Abstract
General equations are developed for a Green and Ampt type analysis of gravity drainage for falling water table conditions in an initially saturated stratified profile of porous material both with and without the presence of an applied surface flux. The particular type of stratification system considered is one in which a coarse sequence of porous material overlies a fine sequence. Two profiles are used in the analysis these being a medium-textured sand overlying a slightly finer sand and the same medium-textured sand overlying a sandy loam. The results obtained by analyzing these cases using the algebraic equations are compared with results obtained from a computer-based numerical analysis of the differential equation describing water movement in unsaturated porous media. The results of the numerical simulations are given in terms of pressure head profiles and water content profiles. From these data, detailed comparisons are made with the Green and Ampt results in terms of the discharge-time relationship and the position of the draining front with time. For the systems considered, the simplified sharp-front analysis gives results of reasonable accuracy suggesting that the model would be satisfactory for certain types of field studies.--Journal abstract.