Availability Factors
 

Availability factors are used to weight inflow concentrations, generally to place greater emphasis on the dissolved (or inorganic fraction) (Walker, 1985, 1999)

Options  are specified on the Edit Model Selections screen accessed from the menu or from the button on the main program screen.

The factors are normally used ONLY by Phosphorus Model 1 and Nitrogen Model 1 .  For all other phosphorus and nitrogen models, availability factors are normally ignored and nutrient balances are based upon Total P and Total N.

If inflow ortho P (and inflow inorganic N, if nitrogen balances are modeled) are not specified by the user, Option 0 (ignore availability factors) should be selected.  Alternatively, availability factors should be set to 1.0 for TP and TN and to 0.0 for Ortho P and Inorganic N on the Edit Model Coefficients screen.

A warning message is generated if a positive availability factor is applied to an input concentration of zero.