1. ERT 468 SURFACE WATER MANAGEMENT
Prepared By:
Mdm. Fathin Ayuni Azizan
Lecturer,
Biosystems Engineering
Programme
LECTURE WEEK 5:
IRRIGATION FACILITIES & IRRIGATION CONVEYANCE

2. Course Content Water intake facilities:
irrigation diversion
intake system (surface & GW intake).
Farm water delivery & storage system:
various form of open channel or pipelines
Pond & tank water storage

3. 1.0 introduction
Irrigation water (surface/GW) delivered -> farm by;
gravity
pumping
It requires:
diversions & intakes
intake structure
built at the entry to IS
Divert water from sources (pond/river/reservoir/aquifer) into the IS.

4. 2.0: TYPES OF INTAKE STUCTURE
2.1: River Intake (RI)
Designed so that the required Q can be diverted or pumped at all times (even during extreme low flow)
Design considerations include:
topography
soil conditions
hydrology & hydraulics
design discharge
water availability
low flow conditions

5. Divert water directly from a river thro diversion structure
(a) Gravity-fed RI
Divert water directly from a river thro diversion structure
diversion structure task:
Diverting & regulating the quantity of river water to primary canal
(a) Gated Control Gravity Intake
Primary Canal

6. (b) Pumped RI
Pump is used when river water level below the level of the irrigated fields
Several types of pumps can be used but the most common is ‘centrifugal pump’
Pump house
Vertical Centrifugal Pump
Pumping plants
required when water must be lifted from the water source
Pump type
Horizontal centrifugal pumps -> used for surface water sources, pump is above the water surface.
Vertical centrifugal pumps -> used with either surface or GW sources

7. Vertical Pumping plants

8. Intake Site Selection for River Intake:
Site free from change of river flow direction, rise/fall in the river bed level with calm & gentle flow
Site of good geological formation & safe from landslides/scouring.
Water quality safe from pollution & intrusion of sea water
Site shall be of easy access & spacious for future extensions & maintenance works

9. 2.2 Impoundment Intake (II)
Involves construction of dam & storage reservoir
Water supplied by gravity & better quality than river water
Types of dam:
concrete/masonry dam
earthen dam

10. Intake Site Selection for Impoundment Intake:
Site closed to the irrigation canal as possible
Site with good road access so that construction & maintenance works can be done
Site having asses to natural drainage to drain excess reservoir water

11. 2.3 Groundwater Intake (GWI) Water abstracted by shallow/deep wells
Advantages:
Can be abstract any time of the day/year.
better water quality.
Do not require storage reservoirs & long delivery pipes
GW pumping system

12. Intake Site Selection for Groundwater Intake:
Site must have good aquifer condition
It located centre or close to the irrigation project.
location of the tube-wells not within the radius of influence of other wells
Site can provide good water quality

13. 3.0: STRUCTURES OF SURFACE WATER INTAKE
a) Canal Head Works
2 structures are necessary to construct:
Structure across the river Structure at the head of canal
called “barrage” called “Head Regulator”

14. (b) Reservoir Outlet Works (c) Pumping Station

15. 4.0: STRUCTURES OF GROUNDWATER INTAKE
a) Water Wells
a hole, usually vertical, excavated in the earth for withdrawal of GW.

16. (b) Tube-well Components

17. 5.0: IRRIGATION CONVEYANCE
Carry water: source farms
In the form of:
open channels
Pipelines
Capacity sufficient to meet:
any amount
any where
any time
Designed as:
environmental friendly
easy to operate & maintain
economically justified
Or combination of both

19. IRRIGATION CANAL
PRIMARY CANAL
SECONDARY CANAL
TERTIARY CANAL

20. - sloped to the direction of flow - either lined or unlined (i) Lined:
(a) Open Channels
- sloped to the direction of flow
- either lined or unlined
(i) Lined:
lined with hard surfaces (concrete & asphalt)
covered with membranes or soil sealants
to reduce maintenance costs, channel sizes & seepage losses (thro channel bed & walls)
(ii) Unlined:
used b’cos low capital costs & ease of construction & relocation

21. -laid on the ground surface or buried -classified as:
(b) Pipelines
-laid on the ground surface or buried
-classified as:
open (low head)
closed (pressurized)
(i) Low head pipelines :
deliver water at pressure that only surface irrigation methods can be employed
Pump is required if pressurized IS to be use
(ii) Pressurized pipelines:
deliver water under adequate pressure for the pressurized IS
equipped with necessary accessories such as:
flow regulator
pressure regulator
water meter
air release & vacuum relief valves

22. 6.0: selection of conveyance
taking into consideration advantages & disadvantages
(a) Open channel
construction cost < pipeline
employed when land is flat & flows are large
(b) Pipeline
Used when conveyance canal is too long due to topographic conditions & possible lower construction cost
widely adopted in large-scale irrigation schemes
buried in the ground
Easier operation & Min. maintenance requirement
Efficiency in water use & more amendable social condition to farmers

24. 6.0: PLANNING & DESIGN CONSIDERATIONS
Factors taken into consideration;
Conveyance capacity
Function of regulation, distribution & delivery
Operation, maintenance & management of the system
Safety of the canal system
Harmony with environment
What to design?
Canal Layout
Lined Canal
Unlined Canal
Pipelines

25. Design of Canal Layout

26. Systems Design

27. MUDA catchment area =965 km PEDU catchment area =171 km
Ahning Dam
PeduDam
Muda Dam
MUDA catchment area =965 km 2
PEDU catchment area =171 km
KEDAH
THAILAND
GENERAL LAYOUT PLAN OF TERTIARY SYSTEM FOR BLOCK ACLBD 8b

29. a) Open Channel Design Design of Lined Canal Wetted perimeter, p
Area of Cross-section, a
Hydraulic radius, R
P = b+c+c
A =((b+t)/2) x d
R = a/p

30. (b) Canal Discharge Capacity
Common method for the design of lined/non-erodible channels are:
Manning Formula
Chezy’s Equation
Discharge, Q (Manning formula),
Where,
Q = Discharge in canal (m3/s)
n = Manning roughness coeff
A = Cross-sect. area of water (m2)
R = Hyd. radius (m)
S = Slope of canal bed
Where,
Q= VA
V = Q/A = 1/n (R2/3 S1/2)

31. Table of Values of Manning’s n
Type and description of channels
Manning’s n
Earth Channels
Straight and uniform
Winding, Sluggish
Slurry Bed, weeds on bank
Small drainage ditches
0.023
0.025
0.035
0.040
Lined Channels
Concrete
Masonry, rubble
Metal, smooth
Wooden
Vegetated waterways
0.015
0.017 – 0.030
0.011 – 0.015
0.011 – 0.014
0.020 – 0.040
Pipes
Cast iron
Concrete drain tile
Steel
Sewer pipes
0.012 – 0.013
0.011
0.015 – 0.017
0.013 – 0.015

32. Canal Types

34. Example:
Assume an earth channel on a grade of 0.10 per cent, depth of water 40 cm, bottom width 40 cm and side slopes 1 ½ to 1. Calculate the velocity of flow water carrying capacity of the channel.

35. (c) Design Steps Step 1: Estimate Manning’s or Chezy’s coeff. Step 2:
Use Figure 9.4 to determine flow depth (y).
Step 3:
Check if ‘y’ is within required limits for the canal type. If not, adjust the canal dimensions & return to step 2.
Step 4:
Calculate the ave. flow velocity from V = Q/A & check that it is within the max. & min. velocity criteria for the canal type. If not, adjust the canal dimensions & return to step 2.
Step 5:
Add required freeboard to ‘y’ & calculate top width of canal
Step 6:
If required, calculate width of canal reserve.

36. Design of Unlined Canal
(a) General Design Concept
Unlined canals properly designed to provide;
Velocity such no serious scouring/sedimentation
Sufficient to carry the design flow
Hydraulic grade sufficient at a proper depth for good water management
Sides slopes that are stables
Low seepage loss
Min. initial & maintenance costs.

37. (b) General Requirements
(i) Losses
Include seepage losses, evaporation losses & operational losses expressed in m3/d/m2 of wetted areas or mm/d.
Seepage = 30 mm/day for lined canal to 20X or more for unlined canal.
The loss of flow in each reach is computed as follows:
Qs = qs PL/84600
Where,
Qs = flow loss to seepage in canal reach (m3/s)
P = wetted parameter (m)
L = length of canal reach (km)
qs = rate of infiltration (mm/day =1/m2/day).

39. (ii) Freeboard
To allow for an increase in the WL above the full supply level

40. (iii) Bank
For operation, maintenance & inspection min. bank width along the canals will be required

41. Discharge capacity in pipelines
Design of Pipelines
Discharge capacity in pipelines
The discharge capacity through a pipeline can be determined by applying the Darcy’s equation.
V= velocity of flow of water through the pipe, cm/sec
H= Available head causing flow (difference in elevation between water level), cm
d= Diameter of pipe, cm
g= acceleration due to gravity, cm/sec2
l= length of pipe
f = Darcy’s roughness coefficient

42. Values of coefficient ‘f’ in Darcy’s equation for pipe flow
Velocity, cm/sec

43. Example:
Determine the discharge capacity of an underground concrete channel line from the following data : Diameter of pipe 15 cm, length of pipe line 150 meters, difference in elevation between water levels at pump stand and discharge is two meters. Assume velocity to be 90cm/sec.

44. END of chapter
5/10/2017