Figure 1

Typical Over-Irrigation of a Landscape

An Introduction to

Landscape Irrigation Simplified

Michael D. Stuver, P.E.

Frederick S. Liljegren, ASLA

Problem

Over-irrigation of landscapes is common

where lush, green landscapes are

sustained by irrigation. Estimates of the

amount of water used for landscape

irrigation typically range from 50 to 70

percent of the water used for urban

purposes. In the state of Utah, nearly

two thirds of residential water is used to

maintain landscapes. Preliminary 1

results of numerous water audits

conducted by Utah State University

Extension in several metropolitan areas

of Utah suggest that the typical

homeowner applies about twice as much

water as is needed each growing season. On many commercial or institutional 2

landscapes, three or four times as much water is applied as is needed. Nearly one third

of the urban water supply is wasted by over-irrigating landscapes. Anecdotal 3

information suggests that this problem is relatively typical in many areas where

landscapes are sustained by irrigation. 

Consequences of over-irrigation can have far-reaching effects. Existing urban water

supplies are being depleted sooner than expected. Existing distribution system capacity

is or will be over-taxed during the summer irrigation season resulting in possible system

failure. As a result, new water supplies and/or increased system capacity will be

expensive to obtain. Over-irrigation can also contribute to groundwater and surface

water contamination as excessive runoff and deep percolation carry fertilizers,

pesticides, and other chemicals into these water supplies. Prolonged runoff from overirrigation can weaken the foundation materials supporting concrete and asphalt

pavement resulting in expensive repairs. Further, many plant problems can be linked to

improper irrigation.

Experience shows the major factors that, individually or in combination, result in overirrigating landscapes include:

1. Irrigation systems that are poorly designed, maintained, and inefficient with

sprinklers improperly placed, out of adjustment, or in need of repair;

2. Irrigations that run off or soak past the depth of the plant roots;
2

3. Irrigations that occur more frequently than required by the landscape.

Informal surveys of homeowners and landscape managers participating in the Bureau of

Reclamation’s landscape irrigation workshops suggest that only about 10 percent of

those in attendance know how much water is being applied by their irrigation systems.

These informal observations have since been validated by a survey conducted for the

Utah Division of Water Resources. The survey found that about 96 percent of the

individuals surveyed lacked adequate information to irrigate their landscapes correctly.

Many homeowners think all sprinklers apply the same amount of water. Most know how

long the system runs but not how much water is applied. Further, the lack of

understanding the concept of uniform application results in the homeowner increasing

run times rather than properly addressing the causes of dry spots in the turf. By

watering to the needs of the dry spots, the rest of the turf is over watered.

Need

In evaluating the problems and causes of over-irrigation, three requirements, referred to

as the “Three S’s,” have been identified for achieving efficient landscape irrigation. 

These requirements are:

1. The System must apply water as evenly to the landscape as is practical.

2. The Setting of the irrigation run time should allow the sprinkler to eliminate runoff

while applying the correct amount of water.

3. The Schedule of each irrigation should meet actual plant water needs throughout the

growing season.

Unless all three S’s are satisfied to the greatest degree practical, inefficient irrigations

will continue. Contemporary efforts to promote more efficient landscape irrigation have

usually only focused on one or two of the S’s. Further, much of the water conservation

advice provided has missed its intended audience. As mentioned above, only about 10

percent of the homeowners and landscape managers know how much water their

irrigation systems are applying. For the other 90 percent, recommendations like “water

deeper less frequently” and “apply 1 inch of water every 4 days” have little or no

meaning. Thus, a different approach is needed to promote more efficient landscape

irrigation.

The Bureau of Reclamation (Reclamation), an agency of the U.S. Department of the

Interior that supplies water to farmers and communities throughout the West, is

committed to making sure scarce water resources are used as efficiently as possible.

The Upper Colorado Region of the Bureau of Reclamation recognized the need for

more tools and techniques to improve landscape irrigation efficiency in the major urban

areas served by its projects. Reclamation identified four basic needs:

1. A simple process to determine the irrigation system performance.
3

Figure 2

Sample LIS Handouts

Figure 3

LIS Video

2. A simple, non-technical process for irrigating correctly that can be understood by the

majority of the homeowners who have been missed in previous campaigns.

3. A more technical approach to proper irrigation that may be required by a limited

number of homeowners, the typical landscape manager, and other irrigation

professionals. This would be the group for whom the Irrigation Association’s

Certified Landscape Irrigation Audit is too complex or too expensive for normal use.

4. A simple to use, inexpensive tool for determining sprinkler system performance.

Solution

Reclamation has developed a simple process called “Landscape Irrigation Simplified” or

“LIS.” LIS addresses all three S’s. LIS provides procedures for determining system

performance, a non-technical process for irrigating home landscapes, and an

intermediate approach to fill the gap between the homeowner’s process and the

Irrigation Association’s Certified Landscape Irrigation Audits. 

LIS concepts have been validated by specialists from the

Utah State University (USU) Center for Water Efficient

Landscapes and the USU Extension Service. The USU

Extension Service County Offices now provide

Reclamation-prepared LIS handout materials (See

Figure 2) as the basis for irrigation recommendations to

local homeowners. Several local water purveyors are

also using Reclamation’s LIS handouts as part of their

water conservation campaigns. 

Reclamation partnered with USU

Extension Service, The Utah Water

Conservation Forum, and several

local organizations to prepare an 8-minute video entitled “It’s Easy

to Save Water” that describes how homeowners can efficiently

irrigate their yards (Figure 3). The video features weather

personalities from two local TV stations and a turf expert from the

USU Extension Service. The Utah Water Conservation Forum has

distributed the video to most municipalities and school libraries

through out the state.

Two major water conservancy districts, the Jordan Valley Water

Conservancy District and the Central Utah Water Conservancy

District, sponsor a program of providing water checks (simplified

water audits) for home, commercial, and institutional landscapes. 

The water checks are performed by USU Extension Service interns

and follow LIS procedures. Reclamation has helped train the

interns for the past three years. The LIS processes are described briefly below.
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Figure 6

Sprinkler system performance test in progress

The System. As previously mentioned, the

sprinkler system, whether permanently

installed or hand moved, must apply the

water as evenly as practical. The design,

installation, and maintenance of the

sprinkler system all affect how evenly the

sprinklers apply water. Sprinklers often

appear to be applying water evenly but

looks can be deceiving. The frequently

appearing dry spots illustrate this problem. 

Figure 4 shows an example of this problem. 

A sprinkler system with typical uniformity

applied the desired seasonal application of

30-inches but some areas only received 12-

inches of water while other areas received

42-inches of water. 

The typical “correction” for the problem is to

repeatedly increase the sprinkler run time until

the dry spots disappear. Figure 5 shows that

with the same sprinkler system, the dry spot

received the desired 30-inches of water but

some areas received as much as 105-inches

of water. The average application jumped

from 30-inches to over 75-inches. The only

way to know if the sprinkler is performing

properly is to measure its performance.

LIS provides a process for determining

sprinkler performance. Containers are

placed in a grid pattern on the turf. The

containers should be at least 3-feet from any

sprinkler. The sprinklers are run for a known

amount of time. A typical sprinkler

performance test is shown in Figure 6. The

sprinkler run time may be just a few minutes

or for the duration of the entire irrigation

event, depending upon the containers used. 

After the test, the depth of water in each

container is observed. Significant

differences in depth of water indicates either

too much or too little water was applied in

Figure 4

Distribution pattern for a sprinkler system

applying an annual application averaging 30-

inches in depth.

Figure 5

Distribution pattern for a typical sprinkler

system applying 30-inches to the “dry” spot.
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some areas. This indicates some repair work is needed before the sprinklers will apply

water evenly.

A more precise approach to determining sprinkler performance requires knowing the

measured depth of water in each container. The measured depths in the containers are

used to calculate the “Distribution Uniformity or DU” of the sprinkler system. A DU of

less than about 0.65 to 0.70 indicates problems with the sprinkler system. 

LIS helps locate and identify sprinkler problems and suggests methods for correcting the

problems. Surprisingly, most repairs are quite inexpensive and easy to fix. After repairs

have been made, the test should be re-run to verify that all problems have been fixed.

The Settings. The settings of the sprinkler controller or timer should allow the sprinklers

to apply the proper amount of water while minimizing or eliminating runoff. The root

zone depth, soil water holding capacity, allowable soil moisture depletion, sprinkler water

application rate, soil water infiltration rate, and the ground slope all combine to affect how

long the sprinklers should be run. A typical irrigation event would apply about 1⁄2-inch of

water. This depth, however, might vary depending upon the daily consumptive use of

the plant during the hottest part of the summer.

LIS suggests three methods for determining the correct run time. In Method #1,

containers are placed in a grid on the turf prior to a normal irrigation event. After the

irrigation has been completed, the amount of water collected in each container is

measured and compared with the appropriate amount of water, for example 1⁄2-inch. If

the amount is not correct, the run time is adjusted and the test repeated during the next

irrigation event. Adjustments may be required over the next two or three irrigation events

to get the correct application depth.

Method #2 involves marking the desired depth on the containers and placing them in a

grid pattern on the turf. The sprinklers are then started and timed to determine the

number of minutes required to fill the containers to the desired level. The run times

would be recorded or set on the sprinkler controller.

Method #3 involves calculating the correct run time. The calculation requires knowing

the average application depth determined during the evaluation of the sprinkler system

along with the length of time the test was run. This is the quickest and most precise

method for determining sprinkler run times.

Low soil infiltration rates or excessive ground slopes may cause water to runoff before

the irrigation application has finished. LIS provides a process for cycling the irrigations

using shorter run times separated with soak cycles. This practice allows the correct

amount of water to be applied while minimizing or eliminating runoff.

The Schedule. Individual irrigation events should be scheduled to meet local water

requirements of the plant. The plant variety, the amount of water applied at the last

irrigation, air temperature, relative humidity, wind velocity, and solar radiation all help to

control how frequently the plant needs to be irrigated. Typically, temperatures are the
6

coolest in the spring and fall so plant water needs are less during these times. Plants

may only need to be irrigated once every 7 to 10 days during the cooler seasons

whereas they may require irrigation every two or three days during the heat of the

summer. Irrigation schedules often vary from one climate zone to another.

A key component of LIS is the irrigation schedule tailored to local horticultural and

climatic conditions. Procedures have been developed for LIS that create daily

consumptive use estimates using local, long-term climate and evapotranspiration data

for the plants. Daily consumptive use estimates are the basis for developing detailed

irrigation schedules. Figure 7 shows a typical detailed irrigation schedule for three

different application amounts. The detailed schedule begins at the start of the growing

season and shows the recommended number of days between irrigations. It shows the

time period during which the recommended number of days applies. As temperatures

warm, the recommended number of days between irrigations is reduced by one day. 

The schedule shows the time period when this new recommended interval applies. The

schedule continues to show the changing recommended intervals and the applicable

time periods throughout the entire growing season. This schedule provides a high

degree of precision in scheduling irrigations throughout the growing season.

The high precision of the detailed irrigation schedule, however, is too complicated for

most homeowners and landscape managers. A more simplified schedule has been

prepared that shows, on a month-by-month basis, the recommended number of days

between irrigations for each month of the growing season. A typical Monthly Irrigation

Schedule is shown in Figure 8 for three application rates. This irrigation schedule allows

the homeowner to simply reset the number of days between irrigations at the beginning

of each month. The recommended intervals, when used in conjunction with a calendar,

can tell when to expect the next irrigation for manually operated systems.

The recommended irrigation schedules are based upon long-term, typically 30-year

average, climatic and evapotranspiration data. Hotter than normal temperatures could

require irrigating sooner than the schedule recommends. Likewise, cool periods or rain

could delay or eliminate a recommended irrigation. LIS encourages homeowners and

landscape irrigation practitioners to frequently check the conditions of the plants and

make any short-term adjustments in the irrigation schedule that might be required. Also,

LIS recommends that if dry spots are noted, the sprinkler system should be checked for

problems, the soil should be checked for abnormalities, and the plants should be

inspected for pests before automatically increasing the frequency of irrigations or

increasing the sprinkler run times.
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Detailed Irrigation Schedule

for

A Typical Location

0.5-inch Application 0.75-inch Application 1.0-inch Application

Start/End Dates Interval, days Start/End Dates Interval, days Start/End Dates Interval, days

04/01 - 04/02 10 04/01 - 04/02 14 04/01 18

04/03 - 04/07 9 04/03 - 04/06 13 04/02 - 04/04 17

04/08 - 04/13 8 04/07 - 04/10 12 04/05 - 04/07 16

04/14 - 04/20 7 04/11 - 04/14 11 04/08 - 04/11 15

04/21 - 04/29 6 04/15 - 04/20 10 04/12 - 04/15 14

04/30 - 05/12 5 04/21 - 04/26 9 04/16 - 04/19 13

05/13 - 06/04 4 04/27 - 05/04 8 04/20 - 04/24 12

06/05 - 08/09 3 05/05 - 05/14 7 04/25 - 04/29 11

08/10 - 08/29 4 05/15 - 05/29 6 04/30 - 05/06 10

08/30 - 09/09 5 05/30 - 08/14 5 05/07 - 05/14 9

09/10 - 09/16 6 08/15 - 08/26 6 05/15 - 05/25 8

09/17 - 09/20 7 08/27 - 09/03 7 05/26 - 06/13 7

09/21 - 09/24 8 09/04 - 09/09 8 06/14 - 07/28 6

09/25 - 09/28 9 09/10 - 09/13 9 07/29 - 08/15 7

09/29 - 09/30 10 09/14 - 09/17 10 08/16 - 08/24 8

10/01 - 10/03 11 09/18 - 09/20 11 08/25 - 08/31 9

10/04 - 10/05 12 09/21 - 09/22 12 09/01 - 09/04 10

10/06 13 09/23 - 09/24 13 09/05 - 09/08 11

10/07 - 10/08 14 09/25 - 09/26 14 09/09 - 09/11 12

10/09 - 10/11 15 09/27 - 09/28 15 09/12 - 09/14 13

10/12 - 10/14 16 09/29 16 09/15 - 09/16 14

10/15 - 10/31 17 09/30 17 09/17 - 09/18 15

10/01 18 09/19 - 09/20 16

10/02 - 10/03 19 09/21 17

10/04 20 09/22 - 09/23 18

10/05 - 10/06 21 09/24 19

10/07 22 09/25 20

10/08 - 10/31 23 09/26 21

09/27 22

09/28 23

09/29 24

09/30 25

10/01 26

10/02 27

10/03 - 10/31 28

Figure 7

Typical Detailed Irrigation Schedule showing irrigation intervals for three application rates
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Figure 7

Performance evaluation cups - Professional Model

and Institutional/Homeowners Model, L-R.

Monthly Irrigation Schedule for A Typical Location

Month

Irrigation Intervals

1/2" Application 3/4" Application 1" Application

March --- --- ---

April Once every 6 days Once every 8 days Once every 11 days

May Once every 4 days Once every 6 days Once every 8 days

June Once every 3 days Once every 5 days Once every 6 days

July Once every 3 days Once every 5 days Once every 6 days

August Once every 3 days Once every 5 days Once every 7 days

September Once every 6 days Once every 8 days Once every 10 days

October Once every 10 days Once every 18 days Once every 26 days

Figure 8

Typical Monthly Turf Irrigation Schedule for Three Application Rates

Performance Evaluation Cups. The most

difficult part of applying good landscape

irrigation practices has been getting good

sprinkler system performance information. 

The Bureau of Reclamation has designed

(U.S. Patent No. 6,779,399) two self standing,

direct reading, water measuring cups for

measuring sprinkler system performance.

The cups, made of durable, clarified

polypropylene plastic, are designed to

simplify the process of assessing sprinkler

system performance. Both cups are selfstacking to ease transport and storage of the

cups. The self-standing feature provided by

the three attached legs simplify deployment

and retrieval of the cups during a sprinkler

evaluation test. The direct reading of application depths eliminates most of the

calculations associated with other measuring devices used to assess sprinkler system

performance.

The Professional Model is 6 3/4-inches tall with a 4 1/4-inch diameter opening. It has

three attached legs that flare outward to form a 6 1/2-inch diameter base. Ten cups form

a stack 12 3/4-inches tall. Each additional cup adds 9/16-inch to the stack. This cup

measures sprinkler application depth in inches or centimeters and volume in milliliters. It

is a low volume cup with high resolution measuring scales used primarily by landscape

irrigation professionals for short duration tests. The three measuring scales

accommodate world-wide use of the cups.
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The smaller cup (the Institutional/Homeowners Model) is 5-inches tall with a 3-inch

opening. Its three attached legs flare out to form a 5-inch diameter base. A stack of ten

cups is 9-inches high. Each additional cup adds 1/2-inch to the stack. This cup is a

higher volume, lower resolution cup than the Professional Model. However, there is very

little practical difference in the resolution of the two cups. This smaller cup is used for

measuring the application of a full irrigation event. This cup only reads application depth

in inches. It is the choice of the institutional landscape practitioner who is restricted to

checking the performance of the sprinkler system during normally scheduled irrigation

events and of the homeowner.

Contacts

Michael D. Stuver, P.E.

US Bureau of Reclamation

125 South State Street, Room 6103

Salt Lake City, Utah 84138-1147

(801) 524-3745

mstuver@uc.usbr.gov

Frederick S. Liljegren, ASLA

US Bureau of Reclamation

125 South State Street, Room 6103

Salt Lake City, Utah 84138-1147

(801) 524-3765

fliljegren@uc.usbr.gov

References

Utah Division of Water Resources. “Utah’s Water Resources: Planning for the 1

Future,” Utah State Water Plan, 2001.

Jackson, Prof. Earl K. Utah State University Cooperative Extension Service. 

2

Personal Contact, 2000.

Jackson, Prof. Earl K. and Sarah A. Gedge. Water Audit Summary 2000. Utah State 3

University Cooperative Extension Service for Salt Lake County. 2001.

Utah Agricultural Experiment Station. Consumptive Use of Irrigated Crops in Utah, 4

Research Report 145. Utah State University. Logan, Utah. 1994 & 1998.