Simulation of Darcian evaporation through a heterogeneous soil layer

Steady, Darcian, 1-D, 1-phase evaporation through a vertically inhomogeneous soil from a horizontal water table is simulated as an optimal control problem, i.e. the hydraulic properties of the porous medium (relative permeability of moisture and capillary water retention curve) are considered as control functions. The Richards nonlinear ordinary differential equation is integrated twice as a boundary value problem on a given interval (vadose zone thickness) and the top soil suction head is taken as a cost function in optimization. The Gardner conductivity-pressure relation and the Ahuja et al. (1989) correlation between saturated conductivity and sorptive number are assumed. A continuous vertical change in permeability is optimized.