Drip Irrigation: An Introduction

Abstract

Drip irrigation is the slow, even application of low-pressure water to soil and plants using plastic tubing placed near the plants' root zone. It is an alternative to sprinkler or furrow methods of irrigating crops. Drip irrigation can be used for crops with high or low water demands. Why consider drip irrigation? Drip irrigation can help you use water efficiently. A well-designed drip irrigation system loses practically no water to runoff, deep percolation, or evaporation. Drip irrigation reduces water contact with crop leaves, stems, and fruit. Thus, conditions may be less favorable for disease development. Irrigation scheduling can be managed precisely to meet crop demands, holding the promise of increased yield and quality. Growers and irrigation professionals often refer to "subsurface drip irrigation," or SDI. When a drip tape or tube is buried below the soil surface, it is less vulnerable to damage during cultivation or weeding. With SDI, water use efficiency is maximized because there is even less evaporation or runoff. Agricultural chemicals can be applied more efficiently with drip irrigation. Since only the crop root zone is irrigated, nitrogen already in the soil is less subject to leaching losses, and applied fertilizer can be used more efficiently. In the case of insecticides, less product might be needed. Make sure the insecticide is labeled for application through drip irrigation. Additional advantages of drip irrigation include the following. ◆ Drip systems are adaptable to oddly shaped fields or those with uneven topography or soil texture; these specific factors must be considered when designing the drip system. Drip systems also can work well where other irrigation systems are inefficient because parts of the field have excessive infiltration, water puddling, or runoff. SuStainable agriculture techniqueS Drip irrigation tubing used to irrigate wine grapes. ◆ Drip irrigation can be helpful if water is scarce or expensive. Because evaporation, runoff, and deep percolation are reduced, and irrigation uniformity is improved, it is not necessary to "overwater" parts of a field to adequately irrigate the more difficult parts. ◆ Precise application of nutrients is possible using drip irrigation. Fertilizer costs and nitrate losses can be reduced. Nutrient applications can be better timed to meet plants' needs. ◆ Drip irrigation systems can be designed and managed so that the wheel traffic rows are dry enough to allow tractor operations at any time. Timely application of herbicides, insecticides, and fungicides is possible. ◆ Proven yield and quality responses to drip irrigation have been observed in onion, broccoli, cauliflower, lettuce, melon, tomato, and cotton. ◆ A drip irrigation system can be automated. For an example of automated drip irrigation, see the Malheur Experiment Station's 1998 onion drip irrigation trial results. (See "Additional resources," page 6.) There are some disadvantages to drip irrigation. For example: ◆ Drip irrigation systems typically cost 500to500 to 1,200 or more per acre. Part of the cost is a capital investment useful for several years, and part is annual. Systems can be more elaborate and costly than necessary. Growers new to drip irrigation might want to start with a simple system on a small acreage. ◆ Drip tape or tubing must be managed to avoid leaking or plugging. Drip emitters are easily plugged by silt or other particles not filtered out of the irrigation water. Emitter plugging also can be caused by algae growing in the tape or by chemical deposits at the emitter.

Full text

Clint Shock, director and professor, Malheur Experi-
ment Station, Oregon State University.
Drip irrigation provides slow, even application
of low-pressure water to soil and plants using
plastic tubing placed in or near the plants’ root
zone. It is an alternative to sprinkler or furrow
methods of irrigating crops. Drip irrigation can
be used for crops with high or low water demands.
Why consider drip irrigation?
Drip irrigation can help you use water
efciently. A well-designed drip irrigation system
loses practically no water to runoff, evaporation,
or deep percolation in silty soils. Drip irrigation
reduces water contact with crop leaves, stems,
and fruit. Thus, conditions may be less favorable
for disease development. Irrigation scheduling
can be managed precisely to meet crop demands,
holding the promise of increased yield and
quality.
Growers and irrigation professionals often
refer to “subsurface drip irrigation,” or SDI.
When a drip tape or tube is buried below the soil
surface, it is less vulnerable to damage due to UV
radiation, cultivation, or weeding. With SDI,
water use efciency is maximized because there
is even less evaporation or runoff.
Agricultural chemicals can be applied more
efciently through drip irrigation. Since only the
crop root zone is irrigated, nitrogen already in the
soil is less subject to leaching losses, and applied
fertilizer can be used more efciently. In the case
of insecticides, less product might be needed.
Make sure the insecticide is labeled for
application through drip irrigation, and follow the
label instructions.
Additional advantages of drip irrigation
include the following.
◆ Drip systems are adaptable to oddly shaped
elds or those with uneven topography or soil
texture; these specific factors must be
considered when designing the drip system.
Drip systems also can work well where other
irrigation systems are inefcient because parts
of the eld have excessive inltration, water
puddling, or runoff.
EM 8782 • Revised March 2013
Drip Irrigation:
An Introduction
C.C. Shock
SuStainable agriculture techniqueS
Drip irrigation tubing used to irrigate wine
grapes.

◆ Drip irrigation can be helpful if water is scarce
or expensive. Because evaporation, runoff, and
deep percolation are reduced, and irrigation
uniformity is improved, it is not necessary to
“overwater” parts of a field to adequately
irrigate the more difcult parts.
◆ Precise application of nutrients is possible
using drip irrigation. Fertilizer costs and nitrate
losses can be reduced. Nutrient applications
can be better timed to meet plants’ needs.
◆ Drip irrigation systems can be designed and
managed so that the wheel trafc rows are dry
enough to allow tractor operations at any time.
Timely application of herbicides, insecticides,
and fungicides is possible.
◆ Proven yield and quality responses are possible
through careful irrigation scheduling made
possible with drip irrigation. Yield and quality
benets have been observed in onion, hops,
broccoli, cauliower, lettuce, melon, tomato,
cotton, and other crops.
◆ A drip irrigation system can be automated. For
an example of automated drip irrigation, see
Shock, et al., 2011 (see “Additional
Resources”).
There are some disadvantages to drip irrigation.
For example:
◆ Drip irrigation systems typically have initial
costs of $1,200 to $1,700 per acre. This cost
range does not include the equipment to install
or retrieve the drip tape or hose in
nonpermanent systems. A drip system for use
on an annual vegetable crop such as onion will
cost about $1,200 per acre, with approximately
$900 in capital costs for pumps, ltration, and
water distribution, and $300 in recurring
annual costs for drip tape.
A drip system using drip tubing with in-line
emitters is more often used for grapes, hops,
orchards, etc. It will cost about $1,700 to
$2,100 per acre and can last 12 to 15 years.
Part of the large variability in the per-acre cost
of drip tubing is related to the distance between
plant rows. For example, grapes are planted in
rows closer than hops, so more tubing is used
per acre, leading to greater cost.
Hard hose with plug-in emitters is most
frequently used for landscape and nursery
applications. The cost per acre of these systems
varies widely, depending on their complexity.
Systems can be more elaborate and costly than
necessary. Growers new to drip irrigation
might want to start with a simple system on a
small acreage.
◆ Drip tape or tubing must be managed to avoid
leaking or plugging. Drip emitters are easily
plugged by silt or other particles not ltered
out of the irrigation water. Emitter plugging
also can be caused by algae growing in the tape
or by chemical deposits at the emitter.
Filtration, acid injection, and chlorine injection
remedies to these problems are addressed in
“System management and maintenance,”
page 5, and “Standard maintenance,” page 6.
Also see the website Maintenance of
microirrigation systems (see “Websites,”
page 6).
◆ You might need to redesign your weed control
program. Drip irrigation might be
unsatisfactory if herbicides need rainfall or
sprinkler irrigation for activation. However,
drip irrigation can reduce weed populations or
reduce weed problems in arid climates by
keeping much of the soil surface dry. Tape
depth must be chosen carefully to accommodate
crop rotations and for compatibility with
operations such as cultivation and weeding.
◆ Except in permanent installations, drip tape
causes extra cleanup costs after harvest. You’ll
need to plan for drip tape disposal, recycling,
or reuse.
Despite all of drip irrigation’s potential
benets, converting to drip irrigation can increase
production costs, especially where an irrigation
system already is in place. Ultimately, there must
be an economic advantage to drip irrigation to
make it worthwhile.
2

Components and design
A wide range of components and system
design options is available. The Digital Drip
Directory (see “Websites,” page 6) lists equipment
and suppliers. Drip tapes, tubes, and emitters vary
greatly in their specications, depending on the
manufacturer and product use (Table 1). The
distribution system, valves, and pumps must
match the supply requirements of the tape. Tape,
depth of tape placement, distance between tapes,
emitter spacing and flow, and irrigation
management all must be chosen carefully based
on crop water requirements and the soil’s
properties. Drip tubing, rather than drip tape,
usually is used for perennial crops such as grapes
or poplar trees.
The wetting pattern of water in the soil from
the drip irrigation tape or tube must reach plant
roots. Selection of emitter spacing and tape depth
depends on the crop root system and soil
properties. Seedling plants such as onions have
relatively small root systems, especially early in
the season.
Drip irrigation system design requires careful
engineering. Design must take into account the
effect of the land’s topography (slope and
contour) on pressure and ow requirements. Plan
for water distribution uniformity by carefully
considering the tape, irrigation lengths,
topography, and the need for periodic ushing of
the tape. Design vacuum relief valves into the
system as needed.
Table 1. Types of drip irrigation systems.
System type
Internal
diameter
(inches)
Wall
thickness
(mil)
Emitter
spacing
(inches)
Emitter
ow rate
(gal/h)
Drip tape 0.375–1.375 4–35 2–36 0.07–0.84
Tubing (drip
line) with in-line
emitters
0.410–0.800 23–47 12–60 0.40–1.80
Hard hose with
punch-in emitters
0.125–1.5* 29–125 custom 0.50–4.0*
*Larger diameter hose and higher rate microsprinkler emitters are available for hard hose systems.
When designing a drip system, rst identify
fairly similar irrigation zones. Irrigation zones
are based on factors such as topography, eld
length, soil texture, optimal tape run length, and
lter capacity. Irrigation system designers use
computer programs to analyze these factors to
design efficient drip systems. Once the drip
system is designed and installed, it is possible to
schedule irrigations to meet the unique needs of
the crop in each zone.
Consider power and water source limitations.
Have your water analyzed by a laboratory that is
qualied to evaluate emitter plugging hazards.
Water quality might create limitations and
increase system costs. Filters must be able to
handle worst-case scenarios. For excellent
resources on water quality assessment and lter
maintenance, see Filtration and Maintenance
Considerations for Subsurface Drip Irrigation
(SDI) Systems (“Other publications,” page 7).
Finally, be sure to include both injectors for
chemigation and ow meters to conrm system
performance.
Filters and pumps
Every trickle counts when you are battling a
water shortage. An ineffective or improperly
managed lter station can waste a lot of water and
threaten a drip system’s tness and accuracy.
In the western U.S., sand media lters have
been used extensively for microirrigation
3

systems. Screen filters and disk filters are
common as alternatives or for use in combination
with sand media lters.
Sand media filters provide filtration to
200 mesh, which is necessary to clean surface
water and water from open canals for drip
irrigation. These water sources pick up a lot of
fine grit and organic material, which must be
removed before the water passes through the drip
tape emitters.
Sand media filters are designed to be self-
cleaning through a “back-ush” mechanism. This
mechanism detects the drop in pressure due to the
accumulation of ltered particles. It then ushes
water back through the sand to dispose of clay,
silt, and organic particles.
Sand used for lters should be between sizes
16 and 20 to prevent excess back flushing.
Because clean water from one lter is needed to
back ush another lter, at least two sand media
lters are generally used. In addition to a sand
media filter, a screen filter can be used as a
prelter to remove larger organic debris before it
reaches the sand media lter, or as a secondary
lter before the irrigation water enters the drip
tube (Figure 1).
For best results, lters should remove particles
four times smaller than the emitter opening, as
particles may clump together and clog emitters.
Screen lters can act as a safeguard if the main
filters fail, or may act as the main filter if a
sufciently clear underground water source is
used.
Figure 1. Drip irrigation system with a prelter, pump station with backow prevention, and chemical
injection site. A pressure control valve is recommended to adjust the water pressure as desired before
it enters the drip lines. A water meter can be placed after the pressure control or between a solenoid
valve and each zone. An air vent provides vacuum relief. Vacuum relief is necessary between the solenoid
valve and the drip tapes to avoid suction of soil into the emitters when the system is shut off.
4
Sub main line
Drip line
Prefilter
(optional)
Pressure
relief
valve
Backflow
prevention
Back wash
Filters
Air vent
Pressure
control
Main line
Water meter
Drip line
Pressure-
reducing
solenoid
valve
ZONE 1
Pump
Chemical
injection
Sub main line
Flush
valves

System management and maintenance
If a drip hose system is used on the soil surface
for perennial crops over a number of years, the
drip hose should be lifted periodically so that
leaves, soil, and debris do not cover the hose. If
the drip hose is not lifted, roots can grow over the
hose, anchor it to the ground, and eventually
pinch off the ow of water.
Flow of water
Place a water ow meter between the solenoid
valve and each zone and record its gauge daily.
This provides a clear indication of how much
water was applied to each zone. Records of water
ow can be used to detect deviations from the
standard ow of the system, which may be caused
by leaks or clogged lines. The actual amount of
water applied recorded on the meter can be
compared with the estimated crop water use (crop
evapotranspiration) to help assure efcient water
management.
Watch for leaks
Leaks can occur unexpectedly as a result of
damage by insects, animals, or farming tools.
Systematically monitor the lines for physical
damage. Leaks in buried hose or tape are
generally difficult to detect. Ponding on the
surface often indicates a leak. Also, pressure
drop and/or ow increase can indicate leaks. It is
important to fix holes as soon as possible to
prevent uneven irrigation.
Chlorine clears clogged emitters
If the rate of water ow progressively declines
during the season, the tubes or tape may be slowly
plugging, resulting in severe damage to the crop.
In addition to maintaining the ltering stations,
regular ushing of the drip tube and application
of chlorine through the drip tube will help
minimize clogs. Once a month, flush the drip
lines by opening the far ends of a portion of the
tubes at a time and allowing the higher velocity
water to ush out the sediment.
Because algae growth and biological activity
in the tube or tape are especially high during
warmer months, chlorine usually is applied at
2-week intervals during these months.
If drip lines become plugged in spite of
maintenance, many cleaning products are
available through irrigation systems suppliers.
Choose a product appropriate for the specific
source of contamination.
Chemigation
Manage irrigation and fertilization together to
optimize efciency. Chemigation through drip
systems efciently delivers chemicals in the root
zone of the receiving plants. Because of the
precision of application, chemigation can be safer
and use less material. Several commercial
fertilizers and pesticides are labeled for delivery
by drip irrigation. Make sure injected products
are compatible with water to prevent chemical
precipitation and subsequent plugging of emitters.
Injection pumps with backflow prevention
devices are necessary to deliver the product
through the drip lines. These pumps allow for
suitable delivery rate control, while backflow
prevention protects both equipment and the water
supply from contamination. Remember that in
Oregon water belongs to the public, not to the
landowner. Other safety equipment may be
required; contact a drip irrigation system supplier
for details.
Fertilizer
Soil microorganisms convert nitrogen (N)
fertilizers to nitrate. Nitrate is water soluble,
available to plants, and subject to leaching loss.
One of the benets of drip irrigation is reduction
or prevention of nitrate loss.
Typically, when irrigation is monitored closely,
less N fertilizer is needed with drip irrigation
systems than with furrow irrigation systems
because the fertilizer is spoon-fed to the root
system and little is lost due to leaching. For
example, if a field is converted from furrow
irrigation to drip irrigation and the amount of N
fertilizer is not reduced, the crop may become
excessively leafy, which can inhibit curing and
5

increase harvest costs as well as losses. Plant
tissue analysis performed by a qualied analytical
lab can help you determine crop nutrition needs
during the season and tailor N fertilizer
applications to actual crop needs.
Fertilizer can be injected through the drip
system. Fertilizers containing sulfate, phosphate,
calcium, or anhydrous or aqua ammonium can
lead to solid chemical precipitation inside the drip
lines, which can block emitters. Obtain chemical
analysis of your irrigation water and seek
competent technical advice before injecting
chemical fertilizers into drip systems.
Placement of tape
Plan for seed emergence. The drip tape must
be close enough to the surface to germinate the
seed if necessary, or a portable sprinkler system
should be available. A tape tube 4 to 5 inches
deep has successfully germinated onion seeds in
silt loam soil. Tape at 12 inches failed to
uniformly germinate onions. Tape placement is
often deeper in other row crops.
Timing and rates
The total irrigation water requirement for crops
grown with a drip system is greatly reduced
compared to a surface ood system because water
can be applied much more efciently with drip
irrigation. For example, with furrow irrigation,
typically at least 4 acre-feet/acre/year of water are
applied to onion elds in the Treasure Valley of
eastern Oregon and southwestern Idaho.
Depending on the year, summer rainfall, and the
soil, 20 to 32 acre-inches/acre of water have been
needed to raise onions under drip irrigation in the
Treasure Valley.
Applying more water than plants need will
negate most of drip irrigation’s benets. The soil
will be excessively wet, promoting disease, weed
growth, and nitrate leaching.
To determine application rates, use
measurements of soil water and estimates of crop
water use (crop evapotranspiration, or “ET”). For
shallow-rooted crops, irrigate only to replace the
soil moisture decit in the top 12 inches of soil.
It usually is not necessary to exceed ET. Local
daily crop evapotranspiration estimates are
available for some U.S. Pacific Northwest
locations on the AgriMet website. For measuring
soil water, see Instrumentation for soil moisture
monitoring (“Websites,” page 7) and Irrigation
Monitoring Using Soil Water Tension (“OSU
Extension Service publications,” page 7). For
planning irrigation scheduling, see Irrigation
Scheduling. (OSU Extension Service
publications,” page 7).
Standard maintenance
Add chlorine or other chemicals to the drip line
periodically to kill bacteria and algae. Acid might
also be needed to dissolve calcium carbonates.
Be sure to follow chemical labels for safe
handling instructions. Acids and chlorine can be
very hazardous.
Filters must be managed and sand changed as
needed. Even with ltration, drip tape must be
flushed regularly. The frequency of flushing
depends on the amount and kinds of sedimentation
in the tape.
Other management factors
Root intrusion must be controlled for some
crops. Rodents must be controlled, especially
where drip tape is buried.
Additional resources
Websites
AgriMet—daily crop evapotranspiration
estimates for some U.S. Pacific Northwest
locations (http://www.usbr.gov/pn/agrimet/)
Digital Drip Directory—a list of equipment and
suppliers (http://www.trickle-l.com/new/
directory/)
Drip irrigation discussion group—search features
and discussions of all sorts of problems (http://
www.trickle-l.com)
How to nd irrigation information on the Internet
(http://www.trickle-l.com/new/onthenet)
6

Instrumentation for soil moisture monitoring
(http://www.cropinfo.net/AnnualReports/1997/
instrumentation.wq.php)
Kansas State University SDI website (http://www.
oznet.ksu.edu/sdi)
Maintenance of microirrigation systems (http://
ucanr.org/sites/Microirrigation)
Microirrigation for Sustainable Water Use.
Microirrigation Research Group W2128.
(http://www.cropinfo.net/W-128/w128.html)
OSU Extension Service Catalog (http://extension.
oregonstate.edu/catalog/)
OSU Extension Service publications
The following Oregon State University
Extension Service publications are available
online or for purchase at http://extension.
oregonstate.edu/catalog/.
Iida, C.L. and C.C. Shock. 2007. The Phosphorus
Dilemma, EM 8939-E.
Iida, C.L. and C.C. Shock. 2008. Make
Polyacrylamide Work for You, EM 8958-E.
Shock, C.C., B.M. Shock, and T. Welch. Revised
2013. Strategies for Reducing Irrigation Water
Use, EM 8783.
Shock, C.C., F.X. Wang, R. Flock, E. Feibert,
C.A. Shock, and A. Pereira. Revised 2013.
Irrigation Monitoring Using Soil Water
Tension, EM 8900.
Shock, C.C., R. Flock, E. Feibert, C.A. Shock,
and J. Klauzer. Revised 2013. Drip Irrigation
Guide for Onion Growers, EM 8901.
Shock, C.C., R. Flock, E. Feibert, A. Pereira, and
M. O’Neill. Revised 2013. Drip Irrigation
Guide for Growers of Hybrid Poplar, EM 8902.
Shock, C.C., F.X. Wang, R. Flock, E. Eldredge,
and A. Pereira. Revised 2013. Successful
Potato Irrigation Scheduling, EM 8911.
Shock, C.C., E. Feibert, L. Jensen, and J. Klauzer.
2010. Successful Onion Irrigation Scheduling,
SR 1097.
Smesrud, J., M. Hess, and J. Selker. Reprinted
2000. Western Oregon Irrigation Guides,
EM 8713.
Other publications
Alam, M., T.P. Trooien, F.R. Lamm, and
D.H. Rogers. 2002. Filtration and Maintenance
Considerations for Subsurface Drip Irrigation
(SDI) Systems. Manhattan, KS: Kansas State
University Agricultural Experiment Station
and Cooperative Extension Service.
http://www.ksre.ksu.edu/mil/Resources/
Subsurface%20Drip%20Irrigation/mf2361.pdf
Bisconer, I. 2011. Toro Micro-irrigation Owner’s
Manual. El Cajon, CA: The Toro Company.
http://media.toro.com/Documents/Agriculture/
ALT179_Owners_Manual_Complete.pdf
Burt, C.M., K. O’Connor, and T.A. Ruehr.1995.
Fertigation. California Polytechnic State
University.
Burt, C.M. and S.W. Styles. 2011. Drip and
Micro Irrigation Design and Management for
Trees, Vines, and Field Crops. California
Polytechnic State University. To order: The
Irrigation Training and Research Center,
California Polytechnic State University, San
Luis Obispo, CA 93407 (telephone 805-756-
2434; http://www.itrc.org/publications.htm).
Chemigation in Tree and Vine Micro Irrigation
Systems. University of California Irrigation
Program. Agriculture and Natural Resources
Publication Number 2159. http://anrcatalog.
ucdavis.edu
Hanson, Fipps, and Martin. 2000. Drip irrigation
of row crops: What is the state of the art? In:
Proceedings of the 4th Decennial Irrigation
Symposium. http://www.ksre.ksu.edu/sdi/
Abstracts/Drip Irrigation of Row Crops.htm
Hassan, F.A. 1998. Microirrigation Management
and Maintenance. Fresno, CA: Agro Industrial
7

Extension work is a cooperative program of Oregon State University, the U.S. Department of Agriculture, and Oregon counties. Oregon State
University Extension Service offers educational programs, activities, and materials without discrimination based on age, color, disability, gender
identity or expression, genetic information, marital status, national origin, race, religion, sex, sexual orientation, or veteran’s status. Oregon State
University Extension Service is an Equal Opportunity Employer.
Revised October 2006. Revised March 2013.
© 2013 Oregon State University.
Management. Available from Farouk A.
Hassan, Ph.D., irrigation and soils advisor,
Agro Industrial Management, P.O. Box 5632,
Fresno, CA 93755 (telephone 209-224-1618,;
fax 209-348-0721; e-mail fahassan@ aol.com).
Lamm, F.R., J.E. Ayars, and F.S. Nakayama
(eds.). 2007. Microirrigation for Crop
Production—Design, Operation and
Management. Elsevier Publications. http://
www.elsevier.com/books/microirrigation-for-
crop-production/lamm/978-0-444-50607-8
Rogers, D.H., F.R. Lamm, and M. Alam. 2003.
Subsurface Drip Irrigation Systems (SDI)
Water Quality Assessment Guidelines.
Manhattan, KS: Kansas State University
Agricultural Experiment Station and
Cooperative Extension Service. http://www.
ksre.ksu.edu/sdi/Reports/2003/mf2575.pdf
Schwankl, L. 1996. Micro-Irrigation of Trees and
Vines. 1996. University of California Irrigation
Program. Agriculture and Natural Resources
Publication Number 21599. http://anrcatalog.
ucdavis.edu
Shock, C.C., E.B.G. Feibert, L.D. Saunders,
L.B. Jensen, S.K. Mohan, R.S. Sampangi, and
H. Pappu. 2011. Management of onion cultural
practices to control the expression of Iris
Yellow Spot Virus. pp 23–41. In Shock, C.C.
(ed.). Oregon State University Agricultural
Experiment Station, Malheur Experiment
Station Annual Report 2010, Department of
Crop and Soil Science Ext/CrS 132. http://
www.cropinfo.net/AnnualReports/2010/
OnionIYSV.php
Van der Gulik, T. 1999. B.C. Trickle Irrigation
Manual. 1999. British Columbia Ministry of
Agriculture and Food, Resource Management
Branch. To order: Irrigation Association of
British Columbia, 2300 Woodstock Drive,
Abbotsford, BC, Canada, V3G 2E5 (telephone
604-859-8222).
Acknowledgments
Funding to help prepare this publication was
provided in part by an Oregon Watershed
Enhancement Board grant.
8