Hydrogeology studies the distribution and movement of groundwater in the soil and rocks. It is an interdisciplinary subject which also considers the aspects of chemistry, the physical nature of soil and rocks, biological matter and the legal interactions between soil, water, nature and society. Groundwater flows following the pressure gradients which match the fractures and conduits in circuitous paths. Evidenltly, groundwater does not always flow in the subsurface down-fill following the surface topography
The mathematical relationships used to describe the flow of water through porous media are the diffusion and Laplace transform equations. Steady groundwater flow is simulated using electrical, elastic and heat conduction analogies. The interplay of the different facets of a multi-component system requires both theoretical and experimental knowledge.
Porosity, an important concept in this area of study, is the fraction which indicates the amount of pore space between unconsolidated soil particles or within a fractured rock. It is an aquifer property. The majority of groundwater movement is dependent on porosity and much is available to allow for flow. Permeability on the other hand is the expression of the connectedness of the pores. An example of this is a pumice stone. A pumice stone, in its un-fractured state, makes a poor aquifer.
Title Image Credit: Dale Ellerm / flickr.com