peak simulation

[Has]

Dear SWAT users,

I am calibrating a watershed of 6,000 sq.km in southern Canada. My NS is almost 0.65 and the base-flow simulation looks very similar to the base-flow observation, but the problem lies in peaks, specially large peaks. Well, currently, the parameters I am using for my calibration are: alpha_bf, gw_delay, esco, snow temperatures, surlag, gwqmn, revap, cnmax, cn2, ch_n2, ch_k2 and soil properties. Am I missing a parameter which causes malfunction in peak simulation?

Thank you in advance,

Has.

[Jim Almendinger]

Surface-water bodies (pond, wetlands) and even depressions too small to retain water permanently can all affect the hydraulic response of a watershed, and could reduce peak flows by providing storage on the landscape.  I would think southern Canada, being glaciated terrain, would have many of these feature -- are you accounting for them?  Potholes, ponds, wetlands, and reservoirs are options in SWAT.  

Otherwise -- reducing CNs to increase infiltration at the expense of surface runoff is a common method.  And snowmelt peaks are always difficult to control.  Allowing some melting over winter to reduce snowpack can reduce the snowmelt peak.  

-- Jim

Dr. James E. Almendinger, Senior Scientist
St. Croix Watershed Research Station
Science Museum of Minnesota
16910  152nd St. N
Marine on St. Croix, MN  55047
tel: 651-433-5953 X 19
fax: 651-433-5924
email: din...@smm.org
web: www.smm.org/SCWRS/

[S.Z.Samadi]

Have you seen this handout of Dr. Srini's?  It might be a helpful place
for you to start for understanding calibration:

http://swat.tamu.edu/media/1315/swat-calibration-techniques_slides.pdf

Best, S

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[Stalled Mower]

I would concentrate on SURLAG first compare the ressession curve as well as the peak magnitudes - small changes in Surlag don't make a huge difference so try putting it right up or down to start with. I also found DEPIMP was an important parameter in controlling the flow split: mostly because I am simulating tile drainage, but it may still be worth some consideration.

Are your modelled peaks to high or too low?

Regards,

Phil