Nico Goldscheider - Academia.edu (original) (raw)

Papers by Nico Goldscheider

EGU General Assembly Conference Abstracts, Apr 1, 2012

Nitrate (NO 3 −) contamination of groundwater associated with agronomic activity is of major conc... more Nitrate (NO 3 −) contamination of groundwater associated with agronomic activity is of major concern in many countries. Where agriculture, thin free draining soils and karst aquifers coincide, groundwater is highly vulnerable to nitrate contamination. As residence times and denitrification potential in such systems are typically low, nitrate HESSD 11, 4131-4161, 2014 Nitrate response of karst springs to high rainfall events M. Huebsch et al.

EGU General Assembly Conference Abstracts, Apr 1, 2018

The construction of the combined ship lock weir in Hessigheim, Germany, created a river stage dif... more The construction of the combined ship lock weir in Hessigheim, Germany, created a river stage difference of more than 6 m and intensified subsequently the surface–subsurface water exchange and modified the natural subsurface flow field. In the sulfate-bearing hydrogeological setting, increased infiltration and intensified subsurface flow triggered related dissolution processes. Soon after construction, the structure started suffering from subsidence due to progressive leaching and demanded extensive grouting. In the course of approximately 25 years, groundwater heads and subsurface sulfate concentrations responded distinctively to grouting campaigns. The analysis confirms that as a result of its high solubility and altered hydrogeological conditions, gypsum karst develops on a human rather than on a geological time scale. Grouting measures considerably slowed down these processes, however, at the cost of subsurface flow field variations which will ultimately transfer the zone of enh...

Hydrogeology Journal, 2018

Dense non-aqueous phase liquids (DNAPLs) can easily penetrate into karst aquifers, may accumulate... more Dense non-aqueous phase liquids (DNAPLs) can easily penetrate into karst aquifers, may accumulate in the sediment-filled depressions of conduits, and constitute a long-term source of groundwater contamination. In contrast to porous media, DNAPL dissolution in karst settings has not received much attention. This study investigated the dissolution of sediment-entrapped DNAPLs using a laboratory analogue model corresponding to a syphon structure partly filled by sediments and using numerical simulations. The mass transfer rate increased with an increasing conduit Reynolds number (Re) and increasing conduit angle, as both of these factors led to a more intense hyporheic flow in the sediments. In addition, the mass transfer rate increased linearly with the average flow velocity in the sediment and was higher than expected for an infinite porous medium considered as a reference case. The enhanced mass transfer rate can be explained by the curved streamlines associated with hyporheic flow, which transport solutes away from the DNAPL interface. This study demonstrates that hyporheic flow through karst sediment is a possible mechanism for the mobilization of DNAPL components and might explain the persistent occurrence of such contaminants in karst springs.RésuméLes liquides denses en phase non aqueuse (LDNAs) peuvent facilement pénétrer dans les aquifères karstiques, peuvent s’accumuler dans les dépressions remplies de sédiments des conduits et constituer une source à long terme de contamination des eaux souterraines. Contrairement aux milieux poreux, peu d’attention n’a été porté sur la dissolution du LDNA dans des environnements karstiques. Cette étude a exploré la dissolution des LDNAs piégés au sein des sédiments à l’aide d’un modèle analogue de laboratoire correspondant à une structure d’un siphon partiellement remplie par les sédiments et de simulations numériques. Le taux de transfert de masse augmente avec un nombre croissant de Reynolds (Re) et un angle de conduit croissant, ces deux facteurs entraînant un écoulement hyporhéique plus intense dans les sédiments. De plus, le taux de transfert de masse augmente linéairement avec la vitesse moyenne de l’écoulement dans les sédiments et est plus élevé que prévu pour un milieu poreux infini considéré comme un cas de référence. Un taux de transfert de masse amélioré peut être expliqué par les lignes de flux incurvées associées à l’écoulement hyporhéique, qui transporte les solutés loin de l’interface LDNA. Cette étude démontre que l’écoulement hyporhéique à travers les sédiments karstiques est un mécanisme possible pour la mobilisation des composants de LDNA et pourrait expliquer la présence persistante de tels contaminants dans les sources karstiques.ResumenLos líquidos densos en fase no acuosa (DNAPL) pueden penetrar fácilmente en los acuíferos kársticos, acumularse en las depresiones rellenadas de sedimentos de los conductos y constituir una fuente de contaminación del agua subterránea a largo plazo. A diferencia de los medios porosos, la disolución de DNAPL en ámbitos kársticos no ha recibido mucha atención. Este estudio investigó la disolución de DNAPL atrapados en sedimentos usando un modelo analógico de laboratorio que corresponde a una estructura de sifón parcialmente rellena de sedimentos y utilizando simulaciones numéricas. La tasa de transferencia de masa aumentó con un número creciente de Reynolds (Re) e incrementó el ángulo del conducto, ya que ambos factores condujeron a un flujo hiporreico más intenso en los sedimentos. Además, la tasa de transferencia de masa aumentó linealmente con la velocidad de flujo promedio en el sedimento y fue más alta de lo esperado para un medio poroso infinito considerado como un caso de referencia. La velocidad de transferencia de masa mejorada puede explicarse por las líneas de corriente curvas asociadas con el flujo hiporreico, que transportan los solutos lejos de la interfaz DNAPL. Este estudio demuestra que el flujo hiporreico a través del sedimento kárstico es un posible mecanismo para la movilización de componentes DNAPL y podría explicar la presencia persistente de dichos contaminantes en los manantiales kársticos.摘要重质非水相液体可以很容易地进入岩溶含水层,可能会积聚在管道内沉积物填充的洼地中,成为长期的地下水污染源。相比于孔隙介质,岩溶环境下重质非水相液体的溶解并未受到人们很大的关切。本研究采用实验室类似物模型以及采用数值模拟调查了沉积物截获的重质非水相液体的溶解,这个类似物模型相当于弯管结构,部分充填沉积物。传质速率随着管道雷诺数的增加以及管道角度的增加而增加,因为这两个因素导致沉积物中更强烈的伏流。此外,传质速率随着沉积物中的平均水流速度线性增加,在被认为是一个参考案例的无限孔隙介质中高于预期。增强的传质速率可以由与伏流相关的弯曲河流线解释,伏流可以把溶质从重质非水相液体界面传送到别处。本研究说明,伏流通过岩溶沉积物是重质非水相液体成分活动的一个可能途径,可以解释岩溶泉中这种污染物长期存在的现象。ResumoOs líquidos densos de fase não aquosa (LDFNAs) podem facilmente penetrar em aquíferos cársticos, podendo se acumular em depressões cheias de sedimentos nos condutos, constituindo uma fonte de contaminação de longo prazo das águas subterrâneas. Em contraste com os meios porosos, a dissolução de LDFNA em ambientes cársticos não tem recebida muita atenção. Este estudo investigou a dissolução de LDFNAs aprisionados em sedimentados usando um modelo…

Hydrogeology Journal, 2017

To deal with the challenge of groundwater over-extraction in arid and semi-arid environments, it ... more To deal with the challenge of groundwater over-extraction in arid and semi-arid environments, it is necessary to establish management strategies based on the knowledge of hydrogeological conditions, which can be difficult in places where hydrogeological data are dispersed, scarce or present potential misinformation. Groundwater levels in the southern Jordan Valley (Jordan) have decreased drastically in the last three decades, caused by over-extraction of groundwater for irrigation purposes. This study presents a local, two-dimensional and transient numerical groundwater model, using MODFLOW, to characterise the groundwater system and the water balance in the southern Jordan Valley. Furthermore, scenarios are simulated regarding hydrological conditions and management options, like extension of arable land and closure of illegal wells, influencing the projection of groundwater extraction. A limited dataset, literature values, field surveys, and the ‘crop water-requirement method’ are combined to determine boundary conditions, aquifer parameters, and sources and sinks. The model results show good agreement between predicted and observed values; groundwater-level contours agree with the conceptual model and expected flow direction, and, in terms of water balance, flow volumes are in accordance with literature values. Average annual water consumption for irrigation is estimated to be 29 million m3 and simulation results show that a reduction of groundwater pumping by 40% could recover groundwater heads, reducing the water taken from storage. This study presents an example of how to develop a local numerical groundwater model to support management strategies under the condition of data scarcity.RésuméPour relever le défi de la surexploitation des eaux souterraines dans les milieu arides et semi-arides, il est nécessaire d’établir des stratégies de gestion basées sur la connaissance des conditions hydrogéologiques. Cela peut être difficiles dans les endroits où les données hydrogéologiques sont dispersées, rares ou présentent une désinformation potentielle. Les niveaux des eaux souterraines dans le Sud de la Vallée du Jourdain (Jordanie) ont diminué de façon drastique au cours des trois dernières décennies, en raison de la surexploitation des eaux souterraines à des fins d’irrigation. Cette étude présente un modèle numérique bidimensionnel et transitoire des eaux souterraines à l’échelle locale, utilisant MODFLOW, afin de caractériser le système aquifère et le bilan hydrique dans la vallée méridionale du Jourdain. En outre, des scénarios sont simulés en ce qui concerne les conditions hydrologiques et les options de gestion, comme l’extension des terres arables et l’arrêt d’exploitation de puits illégaux, influençant la projection de l’exploitation des eaux souterraines. Un ensemble de données limité, des valeurs de la littérature, des enquêtes de terrain, et la ‘méthode d’évaluation de la demande d’eau des cultures’ sont combinés pour déterminer les conditions aux limites, les paramètres de l’aquifère, et les termes sources et puits. Les résultats du modèle montrent une bonne cohérence entre les valeurs prédites et observées; les contours piézométriques sont concordants avec le modèle conceptuel et les directions d’écoulement attendues, et, du point de vue du bilan hydraulique, les volumes écoulés sont conformes aux valeurs de la littérature. La consommation annuelle moyenne en eau pour l’irrigation est estimée à 29 millions m3 et les résultats des simulations montrent qu’une réduction des pompages d’eau souterraine de 40% pourrait permettre de récupérer les niveaux piézométriques, limitant ainsi les prélèvements d’eau stockée. Cette étude présente un exemple de la façon de développer un modèle numérique des eaux souterraines à l’échelle locale pour soutenir les stratégies de gestion en condition de rareté de données.ResumenPara enfrentar el desafío de la sobreextracción de agua subterránea en ambientes áridos y semiáridos, es necesario establecer estrategias de gestión basadas en el conocimiento de condiciones hidrogeológicas. Esto puede ser difícil en lugares donde los datos hidrogeológicos son dispersos, escasos o presentan posibles informaciones erróneas. Los niveles de agua subterránea en el valle del Jordán meridional (Jordania) han disminuido drásticamente en las últimas tres décadas, causado por la sobreexplotación de aguas subterráneas con fines de riego. Este estudio presenta un modelo numérico de aguas subterráneas local, bidimensional y de régimen transiente, utilizando MODFLOW, para caracterizar el sistema de aguas subterráneas y el balance hídrico en el valle del Jordán meridional. Además, se simulan escenarios sobre condiciones hidrológicas y opciones de gestión, como la extensión de tierras de cultivo y el cierre de pozos ilegales, que influyen en la proyección de la extracción de aguas subterráneas. Un conjunto de datos limitado, valores obtenidos de la literatura, evaluaciones en terreno y el…

Hydrogeology Journal, 2017

Karst aquifers in semi-arid regions are particularly threatened by surface contamination, especia... more 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.ZusammenfassungKarstgrundwasserleiter in semiariden Gebieten sind im besonderen Maße von Oberflächenverschmutzung bedroht, vor allem während der Wintersaison, wenn extrem variabler Niederschlag von hoher Intensität vorherrscht. Eine zusätzliche Herausforderung stellt die künstliche Grundwasseranreicherung mit Niederschlagswasser dar, da Karstgrundwasserleiter eine hohe räumliche Variabilität in ihren hydraulischen Eigenschaften aufweisen. In diesen Fällen sind angepasste Schutzkonzepte erforderlich, die das Zusammenspiel von Oberflächenwasser und Grundwasser berücksichtigen. In dieser Studie wird ein kombiniertes Schutzkonzept für das Oberflächeneinzugsgebiet der künstlichen Grundwasseranreicherungsanlage am Wala Stausee und dem unterstromig gelegenen Hidan Brunnenfeld in Jordanien entwickelt. In Beiden wurden wiederholt bakteriologische Verunreinigungen festgestellt. Die Variabilität der Grundwasserqualität lässt sich durch Korrelation der Kontaminationsereignisse mit Niederschlagsereignissen und Infiltration aus dem Stausee erklären. Beides führt zu erhöhtem Abfluss im Wadi unterhalb des Stausees, hervorgerufen durch Oberflächenabfluss und Grundwasseraustritte. Ein Tracerversuch bestätigte die Infiltration des Oberflächenflusses in den Untergrund über Pools entlang des Wadi Wala. Eine intrinsische Karstvulnerabilitäts- und Risikokarte wurde entwickelt und an die regionalen Besonderheiten angepasst, um die Abtrennung des Einzugsgebiets durch den Wala Staudamm und das Zusammenwirken von Oberflächenwasser und Grundwasser zu berücksichtigen. Die Umsetzung der vorgeschlagenen Schutzzonen für das Brunnenfeld und das Reservoir wird dringend empfohlen, da die Ergebnisse ein extremes Kontaminationsrisiko durch Viehzucht, Ackerbau und menschliche Besiedlung entlang des Wadis zeigen. Die angewandten Methoden können auf andere künstliche Grundwasseranreicherungsanlagen in ähnlichen Karstgebieten semiarider Regionen übertragen werden.RésuméLes aquifères karstiques dans les régions semi-arides sont particulièrement menacés par une contamination provenant de la surface, surtout pendant les saisons hivernales où prévaut une pluviométrie extrêmement variable de fortes intensités. Un défi supplémentaire existe lorsque la gestion de la recharge par les eaux pluviales est. appliquée, car les aquifères karstiques présentent une grande variabilité spatiale des propriétés hydrauliques. Dans ces cas, des concepts de protection adaptée sont nécessaires pour traiter la question des interactions entre les eaux de surface et les eaux souterraines. Dans cette étude, une approche combinée de protection est. développée pour le bassin versant du site de recharge de l’aquifère au niveau du réservoir de Wala en Jordanie et du champ de captage d’Hidan situé en aval hydraulique, tous les deux sujets à une contamination bactériologique fréquente. La variabilité de la qualité des eaux souterraines a été évaluée en corrélant les événements de contamination avec les précipitations, et à la recharge à partir du réservoir. Les deux déclenchent une augmentation du débit de l’oued en aval du réservoir due à la génération d’un ruissellement de surface et à l’infiltration vers les eaux souterraines, respectivement. Un essai de traçage a vérifié la voie principale de…

Journal of Hydrology, 2016

Spring discharge often responds to rainfall with a rapid increase followed by a slower recession,... more Spring discharge often responds to rainfall with a rapid increase followed by a slower recession, and the mode of recession is often exponential-like. We propose a new model of the response of spring discharge to rainfall based on the square law for turbulent conduit flow. The new non-exponential model is compared against the exponential model under specific constraints. A hydrograph of St. Marks River in Florida is used to illustrate that when the change in "sinkhole head" (defined as the hydraulic head at the upstream end of the karst conduit connected to the spring) is relatively small, the solution of the new model is close to that of the exponential model, which extends the validity and application of the exponential solution. When the change in sinkhole head is very large, the solutions from the two models clearly differ from each other. Limitations of the non-exponential model are analyzed by simulation of a hydrograph observed downstream of Wakulla Springs. It is concluded that both solutions are applicable when spring response is smaller than or comparable to the base flow, but are nonphysical when the response is much larger than the base discharge.

Journal of Hydrology, 2016

In semi-arid regions with high seasonal variability of water availability, adaptive management st... more In semi-arid regions with high seasonal variability of water availability, adaptive management strategies and technical measures are required to ensure the sustainable use of water resources. In this study, managed recharge of storm water into a karst aquifer and the water level fluctuations related to pumping in a nearby wellfield were simulated at Wadi Wala, Jordan. We used a numerical equivalent porous medium (EPM) approach with specific adaptations to account for the heterogeneity and anisotropy of the karst aquifer. The model domain was vertically projected along the wadi course, resulting in a 2dimensional model, and subdivided into hydraulic zones representing the karst-specific flow pattern of fast flow and slow depletion. Results show satisfying agreement of measured and simulated groundwater tables from 2002 to 2012 and predict a lowering of the average groundwater table until 2022 of around 2.7 m in the immediate surroundings of the reservoir and an increased depletion towards the wellfield, mainly caused by sedimentation in the reservoir and an associated decrease in infiltration. Abstraction at the wellfield changed considerably over the regarded time period and strongly influences the groundwater fluctuations, which shows the need of improved pumping management and monitoring. The results can serve as a basis for decision makers regarding an optimization of water management at the reservoir and wellfield. Furthermore, the presented numerical approach can be transferred to karst regions with similar physio-geographical conditions to assess managed aquifer recharge.

Hydrogeology Journal

The effectiveness of using a groundwater geochemistry approach in karst hydrogeologic research is... more The effectiveness of using a groundwater geochemistry approach in karst hydrogeologic research is highlighted. In particular, this approach is useful for preliminary investigations, such as for the study described here on the Dong Van karst aquifer system in Northern Vietnam. Analyses of different groundwater chemistry parameters complement each other, to clarify hydrochemical processes that are occurring in the karst system. The results of this study show that major ion composition can be used to clarify water chemistry signatures, as well as to identify the mixing processes and water–rock interactions in aquifers. Meanwhile, trace element concentrations and rare earth element patterns can be used as potential natural tracers when some processes are not revealed through conventional hydrochemical methods. These natural tracers can also be used to identify contaminant sources and/or contaminant transport pathways in karst aquifers. Viewed holistically, the groundwater geochemistry a...

Hydrogeology Journal

Karst areas contain valuable groundwater resources and high biodiversity, but are particularly vu... more Karst areas contain valuable groundwater resources and high biodiversity, but are particularly vulnerable to climate change and human impacts. Land-use change is the cause and consequence of global environmental change. The releases of the Climate Change Initiative-Land Cover (CCI-LC) and World Karst Aquifer Map (WOKAM) datasets have made it possible to explore global land-use changes in karst areas. This paper firstly analyses the global karst land-use distribution in 2020, as well as the land-use transition characteristics between 1992 and 2020. Then, two indicators, proportion of land-use change and dominant type of land-use change, are proposed to identify the spatial characteristics of land-use change in global karst areas. Finally, three examples of land-use change in karst areas are analyzed in detail. Land-use types and proportions of the global karst areas from large to small are as follows: forest (31.78%), bare area (27.58%), cropland (19.02%), grassland (10.87%), shrubla...

Water Resources Research, 2019

Effective groundwater monitoring networks are important, as systematic data collected at observat... more Effective groundwater monitoring networks are important, as systematic data collected at observation wells provide a crucial understanding of the dynamics of hydrogeological systems as well as the basis for many other applications. This study investigates the influence of six groundwater level monitoring network (GLMN) sampling designs (random, grid, spatial coverage, and geostatistical) with varying densities on the accuracy of spatially interpolated groundwater surfaces. To obtain spatially continuous prediction errors (in contrast to point cross‐validation errors), we used nine potentiometric groundwater surfaces from three regional MODFLOW groundwater flow models with different resolutions as a priori references. To assess the suitability of frequently‐used cross‐validation error statistics (MAE, RMSE, RMSSE, ASE, and NSE), we compared them with the actual prediction errors (APE). Additionally, we defined upper and lower thresholds for an appropriate spatial density of monitorin...

Integrated Water Resources Management: Concept, Research and Implementation, 2016

The Lower Jordan Valley in the Middle East comprises parts of Israel, Jordan and the Palestinian ... more The Lower Jordan Valley in the Middle East comprises parts of Israel, Jordan and the Palestinian Territories and is amongst the water scarcest regions worldwide. As the average water availability per person is below 150 m³/year, this region is facing absolute water scarcity. The water resource systems are overexploited and subject to further stress through high population growth, climate change and the recent migration of refugees from Syria. Declining water levels of the Dead Sea and within the regional aquifers are visible evidence of overexploitation. Further, salinization and contamination including pharmaceutical residues in surface and groundwater indicate the strong deterioration of water quality by anthropogenic activities. Integrated Water Resource Management (IWRM) is a concept to address these water related issues but needs to be incorporated into the water strategies of the riparian states. SMART (Sustainable Management of Available Resources with Innovative Technologies) is a research and development project within the framework of IWRM and has the overall goal to develop a transferable concept for a sustainable water resource management in the Lower Jordan Valley. Besides natural available freshwater, unconventional sources such as treated waste water, artificially recharged groundwater, and desalinated brackish groundwater are considered. Based on detailed water balances, management concepts have been developed and applied to allow the assessment of the current state of the water resources, as well as the future development, taking the actions of the respective water strategy into account. The SMART approach is transferable to other regions in the world suffering under natural and/or manmade water scarcity.

We use the magnitude and centroid period of Rayleigh wave along with the amplitude of fluctuation... more We use the magnitude and centroid period of Rayleigh wave along with the amplitude of fluctuations of water level in a well to calculate effective porosity of a karst aquifer at the site scale. The radial and vertical displacements of Rayleigh wave are first related to the confining pressure of rock, which is then related to fluid pressure via the Gassmann equation. Three seismograms recorded at station 633A of the USARRAY and the induced responses of Well J-17 in the Edwards Aquifer (Texas) allow the calculation of an effective porosity between 17.0 and 24.4 percent, the average of which is close to the total porosity of core samples determined by geophysical well logs. This paper provides an innovative method to measure effective porosity in aquifers. Because of the long wavelengths of Rayleigh wave, the interdisciplinary approach is advantageous in that the resulting effective porosity is at the site scale which includes large conduits or voids

A tracer test during low-flow conditions was carried out in the karstic aquifer of Sierra de las ... more A tracer test during low-flow conditions was carried out in the karstic aquifer of Sierra de las Nieves (Málaga) in order to assess its hydrogeological functioning and vulnerability to contamination. Two kilogrammes of Eosine were injected in an active siphon located in the Sima del Aire cave shaft (-640 m) at the end of August 2003. The springs were sampled until November 2003. For more than 50 days, the tracer was not detected at any of the springs. After several rainfall events in October 2003, a signal was observed in the two Río Grande springs. The first arrival of Eosine appears before the increase of spring discharge and the dilution effect of the most important rainfalls (86 mm, October 25th). The calculated groundwater velocities (below 4 m/hour) are not representative of the dry period because rainfall forced the Eosine transport. However, they give an idea about the long residence time if a contamination event occurs during low-flow condition

Hydrogeology Journal, 2022

Anisotropic fast-marching algorithms are computationally efficient tools for generating realistic... more Anisotropic fast-marching algorithms are computationally efficient tools for generating realistic maps of karst conduit networks, constrained by both the spatial extent and the orientation of karstifiable geologic units. Existing models to generate conduit network maps are limited either by high computational requirements (for chemistry-based models) or by their inability to incorporate the effects of elevation and orientation gradients (for isotropic fast-marching models). The new anisotropic fast-marching approach described here provides a significant improvement, though it imitates rather than reproduces actual speleogenetic processes. It can rapidly generate a stochastic ensemble of plausible networks from basic geologic information, which can also be used as input to karst-appropriate flow models. This paper introduces an open-source, easy-to-use implementation through the Python package pyKasso, then describes its application to a well-mapped geologically complex long-term stu...

EGU General Assembly Conference Abstracts, Apr 1, 2012

Nitrate (NO 3 −) contamination of groundwater associated with agronomic activity is of major conc... more Nitrate (NO 3 −) contamination of groundwater associated with agronomic activity is of major concern in many countries. Where agriculture, thin free draining soils and karst aquifers coincide, groundwater is highly vulnerable to nitrate contamination. As residence times and denitrification potential in such systems are typically low, nitrate HESSD 11, 4131-4161, 2014 Nitrate response of karst springs to high rainfall events M. Huebsch et al.

EGU General Assembly Conference Abstracts, Apr 1, 2018

The construction of the combined ship lock weir in Hessigheim, Germany, created a river stage dif... more The construction of the combined ship lock weir in Hessigheim, Germany, created a river stage difference of more than 6 m and intensified subsequently the surface–subsurface water exchange and modified the natural subsurface flow field. In the sulfate-bearing hydrogeological setting, increased infiltration and intensified subsurface flow triggered related dissolution processes. Soon after construction, the structure started suffering from subsidence due to progressive leaching and demanded extensive grouting. In the course of approximately 25 years, groundwater heads and subsurface sulfate concentrations responded distinctively to grouting campaigns. The analysis confirms that as a result of its high solubility and altered hydrogeological conditions, gypsum karst develops on a human rather than on a geological time scale. Grouting measures considerably slowed down these processes, however, at the cost of subsurface flow field variations which will ultimately transfer the zone of enh...

Hydrogeology Journal, 2018

Dense non-aqueous phase liquids (DNAPLs) can easily penetrate into karst aquifers, may accumulate... more Dense non-aqueous phase liquids (DNAPLs) can easily penetrate into karst aquifers, may accumulate in the sediment-filled depressions of conduits, and constitute a long-term source of groundwater contamination. In contrast to porous media, DNAPL dissolution in karst settings has not received much attention. This study investigated the dissolution of sediment-entrapped DNAPLs using a laboratory analogue model corresponding to a syphon structure partly filled by sediments and using numerical simulations. The mass transfer rate increased with an increasing conduit Reynolds number (Re) and increasing conduit angle, as both of these factors led to a more intense hyporheic flow in the sediments. In addition, the mass transfer rate increased linearly with the average flow velocity in the sediment and was higher than expected for an infinite porous medium considered as a reference case. The enhanced mass transfer rate can be explained by the curved streamlines associated with hyporheic flow, which transport solutes away from the DNAPL interface. This study demonstrates that hyporheic flow through karst sediment is a possible mechanism for the mobilization of DNAPL components and might explain the persistent occurrence of such contaminants in karst springs.RésuméLes liquides denses en phase non aqueuse (LDNAs) peuvent facilement pénétrer dans les aquifères karstiques, peuvent s’accumuler dans les dépressions remplies de sédiments des conduits et constituer une source à long terme de contamination des eaux souterraines. Contrairement aux milieux poreux, peu d’attention n’a été porté sur la dissolution du LDNA dans des environnements karstiques. Cette étude a exploré la dissolution des LDNAs piégés au sein des sédiments à l’aide d’un modèle analogue de laboratoire correspondant à une structure d’un siphon partiellement remplie par les sédiments et de simulations numériques. Le taux de transfert de masse augmente avec un nombre croissant de Reynolds (Re) et un angle de conduit croissant, ces deux facteurs entraînant un écoulement hyporhéique plus intense dans les sédiments. De plus, le taux de transfert de masse augmente linéairement avec la vitesse moyenne de l’écoulement dans les sédiments et est plus élevé que prévu pour un milieu poreux infini considéré comme un cas de référence. Un taux de transfert de masse amélioré peut être expliqué par les lignes de flux incurvées associées à l’écoulement hyporhéique, qui transporte les solutés loin de l’interface LDNA. Cette étude démontre que l’écoulement hyporhéique à travers les sédiments karstiques est un mécanisme possible pour la mobilisation des composants de LDNA et pourrait expliquer la présence persistante de tels contaminants dans les sources karstiques.ResumenLos líquidos densos en fase no acuosa (DNAPL) pueden penetrar fácilmente en los acuíferos kársticos, acumularse en las depresiones rellenadas de sedimentos de los conductos y constituir una fuente de contaminación del agua subterránea a largo plazo. A diferencia de los medios porosos, la disolución de DNAPL en ámbitos kársticos no ha recibido mucha atención. Este estudio investigó la disolución de DNAPL atrapados en sedimentos usando un modelo analógico de laboratorio que corresponde a una estructura de sifón parcialmente rellena de sedimentos y utilizando simulaciones numéricas. La tasa de transferencia de masa aumentó con un número creciente de Reynolds (Re) e incrementó el ángulo del conducto, ya que ambos factores condujeron a un flujo hiporreico más intenso en los sedimentos. Además, la tasa de transferencia de masa aumentó linealmente con la velocidad de flujo promedio en el sedimento y fue más alta de lo esperado para un medio poroso infinito considerado como un caso de referencia. La velocidad de transferencia de masa mejorada puede explicarse por las líneas de corriente curvas asociadas con el flujo hiporreico, que transportan los solutos lejos de la interfaz DNAPL. Este estudio demuestra que el flujo hiporreico a través del sedimento kárstico es un posible mecanismo para la movilización de componentes DNAPL y podría explicar la presencia persistente de dichos contaminantes en los manantiales kársticos.摘要重质非水相液体可以很容易地进入岩溶含水层,可能会积聚在管道内沉积物填充的洼地中,成为长期的地下水污染源。相比于孔隙介质,岩溶环境下重质非水相液体的溶解并未受到人们很大的关切。本研究采用实验室类似物模型以及采用数值模拟调查了沉积物截获的重质非水相液体的溶解,这个类似物模型相当于弯管结构,部分充填沉积物。传质速率随着管道雷诺数的增加以及管道角度的增加而增加,因为这两个因素导致沉积物中更强烈的伏流。此外,传质速率随着沉积物中的平均水流速度线性增加,在被认为是一个参考案例的无限孔隙介质中高于预期。增强的传质速率可以由与伏流相关的弯曲河流线解释,伏流可以把溶质从重质非水相液体界面传送到别处。本研究说明,伏流通过岩溶沉积物是重质非水相液体成分活动的一个可能途径,可以解释岩溶泉中这种污染物长期存在的现象。ResumoOs líquidos densos de fase não aquosa (LDFNAs) podem facilmente penetrar em aquíferos cársticos, podendo se acumular em depressões cheias de sedimentos nos condutos, constituindo uma fonte de contaminação de longo prazo das águas subterrâneas. Em contraste com os meios porosos, a dissolução de LDFNA em ambientes cársticos não tem recebida muita atenção. Este estudo investigou a dissolução de LDFNAs aprisionados em sedimentados usando um modelo…

Hydrogeology Journal, 2017

To deal with the challenge of groundwater over-extraction in arid and semi-arid environments, it ... more To deal with the challenge of groundwater over-extraction in arid and semi-arid environments, it is necessary to establish management strategies based on the knowledge of hydrogeological conditions, which can be difficult in places where hydrogeological data are dispersed, scarce or present potential misinformation. Groundwater levels in the southern Jordan Valley (Jordan) have decreased drastically in the last three decades, caused by over-extraction of groundwater for irrigation purposes. This study presents a local, two-dimensional and transient numerical groundwater model, using MODFLOW, to characterise the groundwater system and the water balance in the southern Jordan Valley. Furthermore, scenarios are simulated regarding hydrological conditions and management options, like extension of arable land and closure of illegal wells, influencing the projection of groundwater extraction. A limited dataset, literature values, field surveys, and the ‘crop water-requirement method’ are combined to determine boundary conditions, aquifer parameters, and sources and sinks. The model results show good agreement between predicted and observed values; groundwater-level contours agree with the conceptual model and expected flow direction, and, in terms of water balance, flow volumes are in accordance with literature values. Average annual water consumption for irrigation is estimated to be 29 million m3 and simulation results show that a reduction of groundwater pumping by 40% could recover groundwater heads, reducing the water taken from storage. This study presents an example of how to develop a local numerical groundwater model to support management strategies under the condition of data scarcity.RésuméPour relever le défi de la surexploitation des eaux souterraines dans les milieu arides et semi-arides, il est nécessaire d’établir des stratégies de gestion basées sur la connaissance des conditions hydrogéologiques. Cela peut être difficiles dans les endroits où les données hydrogéologiques sont dispersées, rares ou présentent une désinformation potentielle. Les niveaux des eaux souterraines dans le Sud de la Vallée du Jourdain (Jordanie) ont diminué de façon drastique au cours des trois dernières décennies, en raison de la surexploitation des eaux souterraines à des fins d’irrigation. Cette étude présente un modèle numérique bidimensionnel et transitoire des eaux souterraines à l’échelle locale, utilisant MODFLOW, afin de caractériser le système aquifère et le bilan hydrique dans la vallée méridionale du Jourdain. En outre, des scénarios sont simulés en ce qui concerne les conditions hydrologiques et les options de gestion, comme l’extension des terres arables et l’arrêt d’exploitation de puits illégaux, influençant la projection de l’exploitation des eaux souterraines. Un ensemble de données limité, des valeurs de la littérature, des enquêtes de terrain, et la ‘méthode d’évaluation de la demande d’eau des cultures’ sont combinés pour déterminer les conditions aux limites, les paramètres de l’aquifère, et les termes sources et puits. Les résultats du modèle montrent une bonne cohérence entre les valeurs prédites et observées; les contours piézométriques sont concordants avec le modèle conceptuel et les directions d’écoulement attendues, et, du point de vue du bilan hydraulique, les volumes écoulés sont conformes aux valeurs de la littérature. La consommation annuelle moyenne en eau pour l’irrigation est estimée à 29 millions m3 et les résultats des simulations montrent qu’une réduction des pompages d’eau souterraine de 40% pourrait permettre de récupérer les niveaux piézométriques, limitant ainsi les prélèvements d’eau stockée. Cette étude présente un exemple de la façon de développer un modèle numérique des eaux souterraines à l’échelle locale pour soutenir les stratégies de gestion en condition de rareté de données.ResumenPara enfrentar el desafío de la sobreextracción de agua subterránea en ambientes áridos y semiáridos, es necesario establecer estrategias de gestión basadas en el conocimiento de condiciones hidrogeológicas. Esto puede ser difícil en lugares donde los datos hidrogeológicos son dispersos, escasos o presentan posibles informaciones erróneas. Los niveles de agua subterránea en el valle del Jordán meridional (Jordania) han disminuido drásticamente en las últimas tres décadas, causado por la sobreexplotación de aguas subterráneas con fines de riego. Este estudio presenta un modelo numérico de aguas subterráneas local, bidimensional y de régimen transiente, utilizando MODFLOW, para caracterizar el sistema de aguas subterráneas y el balance hídrico en el valle del Jordán meridional. Además, se simulan escenarios sobre condiciones hidrológicas y opciones de gestión, como la extensión de tierras de cultivo y el cierre de pozos ilegales, que influyen en la proyección de la extracción de aguas subterráneas. Un conjunto de datos limitado, valores obtenidos de la literatura, evaluaciones en terreno y el…

Hydrogeology Journal, 2017

Karst aquifers in semi-arid regions are particularly threatened by surface contamination, especia... more 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.ZusammenfassungKarstgrundwasserleiter in semiariden Gebieten sind im besonderen Maße von Oberflächenverschmutzung bedroht, vor allem während der Wintersaison, wenn extrem variabler Niederschlag von hoher Intensität vorherrscht. Eine zusätzliche Herausforderung stellt die künstliche Grundwasseranreicherung mit Niederschlagswasser dar, da Karstgrundwasserleiter eine hohe räumliche Variabilität in ihren hydraulischen Eigenschaften aufweisen. In diesen Fällen sind angepasste Schutzkonzepte erforderlich, die das Zusammenspiel von Oberflächenwasser und Grundwasser berücksichtigen. In dieser Studie wird ein kombiniertes Schutzkonzept für das Oberflächeneinzugsgebiet der künstlichen Grundwasseranreicherungsanlage am Wala Stausee und dem unterstromig gelegenen Hidan Brunnenfeld in Jordanien entwickelt. In Beiden wurden wiederholt bakteriologische Verunreinigungen festgestellt. Die Variabilität der Grundwasserqualität lässt sich durch Korrelation der Kontaminationsereignisse mit Niederschlagsereignissen und Infiltration aus dem Stausee erklären. Beides führt zu erhöhtem Abfluss im Wadi unterhalb des Stausees, hervorgerufen durch Oberflächenabfluss und Grundwasseraustritte. Ein Tracerversuch bestätigte die Infiltration des Oberflächenflusses in den Untergrund über Pools entlang des Wadi Wala. Eine intrinsische Karstvulnerabilitäts- und Risikokarte wurde entwickelt und an die regionalen Besonderheiten angepasst, um die Abtrennung des Einzugsgebiets durch den Wala Staudamm und das Zusammenwirken von Oberflächenwasser und Grundwasser zu berücksichtigen. Die Umsetzung der vorgeschlagenen Schutzzonen für das Brunnenfeld und das Reservoir wird dringend empfohlen, da die Ergebnisse ein extremes Kontaminationsrisiko durch Viehzucht, Ackerbau und menschliche Besiedlung entlang des Wadis zeigen. Die angewandten Methoden können auf andere künstliche Grundwasseranreicherungsanlagen in ähnlichen Karstgebieten semiarider Regionen übertragen werden.RésuméLes aquifères karstiques dans les régions semi-arides sont particulièrement menacés par une contamination provenant de la surface, surtout pendant les saisons hivernales où prévaut une pluviométrie extrêmement variable de fortes intensités. Un défi supplémentaire existe lorsque la gestion de la recharge par les eaux pluviales est. appliquée, car les aquifères karstiques présentent une grande variabilité spatiale des propriétés hydrauliques. Dans ces cas, des concepts de protection adaptée sont nécessaires pour traiter la question des interactions entre les eaux de surface et les eaux souterraines. Dans cette étude, une approche combinée de protection est. développée pour le bassin versant du site de recharge de l’aquifère au niveau du réservoir de Wala en Jordanie et du champ de captage d’Hidan situé en aval hydraulique, tous les deux sujets à une contamination bactériologique fréquente. La variabilité de la qualité des eaux souterraines a été évaluée en corrélant les événements de contamination avec les précipitations, et à la recharge à partir du réservoir. Les deux déclenchent une augmentation du débit de l’oued en aval du réservoir due à la génération d’un ruissellement de surface et à l’infiltration vers les eaux souterraines, respectivement. Un essai de traçage a vérifié la voie principale de…

Journal of Hydrology, 2016

Spring discharge often responds to rainfall with a rapid increase followed by a slower recession,... more Spring discharge often responds to rainfall with a rapid increase followed by a slower recession, and the mode of recession is often exponential-like. We propose a new model of the response of spring discharge to rainfall based on the square law for turbulent conduit flow. The new non-exponential model is compared against the exponential model under specific constraints. A hydrograph of St. Marks River in Florida is used to illustrate that when the change in "sinkhole head" (defined as the hydraulic head at the upstream end of the karst conduit connected to the spring) is relatively small, the solution of the new model is close to that of the exponential model, which extends the validity and application of the exponential solution. When the change in sinkhole head is very large, the solutions from the two models clearly differ from each other. Limitations of the non-exponential model are analyzed by simulation of a hydrograph observed downstream of Wakulla Springs. It is concluded that both solutions are applicable when spring response is smaller than or comparable to the base flow, but are nonphysical when the response is much larger than the base discharge.

Journal of Hydrology, 2016

In semi-arid regions with high seasonal variability of water availability, adaptive management st... more In semi-arid regions with high seasonal variability of water availability, adaptive management strategies and technical measures are required to ensure the sustainable use of water resources. In this study, managed recharge of storm water into a karst aquifer and the water level fluctuations related to pumping in a nearby wellfield were simulated at Wadi Wala, Jordan. We used a numerical equivalent porous medium (EPM) approach with specific adaptations to account for the heterogeneity and anisotropy of the karst aquifer. The model domain was vertically projected along the wadi course, resulting in a 2dimensional model, and subdivided into hydraulic zones representing the karst-specific flow pattern of fast flow and slow depletion. Results show satisfying agreement of measured and simulated groundwater tables from 2002 to 2012 and predict a lowering of the average groundwater table until 2022 of around 2.7 m in the immediate surroundings of the reservoir and an increased depletion towards the wellfield, mainly caused by sedimentation in the reservoir and an associated decrease in infiltration. Abstraction at the wellfield changed considerably over the regarded time period and strongly influences the groundwater fluctuations, which shows the need of improved pumping management and monitoring. The results can serve as a basis for decision makers regarding an optimization of water management at the reservoir and wellfield. Furthermore, the presented numerical approach can be transferred to karst regions with similar physio-geographical conditions to assess managed aquifer recharge.

Hydrogeology Journal

The effectiveness of using a groundwater geochemistry approach in karst hydrogeologic research is... more The effectiveness of using a groundwater geochemistry approach in karst hydrogeologic research is highlighted. In particular, this approach is useful for preliminary investigations, such as for the study described here on the Dong Van karst aquifer system in Northern Vietnam. Analyses of different groundwater chemistry parameters complement each other, to clarify hydrochemical processes that are occurring in the karst system. The results of this study show that major ion composition can be used to clarify water chemistry signatures, as well as to identify the mixing processes and water–rock interactions in aquifers. Meanwhile, trace element concentrations and rare earth element patterns can be used as potential natural tracers when some processes are not revealed through conventional hydrochemical methods. These natural tracers can also be used to identify contaminant sources and/or contaminant transport pathways in karst aquifers. Viewed holistically, the groundwater geochemistry a...

Hydrogeology Journal

Karst areas contain valuable groundwater resources and high biodiversity, but are particularly vu... more Karst areas contain valuable groundwater resources and high biodiversity, but are particularly vulnerable to climate change and human impacts. Land-use change is the cause and consequence of global environmental change. The releases of the Climate Change Initiative-Land Cover (CCI-LC) and World Karst Aquifer Map (WOKAM) datasets have made it possible to explore global land-use changes in karst areas. This paper firstly analyses the global karst land-use distribution in 2020, as well as the land-use transition characteristics between 1992 and 2020. Then, two indicators, proportion of land-use change and dominant type of land-use change, are proposed to identify the spatial characteristics of land-use change in global karst areas. Finally, three examples of land-use change in karst areas are analyzed in detail. Land-use types and proportions of the global karst areas from large to small are as follows: forest (31.78%), bare area (27.58%), cropland (19.02%), grassland (10.87%), shrubla...

Water Resources Research, 2019

Effective groundwater monitoring networks are important, as systematic data collected at observat... more Effective groundwater monitoring networks are important, as systematic data collected at observation wells provide a crucial understanding of the dynamics of hydrogeological systems as well as the basis for many other applications. This study investigates the influence of six groundwater level monitoring network (GLMN) sampling designs (random, grid, spatial coverage, and geostatistical) with varying densities on the accuracy of spatially interpolated groundwater surfaces. To obtain spatially continuous prediction errors (in contrast to point cross‐validation errors), we used nine potentiometric groundwater surfaces from three regional MODFLOW groundwater flow models with different resolutions as a priori references. To assess the suitability of frequently‐used cross‐validation error statistics (MAE, RMSE, RMSSE, ASE, and NSE), we compared them with the actual prediction errors (APE). Additionally, we defined upper and lower thresholds for an appropriate spatial density of monitorin...

Integrated Water Resources Management: Concept, Research and Implementation, 2016

The Lower Jordan Valley in the Middle East comprises parts of Israel, Jordan and the Palestinian ... more The Lower Jordan Valley in the Middle East comprises parts of Israel, Jordan and the Palestinian Territories and is amongst the water scarcest regions worldwide. As the average water availability per person is below 150 m³/year, this region is facing absolute water scarcity. The water resource systems are overexploited and subject to further stress through high population growth, climate change and the recent migration of refugees from Syria. Declining water levels of the Dead Sea and within the regional aquifers are visible evidence of overexploitation. Further, salinization and contamination including pharmaceutical residues in surface and groundwater indicate the strong deterioration of water quality by anthropogenic activities. Integrated Water Resource Management (IWRM) is a concept to address these water related issues but needs to be incorporated into the water strategies of the riparian states. SMART (Sustainable Management of Available Resources with Innovative Technologies) is a research and development project within the framework of IWRM and has the overall goal to develop a transferable concept for a sustainable water resource management in the Lower Jordan Valley. Besides natural available freshwater, unconventional sources such as treated waste water, artificially recharged groundwater, and desalinated brackish groundwater are considered. Based on detailed water balances, management concepts have been developed and applied to allow the assessment of the current state of the water resources, as well as the future development, taking the actions of the respective water strategy into account. The SMART approach is transferable to other regions in the world suffering under natural and/or manmade water scarcity.

We use the magnitude and centroid period of Rayleigh wave along with the amplitude of fluctuation... more We use the magnitude and centroid period of Rayleigh wave along with the amplitude of fluctuations of water level in a well to calculate effective porosity of a karst aquifer at the site scale. The radial and vertical displacements of Rayleigh wave are first related to the confining pressure of rock, which is then related to fluid pressure via the Gassmann equation. Three seismograms recorded at station 633A of the USARRAY and the induced responses of Well J-17 in the Edwards Aquifer (Texas) allow the calculation of an effective porosity between 17.0 and 24.4 percent, the average of which is close to the total porosity of core samples determined by geophysical well logs. This paper provides an innovative method to measure effective porosity in aquifers. Because of the long wavelengths of Rayleigh wave, the interdisciplinary approach is advantageous in that the resulting effective porosity is at the site scale which includes large conduits or voids

A tracer test during low-flow conditions was carried out in the karstic aquifer of Sierra de las ... more A tracer test during low-flow conditions was carried out in the karstic aquifer of Sierra de las Nieves (Málaga) in order to assess its hydrogeological functioning and vulnerability to contamination. Two kilogrammes of Eosine were injected in an active siphon located in the Sima del Aire cave shaft (-640 m) at the end of August 2003. The springs were sampled until November 2003. For more than 50 days, the tracer was not detected at any of the springs. After several rainfall events in October 2003, a signal was observed in the two Río Grande springs. The first arrival of Eosine appears before the increase of spring discharge and the dilution effect of the most important rainfalls (86 mm, October 25th). The calculated groundwater velocities (below 4 m/hour) are not representative of the dry period because rainfall forced the Eosine transport. However, they give an idea about the long residence time if a contamination event occurs during low-flow condition

Hydrogeology Journal, 2022

Anisotropic fast-marching algorithms are computationally efficient tools for generating realistic... more Anisotropic fast-marching algorithms are computationally efficient tools for generating realistic maps of karst conduit networks, constrained by both the spatial extent and the orientation of karstifiable geologic units. Existing models to generate conduit network maps are limited either by high computational requirements (for chemistry-based models) or by their inability to incorporate the effects of elevation and orientation gradients (for isotropic fast-marching models). The new anisotropic fast-marching approach described here provides a significant improvement, though it imitates rather than reproduces actual speleogenetic processes. It can rapidly generate a stochastic ensemble of plausible networks from basic geologic information, which can also be used as input to karst-appropriate flow models. This paper introduces an open-source, easy-to-use implementation through the Python package pyKasso, then describes its application to a well-mapped geologically complex long-term stu...