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Sustainable Water Management of Paddy FieldsSustainable Water Management of Paddy FieldsIIn Adapting to Climate Change n Adapting to Climate Change

Sustainable Water Management of Paddy FieldsSustainable Water Management of Paddy FieldsIIn Adapting to Climate Change n Adapting to Climate Change

Dr. Shen-Hsien Chen

International Society of Paddy and Water Environment Engineering (PAWEES)

March 18, 2009

SpeakerSpeaker’’s Corners Corner

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Outline Outline

I. Introduction to PAWEESII. Impact Assessment of

Climate Change on Paddy and Water Environment

III.Adaptation Strategy to

Mitigate Impacts

IV.PAWEES’s Contributions in

Water Management of

Paddy Fields

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I. Introduction to PAWEES

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EstablishmentEstablishment Initiated by Japan, Korea, and Taiwan

Established in January 2003, just prior to WWF3

MissionMission Build and distribute a new system of science and technology

in agricultural engineering

Deal with water issues linked to the environment, food security, and poverty

2008 PAWEES Conference2008 PAWEES Conference

Theme: Impact assessment and adaptation strategy of paddy & water management due to global climate change

International Society of Paddy & Water International Society of Paddy & Water Environment Engineering (PAWEES)Environment Engineering (PAWEES)

I. IntroductionI. Introduction

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II. Impact Assessment of Climate Change on Paddy and Water Environment

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Changes of climate (e.g., air temperature, precipitation, and evapotranspiration) would have direct effects on rice plant growth.

They would also cause hydrological pattern changes of an area or basin with paddy fields.

The impacts on paddy & water environment are believed to have complicated processes so that they are difficult to be assessed precisely.

Although the impacts might be different from place to place, they have been indeed observed more and more.

Climate Change and its impacts on Paddy and Water Environment

II. ImpactII. Impact AssessmentAssessment

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Japanese CaseA study was conducted to assess the future possible

changes in rice cultivation in the 2070s.

The results show that the mean yield and total production of rice would increase in years with cool summer, while decrease with hot summer.

II. ImpactII. Impact AssessmentAssessment

Korea CaseA study was conducted to assess the future

potential impact of climate change on the inflow from agricultural watershed and its temporal variation of reservoir storage in 2020s, 2050s, and 2080s.

The results show that the future decreased inflows

in autumn would affect the reservoir storage during the period of autumn and winter, and cause a severe spring drought if rainfall is insufficient.

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1154mm1154mm 1657mm1657mm

1056mm1056mm

y = 0.0773x - 132.87

0

5

10

15

20

25

30

35

1961 1966 1971 1976 1981 1986 1991 1996 2001 2006

Year

Rain

fall Inte

nsity(m

m/d

ay)

Rainfall Intensity

Linear Fit

II. ImpactII. Impact AssessmentAssessment

0 1 2 3 4 5 6 7 8 9 10

1951-1960

No. of years

3.1

3.2

2.9

3.4

3.3

6.9

Average annual times

< 3 times/yr 4times/yr 5times/yr 6times/yr

7times/yr 8times/yr 10times/yr

1961-1970

1971-1980

1981-1990

1991-2000

2001-Sep. 2008

0 1 2 3 4 5 6 7 8 9 10Average times

Times of typhoons attacked Taiwan from 1951-2008

Rain

fall inten

sity

Year

Trend of rainfall intensity for Keelung Station in Taiwan from 1961 to 2006 Daily and cumulate rainfalls in the

plum rains season from 1989 to 2006

Taiwan Case Some observed changes of

hydrological cycle do match the expected impacts of climate change.

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Taiwan Case (cont’d) The irrigation of paddy rice for first crop duri

ng dry season needs more water than second crop during wet season.

The shortage of rainfalls in dry seasons has had a significant impact on the first crop of paddy rice in Taiwan.

Fallow of paddy fields for supplying agricultural water to domestic users even makes the situation worse.

In adapting to climate change, the first crop of paddy rice should be considered to adopt other up-land crops, such as corn, soybean and sweet potatoes, to conserve the scarce water in dry season for other high productivity uses.

II. ImpactII. Impact AssessmentAssessment

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III. Adaptation Strategy to Mitigate Impacts

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III. AdaptationIII. Adaptation StrategyStrategy

Adaptation Strategies to Mitigate the Impacts (1)

Assess: Assess the most vulnerable areas of paddy fields and periods of

cultivation to climate change impacts

Re-evaluate: Re-evaluate the resistance or supply ability of existed

agricultural water infrastructures and determining if they needed to be

functionally rebuilt and expanded

Minify: Create diversified, distributed, and shock-flexible units and

backup systems.

ARMING for Climate Change!

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III. AdaptationIII. Adaptation StrategyStrategy

Adaptation Strategies to Mitigate the Impacts (2)

Implement: Select, prioritize, and phase implementation of specific

adaptation strategies

No-regret: Reduce, stop, or even avoid the actions assured to result in

hazards to paddy and water environment, and keep or even enhance those

benefit systems

Gather: Gather all stakeholders’ opinions and make the best decision

ARMING for Climate Change!

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IV. PAWEES’s Contributions in

Water Management of Paddy Fields

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農業地帶

排水水路

Evapotranspiration• Increase probabilities of rainfall• Regulate microclimate

Percolation• Purify water quality• Collected to provide the

source of return flow

Return Flow• Reuse to provide for

other users

Domestic use

Industrial use

Agricultural use

Detention• Retain significant amount

of irrigational water or floodwater by deep water management or deep ponding (Japan)

IV. PAWEES’sIV. PAWEES’s Contributions Contributions

Novel Concept:Novel Concept: Multiple functions of Paddies Multiple functions of PaddiesNovel Concept:Novel Concept: Multiple functions of Paddies Multiple functions of Paddies

Phorizontal >>Pvertical (Korea)

Paddy fields

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6 cm

Regular Application

New Application

18 cm25 cm

Topic 1: Deep Water Management (1)Topic 1: Deep Water Management (1)Topic 1: Deep Water Management (1)Topic 1: Deep Water Management (1)

Advantages: In terms of water storage aspect, extra water obtained can be stored

in paddy fields as well as underground aquifers. In terms of flood detention aspect, lots of paddy fields with taller

border means more space for detaining or storing floodwater. In terms of paddy production aspect, deeper water can protect stem

of paddy from storms, and the quality and productivity of paddy rice are almost the same as and even better than those in the past.

Playgrounds, green spaces, schools, etc.

Watershed

Paddy fields

IV. PAWEES’sIV. PAWEES’s Contributions Contributions

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Demand for raw water

Demand for water of good quality

Paddyfields

Natural river or drainage(non-guaranteed water quality) Treatment

plant

Cut-off gate

Externally Discharge sewage is strictly prohibited

Users

Topic 2: Agricultural Return Flow (1)Topic 2: Agricultural Return Flow (1)Topic 2: Agricultural Return Flow (1)Topic 2: Agricultural Return Flow (1)

Separated ditch for collecting return flow

Pond for storage

Users

IV. PAWEES’sIV. PAWEES’s Contributions Contributions

Drainage ditches

Irrigational ditches

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IV. PAWEES’sIV. PAWEES’s Contributions Contributions

Topic 2: Agricultural Return Flow (2)Topic 2: Agricultural Return Flow (2)Topic 2: Agricultural Return Flow (2)Topic 2: Agricultural Return Flow (2)

Conventional way-- “Differential”

Distribute supply to the sectors with demands

Source of supply

Conveyance system

Distribution system

Domestic water users

Agricultural

water users

Domestic water users

Industrial water usersDrainage system

Return flow

Specify the nearest supply based on integrated demands

New concept-- “Integral”

Paddy field

Paddy field

Advantages:Better water quality because of paddy purificationLow costs of conveyance systems because of short distanceLess argument among sectors because of return flow of paddy fieldsMore flexibility of allocation because of stable return flow

Successful application in “Midori” of Japan

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Sea

Shallow subsurfacehorizontal percolation

Paddy field

Sludge wall in plow zone

Arable Land

Salty water vapor

Windbreak forest

Coast N

Field in Taiwan

IV. PAWEES’sIV. PAWEES’s Contributions Contributions

Sludge SludgeSludge

Windbreak trees

Topic 3: Land Conservation Strategy (1)Topic 3: Land Conservation Strategy (1)Topic 3: Land Conservation Strategy (1)Topic 3: Land Conservation Strategy (1)

Without irrigation

PaddiesAugust, 2008 March, 2009

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Shallow subsurfacehorizontal percolation

Wetland Paddy

Sludge wall in plow zone

Windbreak forest

Without irrigation

N

IV. PAWEES’sIV. PAWEES’s Contributions Contributions

Lake Chad Basin Sahara

Airborne dust

Chad, Africa

Topic 3: Land Conservation Strategy (2)Topic 3: Land Conservation Strategy (2)Topic 3: Land Conservation Strategy (2)Topic 3: Land Conservation Strategy (2)

Reduced Lake Chad

Sahel Area

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Creek irrigation in Japan (for over 300 years)

Arable land in Lake Chad Basin

Map source: http://www.google.com Map source: http://web-japan.org

“Furrow Recharge Technique”(Japan)- Widen and deepen the drainage ditches to

collect more percolation from the bottomPaddy field

Irrigational ditch

Drainage ditch

Prospect of Chad in the future

Crop Rotation in Taiwan (for 80 years)

Topic 3: Land Conservation Strategy (3)Topic 3: Land Conservation Strategy (3)Topic 3: Land Conservation Strategy (3)Topic 3: Land Conservation Strategy (3)

Current

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Thank you for Listening!

Paddy field in Taiwan