Flow Pathways
The Flow Pathway Property defines how Stock amounts move between pools, either automatically or as triggered by a transition event.
Like the Transition Pathways, this property has tabs along the bottom of the window. The first tab shows a diagram of the pathways which has similar behavior to the transition pathway diagram version. The second tab lists the stocks in the diagram and their position on the screen. The third tab lists the Flow pathways, and includes the following fields:
Iteration (optional)
The Iteration that this pathway applies to. This is an optional field and if left blank the pathway will apply to all iterations.
Timestep (optional)
The Timestep that this pathway applies to. This is an optional field and if left blank the pathway will apply to all iterations.
From Primary Stratum (optional)
The Primary Stratum associated with the flow pathway. This is an optional field and if left blank the pathway will apply to all primary strata.
From Secondary Stratum (optional)
The Secondary Stratum associated with the flow pathway. This is an optional field and if left blank the pathway will apply to all secondary strata.
From Tertiary Stratum (optional)
The Tertiary Stratum associated with the flow pathway. This is an optional field and if left blank the pathway will apply to all tertiary strata.
From State Class (optional)
The unique label (e.g. cover type and structural stage) associated with the source State Class of the flow pathway. This is an optional field and if left blank the pathway will apply to all state classes.
From Min Age (optional)
The minimum cell age required for the flow pathway. This is an optional field and if left blank the pathway will apply to all ages. When multiple flow pathway records meet the minimum age criterion, the one with the highest minimum age will be used.
From Stock Type
The source Stock for the flow pathway. This is a required field. The flow pathway will move quantities from the source stock and add them to the destination stock.
To Stratum (optional)
The destination Stratum associated with a flow pathway. This is an optional field and if left blank the flow pathway will apply to all destination strata.
To State Class (optional)
The destination State Class associated with a flow pathway. This is an optional field and if left blank the flow pathway will apply to all destination state classes.
To Min Age (optional)
The minimum destination cell age required for the flow pathway. This is an optional field and if left blank the pathway will apply to all destination ages. When multiple flow pathway records meet the minimum destination age criterion, the one with the highest minimum age will be used.
To Stock Type
The destination Stock for the flow pathway. This is a required field. The flow pathway will move quantities from the source stock and add them to the destination stock.
Transition Group (optional)
The Transition Group associated with the flow pathway. This is an optional field. If left blank the flow pathway is considered automatic and will be invoked every timestep. If the transition group is specified, the flow pathway will only be invoked when the transition group occurs to a cell.
State Attribute Type (optional)
This is an optional field that can be used to specify the State Attribute used to define the quantity of material associated with the flow pathway. For example, a Net Primary Productivity state attribute could be defined for each state class which would be used to define the amount of carbon moving from the atmosphere stock to the biomass stock. If left blank, quantities of moving material associated with the flow pathway will be based on the total quantity of material present in the stock at the time the pathway is invoked.
Flow Type
This is a required field specifying the Flow Type associated with this flow pathway.
Target Type
This field allows a user to define what the amount represented by the flow pathway settings is targeting, with options being the flow, the resulting source stock, or the resulting destination stock. The options are:
- Flow - Amount represents a target for the flow amount.
- To Stock - Amount represents a target for the resulting To Stock. Flow amount is calculated as (Amount) - (Pre-Flow To Stock). If no Attribute value is specified, Amount represents resulting proportion of To Stock post flow (i.e., 1.5 means that To Stock increases by 50%).
- From Stock - Amount represents a target for the resulting From Stock. Flow amount is calculated as (Pre-Flow From Stock) - (Amount). If no Attribute value is specified, Amount represents resulting proportion of From Stock post flow (i.e., 0.8 means that From Stock decreased by 20%).
If no Target Type is specified, then assume same behavior as if Flow option was selected.
Multiplier
This is a required field that is multiplied against the quantity of material being moved from the source to the destination stock. When a state attribute specifies the quantity of material, that absolute quantity is adjusted by the multiplier. When no state attribute is specified, the multiplier defines the proportion of the total material present in the source stock that will be moved to the destination stock.
Transfer to Stratum (optional)
Use of any of the 'Transfer to' fields implies a Lateral Flow. Lateral flows move stock laterally from one cell to another. When lateral flows are invoked for a simulation cell, the flow moves the stock amount off of that simulation cell. The 'Transfer to' field is used to allocate stock moved away from all simulation cells for that Flow Type to a set of destination cells based on the 'Transfer to' fields selected. For example, users may define lateral flow pathways for soil carbon from an upslope stratum to a riparian stratum. ST-Sim will invoke this lateral flow for each upland stratum cell and remove the allocated stock amount. The model will then reallocate the total amount of stock moved through this process to all cells in the riparian stratum.
Transfer to State Class (optional)
See above 'Transfer to Stratum'.
Transfer to Min Age (optional)
See above 'Transfer to Stratum'.