Measuring and Conserving Irrigation Water

1. Measuring and Conserving
ATTRA Irrigation Water
A Publication of ATTRA - National Sustainable Agriculture Information Service • 1-800-346-9140 • www.attra.ncat.org
By Mike Morris and This publication describes how to find the net water application rate for any irrigation system. It fur-
Vicki Lynne ther explains how to calculate the number of hours the system should be operated, describes several
NCAT Energy ways to measure flowing water in an open channel or pipeline, and offers suggestions for irrigating
Specialists with limited water supplies.
© 2006 NCAT
Contents Introduction
T
Introduction ..................... 1 his publication
Finding Net Water explains several
Application in Inches ways to mea-
per Set ................................ 1
sure flowing irriga-
Measuring Flows ............ 6
tion water. Legions of
References ........................ 9
irrigators make crop-
Further Resources .......... 9 watering decisions by
Appendix: Finding guesswork, imitation of
flow rate with a
bucket test ...................... 10 the neighbors, or “the
way it’s always been
done.” If this sounds
familiar, this publica-
tion is for you.
A basic understanding
of your system’s capac- NCAT photo
ity to deliver water is
a very powerful piece
of knowledge, one that allows you to take track crop water use (evapotranspiration)
a more scientific approach to the irrigation as the season goes by. Your local Natural
process, achieve greater control, and begin Resources Conservation Service (NRCS),
conserving water without compromising Extension, or soil and water conservation
crop yields. First and foremost, all irriga- district office should be able to assist you.
tors need to know their system’s net water
application rate, measured in inches per Finding Net Water Application
ATTRA—National Sustainable
hour or inches per irrigation. in Inches per Set
Agriculture Information Service
is managed by the National Cen- Not covered in this publication are some Some sprinkler systems, and most sur-
ter for Appropriate Technology equally basic skills essential to irrigation face irrigation systems, apply water in one
(NCAT) and is funded under a
grant from the United States management. All irrigators should know location for a period of time before being
Department of Agriculture’s general irrigation guidelines for the crops turned off or moved to another area of the
Rural Business-Cooperative Ser-
vice. Visit the NCAT Web site they grow. All irrigators should know how field. This period is often called a set or set
(www.ncat.org/agri. to check soil moisture levels. (Please refer time. Other sprinkler systems, such as cen-
html) for more informa-
tion on our sustainable to the ATTRA publication Soil Moisture ter pivots and linear-move systems, move
agriculture projects. Monitoring.) Most irrigators should also more or less continuously. Their set time is

2. Table 1 shows attainable system effi-
ciencies for some irrigation systems:
the percentage of water that actually
enters and remains in the root zone.
These are only average values for
well-managed and well-maintained
systems. Soil texture will heavily
influence how your system’s efficiency
compares to the ranges below. In sit-
uations where true application effi -
ciency is hard to estimate, measured
distribution uniformity (DU) may be
the most accurate “system efficiency”
value to use in the formulas and cal-
culations below. DU measures how
uniformly water infi ltrates into the
soil in various parts of a field. Talk
to your local NRCS office or soil and
water conservation district for help
measuring your DU.
NCAT photo
considered to be the period needed to cover
the entire irrigated area. Table 1. Attainable Irrigation System Application
Good irrigation management requires that Efficiencies
you know how much water the irrigation
system delivers to a crop’s roots over a given
period of time. You can then adjust the System Type Efficiency (%)
duration or frequency of your sets so the
amount of water you put into the soil equals Surface Systems
the amount that plants have used up. Level border 60-80
Furrow 60-80
Finding System Efficiency Surge 65-80
In any irrigation system, some water is Graded border 55-75
lost or fails (for a variety of reasons) to Corrugate 40-55
become available to the plant roots. For Wild Flood 25-40
example, water is lost to deep percolation,
wind drift, runoff, and evaporation during Sprinkler Systems
application. The term net water application Linear move 75-90
refers to the amount of water (in inches of Center pivot (low pressure) 75-90
depth) that your irrigation system actually Fixed solid set 70-85
delivers to the crop root zone during a set. Center pivot (high pressure) 65-80
To calculate net water application, you start Hand move or side roll laterals 60-75
with the gross amount of water applied and Traveling gun 60-70
multiply it by a system efficiency. Stationary gun 50-60
Micro-irrigation systems
Gross water applied × system efficiency = net water applied Surface/subsurface drip 85-95
Micro spray or mist 85-90
Page 2 ATTRA Measuring and Conserving Irrigation Water

3. A Shortcut Method for Most Figure 1. Spacings on Hand Move Sprinklers
Sprinkler Systems
To estimate net water application in inches
per set for most sprinkler systems (but not
pivots), you can simply use the following two
tables. Use Table 2 to convert nozzle size
and pressure to gallons per minute (gpm).
Once you’ve determined the flow rate in
gpm, use Table 3 (along with the correct
spacing for your system) to fi nd your sys-
tem’s gross water application in inches per
hour. Then multiply this number by your
Table 2. Nozzle discharge (gpm)
system efficiency and set duration to fi nd
net water application. Nozzle Nozzle Pressure, psi
Size
For example, consider a side roll system (inch) 30 40 50 60 70
with new 9/64-inch nozzles and 40 pounds
G
3/32 1.4 1.7 1.9 2.0 2.1
per square inch (psi) operating pressure, ood irriga-
1/8 2.6 3.0 3.3 3.5 3.8
with 40-foot by 40-foot sprinkler spacing tion man-
(see Figure 1), and an 11-hour set time 9/64 3.3 3.7 4.2 4.5 4.9
agement
operating at 65 percent system efficiency. 5/32 3.9 4.5 5.0 5.4 5.8
requires that you
11/64 4.7 5.4 6.0 6.6 7.1
From Table 2, find the 9/64-inch nozzle on know how much
3/16 5.5 6.3 7.0 7.7 8.3
the left and read across to the figure under water the irrigation
40 psi. The number is 3.7 gpm. 13/64 6.4 7.4 8.2 9.0 9.7
7/32 7.4 8.6 9.6 0.5 11.3
system delivers to a
Then, using Table 3, fi nd the 40-foot by crop’s roots over a
40-foot spacing on the left and read across Caution: The values in Table 2 are based on new
given period of time.
to the 3 gpm and 4 gpm columns. Since 3.7 nozzles. Flow from worn nozzles can vary significantly
from these values.
gpm is a little more than halfway between,
estimate the gross water application at
0.22 inches per hour. Multiply 0.22 by 11
hours—the set duration—and by 0.65—the You can estimate net water application in
system efficiency percentage. inches per set for any irrigation system if
you know the system’s flow rate, irrigated
Net water application: 0.22 × 11 × 0.65 area, and system efficiency. The calculation
= 1.6 inches per set. is described in the following pages.
Table 3. Water Application — Inches per Hour
Sprinkler gpm/Sprinkler
Spacing 2 3 4 5 6 7 8 9 10 11 12 15 18 20 25
30 x 30 0.21 0.32 0.43
30 x 50 0.25 0.32 0.38 0.44 0.51 0.57 0.64 0.70 0.76
40 x 40 0.18 0.24 0.30 0.36 0.42 0.48 0.54
40 x 60 0.20 0.24 0.28 0.32 0.36 0.40 0.44 0.48 0.60 0.72 0.80
50 x 60 0.19 0.22 0.26 0.29 0.32 0.35 0.39 0.48 0.58 0.64
60 x 60 0.21 0.24 0.27 0.29 0.32 0.40 0.48 0.53 0.67
60 x 80 0.20 0.22 0.24 0.30 0.36 0.40 0.50
www.attra.ncat.org ATTRA Page 3

4. Finding Flow Rate use the total design gpm of your system for
a flow estimate. Be aware, however, that
It is sometimes difficult to estimate flow
design numbers do not take into account
rates for surface irrigation systems, but
increased flow (sometimes significant) due
several methods are possible.
to nozzle wear and pressure variations.
• D itch or pipel i ne: Mea su re Divide the design gpm by the number
f low rates with one of the f low of operating sprinklers on your sprinkler
measuring devices described later system to fi nd the average gpm per sprin-
in this publication. kler. For pivots, use the design gpm for
• Furrow systems: Measure f low the entire pivot.
with one of the portable measur- A more accurate way to find the flow rate for
ing devices available. Or catch the your sprinkler system—especially if it’s an
flow to a single furrow in a bucket older system—is to conduct a simple bucket
of known capacity, and measure the test. (See Appendix.)
time it takes to fi ll the bucket. If you
know the total flow into a furrow
system, you can divide this amount
Finding Irrigated Area
by the number of furrows to find the For most surface irrigation systems, the irri-
flow rate into each furrow. gated area is simply the entire area of the
field. For furrow systems, you can use the
• Siphon tubes: Look up the f low length and spacing of the furrows to esti-
rate in a siphon tube head-discharge mate irrigated area. (See example below.)
chart.
For most sprinkler systems, fi nd the area
To calculate flow rate for most sprinkler
in square feet watered by one sprinkler,
systems, you’ll need to know the aver-
usually described as the distance, in feet,
age gpm per sprinkler. For center pivots,
between sprinklers on the line multiplied by
flow varies along the length of lateral pipe,
the distance, in feet, between mainline riser
and you’ll need to know the gpm for the
valves. Typical areas are 30 feet by 50 feet
entire pivot.
or 40 feet by 60 feet. (See Figure 1 for an
If your sprinkler system is relatively new example.) For pivots, use the entire swept
and the nozzles have little wear, you can area in acres and multiply by 43,560. (The
conversion of acres to square feet.)
Calculating Net Water
Application per Set
To calculate net water application in inches
per set for any irrigation system, use the
following general formula:
Net water application (inches) =
set time (hours) x flow rate (gpm) x 96.3 x system efficiency
irrigated area (sq. ft.)
Note: 96.3 is a conversion factor.
NCAT photo
Page 4 ATTRA Measuring and Conserving Irrigation Water

5. Wheel line, hand line, end tow: Use Wild flood: Use total area flooded
the average flow rate (gpm) for one nozzle. and total flow.
Example: Example:
12-hour set, 8 gpm per sprinkler, 40’x 60’ Seven 24-hour days, 800 gpm flow,
spacing, 65% system efficiency 40-acre field, 20% system efficiency
12 x 8 x 96.3 x 0.65 =2.5 inches net water 7 × 24 × 800 × 96.3 × 0.20 =1.5 inches net
40 x 60 application per set 40 x 43,560 water application
Center pivot system: Use the total Graded furrows: Use furrow length
pivot flow. and spacing.
Example: Example:
11-hour set, 10 gpm flow per furrow,
50-hour rotation, 900 gpm, 130-acre field 660-foot-long × 3-foot-wide furrows,
(= 5,662,800 ft²), 75% system efficiency 50% system efficiency
50 x 900 x 96.3 x .75 =0.6 inches net water 11 × 10 × 96.3 × 0.50 =2.7 inches net
5,662,800 application per set 3 × 660 water application
Note: The wheel line example above uses the fl ow
for one nozzle divided by the area covered by one
nozzle. The pivot formula uses the flow for the entire
pivot divided by the area covered by the entire pivot.
The result is the same—inches per set.
Stationary big gun sprinkler: Use
flow per sprinkler.
Example:
10-hour set, 78 gpm, 120’x 120’
spacing, 50% system efficiency
10 x 78 x 96.3 x 0.50 =2.6 inches net water
application per set
120 x 120
Traveling big gun sprinkler: Use
the following formula:
Net water gpm x 1.6 x efficiency (%)
application = SxW
where W = width between travel lanes in feet,
and S = travel speed in feet per minute (fpm).
Example:
300 feet between travel lanes, 0.4 fpm travel
speed, 400 gpm, 60% system efficiency
400 x 1.6 x 0.6 =3.2 inches net water
0.4 X 300 application
NCAT photo
www.attra.ncat.org ATTRA Page 5

6. Determining the Correct typically include one or more staff gages
(also spelled gauges), installed either on
Set Time the structure itself or in an adjacent still-
Use the same basic formula above to deter- ing well, to determine water depth. (A staff
mine how long it takes to apply a desired gage is simply a vertical staff—resembling
amount of water by inserting the amount an ordinary yardstick—marked with num-
of water you want to apply for “net water bers that indicate water depth.) Using a
application.” table for the specific size and type of struc-
ture, you look up the measured depth and
Set time hours = convert it to a flow rate. More expensive,
net water application (inches) x irrigated area (sq. ft.) but more accurate, electronic measuring
flow rate (gpm) x 96.3 x system efficiency devices are now available to offer continu-
ous flow measurement and recording.
Example:
Wheel line, 8 gpm per sprinkler, Most open channel flow measuring devices
you want to apply 1.2 inches, work only under limited conditions. A
40’x 60’ spacing, 65% system efficiency. structure suitable for a river or large canal
M
ost open will not be the best choice for a small ditch.
1.2 x 40 x 60 = 5.8 hours. Only a few of the more common methods to
channel
8 x 96.3 x .65 Round up to 6 hours measure flows on smaller canals, ditches,
flow mea- and farm turnouts are considered here. A
suring devices work comprehensive guide is the U.S. Bureau of
only under limited For surface irrigation systems, it may be Reclamation’s Water Measurement Manual,
conditions. easier to use the following extremely handy available on the Internet at www.usbr.gov/
formula: pmts/hydraulics_lab/pubs/wmm/index.htm.
To ensure accuracy, the measuring site
Set time hours = must meet a number of conditions:
gross water application (inches) x area irrigated (acres)
• The ditch or canal must have a shal-
flow rate (cfs)
low grade with a relatively straight
Surface Irrigation Example: upstream segment and uniform
Graded borders, 1.2 cfs flow, 10 acre field,
cross-section, little turbulence, and
desired gross water application 1.5 inches. quiet flow.
Correct set time (hours)= 1.5 x 10 = 12.5 hours
• Weirs require more slope than
1.2 flumes or submerged orifices.
• The location must not cause sedi-
ment loading, debris buildup, or
flooding of surrounding areas.
Measuring Flows In selecting a water measurement struc-
You can measure f lowing water in an ture, consider cost, accuracy, ease of mea-
open channel or pipeline using one of surement, construction and maintenance
the methods below. You can also mea- requirements, and state or local water laws
sure water with a simple bucket test at the and regulations.
point where sprinklers apply it to the field
Weirs are easy to construct, install, and
(See Appendix).
use, but require enough ditch slope so that
water can fall freely from the structure to
Measuring Open Channel Flow the downstream water surface. In the case
Open channel methods generally rely on of rectangular and trapezoidal weirs, water
a structure such as a weir, flume, or orifice flows through a sharp-edged rectangular
installed in the channel. These structures or trapezoidal notch. In the case of v-notch
Page 6 ATTRA Measuring and Conserving Irrigation Water

7. weirs, water flows through a sharp-edged Ramp flumes (also known as modified broad-
(usually) 90 degree-angled notch. This crested weirs) are accurate, cost less to build
weir is especially good at handling a wide than most other devices, and are simpler
range of flows. to construct.
Metal
Strip
90¡
Center Line
3H Side
View
Downstream
End
Ditch Bottom
Figure 4. Ramp Flume
Figure 2. V-Notch Weir
Submerged orifices are often used where
ditch slope is insufficient for weirs. They
Flumes are more complex structures than generally cost less than weirs and can fit into
weirs, and include a constricted throat sec- limited spaces, but are susceptible to trash
tion that requires careful construction and build-up. Water flowing through an orifice
installation. Flumes are used where ditch is discharged below the downstream water
and canal grades are relatively flat. They surface. For this
can still be relatively accurate even when dev ice to be
submerged. accurate, it must
be submerged.
Parshall flumes—one of the most common
H1
The meter gate, H2
types—require only about a quarter of a type of sub-
the ditch grade needed for weirs and can merged orifice,
accommodate a wide range of flows. Cut- can be used for
throat flumes are a “throatless” variation on farm turnouts.
the Parshall flume, resulting in simplified The gate can
construction. be used to mea-
sure flow, closed
to shut off flow,
or positioned at
various settings
to reduce or Figure 5. Submerged Orifice
increase flow.
Top View Choosing, installing, and using weirs,
flumes, and submerged orifices is not dif-
ficult. In order to get accurate results,
though, you need to install these devices
properly, maintain them regularly, use
proper measuring techniques, and use the
right calibration curves and tables. Your
Side View local NRCS, Extension, or soil and water
Figure 3. Parshall Flume
conservation district office may be able
to assist you.
www.attra.ncat.org ATTRA Page 7

8. Measuring Pipeline Flow • Don’t over-irrigate. Learn the water-
holding capacity of your soils, their
Flow in a pipeline can be measured very
allowable depletion, and the effective
accurately if the correct measuring device is
root depth and critical growth stages
installed and used properly. These devices
of your crops.
need periodic calibration and maintenance,
and water must be relatively (in some cases, • Focus irrigation on critical growth
very) clean. Accurate measurement requires stages. Depending on the crop,
full pipe flow. you’ll usually see one of two types of
responses to drought stress:
Related ATTRA Pipeline flow is measured by either intrusive
Publications devices (located inside the pipe or inserted 1. Seed crops, cereals, and oilseeds
are most sensitive to drought
through the pipe wall) or external devices.
Drought Resistant Soil stress during flowering or seed
Intrusive flow meters include Venturi, noz-
formation, and relatively insen-
Drought Resource zle, and orifice plate meters that measure
Guide sitive during early vegetative
flow through a constriction within the pipe.
growth. Irrigate enough at the
Energy Saving Tips None have moving parts. They require
onset of seed formation to carry
for Irrigators little maintenance in clean water and are
the crop through seed fill.
The Montana Irriga- installed directly in the pipeline.
tor’s Pocket Guide 2. Perennial crops grown pri-
Propeller meters use a multi-blade propeller marily for forage, and some root
Protecting Water positioned inside the pipe. Propeller meters crops, are relatively insensi-
Quality on Organic can pass some debris, but even moderate tive to moderate drought stress
Farms amounts can foul the blades. for short periods throughout
Soil Moisture Monitor- Pitot tubes are inserted into the side of a the growing season. They can
ing: Low-Cost Tools recover from stress periods with
and Methods
pipe. They require drilling a hole through
the pipe (allowing the insertion of the tube), little reduction in yield. Focus
Sustainable Irrigation making them less convenient and common on irrigating during periods of
(PowerPoint than propeller meters. maximum growth.
presentation)
Non-intrusive (external) flow meters send • Irrigate early in the season. Fill the
Sustainable Soil
ultrasonic or acoustic waves through a pipe root zone to field capacity before hot
Management
and take very accurate measurements of weather starts.
Doppler shift or transit time to calculate • Leave room in the soil for precipita-
flow rate. These devices are clamped onto tion. Crop residue and cover crops
the outside of the pipe wall (nothing is phys- help capture snow and rain and
ically inserted into the pipe) which makes reduce evaporation.
them extremely quick and convenient to • Aim for optimum rather than max-
use. Several types of ultrasonic meters are imum yield (i.e., the greatest yield
currently on the mar- with the least input).
ket. They are costly, in
the range of $1,500 to • Plant drought-tolerant crops or quick-
$10,000, although prices maturing crops that require most of
are dropping, and some their water early in the season.
training is required for • Reduce the amount of land you irri-
accurate measurements. gate and use the saved water on the
remainder, or reduce the amount of
water you apply over the whole irri-
Irrigating with gated area.
Limited Water • Irrigate every other furrow, switch-
Supplies ing at each irrigation. You’ll still get
When water supplies water to one side of each row, gener-
NCAT photo
are short: ally using far less water.
Page 8 ATTRA Measuring and Conserving Irrigation Water

9. References Production Services/Distribution
Kansas State University
NCAT Resources 26 Umberger Hall
Manhattan, KS 66506-3404
Drought Introduction. 2005. By Barbara Bellows. 785-532-5830
PowerPoint presentation. 22 p.
An introduction to droughts, impacts on soils, crops, Selection and Use of Water Meters for Irrigation
and animals with an overview of management prac- Water Measurement. 2003. By Melissa C. Baum,
tices to lessen the impacts of drought. Michael D. Dukes, and Dorota Z. Haman. University
of Florida, Institute of Food and Agricultural Sciences,
Drought Resistant Soil. 2002. By Gainesville, FL.
Preston Sullivan. ATTRA Publication, http://edis.ifas.ufl.edu/AE106
IP 169. 7 p. Descriptions, use, maintenance, and comparison of
Explains how organic matter can dramatically various flow-measuring devices.
increase the soil’s water storage capacity and how
ground cover increases the water infiltration rate while How Good Is Your Water Measurement? 1999. By
lowering soil water evaporation. Both practices reduce Robert Hill. University of Utah Cooperative
the severity of drought and the need for irrigation. Extension Service, Utah State University, Logan, UT.
http://extension.usu.edu/files/engrpubs/biewm01.html
Drought Resource Guide. 2005.
Open channel and pipeline devices, typical prices, and
By Barbara Bellows. 29 p.
sources of equipment. Phone 435-797-1000 to request
www.attra.ncat.org/attra-pub/drought_RL.html
a hard copy.
A comprehensive list of text and Web-base resources,
including links to climate monitoring information,
drought-tolerant plant lists, and drought disaster relief Further Resources
programs. State-specific drought information and U.S. Bureau of Reclamation. 2001. Water Mea-
drought programs are provided at the end of this surement Manual. U.S. Department of the Interior,
document. Washington, DC. 317 p.
The Montana Irrigator’s Pocket Guide. 2003. By USDA-Natural Resources Conservation Service. 1997.
Mike Morris, Vicki Lynne, Nancy Matheson, and Al NRCS Irrigation Guide. Natural Resources Conser-
Kurki. National Center for Appropriate Technology, vation Service, Washington, DC. 702 p.
Butte, Montana. 161 p. www.wcc.nrcs.usda.gov/nrcsirrig/irrig-handbooks-part
A take-to-the-field reference to help irrigators save 652.html
energy, water, and money, it includes guidelines for
water management, equipment maintenance, and
handy conversions and formulas. Get a free printed
Web Sites
copy by calling 800-346-9140 (toll-free). Irrigation Engineering Publications
From the University of Nebraska Institute of
Sustainable Irrigation. 2004. By Agriculture and Natural Resources.
Barbara Bellows. PowerPoint presentation. 46 p. http://ianrpubs.unl.edu/irrigation
Explains sustainable irrigation practices and methods Dozens of publications on irrigation management and
for protecting soil and water quality. hardware.
Other Publications Irrigation Training and Research
Center
Irrigation Water Measurement as From the BioResource and Agricultural Engineer-
a Management Tool. 2002. By Danny H. Rogers, ing Department at Cal Poly State University, San Luis
Gary Clark, and Mahbub Alam. Kansas State Univer- Obispo.
sity Agricultural Experiment Station and Cooperative www.itrc.org
Extension Service, Manhattan, KS. Extensive collection of publications, databases,
www.oznet.ksu.edu/library/ageng2/l878.pdf and links.
Tensiometer installation, use, and
troubleshooting.
Request a hard copy from:
www.attra.ncat.org ATTRA Page 9

10. Water Conserve – Water Conservation Portal For pivots:
A project of Ecological Internet, Inc. Step 1. Measure the flow of one sprinkler in each set
www.waterconserve.info of nozzle diameters along the pivot using the method
A water conservation portal and Internet search tool described for hand move, side roll, or linear move
that provides access to reviewed water conservation systems above.
news and information. Includes news stories,
discussion groups, and links. Seconds to Average gpm/ # of sprinklers Total gpm
fill bucket sprinkler in each set in each set
Wateright
From the Center for Irrigation Technology at California 300 ÷ sec = gpm x = gpm
State University, Fresno. 300 ÷ sec = gpm x = gpm
www.wateright.org
A “multi-function, educational resource for irrigation 300 ÷ sec = gpm x = gpm
water management.” Includes an energy use/cost Total Flow = gpm
calculator, guidelines for estimating fuel require-
ments, options for reducing energy use and costs, and
discussions of various other energy-related topics. Step 2. Estimate flow from the end gun using end gun
pressure and nozzle diameter from the table below.
Appendix: Finding Flow Rate = gpm
with a Bucket Test
For hand move, side roll, or linear move systems:
Measure the flow of one sprinkler per lateral,
Table 4. Estimated End Gun Flow in GPM
situated on relatively level ground. The selected sprinkler
should be about one-third of the way down the length Diameter of end gun nozzle (inches)
of the lateral from the mainline. Use a hose to direct PSI ½ ¾ 1 1½ 2
the flow into a five-gallon bucket. Using a stopwatch,
10 23.6 53.2 94.4 212 378
estimate the time it takes, in seconds, to fi ll the bucket.
For greater accuracy, take more than one reading per 20 33.4 75.3 134 300 534
sprinkler and average the times. Repeat for the other 30 40.9 92.2 164 368 654
sprinklers on other laterals. 40 47.2 106 189 425 755
50 52.8 119 211 485 845
Number of seconds to fill bucket = seconds
Avg gpm/sprinkler = 300 ÷ the number of seconds
Step 3. Add the results from Step 1 and Step 2 above
to calculate total flow for pivot.
300 ÷ seconds = gpm
Total flow per hand line or wheel line = gpm
= Avg gpm/sprinkler x # of sprinklers = gpm
Page 10 ATTRA Measuring and Conserving Irrigation Water

11. Notes
www.attra.ncat.org ATTRA Page 11

12. Measuring and Conserving Irrigation Water
By Mike Morris and Vicki Lynne
NCAT Energy Specialists
© 2006 NCAT
Paul Driscoll, Editor
Amy Smith, Production
This publication is available on the Web at:
www.attra.ncat.org/attra-pub/irrigation_water.html
or
www.attra.ncat.org/attra-pub/PDF/irrigation_water.pdf
IP 280
Slot 280
Version 040306
Page 12 ATTRA