In regulated river systems, storages control the supply of water to consumptive and non-consumptive users, and may also provide flood mitigation, social and environmental services. In a river model, they represent places where water is stored along the river, such as dams, reservoirs, weirs and ponds. Storages operate by maintaining water mass balance.
In Source, the storage node operates by calculating the minimum and maximum discharge based on current inflows and user defined discharge, gain and loss relationships. They maintain water balance and assume that the change in storage height across a time-step is small compared to the storage fluxes. Additionally, it assumes that any flow fluxes into or out of the storage are distributed throughout the time-step. Flows and changes in storage volume are calculated by integrating across the time-step.
For all storages in Source, the following must be configured as a minimum in the node’s feature editor:
- Details of the storage such as its dimensions and capacity;
- Inflows to storages such as stream flow from upstream catchments, rainfall over the storage surface area, recharge from groundwater, and runoff from the catchment surrounding the storage;
- Outflows from the dam, which could be initiated either through controlled releases (to fulfill downstream demand) or uncontrolled flows; and
- Losses that constitute evaporation from the storage surface area and seepage to groundwater.
The editor’s main window (Figure 1) allows you to specify storage details, which are outlined in Table 1. You are recommended to use the same units as those in Dimensions, but you can change them by clicking on their respective units buttons.
Figure 1. Storage node
Table 1. Storage node, details
| Parameter | Definition | Default |
|---|---|---|
| Hydropower generation | A drop-down menu allowing you to choose where to generate spill for hydropower generation. When a storage with an ungated spillway is close to FSL, and inflows would cause the storage to physically spill in the absence of release, the system can find it difficult to accurately determine if the generator could have been used to pass inflows, rather than the spillway. For example, if a storage is at the spill level of the ungated spillway at the start of the time-step, and there is inflow which could have been passed through the generator, the majority of the inflow will pass over the spillway. This situation arises when the correct configuration for a storage with only ungated spillways is used, ie, Don't generate from spill is chosen. Actual generation in such situations would depend on the operating rules for the reservoir, and pattern of inflow though the day. It is not possible to define a single generically applicable solution for this. Similarly, if the storage is below spill level, and inflow is such that the storage would spill without releases, and downstream demand = inflow (and therefore the storage wouldn't physically spill), Source sets a minimum release which is interpreted as physical spill. Choosing Generate using spill will generate from all spill limited ONLY by capacity Choosing Generate using spill; upto downstream orders will generate spill limited by downstream orders and capacity. | Don't generate from spill |
| Full Supply | The level or volume for which uncontrolled flow commences over an un-gated spillway. | Equal to the level of the spillway. |
| Initial Conditions | The initial water level/volume in the storage at the start. This level must be above or equal to the minimum storage water level defined in the storage dimensions relationship. | There is no default value, but it can be a non-integer, with the minimum being the lowest storage dimension level. |
| Dead Storage Capacity | The level or volume below which water cannot be released from the storage. This is different for rules-based and netLP ordering. Refer to the note below. | 0 |
| Node elevation | The node's height above sea level (this value can be negative to represent an elevation below sea level) | 0 |
Operating targets
Operating target refers to the level that the system will attempt to maintain in a downstream storage by transferring water from an upstream storage.
The maximum unregulated operating target captures surplus water during an off-allocation event. It specifies a target level in the storage that is used by the off-allocation system in determining how much water may be allocated to the storage during the off-allocation event.
Figure 2. Storage node, Operating target
Storage dimensions
Storage dimensions can be configured to be either static or vary over time (see Time-varying storage dimensions). You can use time-varying storage dimensions to model the gradual decrease in storage capacity caused by sedimentation, or to model the abrupt increase in storage capacity from implementing a new dam.
Static storage dimensions
To configure dimensions that remain constant for the duration of the model run, select Dimensions » Static Storage Dimension (Figure 3) and then specify the dimensions using level, volume and surface area. Dimensions can be entered manually as a piecewise linear relationship or imported as a comma-separated file (format shown in Table 1). There is no need to specify a start date, this is used for configuring time-varying storage dimensions. You can also export the relationship for use in another scenario. The graph displays a relationship between Level vs Volume or Level vs Surface Area, which can be changed using the drop down menu.
Figure 3. Storage node, Dimensions
Table 2. Storage node, Dimensions (data file format)
| Row | Column (comma-separated) | ||
|---|---|---|---|
| 1 | 2 | 3 | |
| 1 | Level (m) | Volume (ML) | Surface Area (ha) |
| 2 | -10 | 0 | 0 |
| 3 | 0 | 100 | 500 |
| 4 | level | volume | surface area |
Example File
Level,Volume,SurfaceArea
473, 0, 0
475, 100, 0.1
478,4600, 2.9
479,8100, 2.9
Time-varying storage dimensions
Storages can be configured to increase and/or decrease in storage capacity over time, these changes can be gradual or happen in a single time step.
To vary storage dimensions over time, at least two storage dimensions need to be configured, each with a different start date. To add a second storage dimension, right click on Dimensions and select Add Storage Dimension from the contextual menu. This will automatically change the name of the Static Storage Dimension to the Start Date set for that storage dimension (default is 01/01/1880) and create a second storage dimension with a name and a start date set to the next day (02/01/1880).
For each storage dimension, configure the level, volume and surface area relationship as explained for Static Storage Dimensions. Set the Start Date to the date from which the dimensions apply. If the start dates for all storage dimensions are after the start date of the run, then the storage dimension with the earliest start date is used at the beginning of the run.
You can configure how Source interpolates between storage dimensions by selecting Dimensions and then toggling on or off Interpolate Between Storage Dimensions. When toggled off, the second storage dimension will take effect on the configured start date (Figure X, solid lines). When toggled on, the storage dimensions are linearly interpolated between the first start date and the second start date, and so on (Figure X, dashed lines). Note that the start and end dates of the model run do not effect the interpolation.
Changing between storage dimensions
- If the storage volume decreases, then the level is assumed to be constant between the two time steps. This will result in a loss of water, which can be recorded with the Loss to Storage Dimension Change parameter.
- If the storage volume increases, then the volume is assumed to be constant between the two time steps, this may result in a decrease in storage level.
As an illustrative example, a model was configured with constant flow, and a storage with three storage dimensions, with the second storage dimension decreasing in storage capacity relative to the first, and the third storage dimension increasing in storage capacity (Table Y). The model was run from the 01/04/2016 to 01/05/2016. The results of this configuration on Storage Volume, Level and Loss to Storage Dimension Change are shown in Figure X when interpolation was toggled on (solid lines) or off (dashed lines). Note that because the beginning of the run (01/04) is before the first storage dimension starts (05/04), the initial storage dimensions are considered to be those configured for the 05/04, but interpolation does not start until the 05/04.
Table Y. Example of time-varying storage dimensions
Storage Dimension Start Date | Level (m) | Volume (ML) | Surface Area (km2) |
|---|---|---|---|
| 05/04/2016 | 0 | 0 | 0 |
| 100 | 200000 | 1000 | |
| 15/04/2016 | 0 | 0 | 0 |
| 100 | 100000 | 500 | |
| 25/04/2016 | 0 | 0 | 0 |
| 100 | 200000 | 1000 |
Figure X. Example of time-varying storage dimensions.
Constituents
These inputs are required for water quality constituents, and can be specified by selecting Constituents. Ensure that constituents and constituent sources have been defined prior to configuration (using Edit » Constituents). Refer to Constituents - Storage.
Gauged Level
The Apply Unaccounted Difference to Storage level calculation check box allows you to enable modelled values to be overridden by observed values. The storage level forces the parameter to equal the observed value. You can specify the source data as a single value, link it to a time series (using Data Sources) or a function (using the Function Editor), as shown in Figure 4. The storage node icon changes to indicate that modelled data is being overridden (Figure 5).
Figure 4. Storage node, Gauged level
Figure 5. Storage node icon, observed data replaces modelled data
Gauged Releases
This menu item allows you to overwrite modelled storage releases with observed releases. First, click on the disclosure triangle next to Gauged Releases to view a list of available outlet paths, then right click on an outlet path to enable. Enter the observed data either as a single value, a time series (using Data Sources) or a function (using the Function Editor), as shown in Figure 6. The storage node icon changes to indicate that modelled data is being overridden (Figure 5).
Figure 6. Storage node, Gauged releases
Outlets
Outlets (Figure 7) define how water is released from the storage and must be added to allow for spills. In Source, you must specify the following:
- Outlet path – the path (out of the storage node) taken by the outlet. To choose an outlet path, click on the disclosure triangle to open a list of links connected to the node. You can choose the link that is associated with an outlet by right-clicking and choosing the outlet type;
- Outlet types – right-click on Outlets and choose the outlet type from the contextual menu.You can add more than one outlet type per storage. These are shown in Table 3; and
- Storage Outlet Types - You can enter a relationship between storage level and discharge for each outlet as a piecewise linear relationship (format shown in Table 4.).You can also see a piecewise linear relationship accounting for all the release types (eg. if you have a gated spillway and a culvert) in the table for Total Outlet Capacity.
Table 3. Storage Outlet Types
| Outlet Type | Description | Piecewise linear function required |
|---|---|---|
| Culvert | A conduit is used to enclose a flowing body of water. It may be used to allow water to pass underneath a road, railway or embankment. | Level vs discharge |
| Gated Spillway | Controls releases by the operation of gates. This allows for arange of discharges rates for each water level, depending on how wide the gates are opened. | Level vs minimum and maximum discharge |
| Hydropower Valve | The power generated from a hydroelectric system. | Level vs maximum discharge |
| Pump | Used to extract water from the storage (rather than allow discharge). This may be used where the location of the demand is at a higher elevation compared with the storage, or to extract water from the dead storage and which is below other release structures | Level vs maximum water pumped |
| Un-gated Spillway | A structure that controls the spill of water from a storage. It is designed to spill water once the storage is full and ensures that any spills are controlled. This prevents the storage from failing. Un-gated spillway rating tables are used to populate the Discharge table. The full storage level should have a zero discharge and the discharge depth needs to be calculated as the height above the full storage level. | Level vs discharge |
| Valve | Used to release water via a pipe. Valves normally release environmental flows from storages. The valve rating table is used to control the volume of water released via this method. | Level vs maximum discharge |
Table 4. Storage node, Seepage (data file format)
| Row | Column (comma-separated) | |
|---|---|---|
| 1 | 2 | |
| 1 | Level (m) | Seepage (mm/d) |
| 2 | 0 | 0 |
| 3 | level | seepage |
Figure 7. Storage node, Outlets
Rainfall
Rain falling directly over the storage reservoir can be input as a time series, using the Function Editor (such as adding a daily or monthly pattern), or linking to the output of another scenario, as shown in Figure 8. It is assumed to occur only on the surface area. Daily rainfall data near the storage is required and can be obtained from managing agencies, SILO or the Bureau of Meteorology.
Figure 8. Storage node, Rainfall
Evaporation
Evaporation directly from the storage surface can be input as a single value, as a time series or an expression (Figure 9).
Figure 9. Storage node, Evaporation
Seepage
Water can infiltrate into the ground where the soil is not fully saturated. Where groundwater intercepts the surface, water can seep from groundwater into the storage, where infiltration can occur wherever there is a ground/water interface. Seepage (Figure 10) is specified using a piecewise linear relationship between storage level and infiltration volume/time. Note that you cannot specify negative values. The data file format for seepage is shown in Table 4.
Figure 10. Storage node, Seepage
Ordering at storages
The following two options are mutually exclusive. If one is enabled, the other is greyed out (Figure 11).
If Pass Orders Straight Through Storage is enabled (Figure 11), then the storage level for forecasting seepage and evaporation losses is:
- For weirs max (currrent level, Maximum Operating Level); and
- For storages max (currrent level, Full Supply Level).
Otherwise max(currrent level, Operating Target).
If Do Not Order From Upstream Storages is enabled, then the storage acts as if it has no storage nodes upstream of it for the purposes of ordering. This is useful when a storage has the capacity to fulfill all downstream requirements, and will not need to order water from upstream storages.
Performance Improvement
Enabling Do Not Order From Upstream Storages on a storage limits the maximum travel time for any node downstream of it to that storage; storages upstream of it are not considered during maximum travel time calculations. When this option is enabled, the application will do less future prediction of water requirements, improving performance of the ordering phase. This can significantly improve run times in models that have ordering and long travel times.
Figure 11. Storage Node, Ordering
Ownership in storages
In ownership, observed values may not be available for every time-step. Additionally, observed values cannot include negative numbers, as ownership of storages can potentially result in negative shares when you support borrow and payback. Refer to Figure 12 for details and Ownership for more information.
Figure 12. Storage node (Ownership)
| Level | Volume | SurfaceArea |
| 473 | 0 | 0.00E+00 |
| 475 | 100 | 0.1 |
| 478 | 4600 | 2.9 |
| 479 | 8100 | 3.9 |
