IRRIGATION PRINCIPLES. ERT 349 SOIL AND WATER ENGINEERING. Introduction. Importance of Irrigation. Definition “the supply of water to crops and landscaping plants by artificial means” Estimates of magnitude world-wide: 544 million acres (17% of land 1/3 of food production). Purpose.
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ERT 349 SOIL AND WATER ENGINEERING
- boom sprinkler systems: single boom (arm) has many nozzles)
- multiple sprinkler systems: side roll, center pivot etc.
- permanent systems, ex. orchard
- movement may be via hand, tractor or self-propelled
- border irrigation. Water - -introduced at one end of field and allowed to disperse and travel down to other end.
- furrow irrigation. Water introduced through tubes from canal directly into individual furrows.
- very permeable soil so that water can move upwards
- impermeable layer or natural water table near root zone
- low hazard due to salt accumulation since no leach provided by this irrigation method
Daily Water Use:peaks late in afternoon; very little water use at night
Alfalfa: Ft. Cobb, OK
June 26, 1986
Corn Water Use Pattern
Irrigation system must be able to meet peak water use rate or the crop may be lost.
ETc = Kc ETo
AW = (FCv-PWPv)Dr
AW = Available water
FC = volumetric field capacity
PWP = volumetric wilting point
Dr = depth of root zone or depth of layer of soil within the root zone
Refer to Table 15-2 pg. 337.Moisture AccountingSoil Water Reservoir
From Table 15-4
*From Figure 15-3 (pg 344) textbook
IR = [(ET - Pe)(1 + LR)] / Ea
1. Water Conveyance Efficiency:
2. Water Application Efficiency, Ea
3. Water Use Efficiency, Eu
(catch cans placed on a 5 ft x 5 ft grid)
de = effective depth of irrigation, (in. or mm)