The idea is that I want to perform continuous hydrological modeling while integrating the Curve Number (CN). Thank you.
The SCS Curve Number method, as implemented within HEC-HMS, does not allow for infiltrated water to be extracted by evaporation or transpiration. Thus, this method is not appropriate for use in simulations longer than a few days to weeks. However, HEC-HMS does include several other loss methods that allow for infiltrated water to be extracted and are thus suitable for long term simulations. This includes two relatively complicated methods (Soil Moisture Accounting and Layered Green and Ampt) and a relatively simple method (Deficit and Constant). Since you originally inquired about the SCS CN method, I would suggest using the Deficit and Constant method instead since it's already integrated within HEC-HMS.
More information pertaining to these loss methods can be found here:
https://www.hec.usace.army.mil/confluence/hmsdocs/hmsum/4.11/subbasin-elements/selecting-a-loss-method
https://www.hec.usace.army.mil/confluence/hmsdocs/hmsguides/applying-loss-methods-within-hec-hms
https://www.hec.usace.army.mil/confluence/hmsdocs/hmstrm/infiltration-and-runoff-volume/deficit-and-constant-loss-model
Yes, it is possible to integrate the SCS CN method into the HEC HMS software for the Soil Moisture Accounting (SMA) method. The HEC HMS software is a hydrological modeling package developed by the US Army Corps of Engineers, and it allows for customization and adaptation of various hydrological methods.
To integrate the SCS CN method into HEC HMS, you can follow these steps:
1. Open the HEC HMS software and create a new project or open an existing project.
2. In the Project Explorer, navigate to the Schematic Editor.
3. In the Schematic Editor, add a new Subbasin by clicking on the "Add new feature" button.
4. Configure the Subbasin properties, such as the area, elevation, and land use.
5. In the Subbasin Editor, navigate to the Soil Moisture Accounting (SMA) tab.
6. Under the "Method" dropdown menu, select the SCS Curve Number (CN) method.
7. Enter the relevant parameters for the SCS CN method, such as the initial abstraction, runoff curve number, and antecedent moisture condition.
8. Save the changes and proceed to define other components of your hydrological model, such as precipitation, evaporation, and routing.
By integrating the SCS CN method into the HEC HMS software, you can use the SMA approach to simulate the hydrological processes, including runoff estimation, as per the SCS Curve Number method.
Please note that the specific steps and options may vary depending on the version of the HEC HMS software you are using. It is always recommended to refer to the software's user manual or documentation for detailed instructions.
Michael D. Bartles Thank you for your response, I have reviewed the literature on the deficit and constant method as you suggested, but unless I'm mistaken, this method does not take into account land use (Curve Number). I have consulted studies by Singh (2015) 'Development of a Modified SMA Based MSCS-CN Model for Runoff Estimation'; Younghyun Cho (2018) 'Spatially distributed long-term hydrologic simulation using a continuous SCS CN method-based hybrid hydrologic model'; K. Geetha (2007) 'Modifications to SCS-CN Method for Long-Term Hydrologic Simulation,' and these studies address the possibility of modifying certain methods to incorporate the Curve Number in a continuous modeling. However, I am encountering some difficulties in the application.
Asmare Belay Is it possible to select two loss methods simultaneously? I'm not sure I understand steps 5 and 6. I am using versions 4.9, 4.10, and 4.11. Do you have any documentation to recommend?
Thanks
Coulibaly Wawogninlin Brice None of the loss methods within HEC-HMS explicitly incorporate land use in their calculations. However, I think you're referring to parameter estimation using land use and soil type, like the table shown here: https://www.hec.usace.army.mil/confluence/display/HMSTRM/CN+Tables. If so, you can use the same thought process to estimate constant loss rates (in the case of the Deficit and Constant method) or maximum infiltration rate (in the case of the SMA method).
That being said, each loss method within HEC-HMS *does* allow for the specification of directly connected impervious area. Directly connected impervious areas are surfaces where runoff is conveyed directly to a waterway or stormwater collection system. These surfaces differ from disconnected impervious areas where runoff encounters permeable areas which may infiltrate some (or all) of the runoff prior to reaching a waterway or stormwater collection system. No loss calculations are carried out on the specified percentage of the subbasin; all precipitation that falls on that portion of the subbasin becomes excess precipitation and subject to direct runoff.
Finally, Asmare Belay is incorrect. You cannot select two loss methods within a single subbasin element within HEC-HMS.
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