Irrigation

(These parameters apply to the Soil Moisture method. For the Simplified Coefficient Method, see Simplified Coefficient Method, Irrigation; for the MABIA Method, see MABIA, Irrigation; for the Plant Growth Method, see Plant Growth Model Method, Irrigation.)

If you indicate that irrigation is to occur in a Catchment at the time you create the Catchment in the Schematic, the Irrigation tab will appear under the particular Catchment in the Data View. The following irrigation-related variables will require input if the Soil Moisture method is chosen for the Catchment.

Irrigated Area

The percent of area that is irrigated.

Lower Threshold

Irrigate when soil moisture falls below this percent level.

Upper Threshold

Cease irrigation when soil moisture reaches this percent level.

Irrigation Use of Runoff

Percent of this catchment's runoff which can be used for irrigation internally within catchment (diverted before it reaches surface water inflow of runoff link). Note: This will allocate some or all of the runoff for use by the catchment for its irrigation, even if there are higher priority demands downstream, and before all other irrigation supplies the catchment would otherwise use. However, runoff from irrigation is NOT available to be used again for irrigation -- this would be circular. Only the runoff from precipitation and from the soil moisture at the beginning of the timestep is available for irrigation within the catchment. Only runoff links to surface water are considered, not infiltration links to groundwater. See the Calculation Algorithms for details.

Pump Layer

Groundwater layer or layers (as defined in linked MODFLOW model) from which to pump for irrigation. Specify layer=255 for a cell to have pumping come equally from all layers in that cell. To have withdrawals handled instead as negative recharge, specify layer=0. If pump layer>0, WEAP will add cells to the well file if they are not already there. Use the PumpLayer function to specify fractions to pump from several layers. If blank, will default to 0 (negative recharge).

Depending on the setting in General: Basic Parameters, the pump layer can either be entered once for each catchment and will apply to all the land use branches within that catchment, or can be entered separately for each branch within each catchment.

Note: Pump Layer is only used when linked to MODFLOW.

Entered on: Data View, Branch: Catchments, Category: Irrigation, Tabs: Irrigated Area, Lower Threshold, Upper Threshold, Pump Layer.