ABE 1- MODULE 5 Flashcards
-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
-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
-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
-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
-consists of an intake structure or pumping station, a conveyance system, a distribution system, a field
application system, and a drainage system
IRRIGATION SYSTEM
-Soil type
-Slope and topography
-Climate
-Water (quality & quantity)
Natural conditions
Choosing an irrigation method:
-Natural conditions
-Type of crop
-Type of technology
-Required labor inputs
-Crop characteristics and compatibility
-Environmental requirements
Type of crop
never use sprinkler or drip method
high sediments
never use surface method and use overhead instead
high infiltration
never use surface method
high ET
never use sprinkler
strong wind
-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
-Man-animal labor
-Man-machine labor
Required labor inputs
-Costs and benefits (financial)
-Previous experience with irrigation
-Social considerations
-Environmental considerations
water is applied on the soil surface (by flooding the entire area) and allowing the water to infiltrate in the soil
SURFACE IRRIGATION METHODS
- water is applied in the root zone
SUBSURFACE IRRIGATION METHODS
OVERHEAD IRRIGATION
1.watering can
2. hose pipe
3.Sprinkler
(drip or trickle)
MICRO IRRIGATION
-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
-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
-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
-water is flooded without much control
- usually used if there is excessive amount of water
Wild flooding
- Schemes of water distribution
- Rotational distribution
Schemes of water distribution
-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
- watering can
- hose pipe
- 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
- Lined canal (non erodible)
- 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
- bottom slope (S)
◼ for non-erodible channels, the velocity
through the canal must be at least
minimum permissible velocity
