slope-2d
Simulation
of Water Transport Processes in Surface-Sealing Systems
of
Waste Disposal Sites.
A
simulation program written in FORTRAN - 77 by Günter Braun
Surface-sealing
systems have to avoid the infiltration of water into the waste body
and
to minimize the danger of contamination of groundwater.
In
Germany the technical regulation - TASi
- prescribes
a combination of two surface-sealing systems
-
a polyethylene
foil of 2.5 mm thickness
-
over
a mineral clay liner
as a
standard.
But
TASi also
allows cheaper alternatives, if the comparable quality is proven.
With
slope-2d it
is possible to calculate the water budget of alternative sealing systems.
slope-2d
is based on a 2-dimensional numerical solution of the Fokker-Planck-equation,
a partial differential
equation (PDE) which combines the generalised Darcy
law with the
continuity
equation - see below the 3-dim PDE.
slope-2d
was written in FORTRAN - 77.
Four
methods are available for the numerical solution of the PDE:
-
PCADI
- Predictor-Corrector-Alternating-Direction-Implicit,
developed by Hornung and
Messing,
-
ADIPIT
-
an iterative quasi - Newton - ADI -
method,
-
LSOR
- line successive
overrelaxation
and
-
the DuFort
- Fraenkel method.
slope-2d
optimizes the water budget of surface-sealing
systems depending on
-
slope
condition,
-
soil-physical
properties,
-
climatic
conditions and
-
vegetation.
Discretization
of a multi-barrier system (capillary barrier)
Soil-Physical
System Functions
The preprocessing
programme param.exe
calculates the soil-physical system functions
(water
retention, hydraulic conductivity) using the van
Genuchten - Mualem - model.
Root
Intensity
The following
screen shot shows the root density as a function of depth and/or
compartments.
The actual
EvapoTranspiration aET
slope-2d
calculates the potential EvapoTranspiration according to Penman.
The
actual transpiration (aT) is a function of the potential transpiration
(pT)
and
the suction in the root zone.
The
reduction-function for different vegetations can be modified interactively.
Results
The calculated results for
1989 clearly show that the surface-sealing system of the
Georgswerder site is a very
dynamic system regarding water transport processes.
The state of equilibrium
- in german soil-physical literature denoted as field
capacity -
can never be reached.
The Fokker-Planck
- equation do not know this technical term
field capacity.
(see also)
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Last Updated by myself on June, 17, 1999
