PNS/BAFS/PAES 224:2017

Design of a Pressurized Irrigation System – Part B: Drip Irrigation

PNS/BAFS/PAES 224:2017

involves dripping water onto the soil at very low rates (2-20 L/h) from the emitters where water is applied close to plants so that only part of the soil in which the roots grow is wetted

drip irrigation or trickle irrigation

applicator used in drip, subsurface, or bubbler irrigation designed to dissipate pressure and to discharge a small uniform flow or trickle of water at a constant rate that does not vary significantly because of minor differences in pressure

emitters

spacing between emitters or emission points along a lateral line

emitter spacing

deep percolation of water beyond the root zone of plants, resulting in loss of salts or nutrients

leaching

portion of the pipe network between the mainline and the laterals

manifold

measure of the variability of discharge of a random sample of a given make, model and size of emitter, as provided by the manufacturer and before any field operations or aging has taken place determined through a discharge test of a sample of 50 emitters under a set pressure at 20 degree C

manufacturer’s coefficient of variation of CV

manufacturer’s coefficient of variation discharge test sampling size

50 emitters

manufacturer’s coefficient of variation discharge test temperature

20 degrees C

drip emitter spacing which is 80% of the wetted diameter estimated from field tests

optimal emitter spacing

optimal emitter spacing

80% of wetted diamter

width of the strip that would be wetted by a row of emitters spaced at their optimal spacing along a single lateral line

wetted width

consists of valves to control the discharge and pressure in the entire system which may have filters and a a fertilizer or nutrient tank.

control head

takes water from the source and provides the right pressure for delivery into the pipe system

pump unit

contains filters, pressure regulators, air and/or vacuum relief valves

manifold

removes particle to prevent emitter clogging where its net diameter is smaller than one-tenth to one-fouth of the emitter opening diameter.

filter

It is the ratio of the electrical conductivity of irrigation water to the electrical conductivity of saturated soil extract that will reduce the crop yield to zero

leaching Requirement Ratio

Emitter Discharge Exponent for Fully-compensating emitter

0

Emitter Discharge Exponent for Long-path emitter

0.7-0.8

Emitter Discharge Exponent for Tortuous-path emitter

0.5.-0.7

Emitter Discharge Exponent for Orifice type emitter

0.5

Emitter Discharge Exponent for Vortex emitter

0.4

Temperature and Discharge Relationship – as an emitter is subjected to a higher temperature, discharge increases as well, except for ______

vortex-type emitter

emitter: water is routed through a long, narrow passage at laminar flow to reduce the water pressure and to create a more uniform flow; flow areas: 1 mm2 to 4.5 mm2.

long-path emitter

emitter: have relatively long flow paths with larger path cross-section with turbulent flow regime

Tortuous-path emitter

emitter: almost similar with long-path emitters but with shorter water path; ideal for use in very low pressure systems

short-path emitter

emitter: the fully turbulent jet emitted at the outlet of the emitter is broken and converted into drop by drop flow; flow area: 0.2 mm2 to 0.35 mm2

orifice emitter

emitter: its flow path is a round cell that causes circular flow. The fast rotational motion creates a vortex which results to higher head losses that allow for larger openings

vortex emitter

emitter: flushes for a few moments each time the system is started and again when turned off

On-off flushing emitter

emitter: eject large particles during operation since this type has relatively large-diameter flexible orifices in series to dissipate pressure

continuous flushing emitter

emitter: intended for direct or indirect installation in the wall of the irrigation lateral

on-line emitter

emitter: intended for installation between laterals

in-line emitter

emitter: water is discharged from closely spaced perforations, emitters or a porous wall along the lateral line

line-source emitter

emitter: water is discharged from emission points that are individually and relatively widely spaced, usually over 1 m

point-source emitter