Boundary conditions settings

[mjmolivo]

Hello,

Thank you for this very useful tool ! I'm currently learning how to use it and adapt it to my current study on wetlands fonctionnality.

In my situation I am a GIS specialist, but I do not work in hydrology, so pardon my lack of knowledge in this domain. I don't perfectly get the principle of boundary conditions, I saw in the documentation that these elements aren't mandatory in the parameters file, however I care about understanding how it works. I was wondering how those inputs are working, and does the values attributed to the outpoint via v.to.rast (bctype = 4 and bcvalue = 0) are appliable in any geographical context or specifically in the case of the tutorial ?
More precisely, my elevation raster covers a small catchment area at the foot of the Pyrenees (between approx 400 and 500m high).

Thank you in advance for your reply.

[morvayo]

bctype 4 sets a prescribed water depth and bcvalue 0 means zero water depth at those cells

it does not mean zero elevation above sea level so your catchment being at 400 to 500 m does not itself require changing that value

the tutorial applies it at the outlet but whether it fits your catchment depends on the downstream conditions

if downstream water can back up into the wetland a permanently zero depth outlet would not represent that

the boundary types are documented here
https://itzi.readthedocs.io/en/latest/conf_file.html#boundary-conditions

[lrntct]

I'm glad itzi is useful to you!
To complement the answer by morvayo, in combination with bctype=4, bcvalue is a set water depth in a specific cell. At every step, the model will maintain this depth, adding or removing water from the domain as necessary. In the tutorial the goal is to prevent the water from accumulating. But in another application, it could represent a known water level in a body of water.

[mjmolivo]

Thank you for your replies ! Now it is clearer to me.
If you have in mind some works where itzi models were applied and documented in the case of wetland studies, do not hesitate letting me know.