The Unsaturated-Zone flow package simulates vertical flow through the unsaturated zone and into the saturated zone. it approximates the unsaturated flow as a set of kinematic waves. Each wave is divided vertically into a series of zones (a leading wave and several trailing waves) that each have a different water content and hence are affected by different unsaturated hydraulic conductivities. By default each wave has 7 trailing waves and there can be up to 40 kinematic wave sets.
The UZF package also simulates evapotranspiration from the unsaturated and saturated zones.
UZF6: Unsaturated-Zone Flow Package for MODFLOW 6 pane is on the MODFLOW Packages and Programs dialog box under Boundary Conditions | Head Dependant Flux. It is used to activate or deactivate the UZF package in MODFLOW 6 and to specify options in that package.
In MODFLOW 6 models, "multipliers" can be used with UZF boundaries. Multipliers will be used if the "Use Multiplier (MODFLOW 6)" checkbox is checked.. Ordinarily, multipliers are not needed. If multipliers are used, the cell area of the UZF boundary cell is multiplied by the value of the multiplier. One use for multipliers might be when the infiltration or potential evapotranspiration rates are defined using a time-series and it is desired to multiply the the time series values by a different amount at different locations.
Number of trailing wave (ntrailwaves) defines that number of trailing waves for each kinematic wave set.
Number of wavesets (nwavesets) defines the maximum number of kinematic wave sets per cell.
Simulate groundwater seepage (SIMULATE_GWSEEP) If this option is selected, groundwater discharge (GWSEEP) to land surface will be simulated. Groundwater discharge is nonzero when groundwater head is greater than land surface. This option is no longer recommended; a better approach is to use the Drain Package with discharge scaling as a way to handle seepage to land surface. The Drain Package with discharge scaling is described in Chapter 3 of the MODFLOW 6 Supplemental Technical Information.
Save binary UZF budget file (.uzf_budget) If this option is selected, the budget information for the unsaturated zone will be written to a binary file with the extension .uzf_budget.
Don't simulate ET If this option is selected, evapotranspiration will not be simulated. Simuate ET only in unsaturated zone (SIMULATE_ET) If this option is selected, evapotranspiration will be simulated in the unsaturated zone but not in the saturated zone. Simulate unsaturated ET and linear saturated ET (SIMULATE_ET and LINEAR_GWET) If this option is selected, evapotranspiration will be simulated in both the unsaturated and saturated zones. The groundwater evapotranspiration will be simulated using the original ET formulation of MODFLOW-2005. Simulate unsaturated ET and squared saturated ET (SIMULATE_ET and SQUARE_GWET) If this option is selected, evapotranspiration will be simulated in both the unsaturated and saturated zones. The groundwater evapotranspiration will be simulated by assuming a constant evapotranspiration rate for groundwater levels between land surface (TOP) and land surface minus the evapotranspiration extinction depth (TOP-EXTDP). Groundwater evapotranspiration is smoothly reduced from the potential evapotranspiration rate to zero over a nominal interval at TOP-EXTDP. |
Calculate based on water content (UNSAT ETWC) Evapotranspiration in the unsaturated zone will be simulated as a function of the specified potential evapotranspiration rate while the water content (THETA) is greater than the ET extinction water content (EXTWC). Calculate based on capillary pressure (UNSAT ETAE) Evapotranspiration in the unsaturated zone will be simulated simulated using a capillary pressure based formulation. Capillary pressure is calculated using the Brooks-Corey retention function. |
