ETS - Evapotranspiration Segments Package

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Abbreviation in Name file

ETS

Purpose

The Evapotranspiration Segments Package allows simulation of evapotranspiration with a user-defined relation between evapotranspiration rate and hydraulic head.

Documentation

•Banta, E.R., 2000, MODFLOW-2000, the U.S. Geological Survey Modular Ground-Water Model - Documentation of Packages for Simulating Evapotranspiration with a Segmented Function (ETS1) and Drains with Return Flow (DRT1): U.S. Geological Survey Open-File Report 00-466, 127 p.

•Time-varying-parameters.pdf

•release.txt for MODFLOW-2005

Related Packages

•Evapotranspiration

•Riparian Evapotranspiration

•Head-Dependent Flux Boundary packages

Supported in

•MODFLOW-2000

•MODFLOW-2005

•MODFLOW-LGR

•MODFLOW-CFP

•MODFLOW-NWT

•MODFLOW-OWHM

Common Errors

Evapotranspiration is applied to the wrong cells because NETSOP was not set correctly.

Other Notes

•The UZF package simulates evapotranspiration so the ETS package is not normally included in a model that includes the UZF package or at least not in the same locations.

•The evapotranspiration simulated by the ETS package only includes evapotranspiration from the saturated zone. Recharge is sometime calculated as precipitation minus losses between the land surface and the water table. Evapotranspiration from the unsaturated zone would be one such loss. Another such loss would be surface runoff.

Input Instructions

Input to the ETS1 Package is read from the file that is type “ETS” in the name file. All single-valued variables are free format if the option “FREE” is specified in the Basic Package input file; otherwise, the variables have 10-character fields. Arrays are read by an array-reading utility module, either U2DREL or U2DINT (Harbaugh and others, 2000), as indicated. Optional variables are shown in brackets.

FOR EACH SIMULATION

Data Set 0

[#Text]

Item 0 is optional—“#” must be in column 1. Item 0 can be repeated as many times as desired.

[#Text]

Item 0 is optional—“#” must be in column 1. Item 0 can be repeated as many times as desired.

Data Set 1

NETSOP IETSCB NPETS NETSEG

NETSOP—is the evapotranspiration (ET) option code. ET variables (ET surface, maximum ET rate, and extinction depth) are specified in layer variables, ETSS, ETSR, and ETSX, with one value for each vertical column of cells in the model grid. Accordingly, ET is calculated for one cell in each vertical column. The option codes determine the cell within a column for which ET will be calculated.

•If NETSOP = 1, ET is calculated only for cells in the top grid layer.

•If NETSOP = 2, the cell for each vertical column is specified by the user in variable IETS.

•If NETSOP = 3, ET to be applied to the uppermost active cell in each horizontal location.

IETSCB—is a flag and a unit number.

•If IETSCB > 0, it is the unit number to which ETS1-Package cell-by-cell flow terms will be written when “SAVE BUDGET” or a non-zero value for ICBCFL is specified in Output Control (Harbaugh and others, 2000). IETSCB must be a unit number associated with a file listed with type “DATA(BINARY)” or “DATAGLO(BINARY)” in the name file.

•If IETSCB ≤0, ETS1-Package cell-by-cell flow terms will not be written.

NPETS—is the number of evapotranspiration-segments parameters.

In MODFLOW-2000, the maximum number of allowed parameters is 999.  In MODFLOW-2005,-LGR, and -CFP the maximum number of allowed parametersis 2000. In MODFLOW-OWHM, the maximum number of allowed parameters is specified in the Basic package.

NETSEG—is the number of segments used to define the relation of evapotranspiration rate to hydraulic head in the interval where the evapotranspiration rate is variable.

Repeat Items 2 and 3 for each parameter to be defined (that is, NPETS times). Items 2 and 3 are omitted if NPETS = 0.

Data Set 2

[PARNAM PARTYP Parval NCLU [INSTANCES NUMINST]]

If PARNAM is to be a time-varying parameter, the keyword INSTANCES and a value for NUMINST must be entered.

PARNAM—is the name of a parameter to be defined. This name can consist of 1 to 10 characters and is not case sensitive. That is, any combination of the same characters with different case will be equivalent.

All parameter names must be unique.

PARTYP—is the type of parameter to be defined. For the ETS1 Package, the only allowed parameter type is “ETS,” which defines values of the maximum ET flux.

Parval—is the parameter value. This parameter value may be overridden by a value in the PVAL file, the Sensitivity Process (SEN) input file, or by a value generated by the Parameter-Estimation (PES) Process.

NCLU—is the number of clusters required to define a non-time-varying parameter or one instance of a time-varying parameter. Each repetition of Item 3b is a cluster (variables Mltarr, Zonarr, and IZ). Usually only one cluster is needed to define an ETS non-time-varying parameter or instance of a time-varying parameter; however, more than one cluster may be listed.

INSTANCES – is an optional keyword that designates a parameter as time varying. The keyword is case-insensitive; that is, it may be entered in any combination of upper- and lower-case letters. If INSTANCES is present, it must be followed by a value for NUMINST. If INSTANCES is absent, PARNAM is non-time-varying and NUMINST should not be present.

NUMINST – is the number of instances that are included in the definition of a time-varying parameter, where each instance is a series of NCLU clusters. If the keyword INSTANCES is present, NUMINST must be present and must be at least 1. If the keyword INSTANCES is absent, NUMINST should not be present.

Data Set 3a

INSTNAM

Item 3a is read only if PARNAM is time-varying. NUMINST repetitions of Item 3 (parts a and b) are read. After each repetition of Item 3a, NCLU repetitions of Item 3b are read.

INSTNAM – is the name of an instance associated with parameter PARNAM specified in the corresponding Item 2. The name can consist of 1 to 10 characters and is not case sensitive. That is, any combination of the same characters with different case will be equivalent. Names entered for INSTNAM must be unique for any given parameter, but names may be reused for instances associated with different parameters.

Data Set 3b

[Mltarr Zonarr IZ]

Each repetition of Item 3b record is called a parameter cluster. Repeat Item 3b NCLU times. The NCLUrepetitions of Item 3b follow each repetition of Item 3a when PARNAM is time-varying.

Mltarr—is the name of the multiplier array to be used to define the values determined by a parameter. The units of Parval times Mltarr must be (LT−1). The name “NONE” means there is no multiplier array, and the values will be set equal to Parval.

Zonarr—is the name of the zone array to be used to define the cells associated with a parameter. The name “ALL” means there is no zone array, and all cells are associated with the parameter.

IZ—is up to 10 zone numbers (separated by spaces) that define the cells associated with a parameter. These values are not used if Zonarr is specified as “ALL.” Values can be positive or negative, but 0 is not allowed. The end of the line, a zero value, or a non-numeric entry terminates the list of values.

FOR EACH STRESS PERIOD

Data Set 4

INETSS INETSR INETSX [INIETS [INSGDF]]

INETSS—is the ET surface (ETSS) read flag.

•If INETSS ≥0, a layer variable containing the ET surface (ETSS) will be read from item 5 in the ETS1 input file.

•If INETSS < 0, the ET surface from the preceding stress period will be reused.

INETSR—is the ETSR read flag. Its function depends on whether or not parameters are being used.

•If no parameters are being used (NPETS = 0):

oIf INETSR ≥0, a layer variable containing the maximum ET rate (ETSR) will be read from item 6 in the ETS1 input file.

oIf INETSR < 0, the maximum ET rate from the preceding stress period will be reused.

•If parameters are being used (NPETS > 0):

oIf INETSR > 0, INETSR is the number of parameters used to define ETSR in the current stress period. Item 7 defines the names of the parameters.

oIf INETSR < 0, ETS parameters from the preceding stress period are used.

oINETSR = 0 is not allowed. That is, when parameters are used, at least one parameter must be specified for each stress period.

INETSX—is the extinction depth (ETSX) read flag.

•If INETSX ≥0, a layer variable containing the extinction depth (ETSX) will be read from item 8 in the ETS1 input file.

•If INETSX < 0, the extinction depth from the preceding stress period will be reused.

INIETS—is the layer indicator (IETS) read flag. It is read if the ET option (NETSOP) is equal to two or if NETSEG > 1. If NETSEG > 1 and NETSOP is not equal to two, INIETS is ignored and IETS is not read.

•If INIETS ≥0, a layer variable containing the layer indicators (IETS) will be read from item 9 in the ETS1 input file.

•If INIETS < 0, layer indicators used during the preceding stress period will be reused.

INSGDF—is the segment definition read flag. It is read only if NETSEG > 1.

•If INSGDF ≥0, two layer variables to define PXDP and PETM for each of (NETSEG – 1) segment intersections are read from items 10 and 11, respectively, of the ETS1 input file.

•If INSGDF < 0, PXDP and PETM from the preceding stress period will be reused.

Data Set 5

[ETSS(NCOL,NROW)] – U2DREL – If INETSS ≥0

ETSS—is the elevation of the ET surface (L).

Either Item 6 or Item 7 may be read, but not both. If Item 7 is read, it is repeated INETSR times.

Data Set 6

[ETSR(NCOL,NROW)] – U2DREL – If NPETS = 0 and if INETSR ≥0

ETSR—is the maximum ET flux (volumetric flow rate per unit area, LT–1).

Data Set 7

[Pname [Iname] [IETSPF]] – If NPETS > 0 and if INETSR > 0

Iname is read if Pname is a time-varying parameter. If IETSPF is specified for a non-time-varying parameter, Iname must be omitted.

Pname—is the name of a parameter that will be used to define the ETSR variable in the current stress period.

Iname – is an instance name that is read only if Pname is a time-varying parameter. Multiple instances of the same time-varying parameter are not allowed in a stress period.

IETSPF—is an optional format code for printing the ETSR variable after it has been defined by parameters. The format codes are the same as those used in the U2DREL array reading utility module (Harbaugh and others, 2000).

Data Set 8

[ETSX(NCOL,NROW)] – U2DREL – If INETSX ≥0

ETSX—is the ET extinction depth (L). This variable is read only if INETSX ≥0. This is the distance from ETSS not an elevation.

Data Set 9

[IETS(NCOL,NROW)] – U2DINT – If NETSOP = 2 and if INIETS ≥0

IETS—is the layer indicator variable. For each horizontal location, IETS indicates the layer from which ET is removed. It is read only if the ET option (NETSOP) is equal to two and if INIETS ≥0.

If NETSEG > 1, (NETSEG −1) repetitions of items 10 and 11 are read. If NETSEG > 2, items 10 and 11 are read for the uppermost segment intersection, followed by repetitions of items 10 and 11 for successively lower intersections.

Data Set 10

[PXDP(NCOL,NROW)] – U2DREL – If NETSEG > 1 and INSGDF ≥0

PXDP—is a proportion of the extinction depth (dimensionless), measured downward from the ET surface, which, with PETM, defines the shape of the relation between the evapotranspiration rate and head. The value of PXDP must be between 0.0 and 1.0, inclusive. Repetitions of PXDP and PETM are read in sequence such that the first occurrence represents the bottom of the first segment, and subsequent repetitions represent the bottom of successively lower segments. Accordingly, PXDP values for later repetitions (representing lower segments) should be greater than PXDP values for earlier repetitions.

Data Set 11

[PETM(NCOL,NROW)] – U2DREL – If NETSEG > 1 and INSGDF ≥0

PETM—is a proportion of the maximum evapotranspiration rate (dimensionless) which, with PXDP, defines the shape of the relation between the evapotranspiration rate and head. The value of PETM should be between 0.0 and 1.0, inclusive. Repetitions of PXDP and PETM are read in sequence such that the first occurrence represents the bottom of the first segment, and subsequent repetitions represent the bottoms of successively lower segments. Accordingly, PETM values for later repetitions (representing lower segments) generally would be less than PETM values for earlier repetitions.