Study on performance of dry season Study on performance of dry season rotational irrigation for Mae Lao irrigation rotational irrigation for Mae Lao irrigation

project, Thailandproject, Thailand

Naritaka KUBO: Univ. of Tokyo, JapanNaritaka KUBO: Univ. of Tokyo, JapanTakuya TAKEUCHI: Tokyo Univ. of Agri. & Tec., JapanTakuya TAKEUCHI: Tokyo Univ. of Agri. & Tec., JapanUnggoon WONGTRAGOON: Rajamangala Uni. of Tec., Unggoon WONGTRAGOON: Rajamangala Uni. of Tec., ThailandThailandHajime TANJI: NIRE, NARO, Tsukuba, JapanHajime TANJI: NIRE, NARO, Tsukuba, Japan

　　　　 Back GroundBack GroundIn south east Asian countriesIn south east Asian countries……

Irrigation projects were developed primarily Irrigation projects were developed primarily for supplemental supply during rainy seasonfor supplemental supply during rainy season

Constructing new reservoirs makes Constructing new reservoirs makes irrigation possible during dry seasonirrigation possible during dry season

Restricted irrigation areas Restricted irrigation areas because of scare waterbecause of scare water

Necessity of effective water Necessity of effective water useuse

Water supply is not Water supply is not enoughenough

Mae Lao Project site

Mae Lao Mae Lao irrigation irrigation schemescheme

Tributary of the Tributary of the Kok River Kok River belonging to belonging to Mekong River Mekong River basinbasin

Chiang Rai in Chiang Rai in North ThailandNorth Thailand

Irrigation Area : Irrigation Area : 23680 ha23680 ha

Branch 34,848 ha

Branch 25,264 ha

Branch 17,968 ha

Branch 45,600 ha

Mae Lao river

Left Main Canal

Right Main Canal

Mae Lao weir

Mae Suai Dam

Laterals

Streams 0 5 10 km

　　　　 Mae Lao project siteMae Lao project site

18,080 ha

Right Main Canal Right Main Canal （（ RMCRMC ））

- RMC length - RMC length ：： about about 5050 km km

- Secondary canals - Secondary canals ： ： 2323

- Max Q- Max Q ： ： about about 2727 mm33/s/s

Mae Suai Dam

Mae Lao Weir

　　　　 Water deficit in dry seasonWater deficit in dry season

InterviewsInterviews

Branch 1Branch 1　　・　　・ Water deficit occurs partiallyWater deficit occurs partially Branch 2Branch 2　　・　　・ Irrigation area is expanded beyond Irrigation area is expanded beyond

allotted area allotted area

　　・　　・ Water deficit occurs in downstream areasWater deficit occurs in downstream areas Branch 3Branch 3　　・　　・ Water deficit is seriousWater deficit is serious

　　・　　・ No water comes to downstream areasNo water comes to downstream areas

Summary of Summary of interviewsinterviews

Mae Suai Dam can Mae Suai Dam can store 73,000,000 store 73,000,000 mm33

Functional Functional problemsproblems

Managerial Managerial problemsproblems

Illegal activitiesIllegal activities Problem Problem

identificationidentification

Low distribution Low distribution efficiencyefficiency

Unequal water Unequal water distributiondistribution

　　　　 ObjectivesObjectives

Quantitative analysis of effects of facilitiesQuantitative analysis of effects of facilities and and water management on water distribution water management on water distribution performanceperformance

1. Planning phase1. Planning phase Continuous irrigation by non-uniform flow Continuous irrigation by non-uniform flow

modelmodel Effects by physical causes of facilities & Effects by physical causes of facilities &

structuresstructures

2. Execution phase2. Execution phase Rotational irrigation simulated by UIWDC Rotational irrigation simulated by UIWDC

modelmodel Effects by managerial & institutional causesEffects by managerial & institutional causes

　　　　 MethodologyMethodology

Water consumption in Water consumption in paddy fieldpaddy field

⇒⇒ Paddy Tank modelPaddy Tank model

Numerical simulation by Numerical simulation by UIWDC modelUIWDC model（（ Unggoon Unggoon et alet al., 2010., 2010 ））

　　（（ UUnsteady nsteady IIrrigation rrigation WWater ater DDistribution and istribution and CConsumptiononsumption ））

Water movement in Water movement in canalcanal

⇒⇒ 1-D unsteady flow 1-D unsteady flow modelmodel

qx

Q

t

A

quSSgAx

hgA

A

Q

xt

Q

f0

2

Saint-Venant Saint-Venant EquationsEquations

AA ：： Area, Area, QQ ：： Flow, Flow, qq ：： side flow, side flow, hh ：：depth, depth, gg ：： gravitational acceleration, gravitational acceleration, SS

00 ：： bed slope, bed slope, SSff ：： friction slope, friction slope, uu ：：mean velocitymean velocity

inundated

Plow layer

Ground Water

　　　　 Modeling of irrigation Modeling of irrigation systemsystem

Branch 1

Branch 2

5L~12L

Branch 3

13L~22L

HW

1L

2L

3L

4L

Paddy field

CK

Check structure

PFPF

PF

PF

PF

PF PF

PF PF

PF PF

PF PF

PF

PF

Dir

ect

w

ith

dra

wal

Dir

ect

w

ith

dra

wal

Dir

ect

w

ith

dra

wal

Dir

ect

w

ith

dra

wal

CK

CK

CK

Modeling of FTOs and water Modeling of FTOs and water distributiondistribution

HW

J

1R-1L

E

J CK E

CK

CK

SI

SW

CK

J

E

FT

O 2R

FT

O 3R

FT

O 4R

FT

O 5R

FT

O 8R

FT

O 10R

FT

O 11R

FT

O 13R

FT

O 14R

FT

O 9

L

FT

O 1

2L

FT

O 6R

FT

O 7

L

CK1L-RMC

J FT

O 1R

FT

O 2

L

FT

O 3R

FT

O 4

L

FT

O5R

FT

O 6R

FT

O 7

L

FT

O 8

L

1R-2L

E

J

FT

O 9R

FT

O 1

0L

FT

O 1

1L

2L-RMC

SW

J

SW

FT

O 2R

FT

O 1

L

FT

O 3R

FT

O 4

L

FT

O5R

FT

O 7R

FT

O 6

L

FT

O 8

L

FT

O 9R

FT

O 1

0L

FT

O 11R

FT

O 12R

FT

O 1

3L

FT

O 1

4L

FT

O 15R

FT

O 16R

FT

O 17R

3L-RMCCK

FT

O 1

L

FT

O 1R

FT

O 2

L

FT

O 2R

FT

O 3

L

FT

O 3R

RMC

FT

O 4

L

FT

O 4R

CK CK CK

E

E

SI

FT

O 5R

FT

O 5

L

1R-4L

E

JCK CK

E

J FT

O 6R

2R-4L

E

J JSI

FT

O 7R

FT

O 6

L

FT

O 7

L

FT

O 8

L

JFT

O 8R

J

FT

O 9R

FT

O 10R

FT

O 11R

FT

O 9

L

FT

O 12R

CK

FT

O 1

0L

FT

O 13R

CK

FT

O 1

1L

FT

O 1

2L

FT

O 14R

CK

FT

O 1

3L

FT

O 15R

CK

E : Ended Point

J : Joint

CK : Check Gate

SW : Spill Way

SI : Siphon

HW : Head Work

4L-RMCE

1L-4

L

3R-4L

E

4R-4L

E

2L-4

L

E

CK

SI

J

Q2

Q1

Q3

Q4

Q5

Q7

Q6

Q8

Q9

Q10

Q11

Q12

Q13

Q14

Q15

Q16

Q17

3L-RMCCK E

Reach

Reach

Reach

: Computational mesh point

CK

SI

J

Q17

CK E

Reach

Reach

Reach

: Computational mesh point

ΔX

q

(a)

(b)

3L-RMC

　　　　 Intake flow rate Intake flow rate (IFR)(IFR)

Assumptions for CalculationAssumptions for Calculation

Equal water distribution within a branchEqual water distribution within a branch Daily water consumption in paddy field:14.7 Daily water consumption in paddy field:14.7

mm/daymm/day Each branch is calculated independently Each branch is calculated independently Total paddy field area in Branch i : Total paddy field area in Branch i : Ai

Scheduled area to be irrigated in Branch i : Scheduled area to be irrigated in Branch i : Asi

1. Based on water requirement Q1. Based on water requirement Qss

2. Base on non-uniform flow 2. Base on non-uniform flow calculation Qcalculation Qee （（ considering physical considering physical propertiesproperties ））

Exact water volume to irrigate area of Exact water volume to irrigate area of AAsisi

　　⇒　⇒　 Scheduled QScheduled Qsisi for Branch i for Branch i Based on water requirementBased on water requirement

　＝　＝ Paddy water consumption ×APaddy water consumption ×Asisi

+ Seepage loss+ Seepage loss

　　　　 1. Calculation of scheduled IFR Q1. Calculation of scheduled IFR Qss

Canal seepage losses are Canal seepage losses are calculated assuming Full calculated assuming Full

Supply LevelSupply LevelPF

PF PF

PFto be

irrigated

not to beirrigated

Calculated by numerical simulation for Calculated by numerical simulation for non-uniform flow non-uniform flow

IFR at equilibriumIFR at equilibrium

　（　（ useless spillageuseless spillage ＝＝ deficitdeficit ）　）　　　

Spillage

deficit

⇒⇒Equilibrium QEquilibrium Qeiei for Branch ifor Branch i 　　　　

Canal seepage loss Canal seepage loss considering Non-uniform considering Non-uniform

Flow LevelFlow Level

Paddy field

canal

Inlet of FTO

　　　　 2. Calculation of equilibrium IFR 2. Calculation of equilibrium IFR QQee

　　　　 Result (1)Result (1) 　 　 Scheduled area vs. Scheduled area vs. IFR Q IFR Q

No differences No differences at no seepage at no seepage losseslosses

→ → caused by caused by seepage lossesseepage losses

Lower water Lower water level than that of level than that of FSLFSL

Longer distance Longer distance causes more causes more losseslosses

Scheduled Qsi & Equilibrium Scheduled Qsi & Equilibrium QeiQei

Maximum Flow Maximum Flow Rate 27 mRate 27 m33/sec/sec

Scheduled area ratio (Asi/Ai)

Inta

ke F

low

Rate

(m

3/s

)

　　 　　 Result (2)Result (2) 　 　 Scheduled area vs. Scheduled area vs. WSRWSR

Larger canal sectionLarger canal section Lower water levelLower water level Higher threshold of Higher threshold of

FTOFTO

WSR = [WSR = [Actually distributed waterActually distributed water]/[]/[Volume to be Volume to be

distributeddistributed]] (Water supply ratio)(Water supply ratio)

More difficult More difficult withdrawalwithdrawal

Lower WSRLower WSR

More upstream

WS

R

Branch 1 Branch 2 Branch 3

Scheduled area ratio (SAR Asi/Ai)

　　　　 Rotational irrigationRotational irrigation 　（　（ execution execution phasephase ））

5 days

5 days

5 days

Intake Flow Rate Q : 10 Intake Flow Rate Q : 10 mm33/s/s

Field water supply : 3 Field water supply : 3 times of daily water times of daily water requirementrequirement

Observance of rotationObservance of rotation : :

Upstream branches do not Upstream branches do not withdraw water during off-turn withdraw water during off-turn

Strict application ruleStrict application rule::

Water withdrawal stops when Water withdrawal stops when ponded water exceeds 100 ponded water exceeds 100 mm depth, and irrigation re-mm depth, and irrigation re-starts at 80 starts at 80 ％ ％ of soil of soil moisturemoisture

　　　　 Water management Water management conditionsconditions

Observance of rotationObservance of rotation Strict application ruleStrict application rule

Planning water managementPlanning water management （（ Type OType O ））

Possible water managementsPossible water managements Type AType A : :

Direct FTOs use Direct FTOs use riparian rightriparian right and application rule is strict and application rule is strict Type BType B : :

All FTOs observe All FTOs observe rotationrotation and application rule is and application rule is not strictnot strict Type ABType AB : :

Direct FTOs use Direct FTOs use riparian rightriparian right and application rule is and application rule is not not strictstrict

　　 　　 Result (3)Result (3) WSRWSR corresponding to water management corresponding to water management typestypes

1. Low WSR for Branch 1 along RMC1. Low WSR for Branch 1 along RMC

2. High WSR for Branch 2 along RMC at 2. High WSR for Branch 2 along RMC at AB type AB type managementmanagement

3. Low WSR for Branch 3 along lateral 3. Low WSR for Branch 3 along lateral canal at canal at AB type AB type managementmanagement

Along RMCAlong RMC

WS

R

Branch 1 Branch 2 Branch 3

WS

R

Branch 1 Branch 2 Branch 3

Along lateral Along lateral canalcanal

　　 　　 Result (4)Result (4) Direct FTO Direct FTO WSRWSR along RMCalong RMC based on type O based on type O

Larger cross sectionLarger cross section

High inlet of FTOHigh inlet of FTOLower water levelLower water level

Difficult withdrawalDifficult withdrawal

0

0. 2

0. 4

0. 6

0. 8

1

給水

率

Branch 2

Branch 3

Branch 1

Upstream

Downstream

WS

R

OO

Checks, Laterals and Spill ways along Checks, Laterals and Spill ways along

RMCRMC

Sure water withdrawal

Excessive withdrawal

at off-rotation

　　 　　 Result (5)Result (5) Direct FTO Direct FTO WSRWSR in Branches 2 and 3, in Branches 2 and 3, along along RMCRMC based on types of O and AB based on types of O and AB

OO

ABAB

WS

R

Branch 2

Branch 3

WS

R

Branch 2

Branch 3

Excessive withdrawal

at midstream

Water deficit at

downstream

　　 　　 Result (6)Result (6) FTO FTO WSRWSR at lateralsat laterals in Branch 3 in Branch 3 based on types of O and AB based on types of O and AB

OO

ABAB

13L 14L 15L 17L 17La 18L 19L 20L 21L 22L

WS

R

14L 15L 17L 17La 18L 19L 20L 21L 22L13L

WS

R

　　　　 ConclusionConclusion

Influence by structuresInfluence by structures　　　　　　 Water withdrawal is restricted when water level is Water withdrawal is restricted when water level is

low.low. Influence by strictness of water managementInfluence by strictness of water management　　　　　　 One of two observances of rules improves One of two observances of rules improves

waterwater distribution performance considerably distribution performance considerably Other wiseOther wise 　　　　　　 Excessive withdrawal at middle branchExcessive withdrawal at middle branch　　　　　　 Serious water deficit at downstream branchSerious water deficit at downstream branch

Water distribution performance is Water distribution performance is influenced by structures and strictness of influenced by structures and strictness of water managementwater management