Geology Reference
In-Depth Information
Chapter 1
Introduction
Abstract
In addition to classical physical/conceptual hydrological models at
various complexity levels, data driven modelling tools are available in hydrological
literature for last two decades to solve various complex issues in water resources
and environmental science.
This quo-
tation is meaningful in a data based hydrological modelling context due to the
presence of different unsolved queries and deliberate assumptions. In a rush to
develop interesting soft-driven models to solve differ processes issues, researchers
often neglected or avoided in-depth researches on multi-collinearity, input selec-
tion, training data length selection, assuming that soft computing models have an
intrinsic capability of managing extra errors caused by this negligence. Four case
studies are illustrated in this topic. These illustrate different model selection
approaches and rigorously evaluate these approaches with state-of-art models
through detailed and comprehensive experimentation and comparative studies. This
chapter also aims to have a quick look into the critical points of current knowledge
and or methodological approaches on data based modelling in hydrology and Earth
sciences.
“
All models are wrong; some are useful.
”
The hydrological cycle describes the natural phenomenon of continuous movement
and changes of the state of water between the atmosphere and the earth. In mod-
elling aspect, the hydrological cycle can be considered as a closed system because
there are no external inputs or outputs of water to or from the system. The water
movement from the earth
is surface to the atmosphere is supported by solar radia-
tion, while the water movement at and below the surface of the earth is mainly
driven by gravity. The major processes in the hydrological cycle are illustrated in
Fig.
1.1
. The natural phenomena that make up the hydrological cycle are: the
transfer of water, in its gaseous phase from land to the atmosphere (evapotrans-
piration), water transfer in its solid or liquid phases from the atmosphere to the land
surface in the form of precipitation and land based phenomenon runoff, storage,
in
'
ltration and other processes shown in the Fig.
1.1
. In short, solar radiation acts as
a driving force of atmospheric phenomenon and gravity controls processes occur-
ring at the land phase.
