Hydrogeology and groundwater modeling are two professions inseparable today and, as argued by Kresic and Mikszewski (2013), there is not a single reason why every practicing hydrogeologist should also not be a groundwater modeler: groundwater modeling has become an industry standard practice in all aspects of hydrogeology.
Groundwater models are utilized during all phases of Conceptual Site Model (CSM) development. They vary in complexity from simple analytical models used as screening tools to three-dimensional (3D) numerical models that serve as a CSM’s focal point. Computer programs with a graphical user interface (GUI) have many advantages of geographic information systems (GIS) and embody various quantitative relationships between the CSM elements.
They are used to develop quantitative groundwater models which enable hydrogeologists to make educated predictions about the state of the system and its response to changes. These changes may be an increased demand of groundwater use in a watershed, more frequent occurrence of droughts, or impacts of a groundwater remediation technology on contaminant concentrations some distance downgradient of the site.
Fig 1. 3D schematization of the subsurface porous media
Whatever the case may be, a predictive quantitative groundwater model—analytical or numerical—is often used to help guide development of the CSM including optimization of field investigations, test scenarios, support or refute conclusions, and provide final solutions including engineering design elements for a variety of groundwater projects.
Hydrogeologic sense and groundwater modeling
Unfortunately, there exists a lingering distrust of groundwater models among some in the environmental industry and regulatory agencies. There are two primary, interconnected reasons for this distrust:
- A lack of formal education in both hydrogeology and groundwater modeling at most American universities and colleges,
- Groundwater models are often perceived as being too costly, complicated, and unreliable, the reputation “promoted” by those not well (or not at all) versed in key aspects of groundwater modeling, and by various parties with differing agendas.
It does not help that, to perhaps make a memorable phrase, some groundwater professionals, and educators in the past created statements such as “All models are wrong, some are useful”. It is our opinion that this statement alone caused more damage to the groundwater modeling profession than just about anything else, including stakeholders with questionable agendas.
Some professionals and regulators believe groundwater model results to be entirely non-unique, meaning that results can easily be tweaked to fulfill a pre-ordained purpose while still satisfying a calibration standard. To a certain extent, the critics are correct.
The groundwater modeler has tremendous influence over model results and can sway things one way or another by modifying model input parameters that are difficult to trace. For these and other reasons, experts employed by organizations with high-stakes goals—like winning multimillion-dollar lawsuits—may transgress professional ethics and create groundwater models so complex that even experienced hydrogeologists find them difficult to understand.
It is also unfortunate that in many cases non-hydrogeologists (or even worse—non-geologists) end up developing groundwater models and calibrating them, without realizing that some (or many) parts of such models simply do not make hydrogeologic sense. It cannot be emphasized enough that every numeric groundwater model is a non unique solution of the underlying flow field and that it can be trusted only to the extent that the professional reputation of its developer can be trusted.
Fig. 2 Water table contours at the industrial site
The purpose of groundwater modeling
The questions that inevitably arise regarding modeling for any purpose are: “Why do we need to do groundwater modeling in the first place?” and “Can groundwater modeling be performed in a transparent manner that is easy to review and understand?”
To answer the first question, hydrogeologists need groundwater models for two primary reasons: one is to predict future conditions, and the other is to understand how current conditions came to be.
Nearly all projects in hydrogeology require future projections, and the hydrogeologist is relied upon for expert opinion in this matter. Most commonly, the hydrogeologist must evaluate the efficacy of selected interventions in water supply development or hazardous waste remediation (particularly groundwater remediation).
Examples include the installation and operation of new water supply wells or extraction wells associated with pump and treat remediation, the injection of chemical reagents for groundwater remediation (in-situ chemical oxidation), or the stimulation of contaminant biodegradation.
Groundwater models are the best available means of simulating these interventions and most simply, determining if they will work. Modeling can also fill in the gaps between data that has been or will be collected at discrete time intervals thus helping the hydrogeologist better understand and simulate transient processes (Kresic and Mikszewski, 2013.)
Fig 3.The numeric groundwater model developed using Processing Modflow
The answer by many professional hydrogeologists to the second question (“Can groundwater modeling be performed in a transparent manner that is easy to review and understand?”) is a resolute yes, as demonstrated by the industry and regulatory practices, and explained in various textbooks on hydrogeology and groundwater modeling, as well as in the related standards by the American Society for Testing and Materials (ASTM).
The process of learning groundwater modeling
Learning groundwater modeling is a two-phase process:
- learning software
- Applying the best hydrogeologic and modeling practices from experience.
However, the learning curve between those two phases is veiled in mystery and often referred to as “steep” which is why many groundwater and environmental professionals find it challenging to become groundwater modelers without even trying to find out what it is all about.
The first phase (learning software) can be addressed with software tutorials incorporating case studies. However, this knowledge is often limited to a single site or specific (hydro)geologic conditions, thus providing minimal information about the application in real-life situations.
The second phase of this learning curve can be addressed by attending college or professional development courses, learning from textbooks, or learning directly from experienced groundwater modelers. This approach has the potential to provide deep knowledge in the long term. At the same time, the future modeler must be highly self-motivated to learn modeling from books only and must be able to apply this knowledge in practice, such as when working at a supportive consulting and engineering firm.
Groundwater modeling courses – our philosophy of knowledge sharing
With a full understanding that young groundwater professionals have a shortage of time, in every sense, we are creating a series of instructional video materials which serve as the basis for knowledge transfer. They can be viewed multiple times and at personal pace.
The main concept of our core video courses of groundwater modeling is that they are accompanied by a series of short video files which are always available to the student so she or he can independently test their newly acquired knowledge. We are utilizing a powerful, fully functional public domain GUI software Processing Modflow which can be applied directly by industry for creating complex 3D models of groundwater flow, and contaminant fate and transfer. These core courses are developed for novice modelers.
We also offer advanced, custom-made courses and groundwater modeling online course training for more experienced professionals and/or consulting companies, as well as an expert review and refinement of the client’s existing models.
On demand, we can use Groundwater Vistas GUI and advanced modeling and visualization programs such as Groundwater Desk
Kresic, N., and Mikszewski A., 2013. Hydrogeological Conceptual Site Models: Data Analysis and Visualizations. CRC/Taylor & Francis, New York, Boca Raton, FL, 584 p.