Ptak-Fix, Thomas

[["dc.bibliographiccitation.firstpage","33"],["dc.bibliographiccitation.issue","1-2"],["dc.bibliographiccitation.journal","Journal of Hydrology"],["dc.bibliographiccitation.lastpage","45"],["dc.bibliographiccitation.volume","384"],["dc.contributor.author","Brauchler, R."],["dc.contributor.author","Hu, R."],["dc.contributor.author","Vogt, T."],["dc.contributor.author","Al-Halbouni, D."],["dc.contributor.author","Heinrich, Steffen"],["dc.contributor.author","Ptak, Thomas"],["dc.contributor.author","Sauter, M."],["dc.date.accessioned","2018-11-07T08:44:03Z"],["dc.date.available","2018-11-07T08:44:03Z"],["dc.date.issued","2010"],["dc.description.abstract","In this study the potential of cross-well slug interference tests for high resolution aquifer characterization of hydraulic heterogeneity was assessed. The cross-well slug interference tests were performed at the research site \"Stegemuhle\", located in the Leine River valley near Gottingen, Germany. The geological composition of the subsurface, consisting mainly of 3.5 m silt and clay overlying 2.5 m sand and gravel, was determined by geophysical well logging and bore core data. To account for lateral changes a refraction seismic survey was conducted. Based on these data an area, characterized by an aquifer thickness of approximately 2 m and an average hydraulic conductivity of 5.0 x 10(-4) m/s (determined by pumping tests), most appropriate for cross-well slug interference tests, was chosen. Altogether 196 cross-well slug interference tests were performed using a tomographic measurement array. The cross-well slug interference tests were evaluated using type curve analysis, which provided detailed information concerning the vertical changes of hydraulic conductivity and specific storage. To assess hydraulic strata connectivity a travel time based tomographic inversion approach was utilized. The potential of the inversion approach to determine lateral changes could be successfully demonstrated by the reconstruction of the pinch out of a high diffusivity layer close to the bottom of the aquifer. The results demonstrate that the combined evaluation of cross-well slug interference tests based on type curve analysis and travel time inversion allows for the development of a detailed model about subsurface hydraulic heterogeneity. (C) 2010 Elsevier B.V. All rights reserved."],["dc.description.sponsorship","German Research Foundation [BF3379/1-2]"],["dc.identifier.doi","10.1016/j.jhydrol.2010.01.004"],["dc.identifier.isi","000276444700004"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/20118"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","0022-1694"],["dc.title","Cross-well slug interference tests: An effective characterization method for resolving aquifer heterogeneity"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","2013"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Water Resources Research"],["dc.bibliographiccitation.lastpage","2024"],["dc.bibliographiccitation.volume","49"],["dc.contributor.author","Brauchler, R."],["dc.contributor.author","Hu, R."],["dc.contributor.author","Hu, Lening"],["dc.contributor.author","Jimenez, S."],["dc.contributor.author","Bayer, Peter"],["dc.contributor.author","Dietrich, P."],["dc.contributor.author","Ptak, Thomas"],["dc.date.accessioned","2018-11-07T09:26:16Z"],["dc.date.available","2018-11-07T09:26:16Z"],["dc.date.issued","2013"],["dc.description.abstract","A new framework is introduced for hydraulic tomography application and validation in the field. Our motivation is the need for methods that are both efficient and expressive for resolving the spatial distribution of heterogeneous hydraulic properties in aquifers. The presented strategy involves time-efficient field experiments and a computationally efficient inversion scheme. By exploiting the early travel time diagnostics of the hydraulic pressure pulses recorded during tomographic cross-well tests, and new application of attenuation inversion, only short-term pumping tests are required. Many of these can be conducted in one day. The procedure is developed by a numerical experiment with a highly heterogeneous aquifer analogue and then applied to a field case with a shallow, unconsolidated sedimentary aquifer, the Stegemuhle site in Germany. It is demonstrated that the performance of a suite of tomographic short-term pumping tests, data processing and inversion for the reconstruction of heterogeneous diffusivity and specific storage distribution is possible within one day. Additionally, direct-push injection logging is performed at the field site, and the obtained field data is utilized for successful validation of the hydraulic tomograms. We also compare both methods with respect to the necessary requirements, time demand in the field and complexity of interpretation."],["dc.identifier.doi","10.1002/wrcr.20181"],["dc.identifier.isi","000319282100018"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/30265"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Geophysical Union"],["dc.relation.issn","0043-1397"],["dc.title","Rapid field application of hydraulic tomography for resolving aquifer heterogeneity in unconsolidated sediments"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1071"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","Hydrogeology Journal"],["dc.bibliographiccitation.lastpage","1089"],["dc.bibliographiccitation.volume","21"],["dc.contributor.author","Rahman, Mohammad Azizur"],["dc.contributor.author","Wiegand, Bettina A."],["dc.contributor.author","Badruzzaman, A. B. M."],["dc.contributor.author","Ptak, Thomas"],["dc.date.accessioned","2018-11-07T09:22:01Z"],["dc.date.available","2018-11-07T09:22:01Z"],["dc.date.issued","2013"],["dc.description.abstract","A preliminary feasibility assessment of managed aquifer-recharge (MAR) techniques was undertaken for Dhaka City, Bangladesh. Considering the top impermeable-layer (TIL) thickness and the land-use classification, four primary MAR techniques have been suggested: (1) soil-aquifer treatment (SAT) for TIL thickness 0-8 m, (2) cascade-type recharge trenches/pits for TIL thickness 9-30 m, (3) aquifer storage, transfer and recovery (ASR/ASTR) for TIL thickness 31-52 m, and (4) use of natural wetlands to recharge water collected from open spaces. The study suggests that recharge trenches and pits will be the most appropriate MAR techniques, which can be implemented in most parts of the recharge area (ca. 277 km(2)). In case of a recharge trench, the lower parts (15-20 m) that are in direct contact with the aquifer can be backfilled with biosand filters with a reactive layer containing metallic iron (Fe-0) to offer pre-treatment of the infiltrated water. In addition to the suggested four techniques, the regional groundwater flow direction, from the northwest and northeast towards Dhaka City, may allow use of the aquifer as a natural treatment and transport medium for groundwater, if spreading basins are installed in the greater Dhaka area."],["dc.identifier.doi","10.1007/s10040-013-0978-z"],["dc.identifier.isi","000321968900010"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/29242"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Springer"],["dc.relation.issn","1435-0157"],["dc.relation.issn","1431-2174"],["dc.title","Hydrogeological analysis of the upper Dupi Tila Aquifer, towards the implementation of a managed aquifer-recharge project in Dhaka City, Bangladesh"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1091"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Hydrogeology Journal"],["dc.bibliographiccitation.lastpage","1106"],["dc.bibliographiccitation.volume","28"],["dc.contributor.author","Hamdan, Ibraheem"],["dc.contributor.author","Ptak, Thomas"],["dc.contributor.author","Wiegand, Bettina"],["dc.contributor.author","Sauter, Martin"],["dc.date.accessioned","2020-12-10T14:11:08Z"],["dc.date.available","2020-12-10T14:11:08Z"],["dc.date.issued","2020"],["dc.identifier.doi","10.1007/s10040-019-02094-w"],["dc.identifier.eissn","1435-0157"],["dc.identifier.issn","1431-2174"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/70974"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Development of a quantitative transport-time-based groundwater vulnerability model for non-point-source pollution in karst aquifers: a conceptual approach and example from the Tanour and Rasoun spring catchment, north-western Jordan"],["dc.title.alternative","Développement d’un modèle de vulnérabilité quantitative des eaux souterraines basée sur le temps de transport pour des pollutions diffuses d’aquifères karstiques: une approche conceptuelle et un exemple sur le bassin d’alimentation des sources de Tanour et Rasoun, nourd-ouest de la Jordanie"],["dc.title.alternative","Desarrollo de un modelo cuantitativo de vulnerabilidad de las aguas subterráneas a la contaminación de una fuente no puntual en los acuíferos cársticos basado en el tiempo de transporte: un enfoque conceptual y un ejemplo de la Cuenca del manantial de Tanour y Rasoun, en el noroeste de Jordania"],["dc.title.alternative","O desenvolvimento de um modelo quantitativo de vulnerabilidade das águas subterrâneas em aquíferos cársticos, baseado no tempo de transporte de uma fonte de poluição não pontual: uma abordagem conceitual, e o exemplo da bacia hidrográfica de Tanour e Rasoun, noroeste da Jordânia"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1"],["dc.bibliographiccitation.issue","1-4"],["dc.bibliographiccitation.journal","Journal of Contaminant Hydrology"],["dc.bibliographiccitation.lastpage","13"],["dc.bibliographiccitation.volume","101"],["dc.contributor.author","Riva, Monica"],["dc.contributor.author","Guadagnini, Alberto"],["dc.contributor.author","Fernandez-Garcia, Daniel"],["dc.contributor.author","Sanchez-Vila, Xavier"],["dc.contributor.author","Ptak, Thomas"],["dc.date.accessioned","2018-11-07T11:09:58Z"],["dc.date.available","2018-11-07T11:09:58Z"],["dc.date.issued","2008"],["dc.description.abstract","We analyze the relative importance of the selection of (1) the geostatistical model depicting the structural heterogeneity of an aquifer, and (2) the basic processes to be included in the conceptual model, to describe the main aspects of solute transport at an experimental site. We focus on the results of a forced-gradient tracer test performed at the \"Lauswiesen\" experimental site, near Tubingen, Germany. In the experiment, NaBr is injected into a well located 52 m from a pumping well. Multilevel breakthrough curves (BTCs) are measured in the latter. We conceptualize the aquifer as a three-dimensional, doubly stochastic composite medium, where distributions of geomaterials and attributes, e.g., hydraulic conductivity (K) and porosity (phi), can be uncertain. Several alternative transport processes are considered: advection, advection-dispersion and/or mass-transfer between mobile and immobile regions. Flow and transport are tackled within a stochastic Monte Carlo framework to describe key features of the experimental BTCs, such as temporal moments, peak time, and pronounced tailing. We find that, regardless the complexity of the conceptual transport model adopted, an adequate description of heterogeneity is crucial for generating alternative equally likely realizations of the system that are consistent with (a) the statistical description of the heterogeneous system, as inferred from the data, and (b) salient features of the depth-averaged breakthrough curve, including preferential paths, slow release of mass particles, and anomalous spreading. While the available geostatistical characterization of heterogeneity can explain most of the integrated behavior of transport (depth-averaged breakthrough curve), not all multilevel BTCs are described with equal success. This suggests that transport models simply based on integrated measurements may not ensure an accurate representation of many of the important features required in three-dimensional transport models. (C) 2008 Elsevier B.V. All rights reserved."],["dc.description.sponsorship","Spanish CICyT project PARATODO; MIUR"],["dc.identifier.doi","10.1016/j.jconhyd.2008.07.004"],["dc.identifier.isi","000260665800001"],["dc.identifier.pmid","18799231"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/53114"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","1873-6009"],["dc.relation.issn","0169-7722"],["dc.title","Relative importance of geostatistical and transport models in describing heavily tailed breakthrough curves at the Lauswiesen site"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","107"],["dc.bibliographiccitation.journal","Journal of contaminant hydrology"],["dc.bibliographiccitation.lastpage","121"],["dc.bibliographiccitation.volume","177-178"],["dc.contributor.author","Yang, Jie"],["dc.contributor.author","Graf, Thomas"],["dc.contributor.author","Ptak, Thomas"],["dc.date.accessioned","2018-06-28T09:30:59Z"],["dc.date.available","2018-06-28T09:30:59Z"],["dc.date.issued","2015"],["dc.description.abstract","Climate change is expected to induce sea level rise in the German Bight, which is part of the North Sea, Germany. Climate change may also modify river discharge of the river Weser flowing into the German Bight, which will alter both pressure and salinity distributions in the river Weser estuary. To study the long-term interaction between sea level rise, discharge variations, a storm surge and coastal aquifer flow dynamics, a 3D seawater intrusion model was designed using the fully coupled surface-subsurface numerical model HydroGeoSphere. The model simulates the coastal aquifer as an integral system considering complexities such as variable-density flow, variably saturated flow, irregular boundary conditions, irregular land surface and anthropogenic structures (e.g., dyke, drainage canals, water gates). The simulated steady-state groundwater flow of the year 2009 is calibrated using PEST. In addition, four climate change scenarios are simulated based on the calibrated model: (i) sea level rise of 1m, (ii) the salinity of the seaside boundary increases by 4 PSU (Practical Salinity Units), (iii) the salinity of the seaside boundary decreases by 12 PSU, and (iv) a storm surge with partial dyke failure. Under scenarios (i) and (iv), the salinized area expands several kilometers further inland during several years. Natural remediation can take up to 20 years. However, sudden short-term salinity changes in the river Weser estuary do not influence the salinized area in the coastal aquifer. The obtained results are useful for coastal engineering practices and drinking water resource management."],["dc.identifier.doi","10.1016/j.jconhyd.2015.03.014"],["dc.identifier.pmid","25889797"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/15157"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.relation.eissn","1873-6009"],["dc.title","Impact of climate change on freshwater resources in a heterogeneous coastal aquifer of Bremerhaven, Germany: A three-dimensional modeling study"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1533"],["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","Water"],["dc.bibliographiccitation.volume","12"],["dc.contributor.author","Yang, Huichen"],["dc.contributor.author","Hu, Rui"],["dc.contributor.author","Qiu, Pengxiang"],["dc.contributor.author","Liu, Quan"],["dc.contributor.author","Xing, Yixuan"],["dc.contributor.author","Tao, Ran"],["dc.contributor.author","Ptak, Thomas"],["dc.date.accessioned","2021-04-14T08:25:00Z"],["dc.date.available","2021-04-14T08:25:00Z"],["dc.date.issued","2020"],["dc.identifier.doi","10.3390/w12061533"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/17433"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/81493"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-399"],["dc.notes.intern","Merged from goescholar"],["dc.publisher","MDPI"],["dc.relation.eissn","2073-4441"],["dc.rights","CC BY 4.0"],["dc.rights.uri","http://creativecommons.org/licenses/by/4.0/"],["dc.title","Application of Wavelet De-Noising for Travel-Time Based Hydraulic Tomography"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","S0022169422002530"],["dc.bibliographiccitation.firstpage","127678"],["dc.bibliographiccitation.journal","Journal of Hydrology"],["dc.bibliographiccitation.volume","609"],["dc.contributor.author","Xing, Yixuan"],["dc.contributor.author","Liu, Quan"],["dc.contributor.author","Hu, Rui"],["dc.contributor.author","Gu, Hongbiao"],["dc.contributor.author","Taherdangkoo, Reza"],["dc.contributor.author","Yang, Huichen"],["dc.contributor.author","Ptak, Thomas"],["dc.date.accessioned","2022-06-01T09:40:19Z"],["dc.date.available","2022-06-01T09:40:19Z"],["dc.date.issued","2022"],["dc.identifier.doi","10.1016/j.jhydrol.2022.127678"],["dc.identifier.pii","S0022169422002530"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/108698"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-572"],["dc.relation.issn","0022-1694"],["dc.rights.uri","https://www.elsevier.com/tdm/userlicense/1.0/"],["dc.title","A general numerical model for water level response to harmonic disturbances in aquifers considering wellbore effects"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","92"],["dc.bibliographiccitation.issue","1-2"],["dc.bibliographiccitation.journal","Journal of Contaminant Hydrology"],["dc.bibliographiccitation.lastpage","118"],["dc.bibliographiccitation.volume","88"],["dc.contributor.author","Riva, Monica"],["dc.contributor.author","Guadagnini, L."],["dc.contributor.author","Guadagnini, Alberto"],["dc.contributor.author","Ptak, Thomas"],["dc.contributor.author","Martac, E."],["dc.date.accessioned","2018-11-07T09:01:52Z"],["dc.date.available","2018-11-07T09:01:52Z"],["dc.date.issued","2006"],["dc.description.abstract","The delineation of well capture zones is of utmost environmental and engineering relevance as pumping wells are commonly used both for drinking water supply needs, where protection zones have to be defined, and for investigation and remediation of contaminated aquifers. We analyze the probabilistic nature of well capture zones within the well field located at the \"Lauswiesen\" experimental site. The test site is part of an alluvial heterogeneous aquifer located in the Neckar river valley, close to the city of Tiibingen in South-West Germany. We explore the effect of different conceptual models of the structure of aquifer heterogeneities on the delineation of three-dimensional probabilistic well catchment and time-related capture zones, in the presence of migration of conservative solutes. The aquifer is modeled as a three-dimensional, doubly stochastic composite medium, where distributions of geo-materials and hydraulic properties are uncertain. We study the relative importance of uncertain facies geometry and uncertain hydraulic conductivity and porosity on predictions of catchment and solute time of travel to the pumping well by focusing on cases in which (1) the facies distribution is random, but the hydraulic properties of each material are fixed, and (2) both facies geometry and material properties vary stochastically. The problem is tackled within a conditional numerical Monte Carlo framework. Results are provided in terms of probabilistic demarcations of the three-dimensional well catchment and time-related capture zones. Our findings suggest that the uncertainty associated with the prediction of the location of the outer boundary of well catchment at the \"Lauswiesen\" site is significantly affected by the conceptual model adopted to incorporate the heterogeneous nature of the aquifer domain in a predictive framework. Taking into account randomness of both lithofacies distribution and materials hydraulic conductivity allows recognizing the existence of preferential flow paths that influence the extent of the well catchment and the solute travel time distribution at the site. (c) 2006 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.jconhyd.2006.06.005"],["dc.identifier.isi","000242317700006"],["dc.identifier.pmid","16904791"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/24535"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","0169-7722"],["dc.title","Probabilistic study of well capture zones distribution at the Lauswiesen field site"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","29"],["dc.bibliographiccitation.issue","1-2"],["dc.bibliographiccitation.journal","Journal of Contaminant Hydrology"],["dc.bibliographiccitation.lastpage","38"],["dc.bibliographiccitation.volume","106"],["dc.contributor.author","Herold, Maria"],["dc.contributor.author","Ptak, Thomas"],["dc.contributor.author","Bayer-Raich, Marti"],["dc.contributor.author","Wendel, Thomas"],["dc.contributor.author","Grathwohl, Peter"],["dc.date.accessioned","2018-11-07T08:30:45Z"],["dc.date.available","2018-11-07T08:30:45Z"],["dc.date.issued","2009"],["dc.description.abstract","A series of integral pumping tests (IPTs) has been conducted at a former gasworks site to quantify the contaminant mass flow rates and average concentration in groundwater along three control planes across the groundwater flow direction. The measured concentration-time series were analysed numerically with the help of the inversion code CSTREAM and a flow and transport model representing the highly heterogeneous aquifer. Since the control planes cover the entire downstream width of the potentially contaminated area, they allow conclusions to be drawn about the current location and spread of the contaminant plume. Previous evaluations of integral pumping tests could calculate three scenarios concerning the spread of the plume around the IPT well: (i) the plume is located to the right of the pumping well, (ii) to the left, or (iii) is distributed symmetrically around it. To create a more realistic picture of the plume position, a series of direct-push monitoring wells were installed along one control plane. The concentrations found in these wells were included in the numerical analysis to condition the numerical inversion results, and allowed the identification of a more pronounced plume centre and fringe, which supports the development of optimised remediation strategies. (C) 2008 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.jconhyd.2008.12.006"],["dc.identifier.isi","000265319600003"],["dc.identifier.pmid","19167131"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/16967"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","0169-7722"],["dc.title","Integral quantification of contaminant mass flow rates in a contaminated aquifer: Conditioning of the numerical inversion of concentration-time series"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]