Transcript Presentation

Study on performance of dry season rotational
irrigation for Mae Lao irrigation project, Thailand
Naritaka KUBO: Univ. of Tokyo, Japan
Takuya TAKEUCHI: Tokyo Univ. of Agri. & Tec., Japan
Unggoon WONGTRAGOON: Rajamangala Uni. of Tec., Thailand
Hajime TANJI: NIRE, NARO, Tsukuba, Japan
Back Ground
In south east Asian countries…


Irrigation projects were developed primarily for
supplemental supply during rainy season
Constructing new reservoirs makes irrigation
possible during dry season
Water supply is not enough
Restricted irrigation areas because
of scare water
 Necessity of effective water use

Mae Lao
Project site
Mae Lao irrigation
scheme



Tributary of the Kok
River belonging to
Mekong River basin
Chiang Rai in North
Thailand
Irrigation Area :
23680 ha
Mae Lao project site
Mae Suai Dam
Branch 4
5,600 ha
Left Main Canal
Mae Lao Weir
Mae Suai Dam
Mae Lao river
Branch 1
7,968 ha
Mae Lao weir
Branch 2
5,264 ha
Right Main Canal
Branch 3
4,848 ha
Laterals
Streams
0
5
10 km
18,080 ha
Right Main Canal （RMC）
- RMC length ：about 50 km
- Secondary canals ： 23
- Max Q： about 27 m3/s
Water deficit in dry season

Interviews

Branch 1
・Water deficit occurs partially

Branch 2
・Irrigation area is expanded beyond allotted area
・Water deficit occurs in downstream areas

Branch 3
・Water deficit is serious
・No water comes to downstream areas
Summary of
interviews



Mae Suai Dam can
store 73,000,000 m3
Low distribution
efficiency
Unequal water
distribution



Functional problems
Managerial problems
Illegal activities
Problem identification
Objectives
Quantitative analysis of effects of facilities and water
management on water distribution performance
1. Planning phase
 Continuous irrigation by non-uniform flow model
 Effects by physical causes of facilities & structures
2. Execution phase
 Rotational irrigation simulated by UIWDC model
 Effects by managerial & institutional causes
Methodology

Numerical simulation by UIWDC model
（Unggoon et al., 2010）
（Unsteady Irrigation Water Distribution and Consumption）
Water movement in canal
⇒ 1-D unsteady flow model

Water consumption in
paddy field
⇒ Paddy Tank model

Saint-Venant Equations
A Q

q
t x
Q   Q 2
 
t x  A

h
  gA  gAS 0  S f   qu
x

A：Area, Q：Flow, q：side flow, h：depth, g：
gravitational acceleration, S0：bed slope,
Sf：friction slope, u：mean velocity
inundated
Plow layer
Ground
Water
Modeling of irrigation system
HW
Direct
withdrawal
Branch 1
PF
Direct
withdrawal
PF
PF
CK
Direct
withdrawal
Branch 2
5L~12L
Direct
withdrawal
CK
Branch 3
13L~22L
CK
PF
1L
Paddy field
2L
CK
PF
PF
Check
structure
PF
PF
PF
PF
PF
PF
PF
PF
PF
3L
4L
CK
FTO 12L
J
FTO 9L
HW
FTO 7L
Modeling of FTOs and water
distribution
CK
(a)
SI
Reach
E
J
FTO 11L
FTO 8L
FTO 7L
FTO 4L
FTO 2L
FTO 14L
FTO 13L
FTO 10L
FTO 8L
FTO 6L
FTO 4L
FTO 1L
CK
CK
CK
CK CK
E
Q14
Q13
Q10
Q4
3L-RMC
J
E
4L-RMC
Reach
q
CK
: Computational mesh point
Q17
FTO 14R
FTO 15R
FTO 12R
FTO 13R
FTO 10R
FTO 11R
4R-4L
E
FTO 9R
E
FTO 8R
3R-4L
E
J
CK
FTO 13L
FTO 12L
FTO 11L
FTO 10L
FTO 9L
2L-4L
FTO 8L
FTO 7L
1L-4L
FTO 5L
FTO 4L
FTO 3L
FTO 2L
FTO 1L
FTO 6L
J
SI
FTO 7R
2R-4L
FTO 6R
1R-4L
FTO 5R
FTO 3R
FTO 4R
FTO 1R
FTO 2R
E
Q17
J
J
CK
J
E
Q16
J
SI
Q15
E
J
RMC
ΔX
Reach
CK
Q12
FTO 17R
FTO 16R
FTO 15R
FTO 12R
FTO 11R
FTO 9R
FTO5R
FTO 7R
FTO 2R
FTO 3R
SI
Reach
E
CK
(b)
E
3L-RMC
CK
Q11
CK
: Computational mesh point
SW
SW
Q9
CK
SI : Siphon
CK
Q7
SW : Spill Way
E
J
CK
Q5
FTO 9R
1R-2L
FTO 6R
FTO5R
FTO 3R
FTO 1R
SW
Reach
CK : Check Gate
Q3
J : Joint
2L-RMC
3L-RMC
Q2
E
E
J
E : Ended Point
J
SI
CK
HW : Head Work
E
CK
Q6
Q8
Reach
Q1
FTO 13R
FTO 14R
FTO 11R
FTO 8R
FTO 10R
FTO 6R
FTO 5R
FTO 4R
FTO 2R
FTO 3R
1R-1L
J
FTO 10L
1L-RMC
Intake flow rate (IFR)
1. Based on water requirement Qs
2. Base on non-uniform flow calculation Qe
（considering physical properties）
Assumptions for Calculation





Equal water distribution within a branch
Daily water consumption in paddy field:14.7 mm/day
Each branch is calculated independently
Total paddy field area in Branch i : Ai
Scheduled area to be irrigated in Branch i : Asi
1. Calculation of scheduled IFR Qs
Exact water volume to irrigate area of Asi
⇒ Scheduled Qsi for Branch i
 Based on water requirement

＝Paddy water consumption ×Asi
+ Seepage loss
Canal seepage losses are calculated
assuming Full Supply Level
to be
irrigated
not to be
irrigated
PF
PF
PF
PF
2. Calculation of equilibrium IFR Qe
Calculated by numerical simulation for nonuniform flow
 IFR at equilibrium
（useless spillage＝deficit）

deficit
⇒Equilibrium Qei for
Branch i
Paddy field
canal
Spillage
Canal seepage loss considering
Non-uniform Flow Level
Inlet of FTO
Result (1) Scheduled area vs. IFR Q
Scheduled Qsi & Equilibrium Qei

Intake Flow Rate (m3/s)

Scheduled area ratio (Asi/Ai)
Maximum Flow Rate
27 m3/sec
No differences at
no seepage losses
→ caused by seepage
losses
 Lower water level
than that of FSL
 Longer distance
causes more losses
Result (2) Scheduled area vs. WSR

WSR = [Actually distributed water]/[Volume to be distributed]
WSR
(Water supply ratio)
Branch 1
Branch 2
Branch 3
Scheduled area ratio (SAR Asi/Ai)
More upstream



Larger canal section
Lower water level
Higher threshold of FTO
More difficult withdrawal
Lower WSR
Rotational irrigation

5 days

5 days
Intake Flow Rate Q : 10 m3/s
Field water supply : 3 times
of daily water requirement
Observance of rotation :
Upstream branches do not
withdraw water during off-turn
 Strict application rule:
Water withdrawal stops when
ponded water exceeds 100 mm
depth, and irrigation re-starts at
80 ％ of soil moisture

5 days
（execution phase）
Water management conditions

Planning water management






（Type O）
Observance of rotation
Strict application rule
Possible water managements
Type A :
Direct FTOs use riparian right and application rule is strict
Type B :
All FTOs observe rotation and application rule is not strict
Type AB :
Direct FTOs use riparian right and application rule is not strict
Result (3)
WSR corresponding to water management types
Along lateral canal
WSR
WSR
Along RMC
Branch 1
Branch 2 Branch 3
Branch 1 Branch 2 Branch 3
1. Low WSR for Branch 1 along RMC
2. High WSR for Branch 2 along RMC at AB
type management
3. Low WSR for Branch 3 along lateral canal at
AB type management
Result (4)
Direct FTO WSR along RMC based on type O
O
1
給水率
WSR
0.8
0.6
0.4
0.2
0
Branch 2
Branch 3 Downstream
2
3
4
6
7
8
10
11
12
13
15
16
19
21
22
23
26
27
29
30
31
33
34
35
36
38
39
40
41
43
45
46
47
48
49
52
55
56
61
63
65
68
71
72
Upstream Branch 1
Larger cross section
High inlet of FTO
Lower water level
Difficult withdrawal
Checks, Laterals and Spill ways along RMC
Result (5)
Direct FTO WSR in Branches 2 and 3, along RMC
based on types of O and AB
WSR
O
Sure water
withdrawal
Branch 2
Excessive
withdrawal
at off-rotation
WSR
AB
Branch 3
Branch 2
Branch 3
Result (6)
O
WSR
FTO WSR at laterals in Branch 3
based on types of O and AB
13L
15L
17L
17La 18L 19L 20L 21L 22L
Water
deficit at
downstream
WSR
AB
14L
Excessive
withdrawal
at midstream
13L
14L
15L
17L
17La 18L 19L 20L 21L 22L
Conclusion

Water distribution performance is influenced by
structures and strictness of water management


Influence by structures
Water withdrawal is restricted when water level is low.
Influence by strictness of water management
One of two observances of rules improves water
distribution performance considerably

Other wise
Excessive withdrawal at middle branch
Serious water deficit at downstream branch