How to auto-assign layer including upper cells (for a river or BC)

[dgiral]

Hello everyone !

I'm currently encountering a problem with my rivers. Basically I want to implement a river in my 3D Grid. I have 8 layers (whose tops and bottoms are not flat), and the head-stage and the elevation of my river are not the same all the time (spatially I mean). Meaning, at one location, I want my river condition to be put from layer 1 to 4, and at another, I want it to be put from layer 1 to 6. And it varies a lot (from one cell to the other next to it). So I could do it cell by cell, but I would be compelled to create a great amount of arcs.

The problem is that I don't know how to easily put my river condition in each cell from the top layer (surface) to the layer containing the elevation of the riverbed. I've seen that there is three options :

- Use layer range

- Auto-assign BC to one cell

- Auto-assign BC including lower cells.

None of the three options fit my problem. In fact, the third one is quite the opposite of what I would like to do. It assigns the BC to the layer containing the elevation of the riverbed plus all the layers beneath it. For a river, I would have expected to assign the condition to all the layers above it. But that option is not available.

So what can I do to solve this problem ?
Thank you for your answers and time !