(1973) n°3 - Royal Academy for Overseas Sciences

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this paper to review this subject and only a brief outline of
some important facts will be given.
G o r h a m (9) has summarized the processes that groundwaters
may have undergone. They are (31):
1. Diagenetic changes associated with the action of bacteria
and the decomposition of organic matter during the early stages
of sedimentation.
2. Compaction during sedimentation;
3. Reactions between constituent minerals and interstitial water
at various stages of diagenesis and metamorphism;
4. Compaction after sedimentation;
5. Membrane filtration.
One of the key issues in hydrogeochemistry is the cause of
the wide variations of salinity of groundwaters. Membrane filtration
has been suggested as an important factor in controlling
the concentration of ions in water-soils systems (1). The study
of salt-sieving by clay of fossil waters, was originated by B re-
d e h o e f t (4a) and explained the origin of many salinity-stratified
groundwaters.
3. A n a l y t ic th eories o f t h e f l o w t h r o u g h po r o u s m e d ia .
3a. Assumptions for homogeneous systems.
Unless the porous medium is a dilute structure, the random
geometry of the boundary in a porous medium is so complex
as to discourage a detailed analysis of the viscous flow seepage
through the medium. Even though there is an extensive literature
in the field of porous media, there is no generally accepted
form of Darcy’s law for nonhomogeneous porous media.
Workers have attempted to develop models that would describe
the macroscopic flow in terms of ensemble average properties
of the medium. Generally speaking, the theories were either
based upon statistical concepts (2, 24, 28) or described a periodic
structure in which a well defined finite cell, playing the role
of a unit lattice, was reproduced throughout the system ( 10,
30). It was thus possible to deduce Darcy’s law for a homogeneous
porous medium from a linearized form of the Navier-
Stokes’equations, as was done by M iller and M iller ( 2 0 ) ,