1. 1 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 18, 2009 Speaker ’ s Corner

2. 2 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

3. 3 I. Introduction to PAWEES

4. 4 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 International Society of Paddy & Water Environment Engineering (PAWEES) I. Introduction

5. 5 II. Impact Assessment of Climate Change on Paddy and Water Environment

6. 6  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. Impact Assessment Assessment

7. 7 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. II. Impact Assessment Assessment 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.

8. 8 1154mm1657mm 1056mm II. Impact Assessment Assessment Times of typhoons attacked Taiwan from 1951-2008 Rainfall intensity 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.

9. 9 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. II. Impact Assessment Assessment

10. 10 III. Adaptation Strategy to Mitigate Impacts

11. 11 III. Adaptation Strategy Strategy Adaptation Strategies to Mitigate the Impacts (1) A ssess : Assess the most vulnerable areas of paddy fields and periods of cultivation to climate change impacts R e-evaluate: Re-evaluate the resistance or supply ability of existed agricultural water infrastructures and determining if they needed to be functionally rebuilt and expanded M inify: Create diversified, distributed, and shock-flexible units and backup systems. ARMING for Climate Change !

12. 12 III. Adaptation Strategy Strategy Adaptation Strategies to Mitigate the Impacts (2) I mplement: Select, prioritize, and phase implementation of specific adaptation strategies N o-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 G ather: Gather all stakeholders’ opinions and make the best decision ARMING for Climate Change !

13. 13 IV. PAWEES’s Contributions in Water Management of Paddy Fields

14. 14 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 ’ s Contributions Contributions Novel Concept: Multiple functions of Paddies P horizontal >>P vertical (Korea) Paddy fields

15. 15 6 cm Regular Application New Application 18 cm 25 cm 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 ’ s Contributions Contributions

16. 16 Demand for raw water Demand for water of good quality Paddy fields 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) Separated ditch for collecting return flow Pond for storage Users IV. PAWEES ’ s Contributions Contributions Drainage ditches Irrigational ditches

17. 17 IV. PAWEES ’ s Contributions Contributions 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 users Drainage system Return flow Specify the nearest supply based on integrated demands New concept-- “Integral” Paddy field 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 Successful application in “Midori” of Japan

18. 18 Sea Shallow subsurface horizontal percolation Paddy field Sludge wall in plow zone Arable Land Salty water vapor Windbreak forest Coast N Field in Taiwan IV. PAWEES ’ s Contributions Contributions Sludge Windbreak trees Topic 3: Land Conservation Strategy (1) Without irrigation Paddies August, 2008March, 2009

19. 19 Shallow subsurface horizontal percolation Wetland Paddy Sludge wall in plow zone Windbreak forest Without irrigation N IV. PAWEES ’ s Contributions Contributions Lake Chad BasinSahara Airborne dust Chad, Africa Topic 3: Land Conservation Strategy (2) Reduced Lake Chad Sahel Area

20. 20 Creek irrigation in Japan (for over 300 years) Arable land in Lake Chad Basin Map source: http://www.google.comMap source: http://web-japan.org “Furrow Recharge Technique”(Japan) - Widen and deepen the drainage ditches to collect more percolation from the bottom Paddy field Irrigational ditch Drainage ditch Prospect of Chad in the future Crop Rotation in Taiwan (for 80 years) Topic 3: Land Conservation Strategy (3) Current

21. 21 Thank you for Listening! Paddy field in Taiwan