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Significance and Use
According to the National Research Council (1), model applications are useful tools to:
Assist in problem evaluation,
Design remedial measures,
Conceptualize and study groundwater flow processes,
Provide additional information for decision making, and
Recognize limitations in data and guide collection of new data.
Groundwater models are routinely employed in making environmental resource management decisions. The model supporting these decisions must be scientifically defensible and decision-makers must be informed of the degree of uncertainty in the model predictions. This has prompted some state agencies to develop standards for groundwater modeling (2). This guide provides a consistent framework within which to develop, apply, and document a groundwater flow model.
This guide presents steps ideally followed whenever a groundwater flow model is applied. The groundwater flow model will be based upon a mathematical model that may use numerical, analytical, or any other appropriate technique.
This guide should be used by practicing groundwater modelers and by those wishing to provide consistency in modeling efforts performed under their direction.
Use of this guide to develop and document a groundwater flow model does not guarantee that the model is valid. This guide simply outlines the necessary steps to follow in the modeling process. For example, development of an equivalent porous media model in karst terrain may not be valid if significant groundwater flow takes place in fractures and solution channels. In this case, the modeler could follow all steps in this guide and not end up with a defensible model.
1.1 This guide covers the application and subsequent documentation of a groundwater flow model to a particular site or problem. In this context, “groundwater flow model” refers to the application of a mathematical model to the solution of a site-specific groundwater flow problem.
1.2 This guide illustrates the major steps to take in developing a groundwater flow model that reproduces or simulates an aquifer system that has been studied in the field. This guide does not identify particular computer codes, software, or algorithms used in the modeling investigation.
1.3 This guide is specifically written for saturated, isothermal, groundwater flow models. The concepts are applicable to a wide range of models designed to simulate subsurface processes, such as variably saturated flow, flow in fractured media, density-dependent flow, solute transport, and multiphase transport phenomena; however, the details of these other processes are not described in this guide.
1.4 This guide is not intended to be all inclusive. Each groundwater model is unique and may require additional procedures in its development and application. All such additional analyses should be documented, however, in the model report.
1.5 This guide is one of a series of standards on groundwater model applications. Other standards have been prepared on environmental modeling, such as Practice E978.
1.6 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to us
1.7 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word “Standard” in the title of this document means only that the document has been approved through the ASTM consensus process.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D653 Terminology Relating to Soil, Rock, and Contained Fluids
E978 Practice for Evaluating Mathematical Models for the Environmental Fate of Chemicals
ICS Number Code 13.060.10 (Water of natural resources)