Geoscience Reference
In-Depth Information
1
INTRODUCTION
1.1
DEFINITION AND SCOPE
Hydrology is literally the science of water. Etymologically, the word has its roots in
ancient Greek, and is a composite, made up of
´
, word. Obvi-
ously, defined this way, the term is much too broad to be very useful, as it would have
ramifications in all scientific disciplines.
Actually, the word hydrology has not always been well defined and even as recently
as the 1960s it was not very clear exactly what hydrology was supposed to cover and
encompass. Price and Heindl (1968), in a survey of many of the definitions that had
appeared in the literature over the previous 100 years, were compelled to conclude that
the question “What is Hydrology?” had not been resolved by their review. Still, they felt
that, in general, there seemed to be a consensus that hydrology is a physical science,
which is concerned mainly with the water cycle of land and near-shore areas; moreover,
there had been a tendency to broaden the term rather than to narrow it, even to the point
of including socio-economic aspects.
Over the past few decades, however, with the growing activity level and the increasing
maturity of this field of endeavor, a more precise definition has emerged. Hydrology is
now widely (see, for example, Eagleson, 1991) accepted to be the science that deals with
those aspects of the cycling of water in the natural environment that relate specifically
with
υδωρ
, water, and
λ
o
γ
o
ς
-
the continental water processes
, namely the physical and chemical processes along
the various pathways of continental water (solid, liquid and vapor) at all scales,
including those biological processes that influence this water cycle directly; and
with
-
the global water balance
, namely the spatial and temporal features of the water
transfers (solid, liquid and vapor) between all compartments of the global system,
i.e. atmosphere, oceans and continents, in addition to stored water quantities and
residence times in these compartments.
Because it is defined as being concerned specifically with continental water processes,
hydrology is a discipline distinct from meteorology, climatology, oceanology, glaciology
and others that also deal with the water cycle in their own specific domains, namely the
atmosphere, the oceans, the ice masses, etc., of the Earth; at the same time, however,
hydrology integrates and links these other geosciences, in that through the global water
balance it is also concerned with the exchanges of water between all these separate
compartments.
