Ptak-Fix, Thomas

[["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","5504"],["dc.bibliographiccitation.issue","7"],["dc.bibliographiccitation.journal","Water Resources Research"],["dc.bibliographiccitation.lastpage","5520"],["dc.bibliographiccitation.volume","51"],["dc.contributor.author","Jimenez, S."],["dc.contributor.author","Brauchler, R."],["dc.contributor.author","Hu, R."],["dc.contributor.author","Hu, Lening"],["dc.contributor.author","Schmidt, S."],["dc.contributor.author","Ptak, Thomas"],["dc.contributor.author","Bayer, Peter"],["dc.date.accessioned","2018-11-07T09:54:55Z"],["dc.date.available","2018-11-07T09:54:55Z"],["dc.date.issued","2015"],["dc.description.abstract","A sequential procedure of hydraulic tomographical inversion is applied to characterize at high resolution the spatial heterogeneity of hydraulic conductivity and specific storage at the field test site Stegemuhle, Germany. The shallow aquifer at this site is examined by five short-term multilevel pumping tests with 30 pumping-observation pairs between two wells. Utilizing travel time diagnostics of the recorded pressure response curves, fast eikonal-based inversion is shown to deliver insight into the sedimentary structures. Thus, the structural information from the generated travel time tomogram is exploited to constrain full calibration of the pressure response curves. Based on lateral extrapolation from the measured inter-well profile, a three-dimensional reconstruction of the aquifer is obtained. It is demonstrated that calibration of spatially variable specific storage in addition to hydraulic conductivity can improve the fitting of the model while the structural features are only slightly changed. At the field site, two tracer tests with uranine and sodium-naphthionate were also performed and their concentrations were monitored for 2 months. The measured tracer breakthrough curves are employed for independent validation of the hydraulic tomographical reconstruction. It is demonstrated that major features of the observed solute transport can be reproduced, and structures relevant for macrodispersive tracer spreading could be resolved. However, for the mildly heterogeneous aquifer, the tracer breakthrough curves can also be approximated by a simplified homogeneous model with higher dispersivity. Therefore, improved validation results that capture specific characteristics of the breakthrough curves would require additional hydraulic measurements."],["dc.description.sponsorship","Swiss National Science Foundation [200021_140450/1]; CCES"],["dc.identifier.doi","10.1002/2014WR016402"],["dc.identifier.isi","000360080200034"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/36640"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Geophysical Union"],["dc.relation.issn","1944-7973"],["dc.relation.issn","0043-1397"],["dc.title","Prediction of solute transport in a heterogeneous aquifer utilizing hydraulic conductivity and specific storage tomograms"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.issue","11"],["dc.bibliographiccitation.journal","Water Resources Research"],["dc.bibliographiccitation.volume","56"],["dc.contributor.author","Liu, Quan"],["dc.contributor.author","Hu, Linwei"],["dc.contributor.author","Bayer, Peter"],["dc.contributor.author","Xing, Yixuan"],["dc.contributor.author","Qiu, Pengxiang"],["dc.contributor.author","Ptak, Thomas"],["dc.contributor.author","Hu, Rui"],["dc.date.accessioned","2021-04-14T08:31:52Z"],["dc.date.available","2021-04-14T08:31:52Z"],["dc.date.issued","2020"],["dc.identifier.doi","10.1029/2020WR027155"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/83735"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-399"],["dc.relation.eissn","1944-7973"],["dc.relation.issn","0043-1397"],["dc.title","A Numerical Study of Slug Tests in a Three‐Dimensional Heterogeneous Porous Aquifer Considering Well Inertial Effects"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]