Em4885 irrigation management practices to protect ground water

IP 2.03.06 - Modify Hand-Line and Side-Roll Sprinkle System Layouts to
Smaller Spacings and Lower Pressures if Wind is a Problem
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CHAPTER 4
Objective
Reduce the detrimental effects of wind on overlap uniformities by reducing the distance
water travels in the air and also creating larger droplets.
Description
This practice is another option for dealing with excess wind. Note that it will result in
higher labor costs as it entails more moves of the laterals. Lower pressures in a sprinkle
system equipped with standard nozzles will generally create larger water droplets and
lessen the distance water travels. The larger droplets are less likely to be moved around
by wind. The shorter lateral moves compensate for the smaller patterns.
IP 2.03.07 - Ensure That Center Pivot Sprinkler/Nozzle Packages
Are Matched to the Infiltration Rate of the Soil
Objective
Reduce transport of sediment and other potential pollutants to surface water supplies.
Description
The nature of center pivot sprinkle systems is such that the application rate of water varies
over the span of the pivot. That is, the application rates under the pivot near the center are
much lower than the rates under the span near the end. This is because the field area
covered by the outside portions of the center pivot are much greater than those covered
by the inside. And, since the pivot will cover those areas in the same amount of time
(one revolution), the amount of water applied per hour must be much greater at the
outer reaches of a pivot.
This is a particular problem for irrigation system designers. They must design a system
that will supply the required amount of water to maintain the crop but do so while not
creating excess runoff due to too high an application rate. The purpose of this Practice is to
ensure a design is used that is matched to the particular field, not just a standard package.