This guide covers techniques that should be used to conduct a
sensitivity analysis for a groundwater flow model. The sensitivity
analysis results in quantitative relationships between model
results and the input hydraulic properties or boundary conditions
of the aquifers.
After a groundwater flow model has been calibrated, a
sensitivity analysis may be performed. Examination of the
sensitivity of calibration residuals and model conclusions to model
inputs is a method for assessing the adequacy of the model with
respect to its intended function.
After a model has been calibrated, a modeler may vary the value
of some aspect of the conditions applying solely to the prediction
simulations in order to satisfy some design criteria. For example,
the number and locations of proposed pumping wells may be varied in
order to minimize the required discharge. Insofar as these aspects
are controllable, variation of these parameters is part of an
optimization procedure, and, for the purposes of this guide, would
not be considered to be a sensitivity analysis. On the other hand,
estimates of future conditions that are not controllable, such as
the recharge during a postulated drought of unknown duration and
severity, would be considered as candidates for a sensitivity
This guide presents the simplest acceptable techniques for
conducting a sensitivity analysis. Other techniques have been
developed by researchers and could be used in lieu of the
techniques in this guide.
This guide is written for performing sensitivity analyses for
groundwater flow models. However, these techniques could be applied
to other types of groundwater related models, such as analytical
models, multi-phase flow models, non-continuum (karst or fracture
flow) models, or mass transport models.
This guide is one of a series on groundwater modeling codes
(software) and their applications, such as Guide D5447 and Guide
D5490. Other standards have been prepared on environmental
modeling, such as Practice E978.
The values stated in inch-pound units are to be regarded as
standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and
are not considered standard.
This standard does not purport to address all of the safety
concerns, 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 use.
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