Baseflow Underestimation (Drops to 0.001 CFS) During Dry Season

[민인경]

Hello everyone,

I am currently calibrating a SWAT+ model, and I am facing a persistent issue with extremely low baseflow during the dry season.

Based on the observed data, the dry season baseflow should be maintained around 1.0 CFS. However, my simulated flow drops drastically to 0.01 CFS (almost zero) during dry periods, while showing flashy, overestimated peak flows during rainfall events.   

  To route more water into the subsurface and increase the baseflow, I have tried the following steps:  

  Soft Calibration (Water Balance): I enabled the water balance soft calibration in SWAT+ Editor and set the base flow ratio (bfr) parameter up to 0.5 ~ 0.6.   
 Deep Aquifer Percolation (deep_seep): I significantly reduced the deep_seep value (down to 0.0 or 0.001) in aquifer.aqu to prevent water loss to the deep aquifer and keep water in the shallow aquifer.

And I calibrated this model  using SWAT+ tool with these parameters;

alpha
flo_min
revap_co
revap_min
bf_max

  Despite these efforts, the baseflow still plummets to 0.001 CFS. It seems like the water infiltrating the soil is either entirely lost to ET or trapped somewhere without reaching the channel as return flow.

  
  Any advice, tips, or parameter recommendations would be greatly appreciated!