Theoretical Analysis of Two‐Dimensional, Transient Flow of Water in Unsaturated and Partly Unsaturated Soils

Abstract The Darcian flow‐equation for two‐dimensional, transient transfer of water in rectangular, unsaturated or partly unsaturated soil slabs was solved numerically with the aid of alternating‐directions, implicit difference methods. Two alternative processes were considered: predominantly horizontal infiltration and ditch‐drainage. The results obtained for the horizontal infiltration process indicate that it involves upward flow‐components which are due, primarily, to a gravity‐induced variation in hydraulic conductivity along the inflow face. These components may materially affect the course of infiltration, especially during its earlier stages. The drainage case results demonstrate that transient water flow within the unsaturated zone and the outflow from the seepage zone may significantly affect the progress of water‐table descent and the total outflow rates.