AG - Agricultural Water Use Package

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Abbreviations in Name file

•AG

Purpose

The AG was developed for GSFLOW to simulate irrigation and water use by cultivated and natural plants.

Documentation

•Niswonger, R.G., 2020. An Agricultural Water Use Package for MODFLOW and GSFLOW. Environmental Modelling & Software, p.104617.

•Input_instructions_AG.pdf

Related Packages

•Streamflow-Routing (SFR)

•UZF - Unsaturated Zone Flow Package

Supported in

MODFLOW-NWT

Other Notes

•The AG was developed for GSFLOW to simulate irrigation and water use by cultivated and natural plants. The AG Package works with the Streamflow-Routing (SFR2) and the Unsaturated Flow (UZF1) Packages and includes capabilities for simulating pumping wells like the WELL Package. Input required for simulating agricultural diversions, supplementary pumping, irrigation, and demand calculations are all specified within the AG Package input file. All exchanges between different packages (SFR2, UZF1, and AG) are calculated within the AG Package; however, the SFR2 and UZF1 Packages must be active to use their capabilities in conjunction with the AG Package. Diversion segments must be specified within the SFR2 Package to apply diverted water as irrigation. All data for supplementary and irrigation wells is specified within the AG Package input file; the AG Package calculates and applies its own boundary conditions to the groundwater flow equation for representing irrigation and/or supplementary wells.

Input Instructions

The AG Package is activated by specifying a file type of “AG” within the MODFLOW-NWT Name file. The AG input file contains 4 different blocks of data, including 1) Options, 2) Time series, 3) Segment and Well Lists, and 4) Stress Period. Stress period data is used to vary agricultural practices during a simulation represented mechanically as the connectivity between segments and irrigation cells, supplemental wells and diversion segments, and wells and irrigation cells, as well as other input values that control agricultural water use.

Block 1: Simulation options

AG Package character variables can be specified in any order and must be proceeded and followed by the character variables OPTIONS and END, respectively.

Data Set 1

Character variable specified to indicate the beginning of the key word options.

Data Set 2

Character variable that suppresses the printing of well lists.

•IRRIGATION_DIVERSION: An optional character variable. When IRRIGATION_DIVERSION is specified, the option to use surface water (SW) for irrigation is activated.

•Numirrdiversions: An optional integer variable. When IRRIGATION_DIVERSION is specified, the integer variable Numirrdiversions also is specified. Numirrdiversions is the maximum number of SFR2 diversion segments in any stress period that will be used for irrigation.

•Maxcellsdiversion: An optional integer variable. When IRRIGATION_DIVERSION is specified, the integer variable Maxcellsdiversion also is specified. Maxcellsdiversion is the maximum number of MODFLOW cells or PRMS HRUs that will receive irrigation from a single SFR2 diversion segment in any stress period.

•IRRIGATION_WELL: An optional character variable. When IRRIGATION_WELL is specified, the option to use groundwater for irrigation is activate.  

•Numirrwells: An optional integer variable. When IRRIGATION_WELL is specified, the integer variable Numirrwells also is specified. Numirrwells is the maximum number of AG wells in any stress period that will be used for irrigation.

•Maxcellswell: An optional integer variable. When IRRIGATION_WELL is specified, the integer variable Maxellswell also is specified. Maxcellswell is the maximum number of MODFLOW cells or PRMS HRUs that will receive irrigation from a single AG well in any stress period.

•SUPPLEMENTAL_WELL: An optional character variable. When SUPPLEMENTAL_WELL is specified, the option to simulate supplemental groundwater for irrigation is active. The AG Package calculates supplemental GW pumping using the difference between the irrigation demand and the surface water diversion.  

•Numsupwells: An optional integer variable. When SUPPLEMENTAL_WELL is specified, the integer variable Numsupwells also is specified. Numsupwells is the maximum number of supplemental wells in any stress period that will pump groundwater.

•Maxdiversions: An optional integer variable. When SUPPLEMENTAL_WELL is specified, the integer variable Maxdiversions also is specified. Maxdiversions is the maximum number of SFR2 diversion segments that are supplemented by a well.

•MAXWELL: An optional character variable. If IRRIGATION_WELL or SUPPLEMENTAL_WELL is specified then MAXWELL also is specified. MAXWELL is included to indicate that the maximum number of unique supplemental and irrigation wells used during a simulation (Nummaxwell) also will be read.

•Nummaxwell: The maximum number of unique supplemental and irrigation wells used during a simulation.

•TABFILES: An optional character variable. TABFILES is included in order set pumping rates using time series input files.

•Numtab: An integer variable equal to the total number of tabular input files for setting the maximum pumping rate for AG irrigation and supplemental wells.

•Maxval: An integer variable equal to the maximum number of values specified for any TABFILE.

An optional character variable. PHIRAMP is included to specify the smoothing interval used to change negative pumping rates to zero when the groundwater cell dewaters. This variable only is used when the Newton Solver is active.

•ETDEMAND: An optional character variable. ETDEMAND is included in order to activate automatic calculation of the net irrigation water requirement. ETDEMAND and TRIGGER cannot be used in the same simulation.

•Accel: An real variable that controls the maximum change in the irrigation diversion or pumped amount between iterations. Values between 0.5 and 10 work well.

An optional character variable. TRIGGER is included to activate the irrigation trigger option. TRIGGER and ETDEMAND cannot be used in the same simulation.

An optional character variable that activates the option for outputting diversions flow rates for specified SFR2 segments used for irrigation. Additional details are specified in the time series data input.

An optional character variable for outputting well pumping rates for specified wells used for irrigation. Additional details are specified in the time series data input.

An optional character variable for outputting irrigation applied to all cells/HRUs supplied by 1 or more specified diversion segments. Additional details are specified in the time series data input.

An optional character variable for outputting irrigation applied to all cells/HRUs supplied by 1 or more specified wells. Additional details are specified in the time series data input.

•DIVERSIONLIST: An optional character variable for outputting a list of all diversion segments and diversion amounts used for irrigation in the AG Package when "SAVE BUDGET" or a non-zero value for ICBCFL is specified in Output Control.

•Unit_diversionlist: An optional integer variable that is the file unit number to which DIVERSIONLIST output is written. This unit number must correspond to a file of type Data specified in the MODFLOW Name file. A negative value indicates output will be written to the LIST file.

•WELLLIST An optional character variable for outputting a list of all active wells in the AG Package and pumped amounts when "SAVE BUDGET" or a non-zero value for ICBCFL is specified in Output Control.

•Unit_welllist An optional integer variable that is the file unit number to which WELLLIST output is written. This unit number must correspond to a file of type Data specified in the MODFLOW Name file. A negative value indicates output will be written to the LIST file.

•WELLIRRLIST: An optional character variable for outputting a list of MODFLOW cells or PRMS HRUs that are irrigated by AG wells and the irrigated amounts when "SAVE BUDGET" or a non-zero value for ICBCFL is specified in Output Control.

•Unit_wellirrlist: An optional integer variable that is the file unit number to which WELLIRRLIST output is written. This unit number must correspond to a file of type Data specified in the MODFLOW Name file. A negative value indicates output will be written to the LIST file.

•DIVERSIONIRRLIST: An optional character variable for outputting a list of MODFLOW cells or PRMS HRUs irrigated by irrigation segments and the irrigated amounts when "SAVE BUDGET" or a non-zero value for ICBCFL is specified in Output Control.

•Unit_diversionirrlist: An optional integer variable that is the file unit number to which DIVERSIONIRRLIST output is written. This unit number must correspond to a file of type Data specified in the MODFLOW Name file. A negative value indicates output will be written to the LIST file.

WELLCBC An optional character variable for outputting cell-by-cell flow terms when "SAVE BUDGET" or a non-zero value for ICBCFL is specified in Output Control.

Unit_cbc An optional integer variable that is the file unit number to which cell-by-cell unformatted list output is written. This unit number must correspond to a file of type Data(binary) specified in the MODFLOW Name file.

Data Set 3

Character variable specified to indicate the end of the character options.

Block 2: Time series output

Time series data can be written to separate formatted output files for selected SFR segments and AG wells used for irrigation. These files are of type “Data” and must be included in the MODFLOW Name file. Time series data are read only if time series character variables are specified in the character options section.

Data Set 4

Character variable specified to indicate the beginning of the time series data block.

Data Set 5

[DIVERSION Segmentnum1 Unit_diversion1]

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[DIVERSION Segmentnumnumtimeseriesdiversion Unit_diversionnumtimeseriesdiversion]

•DIVERSION Character variable indicating that irrigation information for a diversion will be written to a time series output file.

•Segmentnum Integer variable that is the SFR2 segment number.

•Unitdiversion Integer variable that is the formatted output file unit number.

Data Set 6

[DIVERSIONET Segmentnum1 Unit_diversionet1]

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[DIVERSIONET Segmentnumnumtimeseriesdiversionet Unit_diversionetnumtimeseriesdiversionett]

•DIVERSIONET Character variable indicating that crop ET for all cells/HRUs irrigated by a diversion will be written to a time series output file.

•Segmentnum Integer variable that is the SFR2 segment number.

•Unitdiversionet Integer variable that is the formatted output file unit number.

Data Set 7

[WELL Wellnum1 Unit_well1]

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[WELL Wellnumnumtimeserieswell Unit_wellnumtimeserieswell]

•WELL Character variable indicating that irrigation information for a well will be written to a time series output file.

•Wellnum Integer variable that is the AG well number.

•Unitwell Integer variable that is the formatted output file unit number. This file is of type “Data” and is included in the MODFLOW Name file.

Data Set 8

[WELLET Welletnum1 Unit_wellet1]

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[WELLET Wellnumnumtimeserieswellet Unit_welletnumtimeserieswellet]

•WELLET Character variable indicating that evapotranspiration information for a well will be written to a time series output file.

•Welletnum Integer variable that is the AG well number.

•Unitwellet Integer variable that is the formatted output file unit number. This file is of type “Data” and is included in the MODFLOW Name file.

Data Set 9

[WELLALL Unitwellall]

•WELLETALL Character variable indicating that evapotranspiration information summed for all wells will be written to a time series output file.

•Unitwelletall Integer variable that is the formatted output file unit number. This file is of type “Data” and is included in the MODFLOW Name file.

Data Set 10

[WELLETALL Unitwelletall]

•WELLALL Character variable indicating that irrigation information summed for all wells will be written to a time series output file.

•Unitwellall Integer variable that is the formatted output file unit number. This file is of type “Data” and is included in the MODFLOW Name file.

Data Set 11

Character variable specified to indicate the end of the time series data block.

Block 3: Segment and Well lists

SFR segments used for irrigation during any stress period of a simulation must be listed within the SEGMENT LIST data block. Maximum segment diversion rates can be set for each time step using SFR TABFILES, and maximum diversion rates can be set for each stress period using the SFR input variable Q.

Data Set 12

Character variable specified to indicate irrigation diversion segments will be included in simulation. All irrigation segments used in a simulation must be listed.

Data Set 13

[SEGMENTNUMBER1]

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[SEGMENTNUMBERMAXNUMSEGS]

•SEGMENTNUMBER1 Integer value equal to the first irrigation segment used in a simulation.

•SEGMENTNUMBERMAXNUMSEGS Integer value equal to the last irrigation segment used in a simulation.

Data Set 14

Character variable specified to indicate the end segment list data block.

Wells used for irrigation, including those used to supplement surface water diversions, are defined within the WELL LIST. Well numbering is implicitly defined according to the order of wells in the WELL LIST, the first entry is well 1, numbered consecutively to the total number of wells used during a simulation. There are 2 options for specifying information in the WELL LIST. The first option uses TABFILES to vary the maximum pumping rate during a simulation, and the second option uses a single specified value for the maximum pumping rate that does not vary during the simulation.

Input instructions for AG Package TABFILES are included at the end of this document.

Data Set 15

Character variable specified to indicate that AG wells will be included in a simulation.

If character variable TABFILES is specified in the OPTIONS block, then item 16a is read as a space delimited list in free format. Otherwise, item 16b is read.

Data Set 16a

[TABUNIT1 TABVAL1 WELLLAY1 WELLROW1 WELLCOL1]

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[TABUNITNumtab TABVALNumtab WELLLAYNumtab WELLROWNumtab WELLCOLNumtab]

•TABUNIT Integer variable equal to the unit number for the TABFILE used to specify pumping rates for a well.

•TABVAL Integer variable equal to the maximum number of rows to be read from a TABFILE.

•WELLLAY Integer variable equal to the layer number of the cell containing a well.

•WELLROW Integer variable equal to the row number of the cell containing a well.

•WELLCOL Integer variable equal to the column number of the cell containing a well.

If character variable TABFILES is not specified in the OPTIONS block then item 16b is read as a space delimited list in free format.

Data Set 16b

[WELLLAY1 WELLROW1 WELLCOL1 Q1]

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[WELLLAYMaxwell WELLROWMaxwell WELLCOLMaxwell QMaxwell]

•WELLLAY Integer variable equal to the layer number of the cell containing a well.

•WELLROW Integer variable equal to the row number of the cell containing a well.

•WELLCOL Integer variable equal to the column number of the cell containing a well.

•Q Real variable equal to the maximum pumping rate or applied pumping rate.

Data Set 17

Character variable specified to indicate the end of the well list data block.

Block 4: Stress period information

Character variables “STRESS PERIOD” and “END” are required for each stress period. There are 3 options for specifying stress period information: 1) use stress period data for irrigation segments, irrigation wells, or supplemental wells from previous stress period; 2) specify data for all active irrigation segments, irrigation wells, or supplemental wells for stress period; or 3) set all irrigation segments, irrigation wells, or supplemental wells to inactive for a stress period. Combinations of these 3 options can be used for any stress period.

Items 21a and 25a are specified for MODFLOW simulations; items 21b and 25b are specified for GSFLOW simulations. Some values are not used for a simulation due to specifications in the OPTIONS block; dummy values must be specified for unused input variables.

STRESS PERIOD

Data Set 18

An optional character variable. IRRDIVERSION can be specified if character variable IRRIGATION_DIVERSION is specified in the OPTIONS block.

Data Set 19

An integer variable equal to the number of SFR2 segments active during a stress period that will divert water to cells. If NUMIRRSEGSP < 0, irrigation segment data from the previous stress period will be used. If NUMIRRSEGSP =0, all irrigation segments will be set to inactive.

Data Set 20

[SEGID NUMCELLSEG IRRPERIODSEG TRIGGERFACTSEG]

•SEGID An integer variable equal to the SFR2 segment number for the diversion used for irrigation.

•NUMCELLSEG An integer variable equal to the total number of MODFLOW cells or PRMS HRUs that will be irrigated by SFR2 diversion segment SEGID.

•IRRPERIODSEG A real variable equal to the length of time water will be diverted for a single irrigation event. Although this variable is specified for each SEGID, it only is used if the character variable TRIGGER is specified in the options block. Units for this variable are determined from the DIS file input variable ITMUNI. Values should be greater than or equal to the length of the largest model time step during irrigation periods.

•TRIGGERFACTSEG A real variable between 0 and 1 that triggers an irrigation event. If TRIGGERFACTSEG is set to 0.5 then an irrigation event will start when ETo/ETa = 0.5. Although this variable is specified for each SEGID, it only is used if the character variable TRIGGER is specified in the options block.

Data Set 21a (MODFLOW)

[IRRROW_DIVERSION1 IRRCOL_DIVERSION1 EFF_FACT_DIVERSION1 FIELD_FACT_DIVERSION1]

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[IRRROW_ DIVERSIONnumcellseg IRRCOL_ DIVERSIONnumcellseg EFF_FACT_ DIVERSIONnumcellseg FIELD_FACT_ DIVERSIONnumcellseg]

•IRRROW_DIVERSION An integer variable equal to the cell row number that will be irrigated by segment SEGID. This variable only is specified for MODFLOW-only simulations.

•IRRCOL_ DIVERSION An integer variable equal to the cell column number that will be irrigated by segment SEGID. This variable only is specified for MODFLOW-only simulations.

•EFF_FACT_ DIVERSION A real variable equal to the fraction of surface water applied to a cell that can be used to represent crop evapotranspiration and other field losses. If evapotranspiration is being simulated explicitly then set EFF_FACT_ DIVERSION to zero.

•FIELD_FACT_ DIVERSION A real variable equal to the fraction of the diverted water applied to a cell that is used to distribute a diversion among multiple cells. The sum of all FIELD_FACT_ DIVERSION values for a diversion should sum to 1.

Data Set 21b (GSFLOW)

[HRU_ID_ DIVERSION1 DUM_ DIVERSION1 EFF_FACT_ DIVERSION1 FIELD_FACT_ DIVERSION1]

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[HRU_ID_ DIVERSIONnumhruseg DUM_ DIVERSIONnumhruseg EFF_FACT_ DIVERSIONnumhruseg FIELD_FACT_ DIVERSIONnumhruseg]

•HRU_ID_ WELL An integer variable equal to the HRU ID to which pumped water will be applied as irrigation. An integer variable that must be specified but is not used and can be set to zero. This variable only is specified for PRMS-only and GSFLOW simulations.

•DUM_ DIVERSION An integer variable that must be specified but is not used and can be set to zero. This variable only is specified for PRMS-only and GSFLOW simulations.

•EFF_FACT_WELL A real variable equal to the fraction of groundwater applied to a cell that can be used to represent crop evapotranspiration and other field losses. If evapotranspiration is being simulated explicitly then set EFF_FACT_WELL to zero.

•FIELD_FACT_WELL A real variable equal to the fraction of the groundwater applied to a cell that is used to distribute water pumped from a well among multiple cells. The sum of all FIELD_FACT_WELL values for a well should sum to 1.

Data Set 22

An optional character variable. IRRWELL can be specified if character variable IRRIGATION_WELL is specified in the OPTIONS block.

Data Set 23

An integer variable equal to the number of AG wells active during a stress period that will pump water for irrigation on MODFLOW cells or PRMS HRUs. If NUMIRRWELLSP < 0, irrigation well data from the previous stress period will be used. If NUMIRRWELLSP =0, all irrigation wells will be set to inactive.

Data Set 24

[IRRWELLID NUMCELLWELL IRRPERIODWELL TRIGGERFACTWELL]

•IRRWELLID An integer variable equal to the well identification number used to pump groundwater for irrigation.

•NUMCELLWELL An integer variable equal to the total number of MODFLOW cells or PRMS HRUs that receive water from a well.

•IRRPERIODWELL A real variable equal to the length of time water will be pumped for a single irrigation event. Although this variable is specified for each WELL, it only is used if the character variable TRIGGER is specified in the options block and for wells that are not SUP wells. Units for this variable are determined from the DIS file input variable ITMUNI. Values should be greater than or equal to the length of the largest model time step during irrigation periods.

•TRIGGERFACTORWELL A real variable between 0 and 1.0 that triggers an irrigation event. If TRIGGERFACTORWELL is set to 0.5 then an irrigation event will start when ETo/ETa = 0.5. Although this variable is specified for each SEGID, it only is used if the character variable TRIGGER is specified in the options block.

Data Set 25a (MODFLOW)

[IRRROW_WELL1 IRRCOL_WELL1 EFF_FACT_WELL1 FIELD_FACT_WELL1]

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[IRRROW_WELLnumcellwell IRRCOL_WELLnumcellwell EFF_FACT_WELLnumcellwell FIELD_FACT_WELLnumcellwell KCROPnumcellwell]

•IRRROW_WELL An integer variable equal to the cell row number to which pumped water will be applied as irrigation. This variable only is specified for MODFLOW-only simulations.

•IRRCOL_WELL An integer variable equal to the cell column number to which pumped water will be applied as irrigation. This variable only is specified for MODFLOW-only simulations.

•EFF_FACT_WELL A real variable equal to the fraction of groundwater applied to a cell that can be used to represent crop evapotranspiration and other field losses. If evapotranspiration is being simulated explicitly then set EFF_FACT_WELL to zero.

•FIELD_FACT_WELL A real variable equal to the fraction of the groundwater applied to a cell that is used to distribute water pumped from a well among multiple cells. The sum of all FIELD_FACT_WELL values for a well should sum to 1.

•KCROP

Data Set 25b (GSFLOW)

[HRU_ID_WELL1 DUM_WELL1 EFF_FACT_WELL1 FIELD_FACT_WELL1]

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[HRU_ID_WELLnumhruwell DUM_WELLnumhruwell EFF_FACT_WELLnumhruwell FIELD_FACT_WELLnumhruwell]

•HRU_ID_ WELL An integer variable equal to the HRU ID to which pumped water will be applied as irrigation. An integer variable that must be specified but is not used and can be set to zero. This variable only is specified for PRMS-only and GSFLOW simulations.

•DUM_WELL An integer variable that must be specified but is not used. This variable only is specified for PRMS-only and GSFLOW simulations. Any 4-byte integer values can be specified as a dummy value that is not used in the simulation.

•EFF_FACT_WELL A real variable equal to the fraction of groundwater applied to a cell that can be used to represent crop evapotranspiration and other field losses. If evapotranspiration is being simulated explicitly then set EFF_FACT_WELL to zero.

•FIELD_FACT_WELL A real variable equal to the fraction of the groundwater applied to a cell that is used to distribute water pumped from a well among multiple cells. The sum of all FIELD_FACT_WELL values for a well should sum to 1.

Data Set 26

An optional character variable indicating that supplemental well stress period data will be specified.

Data Set 27

An integer variable equal to the number of active supplementary wells during a stress period that will pump groundwater to meet the surface water shortfall for irrigation. If NUMSUPWELLSP < 0, supplementary well data from the previous stress period will be used. If NUMSUPWELLSP =0, all supplementary wells will be set to inactive.

Data Set 28

[SUPWELLNUM NUMSEGWELL]

•SUPWELLNUM An integer variable equal to the AG well number that supplements one or more surface water diversions.

•NUMSEGWELL An integer variable equal to the number of SFR2 segments that will be supplemented by a well.

Data Set 29

[SEGWELLID1 FRACSUP1 FRACSUPMAX1]

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[SEGWELLIDnumsegwell FRACSUPnumsegwell FRACSUPMAXnumsegwell]

•SEGWELLID An integer variable equal to the SFR2 segment number that will be supplemented by a well.

•FRACSUP A real variable between 0 and 1 that is equal to the fraction of the surface water shortfall for segment SEGWELLID that will be supplemented by a well.

•FRACSUPMAX A real variable between 0 and 1 that is equal to the fraction of the surface water demand that is used to calculate the net irrigation water requirement with supplemental groundwater pumping. Supplemental groundwater pumping (𝑄𝑠𝑢𝑝) will be calculated as 𝑄𝑠𝑢𝑝=𝐹𝑅𝐴𝐶𝑆𝑈𝑃∗[FRACSUPMAX∗𝑄𝑑𝑒𝑚𝑎𝑛𝑑−𝑄𝑑𝑖𝑣], where 𝑄𝑑𝑒𝑚𝑎𝑛𝑑 is the specified surface water diversion rate for irrigation.

 

Character variable specified to indicate the end of each stress period data block.