> For the complete documentation index, see [llms.txt](https://water-strategy.gitbook.io/waterstrategy/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://water-strategy.gitbook.io/waterstrategy/tutorials/creating-a-reservoir-system/adding-reservoir-details/adding-reservoir-bathymetry-level.md). # Adding reservoir bathymetry (Level) The water **Level** of a reservoir can be calculatedi n the same way as for a reservoir. A reservoir's water level is required to be able to calculate hydropower. While the Botswana National Model doesn't include hydropower, for completeness it is included in this tutorial. *Please note: Unlike the Area parameter that was defined on the Resevoir node. We will define the Level parameter in the Parameters tab of the Interface. This is to demonstrate the Parameters tab, the Level could be defined also on the node.* Below is an example area Level vs Volume rating table for: | Volume (Mm3) | Level (m) | | ------------ | --------- | | 0 | 1 | | 7 | 8 | | 10 | 16 | | 15 | 18 | | 25 | 20 | When plotted it looks like this:

Relationship between the water level and the reservoir volume

1. Click on the **Parameters** tab on the interface.

2. Click on the **+** to add a new parameter. Select **PYWR\_PARAMETER**

3. In the text field that appears write **'Dam level'**

4. Copy and **Paste** the Json below into the editor and click **Save**. ``` { "type": "InterpolatedVolumeParameter", "node": "Example reservoir", "volumes": [ 0, 7, 10, 15, 25 ], "values": [ 1, 8, 16, 18, 20 ], "interp_kwargs": { "kind": "linear" }, "comment": "volumes: Mm3, values: m" } ```

5. Click on **Timeseries** in the **Outputs** tab to enable the saving of the Level timeseries.

6. Click on **Map** to return to the map view

\ 7\. The Dam level parameter needs to be referenced on the Level attribute on the reservoir, to do this, click on the Reservoir an write the name of the parameter in the Level attribute (**Dam level).** Please note that the name is case sensitive.

8. Run the model. 9. You will see that because the **Dam level** parameter is not defined on the node, the **simulated\_level** is not output on the reservoir node. Instead to view the output, click on the **Network Attributes** button.

10. Click on the **simulated\_Dam level.** Note that the Reservoir node name is in the name of the output of the Parameter.

**The Level time series can be seen below.**

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