ArcAPEX flood routing

[AbdulAziz Bishaw]

Dear all, 

I just want to ask about ArcAPEX version 1501.10_7.7, 2021 release. I was using this version to setup my model. After delineating the watershed and importing daily weather data, I want to get stream flow of the watershed at the outlet point of the watershed, where I have a stream flow record for calibration. So, in the control section of the model, there is a parameter that orders the model to do or not to do flood routing (IHY). When I order the model to do flood routing (IHY > 0,) the model will not run. But when I make IHY=0, the model will run. Could you show me the way to fix this problem? In fact, there is outflow at the watershed outlet without flood routing. But when I try to calibrate it with the observed streamflow, the model performance parameters are very low.

Is there a way in ArcAPEX to input sub-daily data to do flood routing? I just want to calibrate the water balance component of the model; after that, I will continue to crop yield calibration. Is it logically correct to calibrate the water balance parameters of the model with streamflow data recorded at the watershed outlet without using the flood routing option?

Thank you.

[Luca Doro]

For future reference, I am pasting here what Dr. Jaehak Jeong suggests for subdaily flood routing simulation.

There are several options to run APEX subdaily. In general, APEX already had options to use either the daily CN method or subdaily GA method for runoff calculation even before I added subdaily channel routing methods. First, runoff calculation options are as follows based on INFL:

1. INFL=0 to run the CN method (daily).
2. INFL=4 to run the GA method (subdaily) using measured subdaily rainfall.
3. Other INFL between 1-3 to generate subdaily rainfall values using either measured daily rainfall data or from monthly weather statistics table values.

 

In option infl=4, we can use subdaily rainfall data with a specific time interval such as hourly or 15 minutes and run the model at that time step using the measured subdaily rainfall.

 

Then, you choose how to do streamflow routing using IHY:

1. IHY=0 for daily channel flow calculation (no flood routing)
2. IHY=1-4 for subdaily channel flow routing using various methods (IHY=1 for VSC is recommended)

 

These options allow various combinations of runoff calcuations and channel flow calculations. If you have subdaily rainfall data and want to run the model at the time steps the rainfall data were recorded, you follow these steps:

1. In APEXFILE.DAT, add “RFDTLST.DAT” as “FRFD”
2. In the RFDTLST.DAT file, add all subdaily rainfall input files such as rg69b.HLY starting from line 1. Note that only one subdaily rainfall station can be used for the entire watershed, meaning that subdaily simulation only applies to small watersheds in APEX.
3. Prepare *.HLY files accordingly.
4. In APEXRUN.DAT, input IRFT (the HLY station ID that matches the HLY file in RFDTLST.DAT) of the HLY that applies to the watershed.
5. In APEXCONT.DAT, set the following inputs:
   1. DTHY=1 (for hourly time step) or 0.5 (for 30min intervals) or as needed.
   2. INFL=4
   3. IHY==1
6. Make sure subarea and channel slopes are set greater than zero.