IRRIGATION ENGINEERING
Dr. Florante D. Poso, Jr.
Irrigation Water
Water Administration
Soil for Irrigation
IRRIGATION ENGINEERING
Irrigation is the application of water to the soil to
supplement natural precipitation and provide an
environment that is optimum for crop production.
OBJECTIVES OF IRRIGATION
 To Supply Water Partially or Totally
for Crop Need
 To Cool both the Soil and the Plant
 To Leach Excess Salts
 To improve Groundwater storage
 To Facilitate continuous cropping
 To Enhance Fertilizer Application-
Fertigation
IRRIGATION
 The process of artificial application of
water to the soil for the growth of
agricultural crop.
IRRIGATION
A science of planning and designing a
water supply system for agricultural
land to protect the crops from bad
effect of drought or low rainfall.
Necessity of Irrigation
 a) Insufficient rainfall
 b) Uneven distribution of rainfall
 c) Improvement of perennial crops yield
 d) Development of agriculture in the
desert areas
 e) Insurance of drought
Direct Benefit of irrigation
Increase in crop yield
Protection of famine
Improvement of cash crops
Elimination of mixed cropping
Prosperity of farmers
Source of revenue
Overall development of the nation
Indirect Benefits of Irrigation
 Hydroelectric development
Indirect Benefits of Irrigation
 Flood control
Indirect
Benefits of
Irrigation
Domestic and
industrial water supply
Indirect Benefits of Irrigation
 Navigation
Indirect Benefits of Irrigation
 Development of fishery
Indirect Benefits of Irrigation
 Ground water recharges
Ill-effects of Irrigation
 Raising of water Table
Ill-effects of Irrigation
 Formation of marshy area
Ill-effects of
Irrigation
Soil erosion
Ill-effects of Irrigation
 Loss of valuable lands
Ill-effects of Irrigation
 Loss of soil fertility
Ill-effects of Irrigation
 Dampness of weather
 Production of harmful gases
To Understand Irrigation, One Needs
Knowledge of:
 Basic Soil Science/Physics
 Plants
 Water
 Plant/Soil/Water Relations
 Hydraulics
 Hydrology
 General Engineering
Principles
IRRIGATION:
 The process of artificial application of water to the
soil for the growth of agricultural crop.
 A science of planning and designing a water supply
system for agricultural land to protect the crops from
bad effect of drought or low rainfall.
 It includes the following structures for the regular
supply of water to the required command area:
Weir/barrage
Dam/reservoir
Canal system
- The quantity of water used for the artificial application
to the soil through various systems of tubes, pumps,
and sprays. Irrigation is usually used in areas where
rainfall is irregular or dry times or drought is
expected.
Irrigation water supply mainly depends on the surface and
ground water resources. For surface irrigation, river water
needs to be diverted from the river, which significantly
alters the river's flow regime and thus the river ecology in
terms of both biotic and abiotic components.
Irrigation is the process through which controlled
amount of water can be supplied through
artificial means such as pipes, ditches, sprinklers
etc. the main ...
Irrigation helps to grow agricultural crops,
maintain landscapes, and revegetate disturbed
soils in dry areas and during periods of less
than average rainfall.
To plan, direct, and supervise the Water
Systems Operations; including pumping,
storage, transmission, purification, treatment,
and distribution of City water.
- Water management is the whole of activities
that aims to plan, develop, distribute and
make optimum use of ground, surface ...
Soil-plant Water relationships relate the
properties of soil that affect the movement,
retention and use of water. It can be
divided & treated as:
Soil-water relation
Soil-plant relation
Plant-water relations
SOIL-WATER RELATIONSHIPS
Soil Suitability for agricultural practices
 Knowledge of the soils within a potential irrigation
area is essential for economic and technical reasons.
SOIL
 Is a three-dimensional body occupying the upper part of
the earth’s crust and having properties differing from
the underlying rock material as a result of interactions
between climate, living organism, parent material and
relief and which is distinguished from other soils in
terms of differences in internal characteristics and/or
in terms of the gradient slope-complexity, micro
topography, stoniness, and rockiness of the surface.
FIGURE 1- DIAGRAM SHOWING CROSS
SECTION OF SOIL
Water film
Air space
Soil particles
The suitability of soil for agricultural practices may
be affected by physical and chemical soil
characteristics.
The physical characteristics include:
1. Effective Soil Depth
6. Soil Structure
2. Water Holding Capacity
7. Soil Consistence
3. Non-capillary Porosity
8. Soil Permeability
4. Topography
and
5. Texture
Hydraulic Conductivity
Permeability - is the ease with which liquids,
gases and roots pass through the soil.
Hydraulic conductivity is the permeability of the
soil for water. i.e. the ease with which the soil
pores permit water movement. It controls the soil
water movement.
Soil Suitability for agricultural practices
Table 2.1: Size limits of soil separates
Source: United States Department of Agriculture (USDA) and the International Soil Science Society
(ISSS)
Soil separates
Very course sand
Course sand
Medium sand
Fine sand
Very fine sand
Silt
Clay
Particle diameter (mm)
USDA
ISSS
2.0 - 1.0
1.0 - 0.5
2.0 - 0.2
0.50 - 0.25
0.25 - 0.10
0.20 - 0.02
0.10 - 0.05
0.05 - 0.002
0.02 - 0.002
< 0.002
< 0.002
Soil Suitability for agricultural practices

Fig. 2.3: USDA textural triangle
It means that physical properties of soil in
relation to water.
The rate of entry of water in to the soil and its
retention, movement and availability to plant
roots are all physical phenomena. Hence, it is
important to know the physical properties of
soil in relation to water.
Water can exist in either of the following
forms in the soil.
1. Gravitational water
2. Capillary water
3. Hygroscopic water
The following soil moisture contents are of significance
importance in agriculture and are termed soil moisture
constants.
1. Saturation Capacity
2. Field capacity
3. Permanent Wilting Point
The soil moisture tension at PWP ranges from 7 to 32 atm,
depending on the soil texture, kinds of crops and salt
content in the soil solution.
- Since the change in moisture content (∆q) is insignificant
for changes in SMT from 7-32 atm. Hence, 15 atm. is taken as
SMT at PWP.
- At PWP the plant starts wilting, and if no water is given to
the plant, then it will die.
1. Total available water, TAW
The soil moisture between field capacity and
permanent wilting point is called available
water.
This is the water available for plant use. Finegrained soils generally have a wider range of
available moisture than course textured soil.
2. Management allowed deficit, MAD.
The degree to which the volume of water in the soil is
allowed to deplete before the next irrigation is
applied. That is portion of the available moisture,
which is easily extracted by the plant roots. It is
commonly 60 – 80 % of the available water.
MAD = f. TAW, f depends on type of crop and Crop
growing stage.
3. Soil moisture deficit, SMD.
The depletion of soil moisture below field
capacity at the time that particular soil
moisture content, qv , is measured. That is
the amount of water required to bring the soil
moisture back to the field capacity.
Deficit = Fc – soil moisture at that instant.
Figure 2.1: Soil moisture levels and available water
ranges.
Soil moisture levels and available water ranges.
The salt concentration in the water extracted from a saturated
soil (called saturation extract) defines the salinity of this soil.
If this water contains less than 3 grams of salt per litre, the
soil is said to be non saline (see Table below). If the salt
concentration
of of
thethesaturation
extract contains more than 12
Salt concentration
soil water (saturation
g/l, the soil is saidextract)
to be highly saline
Salinity
in g/l
in millimhos/cm
0-3
3-6
0 - 4.5
4.5 - 9
non saline
slightly saline
6 - 12
more than 12
9 - 18
more than 18
medium saline
highly saline
Crops and saline soils
Most crops do not grow well on soils that contain salts.
One reason is that salt causes a reduction in the rate and
amount of water that the plant roots can take up from the soil
(see Fig. 105). Also, some salts are toxic to plants when
present in high concentration.
METEOROLOGY AND HYDROLOGY
Air temperature
Relative humidity
Precipitation
Wind Direction
Solar Radiation
Soil Temperature
Barometric Pressure
Soil Moisture
System of Irrigation
IRRIGATION SYSTEMS
Lift Irrigation
Using man
or
Animal power
Using Mechanical
or
Electrical Power
Flow Irrigation
Inundation
Irrigation
Direct
Irrigation
Perennial
Irrigation
Storage
Irrigation
Lift Irrigation
Flow Irrigation
Method of Distribution of Irrigation
Water
Method of Distribution
Surface
Methods
Furrow
Method
Sprinkler Methods
Overhead Irrigation
Sub-Surface
Methods (Drip)
Contour Farming
Method
Flooding
Method
Uncontrolled Flooding
Free Flooding
Controlled Flooding
Basin Flooding
Check
Flooding
Border Strip
Surface Method of Irrigation
The irrigation method is
distributed to the agricultural land
through the small channels, which
flood the area up to the required
depth.
Surface Method of Irrigation
Sub-Surface Method
The water is applied to the root zone of the crops
by underground network of pipes .
Sub-Surface Method
Sprinkler Irrigation Method
The water is applied to the land in the
form of spray like rain.
Sprinkler Irrigation Method
Feasibility studies of irrigation
projects
 Necessity for irrigation in the region
 Availability of adequate water supply
 Topography of the area
 Cultural practices of the tract
 Adequacy of existing irrigation system if any
 Possibility of growing cash crops or other voluble crops after
provision of irrigation water
 Accessibility to the project site (transportation, Communications
and other required facilities) and construction materials.
 Economical justification for implementing the irrigation scheme.
Data to be collected (Feasibility Study)

1. Physical data

2. Hydrological data

3. Agricultural data

4. Geological data

5. Cartographic data

6. Ecological data

7. Demographic data

8. Economic data

9. Legal data

10. Data in existing project

11. Data on public opinion

12. Flood control data