Irrigating Lawns
There is only one proven method for watering
lawn areas, through the use of popup spray heads.
Although subsurface trickle irrigation has
been developed for use in lawns, installation is costly and renovation
of the lawn soil is required in order for it to be effective.
Lawn grasses require considerably less water to
remain green and healthy than most people may think, but even distribution
of the applied water is essential. It is important to remember that a lawn
is not a single plant, but rather a collection of thousands (or tens of
thousands) of tiny individual plants, each with its own very localized
root system. Because of this, every square inch of the lawn must be covered
by the sprays. Attempting to compensate for gaps in coverage by watering
longer will not work as lateral (capillary) movement of absorbed water
through the soil is extremely limited and the un-watered areas will never
draw enough moisture to thrive. Instead, this will only result in wasting
water by flooding the areas of heavier spray. Overwatering of lawns will
lead to fungal diseases and de-oxygenating compaction of the soil.
The most important factors in maintaining water
use efficiency with regard to lawns are as follows:
System Design -
Coverage must be balanced over the whole lawn. Because most sprayheads
by design do not deliver much water close to the head itself, the location
of each head must be receiving spray from another adjacent head. This is
referred to as 'head-to-head coverage'. Two principle types of sprayheads
are used for lawn watering: fixed-arc sprays and gear
rotors.
Fixed-arc (fan) sprays are more versatile and provide more even coverage
than rotors, but considerably more heads are required. Rotors spray greater
distances by shooting a narrow stream of water while rotating, making them
more cost-effective for watering large, geometric lawns and playing fields,
but useless for lawn areas with single dimensions of less than 20'. Because
the two have different scheduling requirements. fixed-arc sprays and rotors
should never be combined on a single irrigation zone.
Sprayhead Adjustment - Almost
all sprayheads are adjustable and should be checked before being put into
use in the spring to avoid spraying walkways, roadways, walls and other
structures. This is a simple procedure which will greatly reduce water
waste.
Scheduling - Watering of lawns
too often or for too long each session is the single largest contributor
to irrigation water waste. The amount of water actually needed to keep
grass a healthy green is specific to the site, with soil type, slope, sun
exposure and proximity of large trees all being factors. All lawn areas
on a single property should therefore not simply be scheduled for the same
amount of watering, but should be adjusted individually. Zones of rotors,
because they are distributing the same amount of water as fixed-arc sprays
but over a greater area, may need to run up to 50% longer. Most importantly,
watering should always be scheduled for the early morning hours when
mains pressure is highest and water is not being immediately lost to evaporation.
