Em4885 irrigation management practices to protect ground water

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Contact the local WSU Cooperative Extension or SCS offices for advice and assistance.
Local agronomic consultants, irrigation supply centers, and agricultural engineers will also
know which systems are best adapted to specific situations.
IP 2.01.09 - Use Aerial Photography to Identify Patterns that Indicate
Problems with Irrigation/Drainage Management
Objective
Early identification of crop development problems, some of which may be due to poor
irrigation and drainage management.
Description
Aerial photography can be an aid in identifying overall problems in agriculture.
Soil streaks, weed infestations, areas of insect pressure or plant disease, and irrigation
and drainage problems may be readily indicated by aerial observation. Modern techniques
involve the use of infrared film and computer enhancement to increase the usefulness of
aerial photography. Information about available aerial photography services can be found
in local phone books or by contacting WSU Cooperative Extension or the SCS.
SECTION 2 - PRACTICES FOR SURFACE (FURROW/RILL,
BORDER STRIP) IRRIGATION SYSTEMS
Drought Advisory EM4828, Surface Irrigation Systems, published by WSU Cooperative
Extension is a discussion of achieving good distribution uniformity and application efficiency
with surface irrigation systems.
There are two variables that control how much water infiltrates during an irrigation using a
surface irrigation system, 1) the infiltration rate of the soil and 2) the opportunity time. The infiltration
rate is how fast water will soak into a soil. Infiltration rates usually change throughout a season
due to irrigations and cultivations and normally decrease continuously throughout an irrigation
(although most soils will reach what is known as a “basic intake rate” at some point in the irrigation).
Opportunity time is the amount of time that water is on the surface of the soil at a particular
point. If water is running in a furrow for 24 hours, then the top of the furrow has had 24 hours of
opportunity time. The bottom of the furrow has had something less than 24 hours because it takes
time for water to travel from the top of the furrow to the bottom.
There are three aspects of overall distribution uniformity with furrow/rill irrigation systems:
1) down-row uniformity, 2) cross-row uniformity, and 3) soils variability. They are depicted in
Figures 4-10, 11, and 12.
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