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