Modeling of the Negro River estuary (Argentina)

Hello. I am trying to model the estuary of the Negro River. I've been trying for a long time to find a suitable model, but I can't get the model to run correctly.
The domain is as follows (due to the availability of metering stations). I have the following options:
1- Model with a single grid for the entire domain including the section of the Negro River (blue box in image 1).
2- Model a parent model and then include a submodel with a curvilinear grid for the river (image 2).
According to what you can see, what can you advise me?
I was trying to run the model with the option mentioned in point 1, and this throws the error that I show in image 3.
Is there any possibility of being able to do these queries in a personalized way? Thanks.