1- Model runs during 1980-2017.

2- You could calibrate the model for any days and/or months and/or years during these years.

3- To set up model, you do not need observed discharge data. You will use the observed discharge data in SWAT-CUP.

4- Also, you could calibrate your model for different periods for example 2000-2004, 2006-2007, 2008-2010. I mean, any period during 1980-2017 is possible.

5- It could be better (and maybe necessary) to have some years for the warm-up period (e.g. 3 years). If you use 3 years (1980-1981-1982) you will not have the output for these years.

Good luck,

Mamad

check the swat version in your sorftware. usually, SWAT and ARCSWAT have different setups in different versions.

Calibration can only be carried during 2000 to 2015 (because you have flow data only during this period)

But you can run the model from 1980 to 2015 (when you have climate data)