The Dam

The Dam is the reservoir element that can move water from the reservoir pool to the downstream system and is the primary element to which you will add outlets and outlet groups. In the Reservoir Tree, the dam is a special type of outlet group. What makes the dam special are three features that standard outlet groups don't have:

1. The dam is attached directly to the reservoir
2. The dam can be assigned a leakage element
3. The dam is the default release element of a reservoir — an overflow weir. Even if you do not add outlets to it, the dam itself is a weir that ResSim models using the standard weir equation and a (hard-coded) weir coefficient of 3.0. To define the weir, you must provide:

Elevation at top of dam —the elevation at which overtopping of the dam will occur (i.e., the weir crest).

Length at top of dam —the length of the dam or the length of the section of the dam that will overtop (the weir length).

If you do not want ResSim to compute dam overflow or if you want to specify the overflow capacity using a separate outlet, enter zero for the length of the dam.

The computed overflow from the dam will be combined with leakage and will be appear in the output as "Dam L&O".

The computed overflow will also be calculated based on the length of the top of dam. If a user has a simulation where the dam overtops and the flow looks unrealistically high, this could be the cause.

When you select the Dam node in the Reservoir Tree, the Edit Panel displays the Dam pane ("Figure: Reservoir Editor - The Dam").

Below the name of the Dam, the Dam pane contains a non-editable table displaying the Composite Release Capacity of the dam. The thumbnail plot to the right of the Composite Release Capacity table displays three curves, one for each release capacity column shown in the table. The Controlled capacity curve is blue, the Uncontrolled capacity curve is red, and the Total capacity curve is green. Be aware that the uncontrolled capacity in the table does not include the overflow capacity of the dam itself.