E3250 - Hydrosystems Engineering
Software:
Groundwater Modeling System (GMS)
Groundwater Capture Zone Exercise for Remediation Design System
A common scenario encountered by environmental engineers is that of controlling or remediating contaminant plumes within groundwater aquifers. As water travels from areas of high to low head, it carries contaminants with it. These may eventually discharge into rivers, lakes or other surface water bodies, or contaminate drinking water supplies obtained from groundwater wells. Understanding the hydrologic properties of an aquifer is critical to impeding or altogether eliminating the progress of contaminant plumes. Often, this is done by controlling the flow of water within the aquifer through a series of strategically placed extraction wells, such that the contaminated water is captured by the extraction well network.
In this exercise, a series of extraction well networks are designed, such that their modeled groundwater capture zones (Figure 1) encompass an observed contaminant plume under different remediation scenarios. The exercise is derived from an actual groundwater flow model (Figure 2) and observed contaminant plume, developed by an environmental consulting firm for a groundwater remediation project. Widely-recognized computer programs are used, i.e., the MODFLOW/MODPATH numerical groundwater simulation package and the Groundwater Modeling System (GMS) for pre- and post-processing as well as visualization. Thus students are exposed to a real-world environmental engineering problem, and also powerful computing tools that are commonly used by practicing environmental engineers.
The exercise is essentially a computer-based laboratory session, designed to be completed in a single 2.5 hour class. All modeling software and inputs are fully developed and tested before the laboratory session. Detailed and illustrated instructions for running the relevant aspects of the model are provided, so students focus on the simulation exercise rather than the mechanics of running the model. The objective is to use the modeling platform as a tool to better understand groundwater flow concepts, not to provide training on how to expertly run MODFLOW or GMS. Figure 3 highlights the main features in the GMS workspace that students will make use of in this exercise.
This exercise is intended to reinforce the groundwater flow material that is covered in CIEE E3250 Hydrosystems Engineering, such as the relationship between hydraulic head and flow direction, well hydraulics, and numerical analysis techniques. Furthermore, the exercise demonstrates the ability of numerical methods to solve more complex and realistic problems than what can typically be done using analytical methods, including three-dimensional heterogeneity and the influence of multiple wells on an ambient groundwater flow field.
Figure 1: Capture zone for two pumping wells (on the right) and one injection well (on the left). The black lines are particle paths as determined by the user-defined well pumping rates and site characteristics.
Figure 2: A 3-dimentional site rendering. The user defines the sizes and characteristics of each gridded cell. The orange dots have hydraulic heads associated with them, and determine the horizontal gradient across the site.
Figure 3: GMS workspace with
basic features labeled.
