Flood irrigation
is the oldest and most common irrigation system used in the world. Because it
is an old method, many people think it is an inefficient, but this is not
necessarily true. Given the proper conditions of soil type, slope, length of
water run, and flow rates, it can be a highly efficient. First, a shallow dam is raised
the entire perimeter of the area to
be watered. Water is then allowed to flow over the soil until
the dammed area is completely covered. This should
be used only if the area is level and the soil contains enough clay to
cause the water to spread out over the surface and
penetrate
slowly
and evenly. The soil must not
remain flooded with water for more than a few hours.
ADVANTAGES:
Useful where alkaline water
causes a buildup of salts to toxic levels in the soil. Flooding flushes down
the excess salts out of the soil.
Choosing
flood irrigation system
Flood
irrigation is generally well suited to mature orchards where the root zones are
widely dispersed and the orchard is almost completely canopied. It assures
better distribution than sprinklers whose patterns might be disrupted by trees,
and gives a more uniform wetted area than can be realistically accomplished by
drip emitters.
The
best systems consider soil type, slope, length of run and quantity of water
available as integral parts of an efficient system.
Factors
in system design
Flood
system designs can be adjusted to work to greater advantage. Grade or slope can
be controlled through land leveling; application width can also be controlled
using borders; another effective method for improving flood system efficiency
is controlling the length of the water run. The amount of water available to
any one border at any one time can also be regulated for flood irrigation
management.
All
these techniques are site determined. They can be adapted to almost any
conditions, but those conditions must be taken into consideration before the
system is designed. The amount of water applied can be measured using an
inexpensive flume made of two pieces of PVC pipe.
DISADVANTAGES:
Flooding
can waste water because it is easy to apply much more water than is required to
meet plant needs. Runoff is hard to avoid. Also, rapidly growing plants are
injured by the low oxygen levels present and fruits resting on flooded soil
stay wet, often resulting in rot.