Page 104 - GRIHA Manual Volume II - Introduction to National Rating System
P. 104
96 Griha Manual: Volume 2
Figure 3 Spray-type sprinkler
Sprinkler with large guns
Gun sprinklers are large sprinklers that discharge high-flow rates at high pressures. Since water is
sprayed over greater distances, at greater heights, and at greater velocities, greater amounts of water
are typically lost to wind drift and evaporation than from solid set systems. Portable guns irrigate
circular land areas. They are moved from one location to the other, usually with some overlap of the
previously irrigated area. Because of non-uniform water applications where patterns overlap, and
because of the greater wind drift and evaporation losses, portable
guns typically have lower application efficiencies than solid set
systems. Travelling guns are self-propelled. They move slowly across
the field, irrigating rectangular strips of land. This continual motion
compensates for non-uniformity in the application pattern in the
direction of travel, resulting in greater uniformity in the direction
of travel than between the irrigated strips. Because of insufficient
overlap at start-up and at the end of a length of run, water is applied
more efficiently for long lengths of run than for short run lengths.
Travelling guns typically have greater application efficiencies than
portable guns because of the greater uniformity that occurs in the Figure 4 Gun sprinkler
direction of travel.
Seepage
Seepage irrigation is also referred to as ‘sub-irrigation’. This method utilizes either open ditches or
buried perforated tubing to maintain the water table at a desired level near the bottom or just
below the crop root zone. Seepage irrigation requires a shallow restrictive layer of soil that allows a
perched water table. Earlier seepage irrigation systems consisted of open ditch conveyance systems
as well as open ditches in the fields to maintain a given water table. In an effort to improve efficiency
of the system, the open ditch conveyance system can be changed to a semi-closed system where
the water is supplied at the head of the field ditches by underground main lines.
Crown lood
With this system, water furrows are filled with enough water to cause the water level to rise to the
tree trunks (crowns) on the beds. Water is left in the water furrows for a few hours for 2 days so that
it can move into the soil beds. The field ditches are then drained. Application efficiencies of crown
flood systems greatly depend on the soil hydraulic characteristics, permeability of restrictive layers,
Figure 3 Spray-type sprinkler
Sprinkler with large guns
Gun sprinklers are large sprinklers that discharge high-flow rates at high pressures. Since water is
sprayed over greater distances, at greater heights, and at greater velocities, greater amounts of water
are typically lost to wind drift and evaporation than from solid set systems. Portable guns irrigate
circular land areas. They are moved from one location to the other, usually with some overlap of the
previously irrigated area. Because of non-uniform water applications where patterns overlap, and
because of the greater wind drift and evaporation losses, portable
guns typically have lower application efficiencies than solid set
systems. Travelling guns are self-propelled. They move slowly across
the field, irrigating rectangular strips of land. This continual motion
compensates for non-uniformity in the application pattern in the
direction of travel, resulting in greater uniformity in the direction
of travel than between the irrigated strips. Because of insufficient
overlap at start-up and at the end of a length of run, water is applied
more efficiently for long lengths of run than for short run lengths.
Travelling guns typically have greater application efficiencies than
portable guns because of the greater uniformity that occurs in the Figure 4 Gun sprinkler
direction of travel.
Seepage
Seepage irrigation is also referred to as ‘sub-irrigation’. This method utilizes either open ditches or
buried perforated tubing to maintain the water table at a desired level near the bottom or just
below the crop root zone. Seepage irrigation requires a shallow restrictive layer of soil that allows a
perched water table. Earlier seepage irrigation systems consisted of open ditch conveyance systems
as well as open ditches in the fields to maintain a given water table. In an effort to improve efficiency
of the system, the open ditch conveyance system can be changed to a semi-closed system where
the water is supplied at the head of the field ditches by underground main lines.
Crown lood
With this system, water furrows are filled with enough water to cause the water level to rise to the
tree trunks (crowns) on the beds. Water is left in the water furrows for a few hours for 2 days so that
it can move into the soil beds. The field ditches are then drained. Application efficiencies of crown
flood systems greatly depend on the soil hydraulic characteristics, permeability of restrictive layers,
