most susceptible to nitrate contamination associated with agricultural systems. Alluvial and other unconsolidated aquifers are the most vulnerable and shallow carbonate aquifers provide a substantial but smaller contamination risk. Where any of these aquifers are overlain by permeable soils the risk of contamination is larger. Irrigated systems can compound this vulnerability by increasing leaching facilitated by additional recharge and additional nutrient applications. The agricultural system of corn, soybeans, and hogs produced significantly larger concentrations of groundwater nitrate than all other agricultural systems, although mean nitrate concentrations in counties with dairy, poultry, cattle and grains, and horticulture systems were similar. If trends in the relation between increased fertilizer use and groundwater nitrate in the United States are repeated in other regions of the world, Asia may experience increasing problems because of recent increases in fertilizer use. Groundwater monitoring in Western and Eastern Europe as well as Russia over the next decade may provide data to determine if the trend in increased nitrate contamination can be reversed. If the concentrated livestock trend in the United States is global, it may be accompanied by increasing nitrogen contamination in groundwater. Concentrated livestock provide both point sources in the confinement area and intense non-point sources as fields close to facilities are used for manure disposal. Regions where irrigated cropland is expanding, such as in Asia, may experience the greatest impact of

Groundwater-flow model and effects of projected groundwater use in the Ozark Plateaus Aquifer System in the vicinity of Greene County, Missouri - 1907-2030

USGS Publications Warehouse

Richards, Joseph M.

2010-01-01

Recent and historical periods of rapid growth have increased the stress on the groundwater resources in the Ozark aquifer in the Greene County, Missouri area. Historical pumpage from the Ozark aquifer has caused a cone of depression beneath Springfield, Missouri. In an effort to ease its dependence on groundwater for supply, the city of Springfield built a pipeline in 1996 to bring water from Stockton Lake to the city. Rapid population growth in the area coupled with the expanding cone of depression raised concern about the sustainability of groundwater as a resource for future use. A groundwater-flow model was developed by the U.S. Geological Survey in cooperation with Greene County, Missouri, the U. S. Army Corps of Engineers, and the Missouri Department of Natural Resources to assess the effect that increased groundwater demand is having on the long-term availability of groundwater in and around Greene County, Missouri. Three hydrogeologic units were represented in the groundwater-flow model: the Springfield Plateau aquifer, the Ozark confining unit, and the Ozark aquifer. The Springfield Plateau aquifer is less than 350 feet thick in the model area and generally is a low yield aquifer suitable only for domestic use. The Ozark aquifer is composed of a more than 900-foot thick sequence of dolomite and sandstone in the model area and is the primary aquifer throughout most of southern Missouri. Wells open to the entire thickness of the Ozark aquifer typically yield 1,000 gallons per minute or more. Between the two aquifers is the Ozark confining unit composed of as much as 98 feet of shale and limestone. Karst features such as sinkholes, springs, caves, and losing streams are present in both aquifers, but the majority of these features occur in the Springfield Plateau aquifer. The solution-enlarged fracture and bedding plane conduits in the karst system, particularly in the Springfield Plateau aquifer, are capable of moving large quantities of groundwater through

Groundwater Dynamics in Fossil Fractured Carbonate Aquifers in Eastern Arabian Peninsula

NASA Astrophysics Data System (ADS)

Farag, A. Z. A.; Heggy, E.; Helal, M.; Thirunavukkarasu, D.; Scabbia, G.; Palmer, E. M.

2017-12-01

The Eastern Arabian Peninsula, notably the Qatar Peninsula, represents one of the highest natural groundwater discharge areas for the Arabian platform fossil aquifer system. Groundwater flow dynamics in these aquifers trace the paleoclimatic conditions that have prevailed the Arabian Peninsula during the Quaternary. In such settings, connections between aquifers strongly affect the flow dynamics, water quality and availability as well as karst formation and landscape evolution. Geological structures such as folds, faults and fractures are central to aquifer connectivity, yet their role on groundwater flow is poorly understood. Herein, we performed a detailed mapping of exposed and buried structural features in Qatar using Landsat, Sentinel and ALOS-PalSAR scenes, correlated with field and laboratory measurements to understand their role in aquifer connectivity and groundwater dynamics. Our results suggest that E-W oriented fold-related faults act as vertical conduits along which artesian upward leakages from the deep aquifers (e.g. Aruma and Umm er Radhuma) take place into the shallower aquifers (e.g. Rus and Dammam). Evidence includes: (1) the high potentiometric surfaces of deep aquifers (6 to 25 m amsl) compare to the shallower aquifers (2-3 m amsl for the same region); (2) anomalous elevation of groundwater levels and steeper hydraulic gradients in densely faulted regions; (3) mixed isotopic composition in shallow aquifers (δ18O: -5 to -2 ‰, δ2H: -40 to -10 ‰) between reported deep fossil waters (δ18O: -6.3 ‰, δ2H: -55 ‰) and modern meteoric waters (weighted average: δ18O: -0.6 ‰, δ2H: 4 ‰); (4) abundant meso-crystalline fibrous gypsum veins along fault zones in the Dammam Formation (up to 28 m amsl) in southern Qatar where the anhydritic member of the Rus Formation predominates the subsurface leading to gypsum oversaturation of groundwater. The similarity of crystal morphology (platy crystals under SEM), mineralogical compositions from XRD