Hydrus 1D Tutorial. Example: Infiltration and drainage in a large caisson. 1) Basic model setup. Sebastian Bauer Geohydromodellierung

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1 Sebastian Bauer Geohydromodellierung Modellieren in der Angewandten Geologie Sommersemester 2008 Hydrus 1D Tutorial Example: Infiltration and drainage in a large caisson 1) Basic model setup Start Hydrus 1D Project Manager Button "New" Name: Infiltr1 Description: Infiltration and drainage in a large caisson Button "OK Main Processes Heading: Infiltration and drainage in a large caisson Simulate: Water Flow Button "Next Geometry Information Length Units: cm Number of soil materials: 1 Number of Layers for mass balances: 1 Decline from vertical axis: 1 Depth of the soil profile: 600 cm Time Information Time Units: Hours Initial Time: 0 Final Time: 5 Initial Time Step: Minimum Time Step: Maximum Time Step: 0.5 No Time Variant Boundary Condition Print Information T-Level Information every 1 time steps Screen Output OK

2 Number of Print Times: 4 Button "Select Print Times" Enter Print Times: 1, 2, 4, 5 Button OK Water Flow - Iteration Criteria Maximum number of iterations: 20 Water content tolerance: Pressure head tolerance: 1 Leave others as suggested (3; 7; 1.3; 0.7; 1e-6; 10000) Water Flow - Soil Hydraulic Model Single Porosity Models: Van Genuchten Mualem Hysteresis: No hysteresis Water Flow - Soil Hydraulic Parameters Qr Qs Alpha n Ks I (These are θr= residual soil water content, θs = saturated soil water content, α = parameter in soil water retention curve (van Genuchten α), n = van Genuchten n, Ks = saturated hydraulic conductivity, I = tortuosity factor for saturated hydr. cond.) Catalogue of Soil Hydraulic Properties: Nothing selected Water Flow - Boundary Conditions Upper Boundary Condition: Constant Pressure Head Lower Boundary Condition:: Free Drainage Initial Condition: In the Water content Soil Profile - Graphical Editor OK and Save to start PROFILE application Menu: Conditions->Profile Discretisation Select Number and enter 121 Menu: Conditions->Initial Conditions->Pressure Head or Toolbar: red arrow Button "Edit condition" Select with Mouse (left Mouse Button) the first node all through the last node and specify top and bottom values as 0.10 initial water saturation distribution. Mark then just the first node and set to Deactivate Use top value for both. Menu: Conditions->Observation Points Button "Insert", Insert nodes by clicking on the model area with the mouse and pressing left mouse button at 0, 100, 200, 300, and 400 cm depth (coordinates bottom right corner of

3 screen) Menu: File->Save Data Menu: File->Exit Soil Profile - Summary Execute HYDRUS Hit Enter in black window to close Hydrus 1D application View OUTPUT: Hydrus 1D offers a few standard possibilities: Observation Points Time curves at observation points Profile Information Values of pressure, water content, etc. versus depth Water Flow - Boundary Fluxes and Heads Fluxes and variable values at model boundaries Soil Hydraulic Properties Displays functional relations between water content, pressure and hydraulic capacity: Capillary pressure water content curve, hydraulic conductivity water content curve, hydraulic capacity water content curve Look closely at these functions and switch variables at axes. Run Time Information Gives Time step length and iteration number Mass Balance Information Water mass balance Close Project

4 Example Output:

5 2) Parameter Study Copy the file Infiltr1 and the corresponding subdirectory Infiltr1 to file Infiltr2 and subdirectory Infiltr2 (copy and rename) Change the homogeneous material distribution to a heterogeneous material distribution. Geometry Information Number of soil materials: 2 Button "OK" Water flow: soil hydraulic parameters: Enter values for material two by clicking in any field of the second line of the table and by selecting a different material (e.g. sand) from the Catalogue of Soil Hydraulic Properties Time Information: Increase the simulation time to 10 h (= Final time) Print Information: Number of print times: 10 Select print times: 1, 2,, 10 Start PROFILE application(soil profile graphical editor) Conditions -> Material Distribution Select Edit Condition Select with mouse the area in the model area, where the new material should be, i.e. between 200 and 400 cm depth. Enter corresponding material group. Rerun application and inspect output files. Try different standard parameterisations by using the Catalogue of Soil Hydraulic Properties from Water Flow - Soil Hydraulic Parameters and compare the results obtained. Sometimes you will have to change the time frame, as infiltration will take longer.

6 3) Drainage of caisson Copy the file Infiltr1 and the corresponding subdirectory Infiltr1 to file Drainage1 and subdirectory Drainage1 (copy and rename) Change the settings, so that drainage can be simulated. Water Flow - Boundary Conditions Upper Boundary Condition: Constant Flux Lower Boundary Condition: Constant Pressure head Initial Condition: In the Water content Upper boundary flux: 0 Time Information Time Units:Hours Initial Time: 0 Final Time: 100 Initial Time Step: 1.0e-6 Minimum Time Step: 1.0e-7 Maximum Time Step: 0.5 No Time Variant Boundary Condition Print Information T-Level Information every 1 time steps Screen Output OK Number of Print Times: 4 Button "Select Print Times" Enter Print Times: 1, 4, 20, 100 Button OK Start PROFILE application (Soil profile graphical editor) Conditions -> Initial condition -> Pressure head/water content Select Edit Condition : Everywhere 0.33 Save and Exit. Rerun Application Try rerunning Hydrus using an initial water content of What happens and why?

7 Example Output:

8 4) Transport in soil column Copy the file Infiltr1 and the corresponding subdirectory Infiltr1 to file Transp1 and subdirectory Transp1 (copy and rename) Change the settings, so that solute transport can be simulated along with the infiltration Main Processes Heading: Infiltration and drainage in a large caisson Simulate: Water Flow and Solute Transport Button "Next 8 times Solute Transport Look at all numbers but leave them as they are. Lower right corner: Set number of solutes 1 Pulse duration 1 Solute Transport Parameters Change long. dispersivity to 1 cm Change solute Diffusion coefficient and gas diffusion coefficient to 0.0 Solute Transport and Reaction Parameters Set KD = Nu = Henry = 0; Beta = 1; all *sink and alpha = 0 Solute Transport Boundary condition Upper boundary condition: Concentration BC Lower boundary condition: Zero concentration gradient Set BC to 1 Start PROFILE application (Soil profile graphical editor) Conditions -> Initial condition ->Concentration (for concentration 1) Select Edit Condition : Everywhere 0.0 Save and Exit. Rerun Application Variation: Set Solute Transport BC to 0. Set initial condition for solute 1 to 1 between 150 and 175 cm depth. Rerun application