Model:TopoFlow-Infiltration-Richards 1D

Contact

Name	Scott Peckham
Type of contact	Model developer
Institute / Organization	CSDMS, INSTAAR, University of Colorado
Postal address 1	1560 30th street
Postal address 2
Town / City	Boulder
Postal code	80305
State	Colorado
Country	USA"USA" is not in the list (Afghanistan, Albania, Algeria, Andorra, Angola, Antigua and Barbuda, Argentina, Armenia, Australia, Austria, ...) of allowed values for the "Country" property.
Email address	Scott.Peckham@colorado.edu
Phone	303-492-6752
Fax

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TopoFlow-Infiltration-Richards 1D

Metadata

Summary Also known as Model type Single Model part of larger framework Note on status model Date note status model Technical specs Supported platforms Unix, Linux, Mac OS, Windows Other platform Programming language Python Other program language None (but uses NumPy package) Code optimized Single Processor Multiple processors implemented Nr of distributed processors Nr of shared processors Start year development 2001 Does model development still take place? Yes If above answer is no, provide end year model development Code development status When did you indicate the 'code development status'? Model availability As code, As teaching tool Source code availability (Or provide future intension) Through CSDMS repository Source web address Source csdms web address Program license type Apache public license Program license type other Memory requirements Standard Typical run time Minutes to hours In/Output Describe input parameters The input variables used for modeling infiltration and unsaturated vertical flow with the 1D Richard's equation are defined as follows: K_s = saturated hydraulic conductivity (m / s) K_i = initial hydraulic conductivity (m / s) (typically much less than K_s) θ_s = soil water content at ψ = 0 (unitless) (often set to the soil porosity, φ) θ_i = initial soil water content (unitless) θ_r = residual soil water content (unitless) (must be < θ_i) ψ_B = bubbling pressure head (meters) (also called air-entry pressure, ψ_ae) ψ_A = pressure head offset parameter (meters) λ = pore-size distribution parameter (unitless) (alt. notation = 1/b ) η = 2 + (3 * λ) (unitless) (see Notes) c = transitional Brooks-Corey curvature parameter (unitless) (see Notes) dznodes = vertical distance between nodes (meters) nnodes = number of subsurface vertical nodes The behavior of this component is controlled with a configuration (CFG) file, which may point to other files that contain input data. Input format ASCII, Binary Other input format Describe output parameters Output format ASCII, Binary Other output format Pre-processing software needed? Yes Describe pre-processing software Another program must be used to create the input grids. This includes a D8 flow grid derived from a DEM for the region to be modeled. The earlier, IDL version of TopoFlow can be used to create some of these. Post-processing software needed? Yes Describe post-processing software None, except visualization software. Grid sequences saved in netCDF files can be viewed as animations and saved as movies using VisIt. Visualization software needed? Yes If above answer is yes Other visualization software VisIt Process Describe processes represented by the model The Richards 1D method for modeling infiltration. Describe key physical parameters and equations Equations Used by the 1D Richards' Equation Method v = K * (1 - ψ_z) = Darcy's Law for vertical flow rate (m / s) v_z = J - θ_t = conservation of mass, with source/sink term J Θ_e = (θ - θ_r) / (θ_s - θ_r) = effective saturation or scaled water content (unitless) θ_r = θ_s ( abs(ψ_B) / 10000)^λ = residual water content (unitless) K = K_s * Θ_e^η/λ = hydraulic conductivity (m / s) (see Notes below) ψ = ψ_B (Θ_e^-c/λ - 1)^1/c - ψ_A = pressure head (meters) (see Notes below) These equations are used to compute the time evolution of 1D (vertical, subsurface) profiles for (1) soil moisture, θ, (2) pressure head, ψ, (3) hydraulic conductivity, K and (4) vertical flow rate, v. TopoFlow solves these equations separately to get time-evolving profiles for every grid cell in a DEM. The result is a 3D grid for each of these four variables that spans the unsaturated zone. The third equation above just defines a variable that is used in the 4th and 5th equations, so the coupled set constitutes 4 equations to be solved for 4 unknowns. These equations can be combined into one nonlinear, parabolic, second-order PDE (partial differential equation) known as the one-dimensional Richards' equation. Describe length scale and resolution constraints Recommended grid cell size is around 100 meters, but can be parameterized to run with a wide range of grid cell sizes. DEM grid dimensions are typically less than 1000 columns by 1000 rows. Describe time scale and resolution constraints The basic stability condition is: dt < (dx / u_min), where dt is the timestep, dx is the grid cell size and u_min is the smallest velocity in the grid. This ensures that flow cannot cross a grid cell in less than one time step. Typical timesteps are on the order of seconds to minutes. Model can be run for a full year or longer, if necessary. Describe any numerical limitations and issues This model/component needs more rigorous testing. Testing Describe available calibration data sets This model/component is typically not calibrated to fit data, but is run with a best guess or measured value for each input parameter. Upload calibration data sets if available: Describe available test data sets Available test data sets: Treynor watershed, in the Nishnabotna River basin, Iowa, USA. (Two large rainfall events.) Small basin in Kentucky. Inclined plane for testing. Arctic watershed data from Larry Hinzman (UAF). See /data/progs/topoflow/3.0/data on CSDMS cluster. Upload test data sets if available: Describe ideal data for testing Several test datasets are stored on the CSDMS cluster at: /data/progs/topoflow/3.0/data. Other Do you have current or future plans for collaborating with other researchers? Collaborators include: Larry Hinzman (UAF), Bob Bolton, Anna Liljedahl (UAF), Stefan Pohl and others Is there a manual available? Yes Upload manual if available: Model website if any This site. Model forum / discussion board Comments About this component: This component was developed as part of the TopoFlow hydrologic model, which was originally written in IDL and had a point-and-click GUI. For more information on TopoFlow, please goto: http://csdms.colorado.edu/wiki/Model:TopoFlow. When used from within the CSDMS Modeling Tool (CMT), this component has "config" button which launches a graphical user interface (GUI) for changing input parameters. The GUI is a tabbed dialog with a Help button at the bottom that displays HTML help in a browser window. This component also has a configuration (CFG) file, with a name of the form: <case_prefix>_channels_diff_wave.cfg. This file can be edited with a text editor. The Numerical Python module (numpy) is used for fast, array-based processing. This model has an OpenMI-style interface, similar to OpenMI 2.0. Part of this interface is inherited from "CSDMS_base.py". Introduction History Papers Issues Help Input Files Output Files Download Source