Parameter	Units	NetSTORM code
Evaporation	inches per day - 12 monthly values	EVAP
Interevent dry period definition	hours	INTR
Percent Capture algorithm	hours	TAIL
Start date	YYYY mm dd hh	TIME
End date	YYYY mm dd hh	END
Minimum wet hour precipitation	inches	MIND
Primary rain gage number	none	GAGE

 

NetSTORM includes two algorithms for computing percent capture for a structure.  The method is specified by the user in the NetSTORM | Control | Run Parameters table.

 

The flow-based algorithm (TAIL < 0) computes capture based on all stormflow at a structure, as well as dry- weather flow during hours with precipitation.  This calculation can be subject to error under certain conditions, as the model estimates the dry weather  flow as the fixed component of the flow at a structure during the time the model runs, adjusted by the difference between the number of hours the model runs minus the number of hours with precipitation.  (The model runs only at times when runoff is occurring, or when storage in some part of the system is in use.)  This method may also produce undesireable results when an external hydrograph is read from file, as the external hydrograph is considered wet- weather flow.

 

The storm-based algorithm (TAIL > 0) computes capture during the hours when runoff is occurring plus during a user- specified number of hours after precipitation ceases.  This may underestimate capture for systems with long storage times, where stormflow occurs long after precipitation stops.  It will produce results similar to the flow-based method when a long post-storm time is specified, and will yield smaller capture volumes when a short post-storm time is specified.  This method is recommended when external hydrographs are read.

 

MIND is used to compute how many hours of wet weather there are in a year. The user can thus exclude periods of drizzle from the tabulation of the wet weather duration for the year. This does not affect overflow calculations.

 

GAGE is used to tabulate how many hours of wet weather there are in a year and to report precipitation statistics. Its setting only matters when multiple rain gages are used.