Inquiry Regarding Sub-Area Settings in APEX Model

[Lars Carter]

Dear All,

I am currently working with the APEX model and have a few inquiries regarding the sub-area settings:

1.What is the minimum area that can be set for the basic operational unit sub-area in the APEX model?
2.I have observed that when I set a smaller area threshold for the sub-areas, the model calculations terminate midway. Could you please explain the reason for this?
3.Despite setting the sub-area to a smaller size, I have noticed inconsistencies in land use types within some of the divided sub-areas. What could be the cause of this?
Thank you for your time and assistance. I look forward to your response.

Best regards,

Xu

[Luca Doro]

Dear Xu,

I think I need some clarifications to answer your questions.

1. When you mention the minimum area that can be set for the subarea, are you talking about the APEX variable called WSA? (See the user manual for the meaning of WSA). If the answer is yes, there should not be a minimum value as long as the number fits the format allowed for the WSA field.
2. In this case, I think you are talking about the threshold available in the ArcAPEX interface. Is this true? If this is true, the problem could be because of the number of subareas created during the delineation process. But this is only a speculation and more further details are needed. For instance, do you get any error message when the model stops?
3. Once again, I think you are using the ArcAPEX interface and you are referring to the delineation process. Keep in mind that ArcAPEX the initial delineation of subareas is based on landscape features (slopes and position), and then soil, and management, are considered. Not always a subarea corresponds 100% to a specific field. Please, give us more information about this.

Luca

[Lars Carter]

Dear Luca,

Thank you very much for your prompt and insightful response.

I would like to clarify that the parameters I described refer specifically to the homogeneous hydrologic land use units (HLU). Could you please let me know if there is a minimum value for HLU settings?

Additionally, I have encountered an issue where my model terminates midway when there are numerous HLU divisions. For instance, I have 32 subarea and a simulation period of two years, but the model ends after completing the first year's results for the first subarea, without any error messages. I am uncertain about the cause of this behavior.

I appreciate your assistance and look forward to your guidance.

Best regards,

Xu

[Luca Doro]

I would say that there is not a minimum value for the HLU. Are there any specific values that concern you?

A two years simulation with 32 subarea should not be a problem for the model. I think something is wrong in the input files. Can you run the model from the command prompt using a debug version of the executable? In this way, you might be able to get information about the error.

Luca