Some key equations of ground water modelling simply explained

Ground water modelling, using either finite difference or finite elements methods, has become a necessity in modern engineering practice particularly in the fields of mining, water supply, geotechnical work or environmental engineering. There is a need for a simple explanation of the development of some key equations of the software of ground water modelling. The usual treatment of the derivation, in texts and references that are available to most beginners, is highly calculus dependent. The practising engineer, who wishes to understand the basics of this subject and who has not recently completed a course in calculus may find the task of working through the mathematics somewhat daunting. This paper attempts to produce clear, almost calculus free, derivations of some key equations starting from first principles and cast in engineering terms and units. Where calculus is unavoidable, nothing more complicated than partial differentials or Taylor’s expansion are used.