Page 22 - Hydrogeology Principles and Practice

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Introduction 5

(1852–1933) who, for the first time, applied advanced
mathematics to the study of hydraulics. One of his
major contributions was a determination of the rela-
tionship between equipotential surfaces and flow
lines. Inspired by earlier techniques used to under-
stand heat flow problems, and starting with Darcy’s
law and Dupuit’s assumptions, Forchheimer derived
a partial differential equation, the Laplace equation,
for steady groundwater flow. Forchheimer was also
the first to apply the method of mirror images to
groundwater flow problems; for example, the case of
a pumping well located adjacent to a river.
Much of Forchheimer’s work was duplicated in the
United States by Charles Slichter (1864–1946), appar-
ently oblivious of Forchheimer’s existence. How-
ever, Slichter’s theoretical approach was vital to the
advancement of groundwater hydrology in America
at a time when the emphasis was on exploration and
understanding the occurrence of groundwater. This
era was consolidated by Meinzer (1923) in his book
on the occurrence of groundwater in the United
States. Meinzer (1928) was also the first to recognize
the elastic storage behaviour of artesian aquifers.
From his study of the Dakota sandstone (Meinzer &
Hard 1925), it appeared that more water was pumped
from the region than could be explained by the quant-
ity of recharge at outcrop, such that the water-bearing
formation must possess some elastic behaviour in
Fig. 1.4 Irrigation canal supplied with water by a qanat or falaj in
Oman. Photograph provided courtesy of M.R. Leeder. releasing water contained in storage. Seven years
later, Theis (1935), again using the analogy between
heat flow and water flow, presented the ground-
nineteenth century. The French municipal hydraulic breaking mathematical solution that describes the
engineer Henry Darcy (1803–1858) studied the move- transient behaviour of water levels in the vicinity of a
ment of water through sand and from empirical pumping well.
observations defined the basic equation, universally Two additional major contributions in the advance-
known as Darcy’s law, that governs groundwater ment of physical hydrogeology were made by Hubbert
flow in most alluvial and sedimentary formations. and Jacob in their 1940 publications. Hubbert (1940)
Darcy’s law is the foundation of the theoretical aspects detailed work on the theory of natural groundwater
of groundwater flow and his work was extended flow in large sedimentary basins, while Jacob (1940)
by another Frenchman, Arsène Dupuit (1804–1866), derived a general partial differential equation des-
whose name is synonymous with the equation for cribing transient groundwater flow. Significantly, the
axially symmetric flow towards a well in a permeable, equation described the elastic behaviour of porous
porous material. rocks introduced by Meinzer over a decade earlier.
The pioneering work of Darcy and Dupuit was fol- Today, much of the training in groundwater flow
lowed by the German civil engineer, Adolph Thiem theory and well hydraulics, and the use of computer
(1836–1908), who made theoretical analyses of prob- programs to solve hydrogeological problems, is based
lems concerning groundwater flow towards wells on the work of these early hydrogeologists during the
and galleries, and by the Austrian Philip Forchheimer first half of the twentieth century.