Brauchler, Ralf

[["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","350"],["dc.bibliographiccitation.issue","1-2"],["dc.bibliographiccitation.journal","Journal of Hydrology"],["dc.bibliographiccitation.lastpage","362"],["dc.bibliographiccitation.volume","409"],["dc.contributor.author","Hu, R."],["dc.contributor.author","Brauchler, R."],["dc.contributor.author","Herold, Maria"],["dc.contributor.author","Bayer, Peter"],["dc.date.accessioned","2018-11-07T08:50:36Z"],["dc.date.available","2018-11-07T08:50:36Z"],["dc.date.issued","2011"],["dc.description.abstract","Travel time and steady shape inversions are complementary methods for tomographic aquifer characterization. In this work, a combined procedure is presented that facilitates determination of spatial hydraulic conductivity and specific storage distributions in heterogeneous groundwater systems. The procedure is applied to a highly heterogeneous sedimentary aquifer analog that is implemented as a two- and three-dimensional case study in a numerical flow model. By interpreting the observations from multiple simulated short-term pumping tests, the main hydraulic features of the analog are successfully reconstructed. The final results demonstrate the encouraging potential of the combined procedure for identifying the dominant structural elements and composition of sedimentary aquifers. However, limits derived from the test design of hydraulic travel time tomography in our synthetic case study prevented us from resolving small scale (10 cm in size) variability of hydraulic conductivity with high discrepancies (up to 5 orders of magnitude). A better reconstruction of the aquifer hydraulic parameters is expected by utilizing a larger amount of measurements, which involve more test and observation intervals, although such a test design would be less feasible for field applications. Still, this newly combined scheme is very attractive for an up-scaled reconstruction on the sub-meter scale. For the present case study, representative parameter values could be estimated in a computationally efficient way. (C) 2011 Elsevier B.V. All rights reserved."],["dc.description.sponsorship","German Research Foundation [BR3379/1-2]"],["dc.identifier.doi","10.1016/j.jhydrol.2011.08.031"],["dc.identifier.isi","000296601600030"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/21733"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","0022-1694"],["dc.title","Hydraulic tomography analog outcrop study: Combining travel time and steady shape inversion"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["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.artnumber","W03503"],["dc.bibliographiccitation.journal","Water Resources Research"],["dc.bibliographiccitation.volume","47"],["dc.contributor.author","Brauchler, R."],["dc.contributor.author","Hu, R."],["dc.contributor.author","Dietrich, P."],["dc.contributor.author","Sauter, M."],["dc.date.accessioned","2018-11-07T08:59:07Z"],["dc.date.available","2018-11-07T08:59:07Z"],["dc.date.issued","2011"],["dc.description.abstract","In this study the potential of an inversion approach based on hydraulic travel time and hydraulic attenuation tomography was assessed. Both hydraulic travel time and hydraulic attenuation tomography are based on the transformation of the transient groundwater flow equation into the eikonal equation using an asymptotic approach. The eikonal equation allows the calculation of pressure propagation and attenuation along trajectories, which is computationally efficient. The attenuation and travel time-based inversion approaches are naturally complementary: hydraulic travel times are determined by the hydraulic diffusivity, a combination of hydraulic conductivity and specific storage, whereas the attenuation is determined solely by specific storage. The potential of our hydraulic tomographical approach was investigated at a well-characterized sand and gravel aquifer located in the Leine River valley near Gottingen, Germany. The database for the hydraulic inversion consists of 392 cross-well slug interference tests performed between five wells, in which the positions of the sources (injection ports) and the receivers (observation ports), isolated with double packer systems, were varied between tests. The results have shown that the combination of hydraulic travel time and hydraulic attenuation tomography allows the reconstruction of the diffusivity and storage distribution in two and three dimensions with a resolution and accuracy superior to that possible with type curve analysis."],["dc.description.sponsorship","German Research Foundation [BR3379/1-2]"],["dc.identifier.doi","10.1029/2010WR009635"],["dc.identifier.isi","000288083200004"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/23814"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Geophysical Union"],["dc.relation.issn","0043-1397"],["dc.title","A field assessment of high-resolution aquifer characterization based on hydraulic travel time and hydraulic attenuation tomography"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]