The Well package allows the user to specify a volumetric rate of fluid withdrawal or injection. Positive pumping rates represent injection, negative rates represent withdrawals. The pane for this package is on the MODFLOW Packages and Programs dialog box under Specified Flux.
PHIRAMP is the fraction of the cell thickness used as an interval for smoothly adjusting negative pumping rates to 0 for dry cells. Negative pumping rates are adjusted to 0 or a smaller negative value when the head in the cell is equal to or less than the calculated interval above the cell bottom. If PHIRAMP is not specified or specified as 0, MODFLOW-NWT uses a default value of 0.1. When the Well package is used in MODFLOW-NWT, a warning similar to the following will always be printed to the listing file.
NEGATIVE PUMPING RATES WILL BE REDUCED IF HEAD
FALLS WITHIN THE INTERVAL PHIRAMP TIMES THE CELL
THICKNESS. THE VALUE SPECIFIED FOR PHIRAMP IS 0.10000E+00
WELLS WITH REDUCED PUMPING WILL BE REPORTED TO FILE UNIT NUMBER 141
In MODFLOW 6 models, "multipliers" can be used with well boundaries. Multipliers will be used if the "Use Multiplier (MODFLOW 6)" checkbox is checked.. Ordinarily, multipliers are not needed. If multipliers are used, the pumping rate is multiplied by the value of the multiplier. One use for multipliers might be when the pumping rates are defined using a time-series and it is desired to multiply the pumping rate values in the time series by a different amount at different locations.
The user can also specify parameters for the well pumping rate. The final pumping rate will be the parameter value times a multiplier. Objects must be used to define the well pumping rates or well pumping rate multipliers. The user can also set up well pumping rates that do not involve parameters.
Parameters can also be edited in the Manage Parameters dialog box.
