Transcript Sustainable Water Management of Paddy Fields In Adapting to

Theme 1_Topic 1.1_Session 3_Roundtable 3
Drying Rural Areas
Sustainable Water Management of Paddy Fields
In Adapting to Climate Change
Dr. Shen-Hsien Chen
International Society of Paddy and Water Environment Engineering (PAWEES)
March 17, 2009
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Outline
I. Introduction to PAWEES
II. 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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I. Introduction
International Society of Paddy & Water
Environment Engineering (PAWEES)
Establishment
 Initiated by Japan, Korea, and Taiwan
 Established in January 2003, just prior to WWF3
Mission
 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 Conference
 Theme: Impact assessment and adaptation strategy of
paddy & water management due to global climate change
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II. Impact Assessment of Climate Change
on Paddy and Water Environment
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II. Impact
Assessment
Climate Change and its impacts on Paddy
and Water Environment
 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.
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II. Impact
Assessment
Japanese Case
A 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.
Korea Case
A 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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II. Impact
Assessment
< 3 times/yr
4times/yr
5times/yr
6times/yr
7times/yr
8times/yr
10times/yr
Average annual times
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2
3
Average times
4
5
6
7
2001-Sep. 2008
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9
10
6.9
1991-2000
3.3
1981-1990
3.4
1971-1980
Taiwan Case
 Some observed changes of
hydrological cycle do match the
expected impacts of climate change.
2.9
1961-1970
1154mm 1657mm
3.2
1951-1960
3.1
0
1
2
3
4
5
6
No. of years
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8
9
10
Times of typhoons attacked Taiwan
from 1951-2008
Rainfall Intensity
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Rainfall Intensity(mm/day)
Rainfall intensity
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Linear Fit
y = 0.0773x - 132.87
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15
1056mm
10
5
0
1961
1966
1971
1976
1981
1986
1991
1996
2001
2006
Year
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
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II. Impact
Assessment
Taiwan Case (cont’d)
 The irrigation of paddy rice for first crop
during 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.
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III. Adaptation Strategy to Mitigate Impacts
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ARMING for Climate Change!
III. Adaptation
Strategy
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.
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ARMING for Climate Change!
III. Adaptation
Strategy
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
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IV. PAWEES’s Contributions in
Water Management of Paddy Fields
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Novel Concept: Multiple functions of Paddies
IV. PAWEES’s
Contributions
Evapotranspiration
• Increase probabilities of rainfall
• Regulate microclimate
Industrial use
Agricultural use
Domestic use
Detention
農業地帶
Paddy fields
Return Flow
• Reuse to provide for
other users
Phorizontal >>Pvertical (Korea)
• Retain significant amount
of irrigational water or
floodwater by deep water
management or deep
ponding (Japan)
排水水路
Percolation
• Purify water quality
• Collected to provide the
source of return flow
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Topic 1: Deep Water Management (1)
IV. PAWEES’s
Contributions
Watershed
Regular Application
6 cm
New Application
25 cm
18 cm
Playgrounds, green
spaces, schools, etc.
Paddy fields
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.
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Topic 2: Agricultural Return Flow (1)
IV. PAWEES’s
Contributions
Externally Discharge sewage
is strictly prohibited
Irrigational ditches
Paddy
fields
Drainage ditches
Separated ditch for collecting return flow
Cut-off gate
Natural river or drainage
(non-guaranteed water quality)
Pond for
storage
Demand for
raw water
Users
Treatment
plant
Demand for
water of good
quality
Users
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Topic 2: Agricultural Return Flow (2)
Conventional way-- “Differential”
Distribute supply to the
sectors with demands
Source of supply
Domestic
water
users
IV. PAWEES’s
Contributions
New concept-- “Integral”
Specify the nearest supply
based on integrated demands
Paddy field
Return flow
Distribution system
Agricultural
Conveyance system
water
users
Paddy field
Drainage system
Domestic
water
users
Industrial
water
users
Successful application in “Midori” of Japan
Advantages:
Better water quality because of paddy purification
Low costs of conveyance systems because of short distance
Less argument among sectors because of return flow of paddy fields
More flexibility of allocation because of stable return flow
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Topic 3: Land Conservation Strategy (1)
Paddy field
IV. PAWEES’s
Contributions
Windbreak forest
Arable Land
Shallow subsurface
horizontal percolation
Coast
Sea
N
Without irrigation
Salty water vapor
Sludge wall in
plow zone
Paddies
August, 2008
Windbreak trees
Sludge Sludge
Field in
Taiwan
March, 2009
Sludge
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Topic 3: Land Conservation Strategy (2)
Wetland Paddy
IV. PAWEES’s
Contributions
Windbreak forest
N
Lake Chad Basin
Shallow subsurface
horizontal percolation
Sahel Area
Sahara
Without irrigation
Airborne dust
Sludge wall in
plow zone
Chad, Africa
Reduced Lake Chad
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Topic 3: Land Conservation Strategy (3)
Irrigational ditch
“Furrow Recharge Technique”(Japan)
Paddy field
- Widen and deepen the drainage ditches to
collect more percolation from the bottom
Drainage ditch
Current
Prospect of Chad in the future
Crop Rotation in Taiwan
(for 80 years)
Arable land in
Lake Chad Basin
Map source: http://www.google.com
Creek irrigation in Japan
(for over 300 years)
Map source: http://web-japan.org
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Thank you for Listening!
Paddy field in Taiwan
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