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This SRG entry describes how the ownership of water moving via wetland channels can be determined in Source, and how this influences ownership of water where a wetland connects with a river. Requirements are summarised in Table 1. Ownership aspects within a wetland compartment (modelled by the storage node in Source) is covered separately in Ownership in Storages - SRG.
Table 1. Partner user requirements
No | Requirement |
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1 | Ownership of water can be assigned, tracked and reassigned. |
1.1 | Ability to specify initial ownership of water at each location (all water must be assigned to an owner) |
1.2 | Ability to specify the transfer of ownership at a location, represented as a node in the river network. |
1.3 | Borrow and payback is supported, where owners share surpluses to owners that cannot meet their requirements, and can be paid back later. |
1.4 | In every model component, ownership is conserved when it is not explicitly transferred or exchanged, i.e. the following volume equation holds for each owner o: ΔStorageo = Inflowo - Outflowo - Diversiono - Losso + Gaino + Borrowedo - Lento |
2 | Water flowing from a river to a wetland on a wetland link is shared according to rules input by the modeller. |
2.1 | Flow from the river on a wetland link can be shared proportionally, or according to fixed ratio. |
2.2 | When flow from the river in a wetland link is shared proportionally, owners are assigned a share in proportion to their upstream inflow. |
3 | Water flowing into a river from a wetland link retains its ownership, i.e. is treated the same way as upstream inflow. |
4 | Water flowing out from a reservoir via a wetland link is shared according to rules input by the modeller. |
4.1 | Flow from a reservoir via a wetland link can be shared proportionally, or according to fixed ratio |
4.2 | When flow from a reservoir via a wetland link is shared proportionally, owners are assigned a share in proportion to the volume of their water in storage. |
5 | Water flowing into a reservoir via a wetland link retains its ownership, i.e. is treated the same way as upstream inflow. |
Scale
The concept of spatial scale in the context of Ownership relates to the fact that it can apply to all or part of the length of a river system. Ownership status can be updated as often as at every model time step, or less often if required.
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Automatically included with Source.
Table 2. Assumptions and Constraints
No | Assumption/Constraint |
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1 | Owners cannot have a negative share of water in storage or transit |
2 | The sum of each owners’ share of flow or storage volume at a model component will equal the total flow or storage volume for the corresponding component. |
3 | The direction of flow in a wetland link is the direction that has the highest flow volume over the time step. |
Structure & processes
Theory
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- If they are fixed at one or both ends, the modeller configures each owner’s ratio or percentage of the flow entering the wetland link from this end and this remains constant for the model run. At various times during the model run, some owners may not have sufficient water at the source node to sustain their fixed share of flow, while others will have a surplus. When this happens, owners with a deficit will borrow from those with a surplus. This borrow is accounted for, and may be paid back later (see Borrow and Payback - SRG for more information).
- If shares are defined to be proportional, each owner’s share is recalculated in each model time step. This calculation differs according to the type of node connected to the nominated end of the wetland link:
Hydraulic connector node: Each owner’s share is proportional to its current inflow from the upstream standard link:
Equation 1 where:
Sharesource(l, i) - Owner i’s share of outflow from the hydraulic connector along wetland link l
Ii - Owner ’s upstream inflow to the hydraulic connector over the current time step
I - Total upstream inflow to the hydraulic connector over the current time step
Storage node: Each owner’s share is proportional to its current storage volume:
Equation 2 where:
Sharesource(l, i) - Owner i’s share of outflow from the hydraulic connector along wetland link l
Vi - Owner i’’s storage volume.
V - Total volume in the storage.
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For a wetland link l, an owner i’s flow during the current time step (Wli) is:
Equation 3 |
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where:
Sharesource(l, i) - Owner i’s share of outflow from the hydraulic connector along wetland link l
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An owner i’s total wetland flow volume entering/leaving a node over a time step (Wi) is the sum of its flow volume on all connected wetland links:
Equation 4 |
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where:
l - A wetland link connected to the wetland node
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An owner i’’s downstream outflow at a hydraulic connector (Oi) is their upstream inflow minus their wetland flow:
Equation 5 |
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where:
Ii - Owner i’s inflow at the hydraulic connector over the current time step
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An owner’s downstream outflow could be negative if they are assigned a fixed share of wetland outflow that exceeds their upstream inflow. Ownership rules dictate that every owner has non-negative outflow. Hence, owners with a negative (deficit) downstream outflow volume must borrow from others with positive (surplus) flow. The surplus/deficit for each owner is their outflow volume:
Equation 6 |
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Equation 7 |
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The borrow method (described in Borrow and Payback - SRG) will return the amount an owner borrows (Borrowedi) and lends (Lenti). The owner’s outflow is then adjusted.
Equation 8 |
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As flow processing ensures that total downstream outflow is non-negative, this adjustment will ensure every owner has non-negative outflow.
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The storage ownership continuity equation described in Ownership in Storages - SRG is:
Equation 9 |
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where:
Vi2 - Owner ’s volume of water in the reservoir this time step.
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Methodology
Variables used
Table 3. Common
Symbol | Purpose/Description | Units |
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i | Owner index | |
t | Time step index – used for the current time step | |
t - 1 | Index of the previous time step. |
Table 4. Wetland link
Symbol | Purpose/Description | Units |
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Node1 | ‘from’ wetland node at one end of the link – the flow values are positive when flow comes from this node (configured). | n/a |
Node2 | ‘to’ wetland node at the other end of the link – the flow values are negative when flow comes from this node (configured). | n/a |
FixedShare(Source, i) | Owner i’s fixed flow share/ratio when flow is coming from the end of the wetland link (configured - total for all owners adds up to 1). | n/a |
FlowSharing(Source) | Sharing method (fixed/proportional) when flow is coming from the end of the wetland link (configured). | n/a |
Share(i) | Owner i’s share of flow in the wetland link (total for all owners adds up to 1). | n/a |
Source | Node at the end of the wetland link that flow is coming from in the current time step. | n/a |
Source.Type | Type of node at the end of the wetland link that flow is coming from in the current time step – ‘Storage’ or ‘Hydraulic connector’ | n/a |
flow(t) | Wetland link’s total flow volume in timestep t. | volume |
flow(i, t) | Owner i’s volume of the wetland link’s flow in timestep t. | volume |
Table 5. Wetland storage
Property or Method | Purpose/Description | Units |
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F(i) | Owner i’s volume of losses that are fixed for the current time step in the storage. | |
Volume(i, t-1) | Owner i’s volume of water in the storage at the end of the previous timestep (calculated by the standard storage model). | volume |
Volume(t - 1) | Total volume of water in the storage at the end of the previous timestep (calculated by the standard storage model). | volume |
WetlandLoss(i, t) | Total flow volume for owner i to/from wetland links connected to the storage for timestep t. (A positive value is an outflow to the wetland) | volume |
Table 6. Hydraulic connector
Property or Method | Purpose/Description | Units |
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Inflow(i, t) | Inflow volume for owner, i, from a standard link upstream into the hydraulic connector for time step t | volume |
Outflow(i, t) | Outflow volume for owner, i, to a standard link downstream of the hydraulic connector for time step t | volume |
WetlandLoss(i, t) | Total flow volume for owner i to/from wetland links connected to the storage for timestep t. (A positive value is an outflow to the wetland) | volume |
Borrowed(i) | The volume that owner, i, borrowed from other owners to meet their flow deficit. | volume |
Lent(i) | The volume of downstream outflow that owner, i, lent to other owners with a deficit. | volume |
Deficit(i) | The volume that owner, i, needs to borrow from other owners so that they do not have negative downstream outflow. | volume |
Surplus(i) | Surplus (positive) downstream outflow for owner, i, that can be lent to other owners as required. | volume |
Flow phase
Wetland link
For each model time step the following steps are performed after the wetland link flow rate has been calculated to determine wetland link owner values:
- If this link has already been processed ((flow, (i, t) not null), exit here. (Ownership calculations only have to be done once on a wetland link).
- Get the ‘source’ node that flow originates from this time step. Note that a positive flow value indicates that flow moves from Node1 to Node2. (Node1, Node2 are configured).
- If flow(t) > 0, Source = Node1
- Otherwise Source = Node2
- Get the source node’s outflow share. Last time step’s values are used as ownership processing may not have been performed for the node as yet:
- If the FlowSharing(Source) = 'Proportional'
If Source.Type = 'Storage'
Equation 10 Otherwise (hydarulic connector)
Equation 11
Otherwise (sharing is fixed)
Equation 12
- If the FlowSharing(Source) = 'Proportional'
For each owner: Apply the owner’s share to the total to determine their flow volume.
Equation 13
Wetland storage
The following method determines each owner’s share of wetland loss in a storage, and adds it to their total fixed losses:
- Determine total wetland flow per owner using the generic method for a wetland node (See Method Description section below).
- Add each owner’s share of total wetland flow to their share of fixed storage losses:
- Use this fixed loss value in ownership processing as per Ownership in Storages - SRG.
Hydraulic connector
Each owner’s upstream inflow to a hydraulic connector Inflow(i) equals the outflow from the link connected upstream (if none are connected, it is zero). To determine each owner’s share of wetland loss and outflow the following steps are performed:
- Determine total wetland flow per owner WetlandLoss(i) using the generic method for a wetland node (See Method Description section below).
Each owner’s share of downstream outflow is its inflow plus wetland loss/gain:
Equation 14 - If any owner has a negative share of outflow, use the borrow method to bring its share to zero:
Determine owner surpluses and deficits – this is simply their unmodified downstream outflow:
Equation 15 Equation 16 - If any owner deficit > 0, use the Borrow method described in Borrow and Payback - SRG.
Update every owner’s outflows for volumes borrowed and lent:
Equation 17
Method Description
Generic method to calculate wetland loss for a wetland node
To determine total wetland flow per owner WetlandLoss(i):
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- Run the wetland link’s ownership processing – this determines WetlandLink.flow(i, t)
- Add each owner’s share of the wetland link’s flow WetlandLink.flow(i, t) to their wetland flow total WetlandLoss(i). The default ‘upstream’ node on a wetland link is Node1, so if the current flow value is positive, flow is moving away from this node.
- If (this Node = WetlandLink.Node1) the current node has been treated as ‘upstream’, so:
For every owner iEquation 18 - Otherwise: (the node is ‘downstream’ so the flow is a gain)
For every owner iEquation 19
- If (this Node = WetlandLink.Node1) the current node has been treated as ‘upstream’, so:
Data
Input data
Details on data are provided in the Source User Guide.
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Input parameters are summarised in Table 37.
Table
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7. Wetland link: Ownership Parameters
Parameter Name | Parameter Description | Unit type | No. of values | Allowable values & validation rules | Default Value(s) |
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Source Node | Name of a node connected to the wetland link | n/a | 2 | Read only | Name of connected node |
Flow sharing method | Indicates whether the flow from Node will be shared in fixed ratio or proportionally. | n/a | 2 | ‘Fixed Ratio’ or ‘Proportional’ | Proportional |
Flow sharing table: Owner | An owner in the wetland link’s ownership system. | n/a | 1 per owner in o.s. | Read only | Each owner in the storage’s o.s. |
Flow sharing table: Share | Owner’s percentage share of outflow from Node. | % | 1 per owner | Owner percentages must add up to 100% | Equal share of 100 per owner. |
* Note: The initials o.s. refer to the current ownership system.
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Recorded variables are listed in Table 48.
Table
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8. Recorded variables: Wetland flow ownership
Model element | Parameter | Units | Variable/calculation | Freq. | Display format |
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Wetland link + owner | Share | % | Share(i) | Time step | Displayed as: Graph, Table, Statistics (min, max, average over the modelled time period) |
Wetland flow volume | volume | WetlandLoss(i) |