ABSTRACT
InChapter5onSoilMoisture,theintroductiontothecomplexitiesofwater storagebelowthegroundsurfaceconfinedattentiontothewaterheldinthe soilmatrix.Waterwasconsideredinthestaticstate.Inevaluatinggroundwateronalargerscale,itisnecessarytodealwithgroundwaterinmotion. Thedegreeofdifficultythatarisesincalculatinggroundwatermovementis affectedbywhetherthegroundissaturatedornot,sinceintheaerationzone thetwo-phasemixtureofvapourandliquidintheporesorvoidscauses hysteresisinthepressurewatercontenttopermeabilityrelationships.When thevoidsarefilledcompletelywithwater,thosecomplexrelationshipsareno longerrelevantandthemorefamiliarconceptsofsingle-phaseliquidflow canbeapplied,butgenerallynotwithoutsomesimplifyingassumptions.
