Questions Regarding WRF-Hydro 5.4.0 Standalone Version and Output Analysis

[msvramana]

Dear Users,

I hope this message finds you well.

I have recently installed the WRF-Hydro Standalone version 5.4.0 successfully and completed the test case over the Croton, New York domain, following the instructions provided in the official test case documentation and user manual. The model ran successfully without errors.

However, after running the test case, I was unable to locate the surface runoff variable in any of the output files. To further analyze the outputs, I attempted to use Python for reading and visualizing the data. During this process, I encountered some challenges, such as:

• Converting UTM coordinates to geographic coordinates,

• Plotting inundation maps and other variables properly.

I would appreciate your support with the following questions:

1. How can I obtain the surface runoff variable? Is there a specific option in the namelist or another relevant output variable that represents it?

2. Are there any free tools or plugins (e.g., for ArcGIS, QGIS, or Python) recommended for working with WRF-Hydro 5.4.0 output data?

3. Is there a comprehensive user manual or guide for the Standalone WRF-Hydro model, similar to what is available for WRF atmospheric modeling?

Additionally, could you kindly let me know:

• Is there a standard procedure or tool for post-processing and visualization of WRF-Hydro output data?

• Are there any recommended tutorials or example workflows for Python-based analysis of WRF-Hydro results?

Thank you in advance for your guidance and support.

Regards,

MSV

[aubrey]

Hi MSV:

Whether or not you get an output variable for surface runoff depends on your physics configuration and what you are *really* interested in when you say "surface runoff". If you are running a configuration without overland routing active, you will see the land surface model's conceptual "SFCRNOFF" variable in the LDASOUT land model output files. If you are running a configuration with overland routing enabled, WRF-Hydro will explicitly route the land model's excess surface water, so it can become "sfcheadsubrt" in the RTOUT file (ponded water on the surface on the high-res grid) or "qSfcLatRnoff" in the CHRTOUT file (overland flow that flows into a channel cell/reach). So what variable you want to use really depends on your particular application and the process you are interested in.

Our training materials show examples of how to work with WRF-Hydro outputs using Python:

https://github.com/NCAR/wrf_hydro_training/tree/main/lessons/training

We also have a comprehensive user guide:

https://wrf-hydro.readthedocs.io/en/latest/index.html

I believe our gridded outputs should work with standard geospatial applications if you are using a spatial metadata file, but I don't normally use these applications so can't say for sure these all work seamlessly.

Hope that helps.

Thanks!

Aubrey

[nuts sun]

Dear Users,

I have recently installed the WRF-Hydro Standalone version 5.3.0 and successfully ran the test case following the official documentation and user manual. The model executed without any errors.

However, after completing the simulation, I was unable to locate the surface runoff variable in any of the output files (e.g., from the LDASOUT or HYDRO_RST files). I understand that in version 5.4.0, some users have raised similar questions about output variables, and I was wondering if the handling of surface runoff differs in version 5.3.0.

For reference, I have enabled channel routing with the following settings in my namelist:

text

! Switch to activate channel routing...(0=no, 1=yes) CHANRTSWCRT = 1 !<-- Turn on/off channel routing module. ! Specify channel routing option: ! 1=Muskingum-reach, 2=Muskingum-Cunge-reach, 3=Diffusive Wave-gridded channel_option = 2 !<-- If channel routing module is active, select which physics option to use.

Could you kindly advise:

1. Where can I find the surface runoff variable in the output files for WRF-Hydro 5.3.0? Is there a specific namelist option I need to enable, or does it correspond to another variable name (e.g., SFCRUNOFF, UGDRNOFF, or something else)?

2. Is there a detailed output variable guide or technical note for version 5.3.0 that describes the available fields and their units?

Any insights or pointers from the community would be greatly appreciated. Thank you very much for your time and support.

Best regards,
NMV

[aubrey]

Hi NMV:

I believe this was answered above. If you are running with WRF-Hydro's terrain routing schemes you will NOT get the SFCRNOFF term in the land model outputs since that conceptualization is no longer valid. This is intentional. The column land surface models have only a very conceptual representation of runoff terms, so when you activate the WRF-Hydro terrain routing schemes you will get the more explicit/physical runoff components (excess water on the surface, land surface runoff to the channel, baseflow to the channel). What variable you want to use depends on what process you are hoping to represent (infiltration or saturation excess? overland flow? streamflow?).

You should still get UGDRNOFF values. If the WRF-Hydro baseflow model is active, this represents water draining from the soil column into the conceptual baseflow module.

The user guide linked above includes the different output configuration options and the matrix of output variables. If you can't find what you are looking for there, please let us know.

Thanks!

Aubrey

[nuts sun]

Dear Aubrey,

Thank you again for your previous explanation, which was very helpful.

I would like to kindly ask for your further guidance on another related topic.

In my current simulation setup, I am interested in obtaining the Water Yield variable — which I understand in the water balance equation corresponds to P − ET (precipitation minus evapotranspiration). I would like to use this variable for subsequent analysis.

Rather than calculating it manually as P minus ET from separate output fields, I was wondering whether WRF-Hydro (version 5.3.0) can directly output Water Yield as a standalone variable. If so, could you please advise:

1. Is there a specific namelist option or output configuration that enables direct output of Water Yield?

2. If direct output is not available, what would be the recommended way to obtain it with minimal post-processing effort while maintaining accuracy?

I would greatly appreciate any suggestions or best practices you could share.

Thank you very much for your time and continued support.

Best regards,
NMV