civil engineering lectures

1. CE-317 Irrigation & Hydraulic structures
Lecture# 01
(6th semester Civil)
By: Engr. Hayat Hussain
Lecturer Saidu polytechnic institute saidu sharif Swat

2. Contents
• Hydrology
• Hydrological cycle
• Stages of hydrological cycle
• Irrigation and drainage and its role in agriculture
• Surface irrigation
• Subsurface irrigation
• sprinkler irrigation
• Drip irrigation

3. Hydrology
• It is the science dealing with water at its origin (sources, through its
circulation (Transportation) and at its destination. It also covers its
physical, chemical properties and its interaction with the environment

4. The Hydrological Cycle
it is the journey water takes as it circulates from the land to the sky and
back again. It is also known as water cycle.
The total amount of water on the earth and in its atmosphere does not
change but the earth’s water is always in movement. Oceans, rivers,
clouds and rain, all of which contain water, are in a frequent state of
change and the motion of rain and flowing rivers transfers water in a
never-ending cycle. This circulation and conservation of earth’s water as
it circulates from the land to the sky and back again is called the
‘hydrological cycle’ or ‘water cycle’.

5. Explanation:
The sun’s heat provides energy to evaporate water from the earth’s
surface (oceans, lakes, etc.). Plants also lose water to the air – this is
called transpiration. The water vapour eventually condenses, forming
tiny droplets in clouds.
When the clouds meet cool air over land, precipitation (rain, sleet, or
snow) is triggered, and water returns to the land (or sea). Some of the
precipitation soaks into the ground. Some of the underground water is
trapped between rock or clay layers – this is called groundwater. But
most of the water flows downhill as runoff (above ground or
underground), eventually returning to the seas as slightly salty water.

7. • Stages of hydrological cycle
• Evaporation
• Transport
• Condensation
• Precipitation
• Groundwater
• Run-off

8. • Evaporation
Water is transferred from the surface to the atmosphere through
evaporation, the process by which water changes from a liquid to a gas.
The sun’s heat provides energy to evaporate water from the earth’s
surface. Land, lakes, rivers and oceans send up a steady stream of water
vapour and plants also lose water to the air (transpiration).
Approximately 80% of all evaporation is from the oceans, with the
remaining 20% coming from inland water and vegetation.

9. • Transport
The movement of water through the atmosphere, specifically from over the
oceans to over land, is called transport. Some of the earth’s moisture transport
is visible as clouds, which themselves consist of ice crystals and/or tiny water
droplets.
Clouds are propelled from one place to another by either the jet stream,
surface-based circulations like land and sea breezes or other mechanisms.
However, a typical cloud 1 km thick contains only enough water for a milli
metre of rainfall, whereas the amount of moisture in the atmosphere is usually
10-50 times greater than this.
Most water is transported in the form of water vapour, which is actually the
third most abundant gas in the atmosphere. Water vapour may be invisible to
us, but not to satellites which are capable of collecting data about moisture
patterns in the atmosphere.

10. • Condensation
The transported water vapour eventually condenses, forming tiny
droplets in clouds.

11. • Precipitation
The primary mechanism for transporting water from the atmosphere to
the surface of the earth is precipitation.
When the clouds meet cool air over land, precipitation, in the form of
rain, sleet or snow, is triggered and water returns to the land (or sea). A
proportion of atmospheric precipitation evaporates.

12. • Groundwater
Some of the precipitation soaks into the ground and this is the main source of the
formation of the waters found on land – rivers, lakes, groundwater and glaciers.
Some of the underground water is trapped between rock or clay layers – this is
called groundwater. Water that infiltrates the soil flows downward until it encounters
impermeable rock and then travels laterally. The locations where water moves
laterally are called ‘aquifers’. Groundwater returns to the surface through these
aquifers, which empty into lakes, rivers and the oceans.
Under special circumstances, groundwater can even flow upward in artesian wells.
The flow of groundwater is much slower than run-off with speeds usually measured
in centimetres per day, metres per year or even centimetres per year.

13. • Run-off
Most of the water which returns to land flows downhill as run-off. Some of it
penetrates and charges groundwater while the rest, as river flow, returns to the
oceans where it evaporates. As the amount of groundwater increases or
decreases, the water table rises or falls accordingly. When the entire area
below the ground is saturated, flooding occurs because all subsequent
precipitation is forced to remain on the surface.
Different surfaces hold different amounts of water and absorb water at
different rates. As a surface becomes less permeable, an increasing amount of
water remains on the surface, creating a greater potential for flooding.
Flooding is very common during winter and early spring because frozen
ground has no permeability, causing most rainwater and meltwater to become
run-off.

14. Irrigation and drainage
The artificial application of water to land and artificial removal of
excess water from land, respectively. Some land requires irrigation or
drainage before it is possible to use it for any agricultural production;
other land profits from either practice to increase production. Some
land, of course, does not need either.

15. Role of irrigation and drainage in agriculture
Irrigation & Drainage is important since it helps determine future
Irrigation expectations. Irrigation has been a central feature of
agriculture for over 5000 years, and was the basis of the economy and
society of numerous societies, ranging from Asia to Arizona.
Additionally, irrigation also has a few other uses in crop production,
which include protecting plants against frost, suppressing weed growth
in grain fields and preventing soil consolidation. In contrast, agriculture
that relies only on direct rainfall is referred to as rain-fed or dryland
farming. Irrigation is often studied together with drainage, which is the
natural or artificial removal of surface and sub-surface water from a
given area. water is required for agriculture. sometimes this water
requirement is fulfilled by rain, but there are some dry areas where
irrigation is the only process by which water is supplied to crops.

16. Surface irrigation
Surface irrigation is the application of water to the fields at ground
level. Either the entire field is flooded or the water is directed into
furrows or borders.
Types of surface irrigation system
• Furrow irrigation
• Border irrigation
• Basin irrigation

17. • Furrow irrigation
furrows are narrow ditches dug on the field between the rows of crops.
The water runs along them as it moves down the slope of the field. The
water flows from the field ditch into the furrows by opening up the bank
or dyke of the ditch or by means of syphons or spiles. Siphons are small
curved pipes that deliver water over the ditch bank Spiles are small
pipes buried in the ditch bank.

18. • Border irrigation
In border irrigation, the field to be irrigated is divided into strips (also
called borders or border strips) by parallel dykes or border ridges The
water is released from the field ditch onto the border through gate
structures called outlets The water can also be released by means of
siphons or spiles. The sheet of flowing water moves down the slope of
the border, guided by the border ridges.

19. • Basin irrigation
Basins are horizontal, flat plots of land, surrounded by small dykes or
bunds. The banks prevent the water from flowing to the surrounding
fields. Basin irrigation is commonly used for rice grown on flat lands or
in terraces on hillsides Trees can also be grown in basins, where one tree
usually is located in the centre of a small basin

20. Sub surface irrigation system
The applying of water to crop beneath the soil surface either by
constructing trenches or installing under ground perforated pipes is
called sub surface irrigation of subirrigation.
In this system water is discharges into trenches And allowed to stand
during the whole period of irrigation for lateral and upward movement
of water by capillarity to wet the soil between the trenches.
Advantages:
• Maintenance of soil water at favorable tension
• Loss of water by evaporation is held at minimum
• Can be used for soils with low water holding capacity and high
infiltration rate where surface irrigation methods cannot be adopted
and sprinkler irrigation is expensive.

21. Sub surface irrigation system

22. Sprinkler irrigation system
Sprinkler irrigation is a method of applying irrigation water which is
similar to natural rainfall Water is distributed through a system of pipes
usually by pumping. Water under pressure is carried and sprayed into
the air above the crop through a system of Overhead perforated pipes,
nozzle lines, or through nozzles fitted to riser pipes attached to a system
of pipes laid on the ground Nozzles of fixed type or rotating under the
pressure of water are set at suitable intervals in the distribution pipes.
Sprayed water wets both the crop and the soil and, hence, has a
refreshing effect. Water is applied at a rate less than the intake rate of
soil so that there is no runoff. Measured quantity of water is applied to
meet the soil water depletion

23. Sprinkler irrigation system

24. Drip irrigation system
While drip irrigation may be the most expensive method of irrigation, it
is also the most advanced and efficient method in respect to effective
water use. Usually used to irrigate fruits and vegetables System consists
of perforated pipes that are placed by rows of crops or buried along their
root lines and emit water directly onto the crops that need it. As a result,
evaporation is drastically reduced and 25% irrigation water is conserved
in comparison to flood irrigation. Drip irrigation also allows the grower
to customize an irrigation program most beneficial to each crop.
Fertigation is possible.

25. Drip irrigation system

26. Questions and answers

27. Thanks