www.small-scale-hydrology.de

Klaus Bohne

Subsurface hydrologic elementary environmental processes (Program "sheep")

Schematized processes of water flow, which are imagined to occur under constant boundary conditions in subsurface volumes of regular geometry have been named elementary soil hydrologic processes (Kutilek and Nielsen, 1994). Several of these processes are accessible to analytical solutions and don't need a numerical solution of the Richards equation. To treat such problems, the computer code described here makes use of analytical solutions or simple numerical procedures. All methods employed are based on the vanGenuchten-Mualem model of soil hydraulic properties (van Genuchten, 1980). Some of the procedures may be carried out using the bimodal model of soil porosity (Durner, 1994). Just to give examples of parameter values, standard values valid for soil texture classes are provided.

The program deals with problems as follows:

• Calculation of specific water capacity, diffusivity, and matrix flux potential
• Steady-state vertical flow (steady-state capillary rise of groundwater or constant flux infiltration in homogeneous or layered soils)
• Drying of bare soil by evaporation (Gardner's solution)
• Internal drainage in groundwater-affected soils (Crank/Gardner)
• Unit gradient drainage (Sisson equation)
• Infiltration (Ponded infiltration, disc infiltration) (Haverkamp/Green&Ampt)
• An approach to furrow irrigation (Lomen and Warrick)
• Horizontal one-dimensional steady-state groundwater flow between ditches or around wells
• Solute transport restricted to piston flow considering adsorption and decay
• Solute breakthrough for step input and pulse input (convection-dispersion-equation)
• 2-D transient solute propagation in 1-D steady-state groundwater flow (Csanady)
• Steady-state solution to field drainage, calculation of drain spacing
• Non steady-state drain discharge and groundwater hydrograph (Storchenegger's method)

For details readers are referred to the description files.

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