search

inrae / airGRiwrm

airGRiwrm is an extension of the airGR R package for managing semi-distributive hydrological model on an anthropized catchment.
https://inrae.github.io/airGRiwrm/
GNU Affero General Public License v3.0
0 stars 1 forks source link

Area of the catchement issue #1

Closed marcellevarg closed 1 year ago

marcellevarg commented 1 year ago

First, I would like to congratulate the developers, airGRiwrm is an excellent package with many explanatory examples!

I have a question in hydrological terms, when I try to run the model for my basin, I get the following message: Area of the catchment X must be greater than the sum of the area of its upstream catchments.

I don't understand why this needs to be true, because there is the possibility of larger basins draining into smaller ones. If you can solve this doubt of mine, I would be very grateful.

DDorch commented 1 year ago

The area column of the GRiwrm object must be filled with the total catchment area including the upstream ones. So downstream catchments necessarily have an area larger than the upstream ones.

airGRiwrm automatically computes the run-off area of intermediate downstream catchments in CreateInputsModel.

marcellevarg commented 1 year ago

Thanks for the answer! Now I understand how the model was structured regarding the subbasins.

I have two other new questions:

1) Is it possible to calibrate the GR2M in a semi-distributed way? 2) Is the distance between the nodes the length of the flood wave propagation channel?

Thank you very much.

DDorch commented 1 year ago
  1. Is it possible to calibrate the GR2M in a semi-distributed way?

Not yet. The limitation comes from airGR on which airGRiwrm relies. I have opened a ticket in our gitlab repository: https://gitlab.irstea.fr/in-wop/airGRiwrm/-/issues/112. I can't give you a delay for the implementation of GR2M but if you are a bit familiar with R package development, I encourage you to try to remove this limitation and propose your solution :)

  1. Is the distance between the nodes the length of the flood wave propagation channel?

The semi-distribution relies on a "lag" model which applies a constant delay on the simulated flow between upstream and downstream nodes. For a downstream node receiving the flow of several upstream nodes this delay is calculated from one constant propagation speed (the so-called "mean flow velocity" parameter of the Lag model - see airGR::RunModel_Lag in the R console). Therefore, the length between the nodes is used for the delay calculation between each nodes with the formula : delay (s) = 1000 * distance between nodes (km) / propagation speed (m/s)

marcellevarg commented 1 year ago

Thank you for such complete answers! Again, congratulations on the excellent development.