The pane for this package is on the MODFLOW Packages and Programs dialog box under Farm Process. It contains the following subpanes.
•Mandatory Print Flags 2
The Farm Process simulates a variety of effects of Land use (including but not limited to farms) on groundwater and vice versa. For instance, some of the irrigation water applied to fields may contribute to recharge. On the other hand, farms may operate wells to supply irrigation water and may thus act as a sink for groundwater. If Irrigation water is supplied from streams (as simulated by the SFR package), the flow in those streams will be decreased thus affecting availability of water to downstream users. In some places, such as some parts of the western United States, the right to divert water from a surface water source is governed by prior appropriation rules. The Farm process can simulate these effects.
The Farm Process
•estimates consumptive use of water by crops,
•simulates the distribution of surface water to farms,
•simulates and estimates groundwater pumpage to meet the irrigation water demand of each farm,
•identifies whether the available surface water and groundwater are sufficient to meet the farm's need for irrigation water, and
•if surface water and groundwater supplies are insufficient, applies a drought response policy specified by the modeler.
Some of the data the modeler must specify include the following.
•The locations of the farms and various parameters related to the operation of each farm. (See Farm ID in FMP: Farm Process Pane )
•The distribution of the crops in space and time and various parameters related to the amount of water each crop requires. (See Farm Land Use Properties dialog box, and Crop ID in FMP: Farm Process.)
•The spatial distribution of the soils and various parameters related to the movement and storage of water in each soil. (See Farm Soil Properties dialog box.)
•Data related to precipitation, evapotranspiration and climate. (See Precip. in FMP: Farm Process, Ref. Evap. in FMP: Farm Process, and Farm Climate dialog box. )
•The locations of wells operated by farms to supply irrigation water and their maximum capacities (See Farms Wells in FMP: Farm Process.)
•The policy for how water will be used on farms if there is insufficient water for irrigation. (See Water Policy Flags.)
•The policy for deciding which farm gets how much water for irrigation if there is insufficient water for irrigation for all farms. (See Surface-Water Flags.)
•The amount of surface water available for irrigation. (See Farm Allotment dialog box and Water Rights.)
