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 flows 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, four aspects 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 (Feature Editor 14) allows you to specify storage details, which are outlined in Table 8. You are recommended to use the same units as those in Dimensions, but you can change them by clicking on their respective units buttons.
Feature editor 1. Storage node
Table 1. Storage node, details
| Parameter | Definition | Default |
|---|---|---|
|
Full Supply |
The level or volume for which uncontrolled flow commences over an un-gated spillway. |
Equal to the level of the spillway. |
|
Initial Storage |
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 |
The level or volume below which water cannot be released from the storage. |
0 |
Releases from storages are normally assumed to be constant through the time-step (limited by volume to the minimum or maximum release curves). Enabling the Adaptive Storage Release Method checkbox generates a release curve based on the orders combined with the outlet curve. With this option, the storage would release at maximum release rate where the storage couldn’t release at ordered rate. The storage would release at minimum release rate when it was greater than the order. The adaptive storage release method will generate small artifacts when switching between the order and maximum/minimum release rates. However, it should provide better handling of releases when there are multiple outlets with big operating ranges.
Both Minimum operating level and Maximum operating level are only used when the storage is configured as a weir. Outlets MUST be configured correctly, and an ungated spillway must NOT be configured as the default outlet. The storage will not release water to satisfy downstream requirements if this results in the water level dropping below the minimum operating level. Likewise, water will be released to prevent the storage rising above the maximum operating level.
Outlet configuration can override the minimum and maximum operating levels.
Operating target is the level that the system will attempt to maintain in a downstream storage by transferring water from an upstream storage.
Storage dimensions
Select Dimensions (Feature Editor 15) to specify the dimensions of the storage node using level, volume and surface area. It can be entered manually as a piecewise linear relationship or imported as a comma-separated file (format shown in Table 1). The graph displays a relationship between Level vs Volume or Level vs Surface Area, which can be changed using the drop down menu. You can also export the relationship for use in another scenario.
Feature editor 2. Storage node, Dimensions
Table 1. Storage node, Dimensions (data file format)
| Row | Column (comma-separated) | ||
|---|---|---|---|
| 1 | 2 | 3 | |
| 1 | Level (m) | Volume (ML) | Surface Area (ha) |
| 2 | 0 | 0 | 0 |
| 3 | level | volume | surface area |
Constituents
These inputs are required for water quality constituents, and can be specified by selecting Constituents. Ensure that constituents have been defined prior to configuration (using Edit » Constituents). The dialog for configuring constituents is the same as for links. Hence, refer to Links for details.
Gauged Level
The Apply Unaccounted Difference to Storage level calculation checkbox 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 link the source data to a time series, an expression, or the output of another scenario, as shown in Feature Editor 16.
Feature editor 3. Storage node, Gauged level
Gauged Releases
This item shows a list of storage releases that are forced to be equal to observed releases. Click on the disclosure triangle to view these. Then, right click to enable the required release. For each outlet path, you can source observed release from either a time series, an expression, or the output of another scenario, as shown in Feature Editor 17.
Feature editor 4. Storage node, Gauged releases
Oulets
Outlets (Feature Editor 18) 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, clcik on the disclosure traingle 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 9; and
- You can enter a relationship between storage level and discharge for each outlet as a piecewise linear relationship (format shown in Table 10).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.
Note that when there are multiple outlets configured, water will flow down the outlet path assigned to the default spillway. Also, when a minimum flow requirement node is connected downstream of the storage node, water will flow through the path that links it to the storage.
Feature editor 5. Storage node, Outlets
Rainfall
Rain falling directly over the storage reservoir can be input as a time series, using the expression editor (such as adding a daily or monthly pattern), or linking to the output of another scenario, as shown in Feature Editor 19. 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.
Feature editor 6. Storage node, Rainfall
Evaporation
Evaporation directly from the storage surface can be input as a time series, an expression, or linking to the output of another scenario (Feature Editor 20).
Feature editor 7. Storage node, Evaporation
