I2.2 Model Development Process
Model development is closely related to the scientific process of acquiring new,
quantitative knowledge about nature through observation, hypothesizing, and verifying
deduced relationships resulting in the establishment of a credible theoretical framework
for the observed phenomena. The fundamental understanding of a hydrologic system thus
is the product of research synthesized by theory (van der Heijde et al., 1988).
The object of such research is a prototype of a natural system containing selected
elements of a real-world-element hydrologic system. The selection of a particular
prototype system for study is driven primarily by management needs and the researcher’s
personal interest (Figure 1). The conceptual model of the selected hydrologic system
forms the basis for determining the causal relationships among various components of the
system and its environment. These relationships are defined mathematically, resulting in
a mathematical model. If the solution of the mathematical equations is complex or when
many repetitious calculations are required, the use of computers is essential. This requires
the coding of the solution to the mathematical problem in a programming language,
resulting in a computer code. The conceptual formulation, mathematical descriptions, and
the computer coding constitute the prototype model (Figure 1).