Wetland functionality is provided in Source to allow modelling of quasi-two-dimensional situations where flow is governed by hydraulic considerations. Wetlands that may be modelled include both simple wetlands consisting of a single water body, and more complex systems such as Hattah Lakes, which consist of several interconnected wetlands. Key modelling features provided are:
- Hydrological behaviour of perennial or ephemeral water bodies in a wetland. This includes the interaction between storage volume, groundwater seepage, rainfall, evaporation, inflow and outflow. This is modelled using the Storage node.
- Connections within the wetland, and between the wetland and other parts of a river system. This includes inlets to and outlets from water bodies that can either be controlled (regulated) or uncontrolled (unregulated). In cases where flow is governed by head difference or may be in either direction, connections between water bodies are modelled via the Wetland Link. The Hydraulic Connector is used to model situations where the flow into or out of a wetland link is too small to have a material effect on the water level in the river. The Storage node is used when a water body, such as a lake or weir, is part of a wetland system.
- Conservative constituents. When this modelling option is enabled for a scenario, the movement of conservative constituents such as salt can be tracked through a wetland.
- Demand. Wetlands may have ecological, recreational, cultural or consumptive requirements. All demands, including those for wetlands, are modelled via a combination of a Water User node with the appropriate demand model, and Supply Point node(s) that associate water user demand with a physical source of supply.
| Info | ||
|---|---|---|
| ||
| Note: Groundwater fluxes are not considered in the wetlands hydraulic solution as these have negligible effects on the outcome. |
Scale
On a spatial scale, wetland functionality may apply to a single water body, or a complex system of interconnected wetlands (each made up of one or more water bodies). Every water body and connection may be modelled. Flow of water, its ownership (if relevant) and constituents through a wetland is calculated and reported at every model time-step.
Principal developer
This version of Wetland modelling has been developed by eWater CRC for Source.
Scientific provenance
The approach to wetland modelling used in Source is the Cells Model. The Cells Model was used in the formulation of the first Mekong model (Zanobetti et al 1970). This approach is employed by IQQM, which has been used in Australia for many years.
Version
Source 2.19.1
Dependencies
None. A wetland exists in a Source scenario once a Storage node is created.
Assumptions
The following assumptions and constraints apply:
- A uniform water level (ie. level pool) is assumed across each storage compartment
- The variation of water level and flow is assumed to be slow enough that the hydraulic conveyance can be estimated based on a quasi-steady-state assumption.
- The response of a wetland is slow enough that all groundwater, management and ecological responses can be made based on information of the last time-step.
- Daily or sub-daily time-step is small enough for the quasi-steady-state hydraulic response.
Wetland clusters and the "Cells model"
The group of nodes and links that represent a wetland in Source are referred to as a "wetland cluster". These can be Storage nodes, Wetland links and Hydraulic connector nodes.
Figure 1 illustrates some types of wetland that may be represented in Source by nodes in a wetland cluster:
- A wetland without river flow (green box). Examples include upland swamps, or spring fed wetlands on a floodplain.
- A wetland with a single water body (purple box). Examples include billabongs and oxbow lakes.
- A complex wetland with multiple water bodies (pink box). There are multiple paths of river flow through this type of wetland. Examples include the Macquarie. Marshes, Hattah Lakes and Menindee Lakes.
Figure 1. Example wetland clusters
Cells model
In Source each wetland cluster in a scenario is treated as a modelling unit, which is processed using a Cells Model. In this type of model, a wetland consists of a number of storage cells with the movement of water between them described by a set of functions (that are specified by the modeller) and boundary conditions. The main elements of the cells model and the Source components that are used to represent them are shown in Table 1.
...
Table 2. Wetland Configuration parameters
Parameter | Description | Units | Default | Range |
|---|---|---|---|---|
Max iterations | The maximum number of sets of node WSEs (trial solutions) to examine for a wetland cluster in finding an acceptable one, ie. where Precision ≤ Convergence Limit. Equation 33913 of the Flow phase section describes this further. | n/a | 5 | Integer > 0 |
Convergence limit | The upper threshold on error per node for an acceptable wetland cluster solution. At each solution iteration of a wetland cluster’s Cells Model, its Precision is compared to the square of Convergence Limit multiplied by the number of nodes in the cluster to determine whether it is acceptable (and hence the final one). | volume | 1 | Real number > 0 |
Log diagnostics | Indicates whether to create a log of information to diagnose Cells Model processing. Mainly for use when there is no "solution" found for wetland cluster(s). | n/a | No | Yes or No |
These parameters are accessed via the scenario Edit menu, and apply to all wetland clusters in the scenario.
If log diagnostics are required, there are also parameters that determine the location of the log file, the time-steps to be logged, and whether to only log those in which no acceptable Cells Model solution could be found. These parameters are described in more detail in the Source User Guide.
Table
553. Location Control parameters
Parameter | Description | Units | Default | Range |
|---|---|---|---|---|
Elevation | Base elevation of the currently selected node. | m | 0 | Real numbers |
Note that this information is also available in the Schematic Editor on the node’s tool tip.
Table
564. Hydraulic Connector node parameters (average inflow vs WSE)
Parameter | Description | Units | Default | Range |
|---|---|---|---|---|
Average inflow rate | Average inflow rate associated with the WSE | ML/day | 0 | Real numbers ≥ 0 |
Water surface elevation (WSE) | WSE for an average inflow rate | m | 0 | Real numbers |
Table
575. Wetland link parameters
Parameter | Description | Units | Default | Range |
|---|---|---|---|---|
From | Name of the node connected to the link from which outflow is given a positive value and inflow a negative value. | n/a | First node connected | Node names |
To | Name of the other node connected to the link from which outflow is given a negative value and inflow a positive value. | n/a | Second node connected | Node names |
Flow direction | Indicates whether flow can move in both directions | n/a | Bi-directional | Bidirectional or Unidirectional |
Weighting | Represents the point at which conveyance is calculated. Determines the influence of each end of the link’s WSE on conveyance. A value of 0.5 gives each end equal weighting. | n/a | 0.5 | Real numbers between 0 and 1 |
Modified Conveyance vs Water Surface Elevation (or Reduced Level) Table | ||||
Modified conveyance | Modified conveyance for a water surface elevation | m2.5/s | 0 | Real numbers ≥ 0 |
Water surface elevation (WSE) | WSE for a modified conveyance | Elevation (m) | 0 | Real numbers |
Flow Regulation Parameters | ||||
Flow Regulated? | Indicates whether the link is regulated. | n/a | No | Yes or No |
Target flow | Value returned by the selected time series, expression or scenario. It represents a maximum flow rate permitted on the link. Also controls flow direction. SeeRefer to the section on Regulated channel | Volume/time | none | Real numbers |
Table
586. Storage node parameters
Parameter | Description | Units | Default | Range |
|---|---|---|---|---|
Storage Dimensions Table: This describes a relationship between the storage’s Level, Volume and Surface Area | ||||
Level | Maximum depth of water in the storage | m | Row 1: 0 | Real numbers ≥ 0 |
Volume | Volume of water stored in the storage | ML | Row 1: 0 | Real numbers ≥ 0 |
Surface area | Surface area of water in the storage. | Ha | Row 1: 0 | Real numbers ≥ 0 |
Storage Details | ||||
Initial storage level | Initial depth of water in the storage. | Volume: Default m | 100 | Real numbers ≥ 0 |
Minimum operating level | Minimum depth of water to operate the storage at. Below this level no releases are made. | Volume: Default m | None | Real numbers ≥ 0 |
Maximum operating level | Maximum depth of water to be kept in storage. Releases are made to attempt to ensure this depth is not exceeded. | Volume: Default m | None | Real numbers ≥ 0 |
Rainfall and Evaporation: Used to calculate NetEvaporationws | ||||
Rainfall | Value returned by the selected time series, expression or scenario. Used to represent storage inflow/gain due to rain falling on the surface of the water stored. | distance/time: Default mm/day | 0 | Real numbers |
Evaporation | Value returned by the selected time series, expression or scenario. Used to represent storage outflow/loss due to evaporation from the surface of the water stored. | distance/time: Default mm/day | 0 | Real numbers |
Seepage Table: Used to calculate Groundwaterws | ||||
Level | Depth of water in storage associated with the rate of seepage. | Distance: | Row 1: 0 | Real numbers ≥ 0 |
Seepage | Rate of seepage associated with a depth of water in storage. | Volume/time: | Row 1: 0 | Real numbers |
Outlet Level versus Discharge Tables: Used to calculate fSpillo(WSEws) and fomax(WSEws) | ||||
Level | Depth of water in storage associated with a discharge rate. | m | Row 1: 0 | Real numbers ≥ 0 |
Discharge | Discharge rate for a depth of water in storage. | ML/day | Row 1: 0 | Real numbers |
Use of these parameters is described in Storage Nodes (Cells). For a full list of Storage Node parameters, see the Source User Guide.
Output data
Output data is viewed using the Recording Manager. The recorded attribute values (results) are reported for each time-step of the model run. Result Results relevant to wetland Cells Model processing are summarised in the following tables:
Table
597. Wetland cluster (Cluster solver) attributes
Attribute | Description | Units | Range |
|---|---|---|---|
Iterations | Number of solutions (sets of storage node WSE) that were tried for the time-step before one was found with acceptable (ie. Precision ≤ Convergence Limit) or the maximum iteration limit was reached. See Equation 339 under 13. | n/a | Integer, between 0 and the Maximum Iterations setting for Wetlands on the Edit menu. |
Precision | Root mean square of mass balance error volume for the wetland cluster’s storage nodes in its final solution for the time-step. | Volume | Real number > 0. |
Table
608. Storage node attributes
Attribute | Description | Units | Range |
|---|---|---|---|
Cell mass balance error | Value returned from the storage node’s Cells Model mass balance equation, described under Storage Nodes (Cells). This result comes from the final trial solution for the wetland cluster in each time-step. | Volume | Real number. |
Reduced Level or | Elevation at the surface of the water in the storage. This is the Storage Level(depth) plus the base Elevation (see Location Control or the tool tip in the Schematic Editor) | Elevation: | Real number. |
Table
619. Hydraulic connector node attributes
Attribute | Description | Units | Range |
|---|---|---|---|
Average Reduced Water Level | Elevation at the surface of the water at the point in the river represented by the hydraulic connector node. This is based on the upstream inflow rate. | Elevation: | Real number. |
Conveyance flux | Rate of flow (or flux) to/from the wetland(s) connected to the river at the hydraulic connector node. | Volume/time: | Real number |
Total conveyance flow volume | Total volume and direction of flow to/from the wetland(s) connected to the river at the hydraulic connector node over the time-step. Equals Conveyance flux × • time-step length. | Volume | Real number |
Table
6210. Wetland link attributes
Attribute | Description | Units | Range |
|---|---|---|---|
Average flow rate | Rate and direction of flow in the wetland link. See Qc in the Wetland Links (Connectors). | Volume/time: | Real number. |
Total flow volume | Total volume and direction of flow in the link over the time-step. Equals Average flow rate multiplied by • time-step length. | Volume | Real number. |
Average reduced water level | Elevation of the water surface at the point at which the link’s conveyance is calculated; WSEc) described in Wetland Links (Connectors) | Elevation: | Real number. Should be between From node reduced level and To node reduced level. |
From node reduced level | Elevation of the water surface, calculated by the cluster solver, at the end of the link configured to be upstream by default. | Elevation: | Real number |
To node reduced level | Elevation of the water surface, calculated by the cluster solver, at the end of the link configured to be downstream by default. | Elevation: | Real number |
Target flow | Maximum permitted flow rate on the link. Also indicates the permitted flow direction. See the sub-section in Wetland Links (Connectors). | Volume/time: | Real number |
Target flow volume | Same as the Target Flow attribute but expressed as a volume over the time-step. | Volume | Real number |
For a full list of output data for wetland nodes and links, refer to the Source User Guide.
Reference list
Zanobetti, D., Lorgeré, H., Preissmann, A., & Cunge, J.A., 1970, Mekong Delta mathematical model program construction, J. Waterways and Harbors Division, American Society of Civil Engineers, vol.96, no.2, pp.181-199.