Skip common site navigation and headers
United States Environmental Protection Agency
BASINS
Begin Hierarchical Links EPA Home > Water > Water Science > Water Quality Tools > Models > BASINS > Training > Flow Calibration Tutorial > Calibration Scenarios > Storm Flows End Hierarchical Links

 

Training

Flow Calibration Tutorial

Calibration Scenarios

Storm Flows  

  1.   High Simulated Peak Storm Flows, With Poor Simulation Of Storm Runoff Volumes
    1. If interflow is less than surface runoff, increase interflow (INTFW ). Runoff needs to be shifted from surface runoff to interflow to put the water in a slower drainage category. If the associated interflow recession constant (IRC ) is too low, however, interflow will respond like surface runoff and in the increase in INTFW will have little effect.
    2. If interflow is greater than surface runoff, VIII-a also holds, with the additional guidance from HSPF Appendix A clarifying that INTFW  should be increased if IRC >0.6 and INTFW <7.5 in PERLND.
    3. If interflow is greater than surface runoff, increase the interflow recession constant (IRC ) if it is <0.6, or if IRC is <0.7 and INTFW is >= 7.5. These values for IRC are not too high and can be raised further. This should decrease peak flows because the time for time required for interflow to drain following a storm will be increased, flattening the recession.


  2. High Simulated Peak Storm Flows, Good Simulation Of Runoff Volumes For Major Storms
    1. Increase interflow, INTFW , if PERLND has a value for IRC >0.6 for the same reason as VIII-a.
    2. Increase the interflow recession constant, IRC , if PERLND has a value for IRC <0.6. Increasing IRC should flatten the recession and decrease peak flows without a change in volume.


  3. Low Simulated Peak Storm Flows, With Poor Simulation Of Storm Runoff Volumes
    1. If interflow is less than surface runoff, decrease interflow (INTFW ). Runoff needs to be shifted from interflow to surface runoff to put the water in a faster drainage category. If IRC is too low, however, interflow will respond like surface runoff and the decrease in INTFW will have little effect on the peak.
    2. If interflow is greater than surface runoff, X-a holds, with the additional guidance from HSPEXP Appendix A clarifying that INTFW should be decreased if IRC <0.4 and INTFW >1.0.
    3. If interflow is greater than surface runoff, decrease the interflow recession constant, IRC , if it is >0.4, or if IRC >0.3 and INTFW is <= 1.0, in PERLND. The parameter IRC can be still decreased since its values are not too low. This should increase peak flow because the time required for interflow to drain following a storm will be decreased, allowing it to behave more like overland flow.


  4. Low Simulated Peak Storm Flows, Good Simulation of Runoff Volumes For Major Storms
    1. Decrease interflow, INTFW , if PERLND has a value for IRC <0.4 for the same reasons as in X-a.
    2. Decrease the interflow recession constant, IRC , if PERLND has a value for IRC >0.4 since a decrease in IRC should steepen the recession and increase peak flows without a change in volume.


  5. High Simulated Peak Flows and Storm Volume

  6. Increase infiltration (INFILT). The major effect of increased infiltration is to shift drainage from rapid response (surface runoff and interflow) to delayed response (base flow), thus decreasing both simulated storm volumes and simulated storm peaks.
     

  7.   Low Simulated Peak Flows and Storm Volume

  8. Decrease infiltration (INFILT). The major effect of increased infiltration is to shift drainage from rapid response (surface runoff and interflow) to delayed response (base flow). Decreasing this should increase both simulated storm volumes and simulated storm peaks.


IntroductionBack to Calibration Scenarios

 

Water Quality Standards | TMDL | Contact basins@epa.gov

 
Begin Site Footer

EPA Home | Privacy and Security Notice | Contact Us