ABE 1- MODULE 5 Flashcards by Mia Daniella Cayas

-the controlled application of water to arable lands in order to supply crops with the water requirements not satisfied by natural precipitation (NEH, 1991)

-the application of water to soil for the purpose of supplying the moisture essential for plant growth (Hansen, 1979)

IRRIGATION

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-the application of water to soil for any of the following purposes (Hansen, 1979):
- provide crop insurance against short duration crops
- cool the soil and atmosphere, thereby making more
-favorable environment for plant growth
- washout or dilute salts in the soil
- soften tillage pans and clods

IRRIGATION

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-the artificial application of water onto a piece of cropland in sufficient amount and proper time to
promote a favorable rootzone environment and to supply the optimum plant water requirement for good growth and yield

IRRIGATION

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-a manmade water management system, which is required to fulfill the water demands of the crop during
less rainfall
-designed to maximize efficiencies and minimize labor and capital requirements

IRRIGATION SYSTEM

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-consists of an intake structure or pumping station, a conveyance system, a distribution system, a field
application system, and a drainage system

IRRIGATION SYSTEM

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-Soil type
-Slope and topography
-Climate
-Water (quality & quantity)

Natural conditions

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Choosing an irrigation method:

-Natural conditions
-Type of crop
-Type of technology
-Required labor inputs

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-Crop characteristics and compatibility
-Environmental requirements

Type of crop

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never use sprinkler or drip method

high sediments

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never use surface method and use overhead instead

high infiltration

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never use surface method

high ET

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never use sprinkler

strong wind

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-Availability of the system
-Capital investment per capital per hectare
-Operation of the system (technical know-how)
-Maintenance of the system (technical know-how)

Type of technology

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-Man-animal labor
-Man-machine labor

Required labor inputs

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-Costs and benefits (financial)
-Previous experience with irrigation
-Social considerations
-Environmental considerations

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water is applied on the soil surface (by flooding the entire area) and allowing the water to infiltrate in the soil

SURFACE IRRIGATION METHODS

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water is applied in the root zone

SUBSURFACE IRRIGATION METHODS

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OVERHEAD IRRIGATION

1.watering can
2. hose pipe
3.Sprinkler

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(drip or trickle)

MICRO IRRIGATION

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-are horizontal, flat plots of
land, surrounded by small
dykes or bunds
-the banks prevent the water
from flowing to the
surrounding fields; water is
held in the basin at the
desired depth for the
required time
-commonly used for rice
grown on flat lands or in
terraces on hillsides

Basin

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-the field to be irrigated is divided
into strips (also called borders or
borderstrips) by parallel dykes or
border ridges
-water is turned into each strip
through a head gate and flows
downhill the length of the strip
-requires that land be divided into
strips 10-20 m wide and 100-400 m
long

Border

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-furrows are narrow ditches
dug on the field between the
rows of crops
-water runs along the
furrows as it moves down
the slope of the field narrow
ditch between row of plants
-widely used for row crops

Furrow/Corrugation

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-water is flooded without much control
- usually used if there is excessive amount of water

Wild flooding

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Schemes of water distribution
Rotational distribution

Schemes of water distribution

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-water is supplied continuously to all the canals from the primary canal up to the farm ditches and the paddy fields

Simultaneous or continuous distribution

-the supply of water is rotated to the different areas of any of the following practices: -rotation by section along the main canal -rotation by section along the laterals -rotation by section along the sublateral

Rotational distribution

Wherever or whenever water supplies are abundant, farmers are free to use water __________. The practice of supply at will is common in tropical and even in semi-arid countries during the rainy season -- but is generally of little use in large-scale projects.

at will

If water is scarce, __________________, or ______________________is used to ensure equitable distribution. Where the flow pattern is predictable and not too variable in the medium-term, say a few weeks, a common practice is to rotate the flows among individuals or farmer groups.

-time sharing -rationing

- water is applied in the root zone

SUBSURFACE IRRIGATION METHODS

natural subirrigation also known as...

(open ditches)

artificial subirrigation also known as...

(buried perforated pipes)

OVERHEAD IRRIGATION

1. watering can 2. hose pipe 3. Sprinkler

is a versatile means of applying water to any crop, soil, and topographic condition.

Sprinkler irrigation

-use pump and piped systems and the water is led to the field through a pipe in which the water is under pressure -distribute water uniformly through an artificial rainfall -the spraying is accomplished by using several rotating sprinkler heads or spray nozzles

SPRINKLER IRRIGATION SYSTEMS

It is particularly popular in ________________ because: Surface ditches and prior land preparation are not necessary for its operation

humid regions

Pipes are easily transported and provide no obstruction to farm operations when irrigation is not needed

SPRINKLER IRRIGATION SYSTEMS

_______________ is particularly popular in humid regions because: Surface ditches and prior land preparation are not necessary for its operation

SPRINKLER IRRIGATION SYSTEMS

It is suitable for sandy soils or any other soil and topographic condition where surface irrigation may be inefficient or expensive, or where erosion may be particularly hazardous.

SPRINKLER IRRIGATION SYSTEMS

Low rates and amounts of water may be applied; such are required for seed germination, frost protection, and cooling of crops in hot weather.

SPRINKLER IRRIGATION SYSTEMS

Fertilizers and soil amendments may be dissolved in the water and applied through the irrigation system.

SPRINKLER IRRIGATION SYSTEMS

The major disadvantages of sprinkling systems are the __________________ and the ____________________ compared to surface methods.

-high investment cost -high operating cost

-structures used to properly measure, regulate and distribute water from the point of diversion to the point of terminal use -structures used to supply water at the right time and right quantity

IRRIGATION STRUCTURES

General Classes of Irrigation Structures

-permanent structures -temporary structures

Classification based on function: -diversion dams -check gates

Classification based on function: diversion structures

-weirs -parshall flumes

discharge measurement structures

Classification based on function: -headgates -turnouts -offtakes

discharge regulating structures

Classification based on function: flow dividing structures (distribution structures)

division boxes

Classification based on function: miscellaneous structures (conveyance structures)

-inverted siphons -flumes -crossings -drops/chute -underground pipes -tunnels

-a structure built across a river or stream for diverting the streamflow into a canal -it has a headgate for regulating the entry of water into the canal

DIVERSION DAMS

-structures installed at the head of conveyance canals or main canals to regulate the amount of water to be distributed

HEADGATES or HEAD REGULATORS

-also known as rubber sluice, barrage, dam rubber or rubber dam -made of high-strength synthetic fiber fabric force skeleton, internal and external coating rubber for the protective layer, processed into tape, and then its anchoring on the floor as a closed-shaped dam bag -Crest can overflow, and can adjust the dam needed to control the water level upstream, in order to play for irrigation, power generation, navigation, flood, tidal and other benefits

RUBBER DAMS

constructed mainly dam bag, anchoring section, the control section, the base portion and pump.

Structure of Rubber dam

Low energy consumption and the absence of mechanical parts make rubber dams a green technology. The principle of rubber dam operation reduces the need for oils and lubricants to zero. Especially water-filled rubber dams use hydrostatic pressure to erect the barrier. By pumping river water into a gravity shaft system the rubber dam is filled. Thus the energy consumption is defined by the pumping rate or filling time you want to achieve. Moreover the amount of energy needed for production of the dam itself is far less compared with equivalent traditional steel weirs.

Environmentally friendly rubber dams

A concrete structure usually built along the bank of the a river or stream and which draws water to be channeled into an irrigation system

INTAKE STRUCTURES

-structures installed at the secondary or tertiary canals to regulate the amount of water to be distributed

SECONDARY OR TERTIARY GATES

-structures used to raise the upstream water level in a canal above its natural level during periods of low discharges to enable water to flow to the head works of the different canals branching from the main canal, laterals or sublaterals

CHECK GATES or CROSS REGULATORS

serve as an outlet of water in irrigation canals whereby water passes through and discharges into the main farm ditch or service area

TURNOUTS

a rectangular structure which is usually built along the main farm ditch to divide and distribute the flow to the supplementary farm ditches

DIVISION BOXES

-structures installed at the downstream end of a farm ditch to check the direct flow of excess irrigation water into the drainage canals -it is consists of a fall structure combined with a pipe culvert under the canal embankment

END CHECK

flow measuring structures that are placed across the open channel to constrict the flow and allow it to pass over the crest

WEIRS

-an open channel measuring structure in which canal water flows over a wide, flat converging section that widens at the outlet end

PARSHALL FLUMES

a structure for carrying water under pressure by gravity beneath roads, railroads, rivers or streams, various types of drainage channels and depressions

INVERTED SIPHONS

a structure used to convey irrigation water across and above natural depressions such as rivers or creeks

Elevated flume

-usually a rectangular concrete trough supported on a bench excavated into a hillside and through which water flows into an adjoining canal

Bench flume

-a combination siphon and flume that conveys water across a depression, drainage canal or stream usually from a higher to a lower opposite bank; usually a closed rectangular reinforced concrete conduit supported above by the ground columns or piers

SI-flume

-structure constructed across irrigation canals for traffic crossing by man, animal, cart or vehicles

ROAD CROSSING

-structures used to conduct water from a higher to a lower elevation and to diffuse the force of the falling water; -constructed on steeply sloping land to prevent channel scouring and erosion -the inlet of the structure also serves as a control to regulate the water depth in the canal upstream

DROPS or CHUTES

can be a natural channel like that of a river, or an artificial channel like that of an irrigation ditch or partially full pipes

Open channel

TYPES OF CANAL

1. Lined canal (non erodible) 2. Earth canal (erodible)

FLOW MEASUREMENT EQUATION

Q = V x A Q - volumetric flow rate or discharge (m3/s, ft3/s, lps, gpm ) Vave - mean velocity of flow (m/s, ft/s) A - wetted cross sectional area perpendicular to the direction of flow (m2, ft2 )

The velocity of flow is ________ at a little distance below the water surface. The shape of the velocity profile depends on the ___________________.

-maximum -channel roughness

◼ rate of removal of excess water necessary to provide a certain degree of crop protection ◼ used for surface drainage, subsurface drainage, and combination of the two

Drainage Coefficient

◼ rate of removal of excess water necessary to provide a certain degree of crop protection ◼ used for surface drainage, subsurface drainage, and combination of the two

Drainage Coefficient

◼ nature of materials forming the channel

roughness coefficient (n)

based on the angle of repose property of the soil

side slope (z)

◼ topography and head loss consideration

4. bottom slope (S)

◼ for non-erodible channels, the velocity through the canal must be at least

minimum permissible velocity