PUB00012

• Year: 1999
• Title: Sustainability of Ground-Water Resources: U.S. Geological Survey Circular 1186
• CWCB Section: Interstate & Federal
• Author: William M. Alley, Thomas E. Reilly, O. Lehn Franke
• Description: Illustration of the hydrologic, geologic, and ecological concepts to assure wise and sustainable use of ground-water resources
• Publications - Doc Type: Historical

Three terms that have long been associated
with ground-water sustainability need special
mention; namely, safe yield, ground-water mining,
and overdraft. The term "safe yield" commonly
is used in efforts to quantify sustainable ground-
water development. The term should be used with
respect to specific effects of pumping, such as
water-level declines, reduced streamflow, and
degradation of water quality. The consequences
of pumping should be assessed for each level
of development, and safe yield taken as the
maximum pumpage for which the consequences
are considered acceptable. The term "ground-
water mining" typically refers to a prolonged
and progressive decrease in the amount of water
stored in a ground-water system, as may occur,
for example, in heavily pumped aquifers in arid
and semiarid regions. Ground-water mining is a
hydrologic term without connotations about
water-management practices (U.s. Water
Resources Council, 1980). The term "overdraft"
refers to withdrawals of ground water from an
aquifer at rates considered to be excessive and
therefore carries the value judgment of over-
development. Thus, overdraft may refer to
ground-water mining that is considered excessive
as well as to other undesirable effects of ground-
water withdrawals.
In some situations, the focus of attention
may be on extending the useful life of an aquifer
as opposed to achieving long-term sustainability.
This situation-for which the term ground-water
mining is perhaps most fitting-is not addressed

specifically in this report; however, many of the
same hydrologic principles that we discuss herein
still apply.
This introductory discussion indicates that
the concept of ground-water sustainability and
its application to real situations is multifaceted
and complex. The effects of many human activities
on ground-water resources and on the broader
environment need to be clearly understood.
We begin by reviewing some pertinent
facts and concepts about ground water and some
common misconceptions about water budgets and
ground-water sustainability. Individual chapters
then focus on the interactions between ground
water and surface water, on ground-water storage,
and on ground-water quality as each aspect relates
to the sustainability of ground-water resources. We
conclude by discussing the importance of ground-
water data, uses of ground-water models, and strat-
egies to meet the challenges posed in assuring
sustainable use of ground-water resources.
Throughout the report, we emphasize
that development of ground-water resources
has consequences to hydrologic and related envi-
ronmental systems. We discuss relevant concepts
and field examples in the body of the text, and
provide more technical discussion of special topics
and additional field examples in "boxes." An
exception is the next special section, "General Facts
and Concepts about Ground Water." Many readers
familiar with ground-water concepts will want
to go directly to the chapter on "Ground-Water
Development, Sustainability, and Water Budgets."

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