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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 1 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 2 I. Introduction to PAWEES 3 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 4 II. Impact Assessment of Climate Change on Paddy and Water Environment 5 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. 6 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. 7 0 II. Impact Assessment < 3 times/yr 4times/yr 5times/yr 6times/yr 7times/yr 8times/yr 10times/yr Average annual times 1 2 3 Average times 4 5 6 7 2001-Sep. 2008 8 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 7 8 9 10 Times of typhoons attacked Taiwan from 1951-2008 Rainfall Intensity 30 Rainfall Intensity(mm/day) Rainfall intensity 35 Linear Fit y = 0.0773x - 132.87 25 20 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 8 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. 9 III. Adaptation Strategy to Mitigate Impacts 10 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. 11 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 12 IV. PAWEES’s Contributions in Water Management of Paddy Fields 13 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 14 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. 15 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 16 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 17 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 18 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 19 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 20 Thank you for Listening! Paddy field in Taiwan 21