RESEARCH INTERESTS-John R. Hoaglund, III

General Interests:

I enjoy groundwater flow and solute transport modelling at regional scales where the contribution of geology to the hydrologic problem is most significant. Understanding the regional groundwater flow system is essential to assess the impact of both point and non‑point aquifer contamination and nutrient cycling. My current USDA funded research project is related to nitrate loading in watersheds of the larger Susquehanna River watershed, ultimately draining to the Chesapeake Bay. I am specifically researching the effect of transverse anisotropy on ground water flow and travel times. I am generally interested in the relationship of bedrock conductivity and storage parameters to their structural and stratigraphic controls. I also have experience evaluating regolith conductivity and storage parameters, as well as glacial sedimentologic controls on hydrology.

My long term interest is in developing ways to incorporate geological information of all kinds into numerical ground water flow models, specifically in relating structural geology to the hydrologic parameters of bedrock aquifers. Ground water modeling, even among seasoned hydrologists/hydrogeologists, tends to emphasize hydrologic principles (recharge, discharge, flow budgets, aquifer testing, water levels, calibration, etc.) over geologic principles. The key to introducing geology into hydrogeologic modelling is to emphasize the solid model. I have released software that creates 3D solid models from digital elevation models, geologic maps, known stratigraphic relationships, and various reconstruction options, including projection, folding, and faulting:

http://www.emsei.psu.edu/~hoaglund/research.html

The software then converts the solid model, a hydrologically routed DEM, river network, and boundary conditions into large Modflow96 input files, essentially taking an Arc database and converting it to an active groundwater flow model.

Many of the algorithms incorporated in the Viewxsxn software were developed in constructing a regional ground water model of bedrock aquifers in the Michigan Basin as part of the USGS Michigan RASA project. Geologic structure and hydrologic flow discerned from groundwater residence times were crucial to my doctoral research in understanding which geologic process‑‑regional advection, ice loading, or lake loading‑‑was responsible for a saline, isotopically light groundwater mass discovered in a modern groundwater discharge zone. The hydrologic exchange with the Great Lakes from the Michigan Basin, and the geologic processes creating this ground water mass is the subject of a two-paper series summarizing cooperative work with USGS and Michigan State University co-authors. The first paper featured in Ground Water documents a regional ground water flow model, its calibration, and calculation of discharge to three Great Lakes from the shoreline of the Lower Peninsula of Michigan. The second paper published in Geological Society of America Bulletin explains the modern and Pleistocene hydrologic conditions and sources for the saline, isotopically light ground water mass in the Michigan Basin and under Saginaw Bay, Lake Huron. The Pleistocene emplacement and subsequent modern discharge is largely structurally controlled. In more recent papers, I have been exploring the fundamental structural control on hydrologic parameters. A recent paper published by Ground Water explores the relationship between structural dip of bedding, the orientation of transverse anisotropy, and the effect on ground water flow. The paper provides a correction to flow equations for dipping beds when using a skewed model grid typical of many ground water models. If ground water models are to be corrected for transverse anisotropy, the correction requires a continuous definition of bedding orientation for the model domain. My most recent paper, submitted to the Journal of Structural Geology, applies the theory of non-linear regression to estimate parameters of fold-shape models. The unique feature of the technique is the use of both bedding orientation and geologic horizon elevation data in a simultaneous regression.

Although much attention has been paid to hydrologic flow parameters in the field, many groundwater models can be insensitive to these parameters by design. A model can become insensitive to the conductivity and storage parameters when the model domain is improperly designed in terms of its flow (including recharge) and boundary conditions. The most common example is a groundwater flow model which neglects or underestimates regional underflow. It is critical to calibrate models to both head and flow data that properly represent the domain. To that end I am a strong proponent of inverse techniques (ModflowP) and their applications to model calibration, parameter estimation, and sensitivity. There is usually a wealth of reliable observations on the model dependent variable (head) because it can be directly measured. There are usually enough reliable data on model sink terms (outflows) because they can be directly measured from pumping wells and from gaging streams and drains. Unfortunately, source terms (inflows) are usually not directly measurable, but are often estimated, or are assumed equal to measured outflows (e.g. the recharge = baseflow assumption). There are even fewer reliable estimates of the flow parameters because they are indirectly measured from aquifer tests, and are scale dependent. Model-scale parameter estimation (ModflowP) offers a mathematically consistent way of evaluating the model hydrologic parameters. I applied the non-linear regression techniques to the Michigan RASA model, using ModflowP for calibration, parameter estimation, and sensitivity analysis.

Pending Grants:

I have two grants pending at NSF, one to study the regional hydrogeologic budget of Lake Ontario, and the other to continue the Viewxsxn program development.

Past projects:

In past projects, I was involved in coupling a continental scale hydrological model to a climatological model. I also worked on a Pennsylvania Department of Environmental Protection project to incorporate GIS information into 3D ground water models for the purpose of delineating wellhead protection zones. I studied structural jointing in a large granite body as part of a USGS water resources investigation, specifically relating structural jointing to the hydrologic parameters of the Wolf River Granite, Wisconsin.