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

Data Set 2

Data Set 3

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

Data Set 5

[DIVERSION Segmentnum1 Unit_diversion1]

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.

.

[DIVERSION Segmentnumnumtimeseriesdiversion Unit_diversionnumtimeseriesdiversion]

Data Set 6

[DIVERSIONET Segmentnum1 Unit_diversionet1]

.

.

.

[DIVERSIONET Segmentnumnumtimeseriesdiversionet Unit_diversionetnumtimeseriesdiversionett]

Data Set 7

[WELL Wellnum1 Unit_well1]

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.

.

[WELL Wellnumnumtimeserieswell Unit_wellnumtimeserieswell]

Data Set 8

[WELLET Welletnum1 Unit_wellet1]

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.

.

[WELLET Wellnumnumtimeserieswellet Unit_welletnumtimeserieswellet]

Data Set 9

[WELLALL Unitwellall]

Data Set 10

[WELLETALL Unitwelletall]

Data Set 11

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

Data Set 13

[SEGMENTNUMBER1]

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.

.

[SEGMENTNUMBERMAXNUMSEGS]

Data Set 14

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

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]

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]

Data Set 17

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

Data Set 19

Data Set 20

[SEGID NUMCELLSEG IRRPERIODSEG TRIGGERFACTSEG]

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]

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]

Data Set 22

Data Set 23

Data Set 24

[IRRWELLID NUMCELLWELL IRRPERIODWELL TRIGGERFACTWELL]

Data Set 25a (MODFLOW)

[IRRROW_WELL1 IRRCOL_WELL1 EFF_FACT_WELL1 FIELD_FACT_WELL1]

.

.

.

[IRRROW_WELLnumcellwell IRRCOL_WELLnumcellwell EFF_FACT_WELLnumcellwell FIELD_FACT_WELLnumcellwell KCROPnumcellwell]

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]

Data Set 26

Data Set 27

Data Set 28

[SUPWELLNUM NUMSEGWELL]

Data Set 29

[SEGWELLID1 FRACSUP1 FRACSUPMAX1]

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.

.

[SEGWELLIDnumsegwell FRACSUPnumsegwell FRACSUPMAXnumsegwell]