On the Aquifer's Integrated Balance Equations

A general methodology is presented for describing transport phenomena in porous media at a macroscopic level. Then. these macroscopic balance equations are integrated (or averaged) along the vertical for confined. leaky and phreatic aquifers. The results are employed to derive (averaged) aquifer equations for the flow of water and of a solute (hydrodynamic dispersion). It is shown that in all cases, the resulting equation is identical to that derived on the basis of an assumption of horizontal flow (the Dupuit assumption). Macrodispersion, occurring at the aquifer level, is discussed and appropriate coefficients are proposed.