GMS:MT3DMS Source/Sink Mixing Package: Difference between revisions
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The '''Source/Sink Mixing Package | {{MT3DMS Links}} | ||
[[File:MT3D-SourceSinkMixing.jpg|thumb|285 px|The MT3DMS ''Source/Sink Mixing Package'' dialog.]] | |||
The ''Source/Sink Mixing Package'' dialog is used to assign concentrations to [[GMS:MT3DMS_Point_Sources/Sinks_BC|point sources/sinks]] (wells, river/streams, specified head, general head) and [[GMS:MT3DMS_Point_Sources/Sinks_BC|areal sources/sinks]] (recharge, evapotranspiration). In most cases, the concentration is assigned to the incoming water when the sources/sinks are acting in the source mode, i.e., contributing water to the system. In sink mode, the concentration of the outgoing water is equal to the concentration of groundwater in the aquifer and the concentrations assigned to the sources/sinks have no effect because the water and species is being removed by the negative flow out of the ground. The only exception is evapotranspiration. Even though [[GMS:EVT Package|evapotranspiration]] always acts in sink mode, a concentration can be specified. Generally, the assigned concentration is zero which only allows pure water to leave the aquifer. | |||
==Source/Sink Mixing Package dialog== | ==Source/Sink Mixing Package dialog== | ||
The information below describes the dialog. | |||
===Maximum number of Sources/Sinks in Flow Model=== | ===Maximum number of Sources/Sinks in Flow Model=== | ||
MT3DMS needs to know the maximum number of sources/sinks in the flow model. This number is simply the total number of cells in the MODFLOW model that have a source or sink defined at them. This number is computed automatically. | MT3DMS needs to know the maximum number of sources/sinks in the flow model. This number is simply the total number of cells in the MODFLOW model that have a source or sink defined at them. This number is computed automatically. | ||
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A column is provided for each of the species concentrations. Changing the source/sink type for one stress period at a cell will automatically change the type for the remainder of the stress periods at the same cell. | A column is provided for each of the species concentrations. Changing the source/sink type for one stress period at a cell will automatically change the type for the remainder of the stress periods at the same cell. | ||
Point sources/sinks can be added and removed from the list by selecting the Add and Delete buttons. However, when adding new point source/sink, it is usually more convenient to select the 3D grid cells and use the [[GMS: | Point sources/sinks can be added and removed from the list by selecting the '''Add''' and '''Delete''' buttons. However, when adding new point source/sink, it is usually more convenient to select the 3D grid cells and use the [[GMS:MT3DMS Point Sources/Sinks BC|''MT3DMS'' | '''Point Sources/Sinks''']] menu command. | ||
===Initializing Point Source Sinks from MODFLOW=== | ===Initializing Point Source Sinks from MODFLOW=== | ||
An option is included in the | An option is included in the ''Source/Sink Mixing Package'' dialog to initialize the point sources/sinks to be used in the MT3DMS simulation directly from data that have already been defined in a MODFLOW simulation. If a MODFLOW simulation is currently in memory, the buttons in the ''Initialize point sources/sinks from MODFLOW'' dialog can be used. Each button is labeled with a different source/sink type, corresponding to the MODFLOW point sources or sinks. Selecting one of the buttons automatically adds to the list of point sources/sinks. For example, if the '''Well''' button is selected, GMS creates a new well source/sink for each cell where a well is defined in the MODFLOW simulation currently in memory. The initial concentration of each of the new well sources/sinks is zero. In order to utilize the source/sink initialization buttons, the following conditions must be met: | ||
#The MODFLOW package corresponding to the source/sink type to be initialized must have been selected in the MODFLOW Packages dialog. | #The MODFLOW package corresponding to the source/sink type to be initialized must have been selected in the ''MODFLOW Packages'' dialog. | ||
#Point sources or sinks of the type to be initialized must have been defined in MODFLOW. | #Point sources or sinks of the type to be initialized must have been defined in MODFLOW. | ||
=== | ===Specified Concentration Boundary Conditions=== | ||
When entering the concentrations for a specified concentration cell, it is sometimes necessary to specify the concentrations of some of the species but allow the concentrations for the remaining species to vary. This can be accomplished by specifying a negative concentration for the species that are to vary. | When entering the concentrations for a specified concentration cell, it is sometimes necessary to specify the concentrations of some of the species but allow the concentrations for the remaining species to vary. This can be accomplished by specifying a negative concentration for the species that are to vary. | ||
===Areal Sources/Sinks=== | ===Areal Sources/Sinks=== | ||
Recharge and evapotranspiration are known as areally distributed sources and sinks. This is because a value for concentration must be entered for each species for every vertical column of cells in the finite difference grid. This essentially means that a two dimensional array of concentration values must be defined for each species for both recharge and evapotranspiration, depending upon which options are utilized. The buttons labeled Recharge and Evapotranspiration bring up the Areal Source/Sink Array dialog. | Recharge and evapotranspiration are known as areally distributed sources and sinks. This is because a value for concentration must be entered for each species for every vertical column of cells in the finite difference grid. This essentially means that a two dimensional array of concentration values must be defined for each species for both recharge and evapotranspiration, depending upon which options are utilized. The buttons labeled '''Recharge''' and '''Evapotranspiration''' bring up the ''Areal Source/Sink Array'' dialog. | ||
===Reset=== | ===Reset=== | ||
The Reset button deletes all of the data currently defined in the | The '''Reset''' button deletes all of the data currently defined in the ''Source/Sink Mixing package'' and restores the package parameters to the default values. | ||
==Conceptual Model Input== | ==Conceptual Model Input== | ||
In some cases, the simplest way to define both point and areal sources/sinks is with an MT3DMS [GMS:Conceptual Model|conceptual model] in the [[GMS:Map Module|Map module]]. Concentrations can be assigned directly to [[GMS:Feature Objects|points, arcs, and polygons]]; points representing point sources/sinks and polygons representing recharge and evapotranspiration zones. These concentrations are copied directly to the appropriate cells/arrays in the | In some cases, the simplest way to define both point and areal sources/sinks is with an MT3DMS [[GMS:Conceptual Model|conceptual model]] in the [[GMS:Map Module|Map module]]. Concentrations can be assigned directly to [[GMS:Feature Objects|points, arcs, and polygons]]; points representing point sources/sinks and polygons representing recharge and evapotranspiration zones. These concentrations are copied directly to the appropriate cells/arrays in the ''Source/Sink Mixing package'' when the conceptual model is converted to the numerical model with the [[GMS:Map to Models|''Feature Objects'' | '''Map → MT3DMS''']] command. | ||
==Mass Loading== | |||
MT3D can report mass budget information. The mass budget discrepancy is a measure of the internal consistency and accuracy of the transport solution, and it depends on the method of solution and the model parameters. It makes use of the following equation: | |||
:<em>change in mass stored = net mass flux + mass in from sources – mass out from sinks</em> | |||
Some considerations should be made when selecting the "Mass loading" type. The first is to pay attention to the selected units as this will effect the calculation. <!-- mg L^-1 ft3 d^-1 for grids in units of feet.--> For example, if a user wanted to consider a mass loading of 1 mg/d, they would need to divide 1 mg/d by 28.3 L/ft^3 for MT3D to calculate mass loading correctly. | |||
{{Navbox GMS}} | {{Navbox GMS}} | ||
[[Category:MT3DMS]] | [[Category:MT3DMS|Source]] | ||
[[Category:PHT3D|Source]] | |||
[[Category:MT3DMS Dialogs|Source]] | |||
[[Category:PHT3D Dialogs|Source]] | |||
