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Bushland Reference ET Calculator with QA/QC Capabilities
and an iPhone/Android Application
Prasanna H. Gowda1* Jerry E. Moorhead1 Daniel E. Holman2 Thomas H. Marek3 Dana O. Porter2 Terry A. Howell1
Agricultural Engineer Biological Science Technician Software Applications Developer Agricultural Engineer Associate Professor Ret. Laboratory Director
*Presenting Author 1USDA-ARS Conservation and Production Research Laboratory, Bushland, TX; 3Texas A&M AgriLife Research & Extension, Lubbock, TX; 3Texas A&M AgriLife Research & Extension, Amarillo, TX;
REFERENCES
Accurate daily reference evapotranspiration (ET) values
are needed to estimate crop water demand for irrigation
management and hydrologic modeling purposes. The
Bushland Reference ET Calculator was developed by the
USDA-ARS Conservation and Production Research
Laboratory at Bushland, Texas for calculating hourly and
daily grass and alfalfa reference ET. The user-friendly
interface for the calculator was developed using the Java
Programming Language. The calculator uses the ASCE
Standardized Reference Evapotranspiration (ET)
Equation for calculating both grass and alfalfa reference
ET at hourly and daily time steps. Users have the option
of using a single set or time series weather data to
calculate reference ET. Daily reference ET can be
calculated either by summing the hourly ET values for a
given day or by using daily averages of the climatic data.
Although the Bushland Reference ET Calculator was
designed and developed for use mainly by producers and
crop consultants to manage irrigation scheduling, it can
also be used in educational training, research, and other
practical applications. This paper demonstrates desktop
and iPhone/Android versions of the Bushland Reference
ET Calculator that are being distributed through the
USDA-ARS web site to interested users at no cost.
HOURLY AND DAILY ET FROM
HOURLY INPUT – TIME SERIES HOURLY ET – SINGLE VALUE
DAILY ET FROM DAILY INPUT
– TIME SERIES
Daily ET – SINGLE VALUE FRONT PAGE
iPhone APPLICATION
ABSTRACT
BACKGROUND
In agriculture, evapotranspiration (ET) is a major
consumptive use of irrigation water and precipitation. Any
attempt to improve water use efficiency must be based on
reliable and accurate estimates of ET or crop water use,
which includes water evaporation from land and water
surfaces and transpiration by vegetation. Crop-specific
crop water use can be estimated by multiplying reference
ET calculated from meteorological data by an appropriate
crop coefficient derived from lysimeter studies (Marek et
al., 2010). However, the ASCE-EWRI standardized
reference ET equation is very complex to use. Recently, it
was identified by the ASCE-EWRI ET Task Committee
that currently there exists a need for a mobile, user-
friendly ET calculator targeting advanced producers and
crop consultants. For nearly 20 years in the Texas High
Plains, daily reference ET and crop water use data were
provided on a daily basis to producers and crop
consultants by the Texas High Plains ET Network at no
cost. However, this service was recently terminated due to
the lack of funding support. Therefore, there is an
immediate need for a simple reference ET calculator that
can be used by crop consultants and producers to
estimate accurate reference ET and representative crop
water use with locally available weather data for irrigation
scheduling purposes, thereby implementing the latest
water conservation and best management practices.
• Allen, R.G., Walter, I.A., Elliott, R., Howell, T., Itenfisu, D.,
and Jensen, M. (Eds.). 2005. The ASCE standardized
reference evapotranspiration equation. Environmental and
Water Resources Institute of the American Society of Civil
Engineers, Reston, Virginia.
• Marek, T.H., T.A. Howell, R.L. Synder, D. Porter, and T.
Scherer. 2010. Crop coefficient development and application
to an evapotranspiration network. 2010 ASABE-IA Fifth
Decennial Symposium, Phoenix, AZ, Texas AgriLife
Research at Amarillo, AREC 201011-2. 12p.
APPROACH
Reference ET Calculations:
• ASCE-EWRI Standardized
Reference Evapotranspiration
(ET) Equation (Allen et al.,
2005) was used for calculating
both grass and alfalfa reference
ET at hourly and daily time
steps.
• A more complex equation
provided in Appendix D of the
ASCE-EWRI ET manual was
used for estimating clear-sky
solar radiation.
• Daily reference ET can be
estimated either by summing
the hourly ET values for a given
day or by using daily averages
of the climatic data.
Calculator Design and
Development:
• Bushland Reference ET
Calculator was developed
using the Java Programming
Language.
• Efforts are made to design the
interactive pages for more
intuitive data input.
• In single calculation interactive
pages, error flags are added to
identify invalid or missing data.
• Sample input and output files
are provided with the calculator
for time series calculations to
assist users with input and
output formats.
iPhone/Android Versions
• The iPhone/Android versions of
the reference ET calculator can
be used to calculate single
hourly or daily ET values.
• The user has the option to use
a GPS tracking device
embedded in the iPhone to
enter the geographical
coordinates for reference ET
calculation.
• Calculated hourly or daily ET
values for each location will be
stored in a database for
retrieval at a later time.
Bushland Reference ET
Calculator can be downloaded from
the USDA-ARS Conservation and
Production Research Laboratory’s
website at:
http://www.cprl.ars.usda.gov/ETCalculator.html
Cover Page Hourly ET Daily ET
This research was supported by the Ogallala Aquifer Program, a consortium
between USDA-Agricultural Research Service, Kansas State University, Texas
AgriLife Research, Texas AgriLife Extension Service, Texas Tech University,
and West Texas A&M University.
ACKNOWLEDGEMENTS
Hourly ET Daily ET Cover Page
Android APPLICATION
VISUAL INSPECTION PAGE STATISTICS PAGE
INTERACTIVE PAGES