Environmental Engineering Reference
In-Depth Information
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assess the effects of land-use or climate change
of assumptions. Assumptions can relate to the
mechanism of recharge (diffuse or focused), the
timing and the location of recharge, the impor-
tance of other components in the water budget
of an aquifer or watershed, the uniformity of
properties (such as hydraulic conductivity), and
various other aspects or features. Assumptions
inherent to each method are discussed. The
importance of these assumptions needs to be
assessed in the context of each application,
and the reader must decide whether inherent
assumptions are consistent with the concep-
tual model of the hydrologic system under
consideration.
Estimation of recharge is an iterative proc-
ess with continual refinement. The conceptual
model can help guide selection of suitable meth-
ods and indicate where and when the meth-
ods might best be applied. Recharge estimates
obtained early in the course of a study may lead
to refinement of the conceptual model, which,
in turn, could lead to the application of alter-
native estimation techniques. Many methods
described in the following chapters can be
applied with a minimal amount of effort by
using existing data.
on past and future patterns of recharge.
Satisfying these objectives requires recharge
estimates that span a wide range of space and
time scales; therefore, it is unlikely that a single
approach would work for all studies. Spatial and
temporal scales associated with each method
are discussed in the following chapters to
facilitate matching methods with study goals.
Also discussed are expenses, in terms of data
requirements and manpower, for each method,
so the reader can determine whether study con-
straints will permit application of a particular
method.
The selection of methods also must be tied
to the conceptual model of the hydrologic sys-
tem under study. Throughout this first chapter,
the importance of building a sound conceptual
model has been expounded. The final chapter
contains a more detailed discussion of concep-
tual models, along with examples for typical
systems in generic groundwater regions of the
United States.
Chapters 2
through
8
provide
analysis of individual methods for estimating
recharge. Each of these methods is based on a set
