Navigation: Main Menu and Buttons > Object > Object Properties Dialog Box > MODFLOW Features Tab
Ref. Evap in Climate: Farm Process V4 Climate Options Pane
This pane is on the MODFLOW Features tab of the Object Properties dialog box.
REFERENCE_ET is required there are fallow/bare soil cells, Crop Coefficients (Kc) specified, or Crops specified as FRACTIONS (multiple crops per model cell)