< Previous40 • When drawing a rectangle, indicate the position of the first vertex with a single LM click in the MDWA, and indicate the position of the vertex diagonal from the initial vertex with another single LM click6. • When drawing a polygon, single-click the LM button to define the vertices of the polygon that will define the zone extent. The zone will appear in with circles at the vertex locations (see Figure 4-8). The location can of any vertex can be changed by hovering the mouse over it and click-dragging to the new desired location7 Hover the cursor over the circles at vertex locations and line segment mid-points to enable node editing capabilities. Click-drag a node to adjust the size or shape of the model domain. After any change is made, an ‘un-do’ button () will appear next to the last node that was edited. Click on to return to the previous node position. Note changes can only go back one node-edit in the current version of MAGNET. Once the last vertex has been placed, LM click the ‘SaveShape’ button to finalize the zone. This will launch the Zone Attributes menu (see Figure 4-8). This menu consists of 6 sub-menus: ‘Flow Property’; ‘Elevation’; ‘ Transport Property’’; ‘Biochemical’; ‘Sources and Sinks Head Dependent’; and ‘Sources and Sinks Prescribed’. The following subsection provide more details on each sub-menu If the zone needs to be discarded, LM click the ‘Delete’ tab to close the Zone Attributes menu and remove the zone feature from the MDWA. Figure 4-8: Zone feature added to the model domain and the Zone Attributes menu. 4.2.1 Flow Property Attributes 6 Allow for a brief period of time (i.e., at least 2-3 seconds) between LM clicks. Otherwise, the locations of the vertices may not be consistent with what is desired. 7 Any vertex location can also be updated after finalizing the zone. 41 Click on the ‘Flow Property’ tab title to access the Flow Property sub-menu (see Figure 4-8). This sub-menu may be used to assign: • hydraulic conductivity (Kxx) values and anisotropy ratios (Kxx/Kyy and Kxx/Kzz) different from those assigned for the rest of the model domain, or even generate a random Kxx field defined by characteristic scales of variance; • specific yield and specific storage values needed for transient modeling; and • effective porosity values needed for particle tracking and solute transport modeling. Check the radio boxes next to ‘Conductivity’ and ‘Kxx/Kyy’ and/or ‘Kxx/Kzz’ to use the values entered the relevant text boxes to use zone-specific Kxx values and/or Kxx/Kyy and/or Kxx/Kzz values. To generate a random Kxx field, check the radio box next to ‘Random’. The Flow Property Attributes sub-menu can also to create a water budget of the zone added to the model domain. Check the radio box next to ‘Zone Budget’. When the model is simulated/run forward, a zone budget for the zone(s) will be available in the Mass Balance Bar chart when analyzing model results with the ‘ViewResult’ button (see Section 6.2). 4.2.2 Elevation Attributes Click on the ‘Elevation’ tab title to access up the Elevation sub-menu (see Figure 4-9). Check the radio box next to ‘Top Elevation’ to use a constant value as the elevation aquifer top surface for the cells over which the zone extends. Check the radio box next to ‘Bot Elevation’ to use the value in the text box to use a bottom elevation within the zone that is different from the bottom elevation assigned using the Default Parameters and Options menu (see Section 3.3). The bottom boundary of the model within the zone can be assigned as: • a constant value prescribed by the user (choose the radio button next to ‘Constant’); • a surface following the aquifer top elevation surface such that the aquifer has a constant thickness (choose the radio button next to ‘Thickness’); or • a constant elevation that is a prescribed value below the minimum DEM elevation within the model domain (choose the radio button next to ‘Min DEM Minus’). 42 Figure 4-9: Elevation sub-menu (for Zone conceptual features). The ‘Partial Penetration’ options for the Top Elevation and Bottom Elevation (‘Bot Elevation’) allow zone features to partially penetrate a prescribed thickness of the aquifer8. For example, users may wish to restrict a contaminant source to the topmost portion of the aquifer system (see Figure 4-10), or insert a “clay lens” of lower hydraulic conductivity at some locations in the subsurface. Check the radio box(es) next to ‘Top Elevation’ and/or ‘Bot Elevation:’ to apply partial penetration elevation extents for the top and bottom elevation of the zone feature, respectively. The default values of ‘99999’ mean that the elevation will be extracted from the domain-wide elevation inputs. Enter different 8 Partial penetration only applies when multiple (vertical) sub-layers are used (see Section 3.2). Figure 4-10: Example Cross-section results (see Section 5.4) of using and not using Partial Penetration for a zone feature in MAGNET. When partial penetration is not used, the solute source is distributed throughout the aquifer system (i.e., across all computational layers. When it is used, the solute source is restricted to the topmost computational layer. 43 values in the text boxes provided to use values different than the domain-wide inputs. If one of the radio boxes is left unchecked, the domain-wide inputs will be used (see Figure 4-10). 4.2.3 Transport Property Attributes Click on the ‘Transport Property’ tab title to access the Transport Property sub-menu (see Figure 4-9). This sub-menu allows for assigning molecular diffusion and local dispersion coefficients potentially useful for solute transport modeling. Check the radio box next to ‘Molecular Diffusion L’ and/or ‘Molecular Diffusion T’ and input non-zero molecular diffusion coefficients (units: m2/day) to include lateral (L) and transverse (T) molecular diffusion in the solute transport simulations. Similarly check the radio box next to ‘Local Dispersion L’ and/or ‘Local Dispersion T’ and input non-zero local dispersion coefficients (units: m2/day) to include lateral (L) and transverse (T) local dispersion in the solute transport simulations. Solute source concentrations and extents can be added using zones and the Sources and Sinks tabs in the Zone Attributes menu (see subsections 4.2.5 and 4.2.6). Figure 4-11: Transport Property sub-menu (for Zone conceptual features). 4.2.4 Biochemical Attributes Click on the ‘Biochemical’ tab title to access the Biochemical Property sub-menu (see Figure 4-9). This sub-menu allows for assigning retardation and 1st-order decay coefficients potentially useful for solute transport modeling (see Figure 4-12). Check the radio box next to ‘Retardation’ to simulate the retardation of a solute due to biochemical processes or soil:water partitioning. By default, a retardation factor of 1 is used during simulation. Update the value in the text box next to ‘Retardation Factor’, or select the radio box next to ‘Partitioning Kd:’ to use a partitioning coefficient to simulate partitioning of a solute to the solid (sorbed) phase during transport. If a soil density (g/m3) is known, check the radio box next to ‘Soil Particle Density:’ and enter the known value in the provided text box. 44 MAGNET allows for simulating reactive decay of a pollutant (1st-order) by checking the radio box next to ‘First Decay:’. The rate of reaction can be controlled by assigning a first order decay coefficient (units of days-1) or a known half-life (days). For the former, select the radio button next to ‘Coefficient ‘ and enter a non-zero value in the provided text box. For the latter, select ‘Half Life’ and enter a non-zero value in the provided text box. Figure 4-12: Biochemical sub-menu (for Zone conceptual features). 4.2.5 Sources and Sinks (Head Dependent) Click on the ‘Sources and Sinks Head Dependent’ tab title to access the Head Dependent Flux sub-menu (see Figure 4-13). This sub-menu is used to assign the zone as a two-way or one-way source or sink of water, or as a “general head-dependent flux” (see more below in this subsection). Two-way head-dependent flux. To assign the zone as a two-way source (e.g., a lake or pond), check the radio box next to ‘Two-way’. The drop-down menu next to ‘Name’ provides different naming options for the zone feature that will be used in displaying results, e.g., when performing water balance analyses (see Section 6.2). The stage of the water source/sink can be assigned as: • a constant value that does not change with time – select the radio button next to ‘Const:’ and enter the desired value) • a constant value that is time-varying – after selecting the radio button next to ‘Const:’, check the radio box next to the ‘Transient’ button • the aquifer top elevation minus some prescribed value; by default, the stage is set to the aquifer top elevation, as indicated by the value of zero in the text box next to ‘Top E – ’ shown in Figure 4-13. 45 Figure 4-13: Sources and Sinks (Head Dependent) sub-menu (for Zone conceptual features). If the time-varying option is selected, LM click on ‘Transient’ button to open the ‘Transient Data for Lake Stage’ menu (see Figure 4-14). Indicate the starting data and time with the text boxes next to ‘State Date’ (year, month, day, hour). Then, provide the following inputs for each timestep: TimeN – or the number of days since the starting date and time; and ValueN – the stage value corresponding to TimeN. The stage values may be entered in any units; however, if meters are not used, make sure to enter the appropriate multiplier in the text box next to ‘Multiplier to meter:’. For example, to convert from ft. to m, enter 0.3048, as 1 ft.=0.3048m. After all desired changes have been made, LM click the ‘OK’ button. Or click ‘Cancel’ to discard all changes and close the sub-menu. Figure 4-14: Sub-menu for editing transient lake (or other source/sink) stage data. 46 Use the text box next to ‘BotE:’ assign a bottom elevation of the source/sink (e.g., the lake bottom elevation).Use the text box next to ‘Leakance:’ to enter a value (units of day-1) for the leakancy (a factor representing hydraulic conductivity per unit thickness of the land surface). Two-way source concentration. The two-way source/sink can be assigned a solute concentration for the purposes of transport modeling (in the case that the zone is acting as a source). Enter a non-zero value in the text box next to ‘Conc:’ (units: ppm) to apply a source concentration to the source/sink. To assign time-varying source concentration, check the radio box next to the ‘Transient’ button, and then LM click the ‘Transient button Check the radio box next to the ‘Transient’ button to open the Transient Data for Lake Concentration sub-menu (see Figure 4-15). Indicate the starting data and time with the text boxes next to ‘State Date’ (year, month, day, hour). Then, provide the following inputs for each timestep: TimeN – or the number of days since the starting date and time; and ValueN – the concentration value corresponding to TimeN. The concentration values may be entered in any units; however, if ppm are not used, make sure to enter the appropriate multiplier in the text box next to ‘Multiplier to ppm’. After all desired changes have been made, LM click the ‘OK’ button. Or click ‘Cancel’ to discard all changes and close the sub-menu. See Sections 5.2 and 6.1 for details on visualizing solute/contaminant transport results. Figure 4-15: Sub-menu for editing transient lake concentration data. One-way head-dependent flux. One-way head dependent flux allows water to leave the aquifer system in the case that the hydraulic head exceeds the top aquifer elevation, but water may not enter the aquifer system. To assign the zone as a one-way sink of water (e.g., seeps or springs), check the radio box next to ‘One-way’. The drop-down menu next to ‘Name’ provides different naming options for the zone feature that will be used in displaying results, e.g., when performing water balance analyses (see Section 6.2). The stage of the water sink can be assigned as: 47 • a constant value that does not change with time – select the radio button next to ‘Const:’ and enter the desired value) • the aquifer top elevation minus some prescribed value; by default, the stage is set to the aquifer top elevation, as indicated by the value of zero in the text box next to ‘Top E – ’ shown in Figure 4-13. Use the text box next to ‘BotE:’ assign a bottom elevation of the source/sink (e.g., the lake bottom elevation).Use the text box next to ‘Leakance:’ to enter a value (units of day-1) for the leakancy (a factor representing hydraulic conductivity per unit thickness of the land surface). General Head Dependent flux. Check the box next to “General Head Dependent Flux:’ to assign the zone as a pollutant/solute source. This requires assigning a source head (entered as a single value in the text box next to ‘Source head’), the leakancy (units of day-1), and the source concentration (units of ppm). 4.2.6 Sources and Sinks (Prescribed) Click on the ‘Sources and Sinks Prescribed’ tab title to access the Prescribed Flux and Sources sub-menu (see Figure 4-16). This sub-menu allows for assigning: • zone-specific recharge as a prescribed flux, steady or unsteady; • a prescribed head value, steady or unsteady; or • a source concentration, either as “instantaneous”, continuous or time-varying. Figure 4-16: Sources and Sinks (Prescribed) sub-menu (for Zone conceptual features). Prescribed Recharge. Check the radio box next to ‘Recharge:’ and enter a non-zero value (units: inch/year) in the text box to the right of ‘Recharge:’ to apply a prescribed recharge for all model cells over which the zone extends. This value is steady (i.e., the same value will be applied for all time-steps if performing transient simulations). 48 To assign time-varying recharge, check the radio box next to the ‘Transient’ button, and then LM click the ‘Transient button. This opens the ‘Transient Data for Recharge’ sub-menu (see Figure 4-17). Indicate the starting data and time with the text boxes next to ‘State Date’ (year, month, day, hour). Then, provide the following inputs for each timestep: TimeN – or the number of days since the starting date and time; and ValueN – the recharge value corresponding to TimeN. The recharge values may be entered in any units; however, if m/day are not used, make sure to enter the appropriate multiplier in the text box next to ‘Multiplier to m/day:’. For example, to convert from inch/year to m/day, enter 0.00006958, as 1 inch/year = 0.00006958 m/day. After all desired changes have been made, LM click the ‘OK’ button. Or click ‘Cancel’ to discard all changes and close the sub-menu. Figure 4-17: Sub-menu for editing transient recharge data. Prescribed Source Concentration. Check the radio box next to ‘Recharge’ and enter a non-zero value (units: inch/year) in the text box next to ‘Conc:’ to apply a prescribed source concentration (units: ppm) for all model cells over which the zone extends. This value is steady (i.e., the same value will be applied for all time-steps if performing transient simulations). To assign time-varying source concentration, check the radio box next to the ‘Transient’ button, and then LM click the ‘Transient button. This opens the ‘Transient Data for Recharge Concentration’ sub-menu (see Figure 4-18). Indicate the starting data and time with the text boxes next to ‘State Date’ (year, month, day, hour). Then, provide the following inputs for each timestep: TimeN – or the number of days since the starting date and time; and ValueN – the concentration value corresponding to TimeN. The concentration values may be entered in any units; however, if ppm are not used, make sure to enter the appropriate multiplier in the text box next to ‘Multiplier to ppm:’. After all desired changes have been made, LM click the ‘OK’ button. Or click ‘Cancel’ to discard all changes and close the sub-menu. 49 Figure 4-18: Sub-menu for editing transient recharge concentration data. Prescribed Head. Check the radio box next to ‘Prescribed Head:’ to treat the zone as a prescribed head boundary condition. The head can be assigned as: • a constant value that does not change with time – select the radio button next to ‘Constant:’ and enter the desired value; • a constant value that is time-varying – after selecting the radio button next to ‘Constant:’, check the radio box next to the ‘Transient’ button • the aquifer top elevation minus some prescribed value; by default, the stage is set to the aquifer top elevation, as indicated by the value of zero in the text box next to ‘Top E – ’ shown in Figure 4-16Figure 4-13. To assign time-varying recharge, check the radio box next to the ‘Transient’ button, and then LM click the ‘Transient button. This opens the ‘Transient Data for Recharge’ sub-menu (see Figure 4-19). Indicate the starting data and time with the text boxes next to ‘State Date’ (year, month, day, hour). Then, provide the following inputs for each timestep: TimeN – or the number of days since the starting date and time; and ValueN – the head value corresponding to TimeN. The head values may be entered in any units; however, if meters are not used, make sure to enter the appropriate multiplier in the text box next to ‘Multiplier to meter:’. After all desired changes have been made, LM click the ‘OK’ button. Or click ‘Cancel’ to discard all changes and close the sub-menu. Next >