Help with SWAT streamflow calibration

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Rozita pm

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Aug 17, 2026, 7:11:47 AMAug 17

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Hi everyone,

I am currently calibrating a SWAT model for the Little Rock Creek watershed in Minnesota and would appreciate any advice from people with experience in SWAT/SWAT-CUP calibration.

I have been working on streamflow calibration for about two months. At the monthly scale, the model performance is reasonably good, with NSE values around 0.60–0.73 depending on the reach and calibration/validation period. However, when I check the model at the daily scale, I still see problems with storm-event timing. In particular, the simulated hydrograph often responds too early and the recession after the peak is too fast.

I have already tested several parameters related to runoff, routing, and groundwater response, including CN2, OV_N, SURLAG, CH_N2, CH_K2, LAT_TTIME, ALPHA_BF, GW_DELAY, GWQMN, ESCO, SOL_AWC, and SLSUBBSN. Some parameters had little or no effect on the daily hydrograph. OV_N helped slightly by reducing the early response and increasing flow during the following days, but the daily mismatch is still present.

My current monthly performance is approximately:

Reach 1 calibration NSE: ~0.60
Reach 6 calibration NSE: ~0.60
Reach 1 validation NSE: ~0.61–0.63
Reach 6 validation NSE: ~0.71–0.73

At the daily scale, the main issue is not necessarily the total flow volume, but the timing and shape of individual storm events.

I would really appreciate any suggestions on:

which parameters or processes I should investigate next for daily peak timing and recession behavior;
whether it is reasonable to accept the monthly calibration and use daily results mainly as a diagnostic;
whether this type of daily timing issue is common in SWAT when the monthly NSE is acceptable;
and how much further hydrologic calibration is justified before moving to water-quality calibration.

If helpful, I can also share my parameter ranges, monthly calibration results, daily hydrographs, and selected storm-event comparisons.