Clarification on Limitations in Using Observed Discharge for Calibration and Validation in Arjunanadhi Basin Study

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Sarangan K

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Feb 7, 2026, 12:24:23 PM (5 days ago) Feb 7
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Hello Everyone,

I am currently conducting a hydrological modelling study for my postgraduate thesis focusing exclusively on the Arjunanadhi sub-basin using the SWAT model. For my research, only long-term discharge data available correspond to a gauging station located downstream of a reservoir structure. As such, the observed discharge represents regulated releases from the dam rather than natural runoff from the Arjunanadhi catchment.

Furthermore, spatial analysis indicates that the gauging location may receive additional inflows from areas outside the Arjunanadhi basin boundary. Since my modelling domain is restricted only to the Arjunanadhi sub-basin, these adjacent-basin contributions are not represented in the model and may lead to discrepancies between simulated flows and observed discharge.

In view of these constraints, I kindly request guidance on the acceptability of using such observed discharge data for calibration and validation and on the most appropriate methodological practices to adopt. In particular, I seek advice on:

  1. Whether calibration and validation against dam-regulated discharge influenced by unmodelled adjacent catchments is acceptable for academic research when upstream natural-flow stations are unavailable?
  2. Whether explicit inclusion of reservoir operation modules is required in this case?
  3. What limitations should be clearly documented in the methodology and discussion sections?
  4. Any recommended strategies to minimize uncertainty arising from these factors.

I hereby attach the stream gauge location and the river water discharge. Your advice will greatly assist me in ensuring transparency and scientific rigor in my thesis work.

Thank you very much for your time and kind support. Looking forward for your response.

 

Yours sincerely,
Deebendranath Sarangan K
Postgraduate Student
M.E Irrigation Water Management
Anna University, College of Engineering, Guindy,
+91 7010983406
ksara...@gmail.com

bhargav J kachari

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Feb 7, 2026, 12:38:12 PM (5 days ago) Feb 7
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Dear 
You have all the answers in your questions itself.


  1. (Not acceptable)
  2. Yes required
  3. If you include the above two, limitations will be limited. If you don't include it would be difficult to calibrate.
  4. You have greater scope to look at effect of dam/controlled structure in flow which is novel approach.

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Yuvraj

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Feb 8, 2026, 7:24:08 AM (4 days ago) Feb 8
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Dear Bhargav

Can you explain a little more about the explicit inclusion of reservoir operation modules? 

bhargav J kachari

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Feb 8, 2026, 9:15:00 AM (4 days ago) Feb 8
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You can go through SWAT website or simply google it. You will find out the whole procedure. AI may help you a lot

Sarangan K

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Feb 8, 2026, 11:07:14 PM (3 days ago) Feb 8
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Hello there,

Hope you are doing good! About my project, the study area is restricted to Arjunanadhi Sub-basin from where I simulated the FLOWOUT. I have a gauging station at downstream regulated by dam which has flow from both Arjunanadhi and adjacent basin. For calibration and validation, I need only streamflow from the Arjunanadhi basin which is not available. Has only streamflow from both Arjunanadhi and the adjacent basin. How do I proceed with that?

bhargav J kachari

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Feb 9, 2026, 1:30:20 AM (3 days ago) Feb 9
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You can simulated for both.. but validate at individual catchment. If your calibration is correct, the validation at individual catchment station may give you acceptable results. As you have data combining two, it is not possible to validate individually. For this validate in combination is the only solution. What exactly is your objective of the work. You can rearrange the methodology as per objective if resource is not available .

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