This pane is on the MODFLOW Features tab of the Object Properties dialog box.
If a Water Balance Subregion has specified an added irrigation demand, then ADDED_DEMAND_RUNOFF_SPLIT defines the split between becoming surface runoff or deep percolation. This fraction is only is a split for the additional demanded water. It does not apply to losses that originate from irrigation required to meet a land use ET which is defined in the Land_Use Block with the SURFACEWATER_LOSS_FRACTION_IRRIGATION keyword. It must be between 0.0 and 1.0; If not specified then it defaults to 0.1.
Additional demand is defined with the keyword ADDED_CROP_DEMAND FLUX, ADDED_CROP_DEMAND RATE, and LAND_USE block keyword ADDED_DEMAND