| Parameter | Description | Units | Valid Values | Default Values |
| FWLOSS(3) | Scaling factor for transpiration water loss. | 1.0 | ||
| PPRPTS(1) | The minimum ratio of plant-available water to PET which would completely limit production. Typically this value = 0. | 0.0 to 1.0 | 0.0 | |
| PPRPTS(2) | The effect of plant-available water content on the intercept , allows the user to increase the value of the intercept and thereby increase the slope of the line. Typical value is 1.0. | 1.0 | ||
| PPRPTS(3) | The lowest ratio of available water to PET at which there is no restriction on production. Typical value is 0.8. | 0.0 to 1.0 | 0.8 |