Vertical Head and Hydraulic Gradient Profiles for Improved Flow System Conceptual and Numerical Modelling

Meyer, Jessica R.

Vertical Head and Hydraulic Gradient Profiles for Improved Flow System Conceptual and Numerical Modelling

Saturday, November 9, 2013: 2:00 p.m.

Jessica R. Meyer, M.Sc. , Land Resource Science, University of Guelph, Guelph, ON, Canada

Beth L. Parker, Ph.D. , School of Engineering, G360, University of Guelph, Guelph, ON, Canada

Hydrogeologic (or hydrostratigraphic) units (HGUs) are foundational elements of conceptual and numerical models of groundwater flow and contaminant transport. Adequate representation of groundwater flow processes requires that HGUs be delineated on the basis of hydraulic information. However, in practice, delineation of HGUs is often based on data that is indirect with respect to hydraulic properties or blended hydraulic data. Fifteen detailed and depth discrete (i.e., high-resolution) Westbay® multilevel systems (MLSs) have been installed at contaminated, sedimentary rock field sites in Wisconsin, California, and Ontario and used to collect head profiles over multiyear periods. These MLSs were installed to maximum depths between 90 and 260 m and include an average of 3.3 monitoring zones per 10 m. Here we show that high resolution head profiles collected from fractured sedimentary rocks are highly repeatable, indicate the vertical position and thickness of hydraulic conductivity/connectivity contrasts, and provide insight into flow system conditions. In addition, the high resolution head profiles from the Wisconsin site were examined along cross-sections and used to identify laterally extensive contrasts in hydraulic conductivity/connectivity forming the basis for a HGU conceptual model for the site. Comparison to detailed core and geophysical data showed that these laterally extensive hydraulic conductivity/connectivity contrasts were strongly associated with important sequence stratigraphic units but not with lithostratigraphy, which is commonly relied on for positioning well screens. Work is in progress to represent this HGU conceptualization in a three-dimensional FEFLOW groundwater flow model. The high resolution head and vertical gradient field data will be used to validate the model to improve simulation of groundwater flow paths that will support separate transport modeling efforts. This study shows that the position and thickness of units with contrasting hydraulic conductivity/connectivity would not be evident if the density of monitoring zones in the MLSs had been that of conventional profiles.

Jessica R. Meyer, M.Sc., Land Resource Science, University of Guelph, Guelph, ON, Canada

Jessica R. Meyer is currently a postdoctoral fellow with the G360 Centre for Applied Groundwater research at the University of Guelph. She earned degrees in environmental geology (B.Sc., University of Montana, 2002) and hydrogeology (M.Sc., University of Waterloo, 2005 and Ph.D., University of Guelph 2013). Jessica worked as a research project manager for Dr. Beth Parker and Dr. John Cherry at the University of Waterloo (2005-2008) and the University of Guelph (2012-2013) where she helped to advance high resolution field characterization methods, co-developed a relational database system designed to facilitate the collection and management of high resolution field data sets, and managed research activities at a contaminated sedimentary rock field site. Her research focuses on field data based characterization of fractured sedimentary rock flow systems and aquitard hydrology.

Beth L. Parker, Ph.D., School of Engineering, G360, University of Guelph, Guelph, ON, Canada

Beth Parker, Ph.D., University of Guelph Professor in the School of Engineering and Director of the G360 Centre for Applied Groundwater Research, has more than 30 years of experience investigating subsurface contamination at numerous sites around the world, using high resolution data sets for site conceptual model development and testing. Her current research activities emphasize developing improved field and laboratory methods for characterizations and monitoring of industrial contaminants in sedimentary rocks, clayey deposits, and sandy aquifers, and focus on the effects of diffusion in low permeability zones, plume attenuation, and hydrogeologic controls on remediation.