Methods of irrigation
application and systems
application
River
Lateral canal
Supplementary Farm Ditch
Main (or Diversion) Canal
Main Farm Ditch
Dam
TYPICAL COMPONENTS OF AN IRRIGATION SYSTEM
Factors to be considered in
designing an irrigation system
1.Water source (kind & location), quantity,
quality
2.Soil-water-plant relations (drainage,
fertilization, crop, soil properties)
General Objective of Irrigation:
To supply the essential moisture
for plant growth
Gravitational Water
Superflous
Water Saturation Point
Field Capacity
Available Readily Available Moisture
Moisture
Wilting Point
DESIGN PARAMETERS TO BE QUANTIFIED:
1.Soil Texture Data – soil depth, field capacity, wilting
point, available moisture, infiltration rate
2.Crop Data – root depth, ET
3.Water Data – water source location, kind and
quantity; irrigation application time, frequency, &
period
4.Management Data – moisture allowed deficit
AM = FC – WP
As = ρb /ρw
ρb = soil bulk density
ρw = water density
ρb = OD/Vb
Vb = soil bulk volume
= Vs + Vw + Va
Vb = soil bulk volume
= Vs + Vw + Va
Vs = volume of soil particles
Vw = volume of water in the soil
Va = volume of air in the soil
d = (AM/100)•As•D
D = soil root depth or soil depth where water
will be stored
dAM = depth of water at AM
dAM = (AM/100)•As•D
dnet = dmd = dcu
dmd = depth of moisture depletion
dcu = depth of consumptive use
dnet = net depth of water to be applied
dnet = ((FC - CSM)/100)•As•D
CSM ≤ MAD (moisture allowed deficit)
dg = (dnet )/Ea
dg = gross depth of water to be
applied
Ea = irrigation application efficiency
Depth of water applied
G.S.
Depth of water applied by sprinkler irrigation system
Depth of water applied by drip irrigation system
head
G.S. end
Under irrigated
Depth of water applied by surface irrigation system
head
G.S. end
Runoff
Deep percolation
Depth of water applied by surface irrigation system
I,z
Intake depth, z = kta or kta + ct
m Intake rate, I = mtn or mtn + c
c
k
Irrigation application time, t
m & k = intercept, n & a = slope, c = basic intake rate
I = mtn
z = ∫Idt = ∫mtndt = mt(n+1)/(n+1)
k = m/(n+1)
a = n+1
z = kta
Find z when I = mtn + c
Four Methods of Supplying
Irrigation Water to Land
1.SURFACE IRRIGATION
2.SUBSURFACE IRRIGATION
3.SPRINKLER (overhead irrigation)
4.TRICKLE (DRIP) (overhead irrigation)
SURFACE IRRIGATION
• The water was applied directly in the soil
surface
Advantages of Surface Irrigation
1.Low capital investment
2.Need no expensive & complicated
equipment
Disadvantages of Surface Irrigation
1.High labor requirement
2.Low application efficiency
3.Requires well-graded fields
4.Requires large flow rates
Surface irrigation method
1.Uncontrolled or wild flooding
2.Border
3.Basin
4.Check
5.Furrow
6.Corrugation
Uncontrolled or wild flooding – water is
applied from field ditches without any levees
to guide its flow.
-Used when water is abundant & inexpensive
Border-Strip flooding – dividing the land into a
number of strips, preferably not over 10 – 20 m
wide and 100-400 m long, separated by levees
or borders
- Border slope = 0.2-0.4%; Q = 15-300 lps
Border Irrigation – mostly rectangular or
contoured field shapes
- needs large stream size per unit width
- either with open end or not
Furrow Irrigation – construction of small
channels in the field
- can be used in conjunction with basin and
border irrigations
Check flooding – consists of running large
streams into level plots surrounded by levees.
-Used where large Q is available
Basin flooding – similar to border flooding but
shape is normally square or round
- Used extensively to irrigate rice
Basin Irrigation – irrigation of small areas of flat,
level surface, enclosed by dikes
-Favored by moderate to slow intake soils, deep
root, closely spaced crops
-Needs accurate land leveling, well maintained
dikes
- Difficult to use modern farm machinery
Furrow – water is applied along the furrows
thereby reducing the wetted surface by 1/2 –
1/5.
-Preferred slope = 0.5-3% but up to 6% can be
satisfactory, slopes of 10-15% are also
successful for some soils.
-Furrow length = 15 -500 m (100-200 m are
common)
- spacing depends on crops
Furrow Irrigation – construction of small channels in the field
- can be used in conjunction with basin and border
irrigations
- needs low flow rates per unit width
- can be used for steep slopes
- potential salinity hazards between furrows
- higher end losses if no dikes at the end
- limited machinery mobility
- needs one extra tillage practice
- increased erosion potential
Corrugation – small furrows
-Used when Q is small
Sub-irrigation – application of water directly
under the soil surface
Furrow Irrigation – construction of small channels in the field
- can be used in conjunction with basin and border
irrigations
- needs low flow rates per unit width
- can be used for steep slopes
- potential salinity hazards between furrows
- higher end losses if no dikes at the end
- limited machinery mobility
- needs one extra tillage practice
- increased erosion potential
Subsurface irrigation method
• The water was applied beneath the soil
surface
SUBSURFACE IRRIGATION METHODS
1.Controlled by lateral ditches
2.Uncontrolled from excess
application of water to adjacent or
higher lands
Overhead irrigation systems
• Water was applied above the soil surface
• Sprinkler irrigation
• Drip/emitter/trickle irrigation
Dry irrigation head ditch
Main line
lateral line
Overhead irrigation, set sprinkler: Portable pipes (pipes do not
move whilst irrigating). Moveable pipe irrigation lines in California, USA
Moveable pipe irrigation lines, watering bare soil
Furrow irrigation. Note the water coverage of the entire furrow, and the
broken earthen bund (foreground) that permits water to enter.
Release of water from gated pipe, for furrow irrigation of maize
Drainage from end of furrow.
Note the wetting front along
the dry soil of the furrow; low
water flow from furrow into
drain; and the use of mulch to
minimise evaporative losses.
http://www.worldbank.org/html/cgiar/photo/rice.html
for slides of rice paddys
Use of siphon tubes to deliver water to furrows (or borders).
Note the different water levels of the main ditch,
and tubes in the background
Irrigation Siphon in head ditch
An irrigation engineer is to irrigate a crop
planted in furrows of 100m x 100m area. It
was found out that the inflow rate is 0.5 lps
per 100 m. If he decides to have a furrow
spacing of 50 cm and an application depth
of 100 mm, determine:
The time of irrigating each furrow.
the number of furrows that can be irrigated
at the same time if the available water
supply is 7.5 lps
