RiskWare  On-line Reference Manual

Release Level 1.9
Release Date 2000 06


Revision Level 1.0




VLEACH models liquid advection, gas diffusion, and three-phase equilibration in the vadose zone. Current limitations include constant cell dimensions and homogeneous soil properties throughout the profile. Advection solution is time-centered (Crank-Nicholson), space-upward. Diffusion solution is backward-difference (fully-implicit), space-centered. Simultaneous equations are solved in matrix form using the Thomas algorithm.

Chemical and soil input parameters

*  Chemical Parameters:
* KOC   :       Organic carbon distribution coefficient (ml/g)
* KH    :       Henry's constant (dimensionless)
* CMAX  :       Aqueous solubility (mg/l)
* DAIR  :       Free air diffusion coefficient (m2/d)
*  Polygon-specific parameters:
* TITLE :       Description of polygon
* AREA  :       Area of polygon (sq. ft.)
* DELZ  :       Vertical spacing of cells (ft)
* Q     :       Groundwater recharge rate (ft/yr)
* RHOB  :       Dry bulk density of soil (g/ml)
* POR   :       Total effective porosity of soil (dimensionless)
* THETA :       Volumetric water content of soil (dimensionless)
* FOC   :       Organic carbon content of soil (dimensionless)
* CINF  :       Concentration of solute in infiltrating water (mg/l)
* CATM  :       Concentration of solute in atmosphere (
* CGW   :       Lower b'dry condition for gas diffusion:
*       CGW < 0., water table is impermeable to gas diffusion
*       CGW >= 0., fixed concentration at water table, (mg/l)
* NCELL :       Number of vertical cells


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