The document describes an evapotranspiration (ET) component in the JGrass-NewAGE system that offers two models - the FAO Penman-Monteith and Priestley-Taylor models. The component takes various meteorological inputs like net radiation, wind speed, humidity and temperature to estimate potential or actual ET. It is integrated within the Open Modeling Software (OMS) framework and outputs time series of estimated ET that can be visualized in a GIS.

1. Bancheri and Formetta
LINKERS
JGrass-NewAGE: ET component
Marialaura Bancheri*†
and Giuseppe Formetta†
*
Correspondence:
marialaura.bancheri@unitn.it
Dipartimento di Ingegneria Civile
Ambientale e Meccanica, Trento,
Mesiano di Povo, Trento, IT
Full list of author information is
available at the end of the article
†
Code Author
Abstract
These pages teach how to run the EvapoTranspiration (ET) component inside the
OMS 3 console. Some preliminary knowledge and installation of OMS is mandatory
(see @Also useful). This component deals with the estimations of the
evapotranspiration, which is the flux through which the water, in liquid phase, changes
it phase and returns back into the atmosphere in the gas form. Quantification of actual
evapotranspiration is a difficult and a very important task for water resources
management. The JGrass-NewAGE ET component offers two different formulations for
the evapotranspiration modeling: the FAO Penman-Monteith model (1) and the
Priestley-Taylor model (2).The package is perfectly integrated in the system , and is fed
by other components, like the one providing the shortwave radiation (SWRB, (3)).
@Version:
0.1
@License:
GPL v. 3
@Inputs:
• Net radiation (W/m2
);
• Average wind speed (m/s);
• Relative humidity (%);
• Air temperature (◦
C);
• α (-);
• Gmorn(−);
• Gnight(−);
• doHourly (Boolean);
• Start Date (String).
@Outputs:
• Potential evapotranspiration (mm)
@Doc Author: Marialaura Bancheri
@References:
• See References section below
Keywords: OMS; JGrass-NewAGE Component Description; Evapotranspiration
estimation

2. Bancheri and Formetta Page 2 of 6
Code Information
Executables
This link points to the jar file that, once downloaded can be used in the OMS console:
https://github.com/GEOframeOMSProjects/OMS_Project_ET/tree/master/lib
Developer Info
This link points to useful information for the developers, i.e. information about the code
internals, algorithms and the source code
https://github.com/geoframecomponents
Also useful
To run JGrass-NewAGE it is necessary to know how to use the OMS console. Information
at: ”How to install and run the OMS console”,
https://alm.engr.colostate.edu/cb/project/oms).
JGrasstools are required for preparing some input data (information at:
http://abouthydrology.blogspot.it/2012/11/udig-jgrasstools-resources-in-italian.
html
To visualize results you need a GIS. Use your preferred GIS, following its installation
instructions. To make statistics on the results, you can probably get benefits from R:
http://www.r-project.org/andfollowitsinstallationinstruction.
To whom address questions
marialaura.bancheri@unitn.it
Authors of documentation
Marialaura Bancheri (marialaura.bancheri@unitn.it)
This documentation is released under Creative Commons 4.0 Attribution International

3. Bancheri and Formetta Page 3 of 6
Component Description
The NewAge-JGrass ET component offers two different formulations for the evapotraspi-
ration modeling: the FAO Penman-Monteith model, (1), eq. (1), and the PriestleyTaylor
model, (2), eq. (2).
ET0 =
0.408 · ∆ · (Rn − G) + γ · u2 · (es − e) ·
Cp
T +273
∆ + γ · (1 + Cd · u2)
(1)
ET = α ·
∆ · (Rn − G)
∆ + γ
(2)
and
G =



Gmorn · Rn daylight
Gnight · Rn nighttime
(3)
where ET0 or ET are expressed in (mm · day−1
] or (mm · hour−1
); Rn is the net
radiation expressed in (MJ · m2
· day−1) or (MJ · m2
· h−1
); G is the soil heat flux
at the soil surface in (MJm2
day−1) or (MJm2
h−1
); T is the mean daily or hourly air
temperature expressed in (◦
C) ; u2 is the wind speed in (ms−1
); es is the mean saturation
vapor-pressure expressed in (kPa); e is the mean actual vapor-pressure; ∆ is the slope
of the saturation vapor-pressure curve expressed in (kPa ·◦
C−1
); γ is the psychometric
constant expressed in (kPa·◦
C−1
); Cd is a coefficient equal to 0.34 and Cp is a coefficient
equal to 900 in the case of a daily time step and equal to 37 in the case of a hourly time
step.
Detailed Inputs description
General description
The input file is a .csv file containing a header and one or more time series of input data,
depending on the number of stations involved. Each column of the file is associated to a
different station.
The file must have the following header:
• The first 3 rows with general information such as the date of the creation of the file
and the author;
• the fourth and fifth rows contain the IDs of the stations (e.g. station number 8:
value 8, ID, ,8);
• the sixth row contains the information about the type of the input data (in this
case, one column with the date and one column with double values);
• the seventh row specifies the date format (YYYY-MM-dd HH:mm).
All this information shown in the figure 1.

4. Bancheri and Formetta Page 4 of 6
Figure 1 Heading of the .csv input file
Net radiation
The net radiation is given in time series of (W/m2
) values. The conversion from (W/m2
)
to (MJ · m2
) is automatically done by the component.
Average wind speed
The average wind speed is given in time series of (m/s) values.
Relative humidity
The relative humidity is given in time series or raster maps of (% ) values.
Air temperature
The air temperature is given in time series of (◦
C) values. The conversion in (◦
K) is
directly done by the component.
α
α is the Priestley-Taylor coefficient in eq. 2
Gmorn
Gmorn is the coefficient for the soil heat flux during daylight in eq. 3
Gnight
Gnight is the coefficient for the soil heat flux during nighttime in eq. 3
doHourly
doHourly is a boolean field to set the time step of the simulation (”true” is hourly time
step, ”false” is daily).
Start Date
Start Date is a string containing the first day of the simulation.
Detailed Outputs description
The output file will have exactly the same heading of the input file (see fig. 1).
Time series of the evapotranspiration (mm)
The simulated output evapotranspiration is given as a time series at a given point. Its
units are (mm · h−1
) or (mm · d−1
) depending on the temporal resolution chosen by the
end-user. Figure 2 shows the results of a simulation obtained using the Priestley-Taylor
model, (2), and data from a station in the Posina River, Italy.

5. Bancheri and Formetta Page 5 of 6
0 5000 10000 15000
0.000.050.100.150.20
Evapotranspiration: Priestley-Taylor model
Time[h]
ET[mm]
Figure 2 Time series of simulated evapotranspiration, obtained using Priestley-Taylor model and data
from a station in the basin of the Posina River, Italy.
Examples
The following .sim file is customized for the use of model of Priestley-Taylor model in the
ET component. The .sim file can be downloaded from here:
import static oms3.SimBuilder.instance as OMS3
def home = oms_prj
def startDate= "1994 -01 -01 00:00"
def endDate= "1998 -01 -01 00:00"
OMS3.sim {
resource "$oms_prj/lib"
model(while:" reader_data_temp .doProcess") {
components {
" reader_data_temp " "org.jgrasstools .gears.io.
timedependent . OmsTimeSeriesIteratorReader "
" reader_data_rad " "org. jgrasstools .gears.io.
timedependent . OmsTimeSeriesIteratorReader "
"PTEtp" "etp. OmsPriestleyTaylorEtpModel "
"writer_etp" "org.jgrasstools.gears.io.
timedependent . OmsTimeSeriesIteratorWriter "
}
parameter{
" reader_data_temp .file" "${home }/ data/Temperature.csv"
" reader_data_temp .idfield" "ID"
" reader_data_temp .tStart" "${startDate}"
" reader_data_temp .tEnd" "${endDate}"
" reader_data_temp .tTimestep" 60
" reader_data_temp .fileNovalue" " -9999"
" reader_data_rad .file" "${home }/ data/net.csv"
" reader_data_rad .idfield" "ID"
" reader_data_rad .tStart" "${startDate}"
" reader_data_rad .tEnd" "${endDate}"
" reader_data_rad .tTimestep" 60
" reader_data_rad . fileNovalue" " -9999"
// component parameters , (see " Detailed Inputs
description ", for more info)

6. Bancheri and Formetta Page 6 of 6
"PTEtp.pAlpha" 1.06
"PTEtp.pGmorn" 0.35
"PTEtp.pGnight" 0.75
"PTEtp.doHourly" true
"PTEtp.tStartDate" "${startDate}"
"writer_etp.file" "${home }/ output/ ET_priestley .csv"
"writer_etp.tStart" "${startDate}"
"writer_etp.tTimestep" 60
}
connect {
" reader_data_temp .outData" "PTEtp.inTemp"
" reader_data_rad .outData" "PTEtp. inNetradiation "
"PTEtp.outPTEtp" "writer_etp.inData"
}
}
}
Data and Project
The following link is for the download of the input data necessaries to execute the ET
component (as shown in the .sim file in the previous section ) :
https://github.com/GEOframeOMSProjects/OMS_Project_ET/tree/master/data
The following link is for the download of the OMS project for ET component:
https://github.com/GEOframeOMSProjects/OMS_Project_ET
%
References
1. Allen, R.G., Pereira, L.S., Raes, D., Smith, M., et al.: Crop evapotranspiration-guidelines for computing crop water
requirements-fao irrigation and drainage paper 56. FAO, Rome 300(9), 05109 (1998)
2. Priestley, C.H.B.: Turbulent Transfer in the Lower Atmosphere. University of Chicago Press Chicago, ??? (1959)
3. Formetta, G., Rigon, R., Ch´avez, J., David, O.: Modeling shortwave solar radiation using the jgrass-newage system.
Geoscientific Model Development 6(4), 915–928 (2013)