ABSTRACT
Four distinct periods can be distinguished in the development of mathematical models that describe water systems [1]:
The precomputer age (1900-1950). During this time, the focus was entirely on water quality with little concern for the environmental aspects.
The transition period of the 1950s. Data collection was accelerated but the analysis was slow and costly.
The early years of computer use. During the 1960s, the first computer models were developed, and many models were developed during the 1970s due to greater computer access.
The mid-1970s to date. Because of the development of inexpensive microcomputers, models can now be used for routine evaluations.
