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Online Guide to MODFLOW-NWT

Abbreviation in Name file

EVT

Purpose

The Evapotranspiration package is used to simulate a head-dependent flux out of the model distributed over the top of the model and specified in units of length/time.  Within MODFLOW, these rates are multiplied by the horizontal area of the cells to which they are applied to calculate the volumetric flux rates.

Documentation

Harbaugh, A.W., Banta, E.R., Hill, M.C., and McDonald, M.G., 2000, MODFLOW-2000, the U.S. Geological Survey modular ground-water model -- User guide to modularization concepts and the Ground-Water Flow Process: U.S. Geological Survey Open-File Report 00-92, 121 p.

Harbaugh, A.W., 2005, MODFLOW-2005, the U.S. Geological Survey modular ground-water model -- the Ground-Water Flow Process: U.S. Geological Survey Techniques and Methods 6-A16. https://doi.org/10.3133/tm6A16

Merritt, M.L., and Konikow, L.F., 2000, Documentation of a Computer Program to Simulate Lake-Aquifer Interaction Using the MODFLOW Ground-Water Flow Model and the MOC3D Solute-Transport Model: U.S. Geological Survey Water-Resources Investigations Report 00-4167, 146 p.

Time-varying-parameters.pdf

Related Packages

Evapotranspiration Segments

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 NEVTOP was not set correctly.

Other Notes

The UZF package simulates evapotranspiration so the EVT 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 EVT 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 Evapotranspiration (EVT) Package is read from the file that is type "EVT" 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.

FOR EACH SIMULATION

Data Set 0

[#Text]

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

Data Set 1

[ PARAMETER NPEVT]

This optional item must start with the word “PARAMETER”.

Data Set 2

NEVTOP IEVTCB

Repeat Items 3-4 for each parameter to be defined (that is, NPEVT times).

Data Set 3

[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.

Data Set 4a

INSTNAM

Item 4a is read only if PARNAM is time-varying. NUMINST repetitions of Item 4 (parts a and b) are read. After each repetition of Item 4a, NCLU repetitions of Item 4b are read.

Data Set 4b

[Mltarr Zonarr IZ]

Repeat Item 4b NCLU times. Each repetition of Item 4b is called a parameter cluster. The NCLU repetitions of Item 4b follow each repetition of Item 4a when PARNAM is time-varying.

FOR EACH STRESS PERIOD

Data Set 5

INSURF INEVTR INEXDP INIEVT

Data Set 6

[SURF(NCOL,NROW)] -- U2DREL If INSURF 0

Either Item 7 or Item 8 may be read, but not both. If Item 8 is read, it is repeated INEVTR times.

Data Set 7

[EVTR(NCOL,NROW)] -- U2DREL If NPEVT = 0 and if INEVTR 0

Data Set 8

[Pname [Iname] [IEVTPF]] -- if NPEVT > 0 and if INEVTR > 0

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

Data Set 9

[EXDP(NCOL,NROW)] -- U2DREL If INEXDP 0

Data Set 10

[IEVT(NCOL,NROW)] -- U2DINT If NEVTOP = 2 and if INIEVT 0

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