When you're running multi-stream deposition, the order that lines are defined in can influence the final beach elevations for each line. This is because the multi-stream model is not modelling the concurrent deposition of tailings streams, but rather, models them sequentially, in the order that they're defined.
For the example below, there are 2 discharge lines, one in the north and the other in the south.
The command Ooze/Multi-stream deposition/No pond was run with the following parameters:
Running deposition with Line 1 first, followed by Line 2, we end up with final beach elevations of:
- Line 1: 103.8m
- Line 2: 107.5m
The order of deposition can be reversed by rerunning the deposition command and reordering the lines by dragging the row-header up or down.
The final beach elevations are:
- Line 1: 105.2m
- Line 2: 106.3m
The predicted beach elevations for Line 1 can vary by 1.5m and Line 2 by 1.2m, depending on the order that the lines are deposited from. If the deposition strategy is to pour one line, and then the other, then these results are fine. If the lines are deposited concurrently, then these are valid results, however if the lines are operated concurrently, this may not be acceptable.
Manually splitting streams
If this difference is consequential, the modelling can be broken down into smaller steps to better capture the interaction of the 2 streams. This can be done in 2 ways. The first is to halve the volume of tailings poured from each line, and then deposit them twice (or break it down even more if needed). This is shown in the table below.
By breaking the volumes down and depositing more often, the inter-bedding of the tailings streams where they overlap/interact, is better modeled and it gets closer to modelling what would happen if the the streams could be truly modeled simultaneously. While doing this manually is a big deal for a 2 lines and 2 subdivisions, using it for more deposition lines and more than 2 divisions means a lot more user effort.
Split-stream multi-stream deposition
The second way is to use one of the multi-stream deposition Split Stream models. These deposition models will take each line and split them into a series of smaller deposition volumes, based on the user specified number of divisions.
With 2 divisions, the final line elevations are:
- Line 1: 104.3m
- Line 2: 107.3m
Breaking it into smaller divisions:
| Line | 2 Divisions | 4 Divisions | 10 divisions |
| Line 1 | 104.3 | 104.5 | 104.6 |
| Line 2 | 107.3 | 107.1 | 107.0 |
As the number of divisions increases, the run time will also increase, so there will be a practical limit as to how much the streams should be split up.