The module calculates the piezometric head and optionally the groundwater velocity field. The vector components can be visualized with ParaView if they are exported with r3.out.vtk.
The groundwater flow will always be calculated transient. For steady state computation the user should set the timestep to a large number (billions of seconds) or set the specific yield raster map to zero.
(dh/dt)*S = Kxx * (d^2h/dx^2) + Kyy * (d^2h/dy^2) + Kzz * (d^2h/dz^2) + q
Two different boundary conditions are implemented, the Dirichlet and Neumann conditions. By default the calculation area is surrounded by homogeneous Neumann boundary conditions. The calculation and boundary status of single cells can be set with the status map, the following cell states are supported:
The groundwater flow equation can be solved with several numerical solvers. Additionally a direct Gauss solver and a LU solver are available. Those direct solvers only work with quadratic matrices, so be careful using them with large maps (maps of size 10.000 cells will need more than one Gigabyte of RAM).
# set the region accordingly g.region res=25 res3=25 t=100 b=0 n=1000 s=0 w=0 e=1000 -p #now create the input raster maps for a confined aquifer r3.mapcalc "phead = if(row() == 1 && depth() == 4, 50, 40)" r3.mapcalc "status = if(row() == 1 && depth() == 4, 2, 1)" r3.mapcalc "well = if(row() == 20 && col() == 20 , -0.00025, 0)" r3.mapcalc "hydcond = 0.00025" r3.mapcalc "syield = 0.0001" r.mapcalc "recharge = 0.0" r3.gwflow -s solver=cg phead=phead status=status hc_x=hydcond hc_y=hydcond \ hc_z=hydcond q=well s=syield r=recharge output=gwresult dt=8640000 velocity=gwresult_velocity # The data can be visualized with ParaView when exported with r3.out.vtk r3.out.vtk -p in=gwresult,status vector=gwresult_velocity_x,gwresult_velocity_y,gwresult_velocity_z out=/tmp/gwdata3d.vtk #now load the data into ParaView paraview --data=/tmp/gwdata3d.vtk
This work is based on the Diploma Thesis of Sören Gebbert available here at Technical University Berlin, Germany.
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