• 2013 -2016 PhD in Isotope Hydrology (www.sasscal.org), Federal Institute for Geosciences and Natural Resources (BGR), B2.3 Groundwater Resources - Quality and Dynamics.
• 2010 Diploma thesis at National Institute of Water and Atmospheric Research (NIWA), Hydrological Processes Group, Christchurch, New Zealand
• 2004 -2010 Diploma in Hydrology, Faculty of Hydrology, Albert-Ludwigs-University, Freiburg, Germany

• 2016- present PostDoc at University of Saskatchewan (Global Institute for Water Security, School of Environment and Sustainability), Canada
• 2016- present Research Associate at Federal Institute for Geosciences and Natural Resources (BGR), B2.4 - Soil as Resource, Material Properties and Dynamics
• 2012 - 2013 Research Associate at Federal Institute for Geosciences and Natural Resources (BGR), B2.3 Groundwater Resources - Quality and Dynamics
• 2009 - 2011 Project Hydrogeologist at Engineering Consultants Neumann + Schweizer, Freiburg, Germany
• 2008 - 2009 Intern at Swiss Federal Institute of Aquatic Science and Technology (Eawag), Department of environmental chemistry, Dübendorf, Swiss
• 2005 - 2009 Research Assistant at Projects in Solar Energy (PSE AG), Freiburg, Germany

Journal articles

• Marcel Gaj, Jeff McDonnell (in prep), Soil water potential controls isotope fractionation.

• Marleen de Blécourt, Marcel Gaj, Alexander Groengroeft, Thomas Himmelsbach, Annette Eschenbach (in prep): Partitioning understory evapotranspiration in semi-arid ecosystems Namibia using the isotopic composition of water vapor. 
• Marcel Gaj, Matthias Beyer, Markus Weiler, & Thomas Himmelsbach (in prep): Regionalization of actual evaporation rates using post-corrected isotope depth profiles and process modeling,  Hydrogeology Journal.
• Marcel Gaj, Stephan Kaufhold, Paul Koeniger,  Matthias Beyer, Markus Weiler & Thomas Himmelsbach (2016): Mineral mediated isotope fractionation of soil water, Rapid Communication in Mass Spectrometry. DOI: 10.1002/rcm.7787  
• Matthias Beyer, Paul Koeniger, Marcel Gaj, Josefina Hamutoko, Heike Wanke, Thomas Himmelsbach (2015): A Deuterium-based labeling technique for the investigation of rooting depths, water uptake dynamics and unsaturated zone water transport in semiarid environments, Journal of Hydrology. doi:10.1016/j.jhydrol.2015.12.037.
• Matthias Beyer, Marcel Gaj, Josefina Hamutoko, Paul Koeniger, Heike Wanke & Thomas Himmelsbach (2015): Deuterium labeling for the estimation of annual groundwater recharge in semi-arid regions. Isotopes in Environmental and Health Studies. DOI: 10.1080/10256016.2015.1076407.
• Marcel Gaj, Matthias Beyer, Paul Koeniger, Heike Wanke, Josefina Hamutoko & Thomas Himmelsbach (2016): In-situ unsaturated zone stable water isotope (²H and ¹⁸O) measurements in semi-arid environments: a soil water balance. Hydrology and Earth System Sciences doi:10.5194/hessd-12-6115-2015.

• Paul Koeniger, Marcel Gaj, Matthias Beyer & Thomas Himmelsbach (2015). Review on soil water isotope based groundwater recharge estimations. Hydrological Processes. DOI: 10.1002/hyp.10775.