Menu:  Edit Export Coefficients 
 
Edit land use categories & non-point source export coefficients.

These values are used to estimate flow & concentration for tributaries that are classified as NON-POINT inflows (Tributary Type Code = 2 ).  

This screen can be ignored if all inflows are measured directly (Tributary Type Codes <> 2 )

The following equations are used:

   FLOW RATE (hm3/yr) = SUM [ AREA (km2) x RUNOFF (m/yr) ]
 
   LOAD (kg/yr) = SUM [ AREA (km2) x RUNOFF (m/yr) x CONC (ppb) ]
 
   SUM = sum over land use categories
 
Values for unit RUNOFF & CONC are entered for each landuse category. 

Values for the AREA associated with each landuse category are entered on the Edit Tributaries screen. 

A warning message is generated if the estimated flow or load from any tributary is zero.  This will occur if no export coefficients or drainage areas are specified. Up to 8 land use categories can be defined.

The categories do not necessarily have to reflect specific land uses.   For example, to apply a uniform runoff and concentration set to all ungauged tributaries, enter export coefficients and drainage areas for a single land use category.

The specified runoff rate is expressed in units of meters per year (m/yr).  This is an average runoff rate during the AVERAGING PERIOD  (not TOTAL RUNOFF depth)!!!  Special care should be taken in specifying tributary flow rates when the AVERAGING PERIOD does not equal 1 year. Suppose, for example, that the AVERAGING PERIOD is April thru September (=0.5 years) and that the estimated total runoff depth during this period is 0.12 meters. The value specified on the export coefficient input screen in this case should be 0.24 m/yr = ( 0.12 m / .5 years).