About Groundwater Models

A physical model of an aquifer. Source University of Nebraska-Lincoln

At the most basic level, a model is a representation of a larger concept.  As such, a model can never completely replicate a real system.  The best starting point in groundwater modeling is to have a concept in mind, or conceptual model.  This can be a diagram that includes the land surface features, primary aquifer characteristics, flow into and out of the system, and major data inputs.

A conceptual diagram for modeling a contaminated soil and groundwater site. Source: US Department of Energy

Analytical models were the tool of choice prior to the advent of high speed, high power computing.  These are mathematical approaches to understanding one part of an aquifer system. An example might be  mathematically determining the rate of flow through one water-bearing zone with simplified parameters such as uniform sand size.

Numeric models have Computer-generated output of a groundwater model simulation or run. Source: USGS Circular 129 become the standard through the capacity to incorporate numerous variables and large data sets, and to apply more complex equations to different parts of the modeled aquifer.  One standard model used around the world is the US Geological Survey’s MODFLOW.

Understanding development of a model can be broken down into steps.  The following flow chart shows the major steps in modeling, including an analysis of the uncertainties which help in defining the limitations of how a model can be applied.

Bear et al. 1992

Additional Resources:

Arizona Dept of Water Resources, Introduction to Groundwater Modeling in Arizona