PAES Irrigation Structures (Canal Structures, Irrigation Systems, Sprinkler Irrigation, Drip Irrigation, and Small Water Impounding System)

critical depth

depth of water flow where the energy content is at minimum hence, no other backwater forces areinvolved

drop

in-line canal structure designed to convey canal water from a higher level to a lower level, duly dissipating the excess energy resulting fromthe drop in elevation

elevated flume

water conveying conduit or trough which is supported on abutments by piers

equipment crossing

provision for passing of equipment and small machinery

invert

inside bottom or sill of t the conduit

inverted siphon

closed conduit designed to convey canal water in full and under pressure running condition, to convey canal water by gravity under roadways, railways, drainage channels and local depressions

road crossing

conveys canal water under roads or railroads

basin

field that is level in all directions, encompassed by a dike to prevent runoff, and provides an undirected flow of water onto the field

basin irrigation

type of surface irrigation where water is applied to the basin through a gap in the perimeter dike or adjacent ditch; water is retained until it infiltrates into the soil or the excess is drained off.

border irrigation

method of irrigation which makes use of parallel border strips where the water flows down the slope at a nearly uniform depth

border strip

area of land bounded by two border ridges or dikes that guide the irrigation stream from the inlet point of application to the ends of the strip

furrows

small parallel channels, made to carry water in order to irrigate the crop

furrow irrigation

method of irrigation where water runs through small parallel channels as it moves down the slope of the field

head ditch/ supply ditch

small channel along one part of a field that is used for distributing water in surface irrigation

surface irrigation system

application of water by gravity flow to the surface of the field. Either the entire field is flooded (basin irrigation) or the water is fed into small channels (furrows) or strips of land (borders)

Closed Single Basin

Water applied to an individual basin and all of that applied water is allowed to infiltrate. Each basin in the irrigation block is hydraulically independent. Water advances from the inflow point towards the downstream end of the basin in a regular pattern, which may be distorted by surface irregularities. Inflow is normally shutoff before the water reaches the downstream end of the basin

Multiple/ Sequential Basin

Each basin is irrigated separately by a supply channel running along the boundary with a number of adjacent basins. In each basin, the water level in the supply channel controls the water application. When a basin is irrigated, the water level in the channel is raised higher than the soil surface elevation and overflows onto the basin. When the irrigation is completed, the water level in the channel is lowered below the soil surface elevation of the basin and supply is diverted to the next basin. The excess water from the first basin drains back to the supply channel. The next basin is irrigated with the supply discharge plus the drainage water from the upstream basin (or basins)

Direct Method

Irrigation water is led directly from the field channel into the basin through siphons, spiles or bundbreaks.

Cascade Method

Irrigation water is supplied to the highest terrace, and then allowed to flow to a lower terrace and so on.

Open-end Border System

This is usually applied to large borders where the end borders are provided with openings to accommodate free flow of water for drainage

Blocked-end Border System

This is usually applied to small borders where the end borders restrict the further downward flow of water.

Corrugation Irrigation

The water flows down the slope in small furrows called rills which is used for germinating drill-seeded or broadcasted crops. No raised beds are used for crops

Zigzag Furrow

This type of furrow irrigation shall increase the length that the water must travel to reach the end of irrigation run thus, reducing the average slope and velocity of the water. This can be formed down and across the slope by machines.

average pressure

average sprinkler pressure of a lateral

design pressure

pressure required to overcome the elevation difference between the water source and the sprinkler nozzle, to counteract friction losses and to provide adequate pressure at the nozzle for good water distribution

distribution uniformity

numerical value on the uniformity of application for agricultural irrigation systems

irrigation period

time required to cover an area with one application of water

sprinkler irrigation

method of applying irrigation water similar to natural rainfall where water is distributed through a system of pipes by pumping and then sprayed into the air through sprinklers so that it breaks up into small water drops which fall to the ground

sprinkler spacing

distance between two sprinkler heads along the lateral

wetted diameter

diameter of the circular area wetted by the sprinkler when operating at a given pressure and no wind

Pump Unit

delivers water from the source to the pipe system at an adequate capacity

Filtration System

consists of screen openings considerably lower than the nozzle diameter to prevent nozzles from clogging

Sprinklers

device of various nozzle sizes which sprays water over the ground or crop.

Mainline and Submainlines

pipes which convey water from the pump to the laterals

Laterals

deliver water from the mainlines or submainlines to the sprinklers

Set System

operate with sprinklers set in a fixed position

Periodic-Move System

sprinklers that must be moved manually through a series of positions during the course of irrigation

Hand-Move System

composed of portable or buried pipe with valve outlets at intervals for attaching the portable laterals.

Side-roll lateral system

type of mechanical-move system where the lateral pipes are rigidly coupled and each joint of pipe is supported by a large wheel where the lateral line forms the axle for the wheels. This is mechanically moved by an engine mounted at the center of the line.

End-tow lateral system

type of mechanical-move system where it consists of rigidly coupled lateral pipe connected to a buried mainline positioned in the center of the field. Laterals are towed lengthwise over the mainline from one side to the other in an “s” form

Gun and boom sprinkler system

type of mechanical-move system where nozzles are attached to long discharge tubes and rotated by means of a rocker arm drive

Fixed System

sprinkler systems not requiring to be moved during the course of irrigation

Continuous Move System

sprinklers operate while moving in either a circular or straight path

Center-Pivot

sprinkles water from a continuously moving lateral pipeline. The self-propelled lateral is fixed at one end and rotates to irrigate a large cicular area. The fixed end of the lateral, called the pivot point is connected to the water supply.

Linear-Move

combine the structure and guidance system of a centerpivot lateral with a traveling water-feed system similar to a travelling sprinkler

Travelling

high capacity sprinkler fed with water through a flexible hose which is mounted on a self-powered chassis and travels along a straight line while watering

Impact sprinkler

water coming out of the nozzle is directed by the spoon at a 90- degree angle, forcing the arm away from the impact bridge. The arm spring, after absorbing this energy, returns the arm to its original position, which hits the bridge and causes the body to rotate

Rotor and gear rotating sprinkler

water coming out of the nozzle is directed into an offset channel on the rotor plate, which creates a reactionary drive force that turns the sprinkler

Stationary sprinkler

the water both from the sprinkler inlet and through the flow controller reaches the silicon tube, setting the tube in motion and water is spread on the field.

drip irrigation/ trickle irrigation

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

emitters

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

emitter spacing

spacing between emitters or emission points along a lateral line

lateral spacing

spacing between irrigation laterals

leaching

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

manifold

portion of the pipe network between the mainline and the laterals

manufacturer’s coefficient of variation/ Cv

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 200C

optimal emitter spacing

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

wetted widths

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

Control head

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

Pump unit

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

Main, submain lines and laterals

supply water from the control head into the fields which are usually made from PVC or polyethylene hose and should be buried below ground because they easily degrade when exposed to direct solar radiation

Manifold

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

Filter

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

Long–path

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.

Tortuous

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

Short-path

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

Orifice

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

Vortex

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

On-off flushing

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

Continuous flushing

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

On-line

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

In-line

intended for installation between laterals

active storage

volume of water stored in reservoir between the minimum water level and normal water level

dam

any barrier constructed to store water

dam height

vertical distance from lowest point of the ground line to the dam crest

dead storage

volume below the intake structure which is the sediment volume based on 25 years of accumulation in the reservoir

filter drain

dam component which prevents migration of small particles and screen off fine materials that flow with seepage water and prevent piping

homogeneous embankment

dam composed of a single kind of embankment material exclusive for slope protection

Karst topography

geological formation shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rocks such as limestone or dolomite

natural spillway

spillway which is not excavated such as natural draw, saddle or drainage way

normal storage elevation

maximum elevation the water surface which can be attained by the dam or reservoir without flow in the spillway

reservoir

part of the system that impounds the runoff

seepage line/ phreatic line

line with no filter arrangements where seepage occurs

spillway

channel which releases surplus or flood water which cannot be contained in the active storage space of the reservoir

storage capacity

total capacity at normal water surface elevation

structural height

vertical distance measured from the top of the dam down to the bedrock

upstream face

side of the embankment wetted by the impounded water

watershed

area which contributes runoff or drains water into the reservoir

water right

privilege granted by the government to use and appropriate water

well-protected reservoir

reservoir where the upper reaches of the basin is shielded by high mountain barriers

zoned embankment

dam consisting a central impervious core flanked between zones of more pervious materials

Homogeneous/Modified Homogeneous Type

This type of dam shall be considered if the supply of materials of low permeability such as sandy or silty clay and other clayey material is abundant. The embankment material must be sufficiently impervious to provide adequate water barrier.

Zoned Type

This type dam shall be considered if sufficient quantities of both pervious and impervious materials are available.