Variation of irrigated rice yield under the climate change scenarios

Abstract

Atmospheric Carbon Dioxide (CO2) concentration and average daily maximum temperature in Sri Lanka show an increasing trend owing to global climate change, and they are two critical parameters for the rice production. During this study, variations of future rice yield in Kurunegala District were simulated under three conditions together with emission scenarios A2 and B2; viz. a) Present level of CO2 concentration with future
temperatures, b) Present level of temperature with future CO2 concentrations, and c) Future CO2 concentrations with future temperatures. The model predicted that the average rice yield would decrease by 8% and 3.4% with the condition (a) under the emission scenarios A2 and B2 respectively. The condition (b) showed that the
average rice yield would increase by 3.5% and 4.4% under the A2 and B2 scenarios respectively. The condition (c) which represents the future conditions more closely, showed that the average rice yield would increase by 1.7% and 2.4% under the A2 and B2 scenarios respectively

Full text

SAITM Research Symposium on Engineering Advancements
(SAITM – RSEA 2012)
Proceedings of the SAITM Research Symposium on
Engineering Advancements
SAITM – RSEA 2012
27th & 28th April, 2012
Faculty of Engineering
South Asian Institute of Technology and Medicine [SAITM]
P. O. Box 11, Millennium Drive,
Off Chandrika Kumaratunga Mawatha,
Malabe, Sri Lanka.
Major Topics:
1. Computer Science and ICT
2. Electrical, Electronics and Communications
3. Mechatronics and Automation
4. Water and Environment
5. Geotechnical and Soil Mechanics
6. Structural and Transportation
7. Town Planning
8. Urban Management
9. Technology Based Education
10. Project Management

SAITM Research Symposium on Engineering Advancements
(SAITM – RSEA 2012)
The right of publication in print, electronic and any other form and in any language is
reserved by SAITM.
Short extracts from SAITM publications may be reproduced without authorization
provided that the complete source is clearly indicated. Editorial correspondence and
requests to publish, reproduce or translate this publication (articles, papers etc.) in part
or in whole should be addressed to:
Symposium Secretary
Faculty of Engineering
South Asian Institute of Technology and Medicine (SAITM)
P.O. Box 11
Millennium Drive
Off Chandrika Kumaratunga Mawatha
Malabe Sri Lanka.
Tel.: (+94) 11 241 3351
Fax: (+94) 11 241 3332
E-mail: efac@saitm.edu.lk
Web: http://symposium.saitm.edu.lk/
NOTE:
All rights reserved. No part of this publication may be produced, stored and transmitted in any
form, or by any means, without prior written permission from the editor.
The views expressed in the papers are of the individual authors. The editors are not liable to
anyone for any loss or damage caused by any error or omission in the papers, whether such
error or omission is the result of negligence or any other cause. All such liability is declaimed.
Copyright © SAITM – RSEA 2012
ISBN 978-955-0638-01-7

SAITM Research Symposium on Engineering Advancements
(SAITM – RSEA 2012)
Message from the Chairman
SAITM Research Symposium on Engineering Advancements (RSEA) is the second such
event organized by SAITM Faculty of Engineering since its inception in 2009. Following
the highly successful inaugural Research symposium in May 2011, it is indeed an
achievement to continue the event as an annual fixture where students, staff and the
general engineering research community in Sri Lanka benefit.
Notwithstanding a relatively short history of its existence, SAITM Faculty of Engineering
has grown into a remarkable strength both in student numbers as well as by boldly
venturing into many areas where only the state universities in Sri Lanka have hitherto
dominated, thus establishing a firm leadership as a high quality engineering education
provider, at the tertiary level, among the non state sector higher education institutes.
Partnered by the Asian Institute of Technology (AIT), Thailand, SAITM Faculty of
Engineering has thus provided immense opportunities for its students and the
engineering community in Sri Lanka, a forum where advancement of engineering can
blossom. Just as the inaugural RSEA has spurred our students to venture into research
work to achieve higher goals, I am confident; this year’s event will establish the annual
SAITM RSEA as a beginning of a rich tradition.
Prof. Neville Fernando
MBBS (Ceylon)
President / Chairman
South Asian Institute of Technology and Medicine [SAITM]

SAITM Research Symposium on Engineering Advancements
(SAITM – RSEA 2012)
Message from the Dean, Faculty of Engineering
It is with great pleasure that we announce the organizing of the 2012 version of SAITM
Research Symposium on Engineering Advancements (SAITM RSEA 2012) scheduled for
27th and 28th of April 2012. This volume of proceedings of SAITM RSEA 2012 contains
the research papers that are presented on 27th and 28th of April along with extended
abstracts and keynote speeches. All the research papers of this volume have been peer
reviewed. The editors are very much grateful to the authors for contributing research
papers of high quality. We also acknowledge the financial sponsorship provided by
many organizations that has been extremely helpful for organizing a successful research
symposium.
We are pleased to acknowledge the advice and assistance provided by the members of
the Industry Advisory Committee along with many others who volunteered to assist to
make this very significant event a success. It is the earnest wish of the editors that this
volume of proceedings would serve a very useful service with the research community
directly or indirectly involved in the studies related to engineering advancements.
Dr. Sisuru Sendanayake
BSc. Eng (Hons), MSc, PhD (Moratuwa)
Dean, Faculty of Engineering
South Asian Institute of Technology and Medicine [SAITM]

SAITM Research Symposium on Engineering Advancements
(SAITM – RSEA 2012)
Message from the Editor
I warmly welcome you all to the “SAITM- Second Annual Research Symposium on
Engineering Advancements – RSEA 2012”.
Even though the world is experienced with immense science and technological
development countless number of failures in all the sectors ranging from the design and
construction of infrastructure to information technology and telecommunication are
evident today. This is mainly caused by incorrect understanding of knowledge sharing,
lack of awareness and the limited accuracy in transferability of knowledge to the actual
environment. We recognize that active involvement in research, publication and
collaboration and partnerships with the industry can significantly overcome these
issues.
RSEA 2012 is designed to bring together the university students, researchers, scientists
and industrialists to an open and interactive forum where they can discuss and share
knowledge on technological and scientific challenges, practical barriers, theoretical
developments and their applications and limitations in order to bring a sustainable
development. RSEA 2012 opens the platform to cover number of topics which include
Computer Science and ICT, Electrical, Electronics, and Communications, Mechatronics
and Automation, Civil Engineering and Project Management.
In order to ensure the overall quality of the proceedings each submission was subjected
to a minimum of one peer review by an expert in the field as a part of a double blind
review process. In addition, you will be listening to two inspiring keynote addresses by
two outstanding personnel from the academia, Prof. Chintha Jayasinghe, Director of
Postgraduate Studies, University of Moratuwa, Sri Lanka and Prof. Matthew Dailey,
School of Engineering and Technology, Asian Institute of Technology in Bangkok,
Thailand.
My sincere wish is that RSEA will grow from strength to strength in years to come and
continue to address the real world engineering challenges. I am looking forward to
meeting you at the SAITM Research Symposium on Engineering Advancements – 2012.
I also take this opportunity to convey my sincere thank to Prof. Lanaka Udawatta, the
founder of this esteemed event as well as the editor of the RSEA 2011 proceedings for
his dedicated efforts in making the RSEA 2011 to a success.
Dr. N. P. Miguntanna
BSc. Eng(Hons)(Peradeniya), PhD (Queensland University of Technology (QUT), Australia)
The Editor, SAITM – RSEA 2012
South Asian Institute of Technology and Medicine [SAITM]

SAITM Research Symposium on Engineering Advancements
(SAITM – RSEA 2012)
SAITM RSEA 2012 - Programme Committee
 Dr. S. Sendanayake
 Dr. R. S. Mallawaarachchi
 Eng. W. G. C. W. Kumara
 Dr. N. Miguntanna
 Dr. T. Rajakaruna
 Dr. K. K. Wijesundara
 Mr. T. Gunarathne
 Ms. N. Perera
 Ms. P. Liyana Arachchi
SAITM RSEA 2012 – Expert Committee
 Prof. E.M.N. Ekanayake
Department of Electrical & Electronic Engineering,
Faculty of Engineering, University of Peradeniya,
Sri lanka.
E-mail: neka@ee.pdn.ac.lk
 Prof. P.B.R. Dissanayake
Department of Civil Engineering,
Faculty of Engineering, University of Peradeniya,
Sri Lanka.
E-mail: ranjith@civil.pdn.ac.lk
 Dr. Cyril Kariyawasam
Department of Civil and Environmental Engineering,
Faculty of Engineering, University of Ruhuna,
Sri Lanka.
E-mail: cyril@eie.ruh.ac.lk

- 31 -
SAITM Research Symposium on Engineering Advancements
(SAITM – RSEA 2012)
VARIATION OF IRRIGATED RICE YIELD UNDER THE CLIMATE CHANGE
SCENARIOS
W.R.S.S. Dharmarathna1, S.B. Weerakoon2*, U.R. Rathnayake3, Srikantha Herath4
1Department of Civil Engineering, Faculty of Engineering, University of Peradeniya, Peradeniya, Sri Lanka.
2* Corresponding Author, Department of Civil Engineering, Faculty of Engineering, University of Peradeniya,
Peradeniya, Sri Lanka, Email: sbweera@pdn.ac.lk
3Department of Civil Engineering, Faculty of Engineering, University of Peradeniya, Peradeniya, Sri Lanka.
4United Nations University – Institute for Sustainability and Peace (UNU-ISP), Shibuya-ku, Tokyo, Japan.
ABSTRACT
Atmospheric Carbon Dioxide (CO2) concentration and average daily maximum temperature in Sri Lanka show
an increasing trend owing to global climate change, and they are two critical parameters for the rice production.
During this study, variations of future rice yield in Kurunegala District were simulated under three conditions
together with emission scenarios A2 and B2; viz. a) Present level of CO2 concentration with future
temperatures, b) Present level of temperature with future CO2 concentrations, and c) Future CO2 concentrations
with future temperatures. The model predicted that the average rice yield would decrease by 8% and 3.4% with
the condition (a) under the emission scenarios A2 and B2 respectively. The condition (b) showed that the
average rice yield would increase by 3.5% and 4.4% under the A2 and B2 scenarios respectively. The condition
(c) which represents the future conditions more closely, showed that the average rice yield would increase by
1.7% and 2.4% under the A2 and B2 scenarios respectively.
Key words: Rice yield, Climate change, CO2 concentration, Temperature
1. INTRODUCTION
Studying the rice yield variability under the climate
change scenarios has become very important for Sri
Lankans, as rice is their staple food. The average
daily maximum temperature and atmospheric CO2
concentration are increasing as a result of global
climate change and have become the most
important considerations for Sri Lankan rice
production. The increasing trend of daily maximum
temperature could decrease the rice spikelet
fertility and will reduce the yield while the
increasing trend of atmospheric CO2 concentration
could increase the rice yield.
The study was set up to examine the both
temperature and CO2 effects on four rice varieties
that are cultivated in Kurunegala District, Sri
Lanka, under the emission scenarios, A2 and B2
published by the Intergovernmental Panel on
Climate Change (IPCC, 2007). Kurunegala District
is located in the Northwestern Province of Sri
Lanka and there are 25 major irrigation schemes
and about 2500 small village tanks and diversions
based storage irrigation systems for paddy
cultivation [1]. The rice varieties, namely Bg 250
(2 ½ months), At 307 (3 months), Bg 357 (3 ½
months) and Bg 379-2 (4 months) were selected for
the study, to represent both short term and long
term rice varieties.
2. METHODOLOGY
The daily weather variables, rainfall, maximum
temperature and minimum temperature were
forecasted up to year 2090 by using Global Climate
Models (GCMs) data under the Hadley Centre
experiments (HadCM3) for A2 (medium–high
emissions) and B2 (medium–low emissions)
scenarios.
The GCMs data were downscaled into regional
level by using Statistical Downscaling Model
(SDSM 4.2) [2]. The model was calibrated and
validated by using 40 years of observed daily
weather data collected from the Department of
Meteorology, Colombo for the periods from 1961
to 1980 and 1981 to 2000 respectively.
The rice varieties were modeled in the cereals-rice
model of Decision Support System for Agro
technology Transfer (DSSAT 4.5) software [3].
DSSAT is a popular crop growth model that is used
worldwide for modeling phenology, growth and
yield of 30 different crops including rice under
given soil nutrient and daily weather conditions.
For this study, rice model of DSSAT was calibrated
and validated using the observed crop and their
management data collected from the Rice Research
Development Institute (RRDI) farm, Batalagoda
for the Yala (dry) seasons of years 2010 and 2006
respectively.
In order to analyze the future rice yield trends, the
respective rice varieties were simulated in DSSAT

- 32 -
SAITM Research Symposium on Engineering Advancements
(SAITM – RSEA 2012)
with future weather conditions that downscaled by
using SDSM. Atmospheric CO2 concentrations for
future conditions were derived from the scenario
curves of Special Report on Emission Scenarios
(SRES) published by the IPCC under A2 and B2
scenarios [4].
3. RESULTS
As CO2 is an essential component in the production
of plant biomass through the interplay between
photosynthesis and respiration, increase of ambient
CO2 concentration will have direct effects on the
photosynthetic and respiratory processes. Since the
rates of physiological and biochemical reactions of
plants are primarily determined by the temperature,
rising global temperatures will also have a
significant influence on all processes leading to
crop yield formation [5].
Therefore in order to examine the effects of CO2
and temperature on the rice yield, future
simulations were carried out under three conditions
as (a) Present level of CO2 concentration with
future temperatures; (b) Present level of
temperature with future CO2 concentrations; and
(c) Future CO2 concentrations with future
temperatures.
3.1 Present level of CO2 concentration with
future temperatures
When rice is exposed to temperatures higher than
35°C, damages occur according to growth stages.
Furthermore, clear varietal differences affect high
temperature tolerance at different growth stages. A
variety may be very tolerant of high temperatures
at one growth stage but susceptible at another. Rice
is most sensitive to high temperatures at heading
and next most sensitive at about 9 days before
heading. One or two hours of high temperature at
anthesis has a decisive effect on the incidence of
sterility [6].
Present level of CO2 concentration was kept in 370
ppm as observed value in the RRDI farm and rice
varieties were simulated with forecasted future
temperature conditions under the A2 and B2
scenarios. The results showed decreasing trends for
all four rice varieties where short term varieties
with higher decreasing trends especially under the
A2 scenario as it has the higher temperature
increasing trend. The rice yield variations under A2
and B2 scenarios are shown in Figure 1 and 2
respectively.
Figure 1: Variation of rice yield with A2
scenario under condition (a)
Figure 2: Variation of rice yield with B2
scenario under condition (a)
3.2 Present temperature with future CO2
concentrations
Most plants growing in atmospheric CO2 higher
than ambient exhibit increased rates of
photosynthesis. Extremely high level of CO2 also
reduces the stomatal openings of some crop plants.
From that, CO2 reduces transpiration per unit leaf
area while enhancing photosynthesis. Thus it may
lead to improve water-use efficiency (the ratio of
crop biomass to amount of water used in
evapotranspiration). As a result of these
interactions, elevated CO2 alone tends to increase
growth and yield of most agricultural plants [7].
The temperature conditions during the period from
01/01/2011 to 31/12/2020 were kept as the current
temperature level under both A2 and B2 scenarios
and the rice varieties were simulated with future
CO2 concentrations. The results showed an
increasing trend for all four rice varieties under
both A2 and B2 scenarios. The Figure 3 and 4
show the respective rice yield variations under A2
and B2 scenarios respectively.
Figure 3: Variation of rice yield with A2
scenario under condition (b)

- 33 -
SAITM Research Symposium on Engineering Advancements
(SAITM – RSEA 2012)
Figure 4: Variation of rice yield with B2
scenario under condition (b)
3.3 Future CO2 concentrations with future
temperatures
The studies by Desiraju and fellow researchers, [8]
reported that, when it compared with ambient
conditions, the combination of increased CO2 and
increased temperature resulted in a small increase
in biomass and yield in the dry season. In addition,
the International Rice Research Institute (IRRI)
crop modeler John Sheehy and fellow researchers
determined that, as a general rule, for every 75 ppm
increase in CO2 concentration, rice yields will
increase by 0.5 t/ha, but yield will decrease by 0.6
t/ha for every 1 °C increase in temperature [9].
In this case, the rice varieties were simulated in
DSSAT with future CO2 and temperature
conditions. The results showed small increasing
trends (lesser than the trends of condition [b] in
three varieties) under both A2 and B2 scenarios.
The Figure 5 and 6 show the respective variations
under A2 and B2 scenarios.
Figure 5: Variation of rice yield with A2
scenario under condition (c)
Figure 6: Variation of rice yield with B2
scenario under condition (c)
The yield variations under three conditions are
shown in the Table 1 as percentages of base values.
Average rice yields for the period from 2011 to
2020 were considered as the base values. The
minus value indicates decreasing trend.
Table 1: Rice yield variations under three
conditions as percentages of the base values
Condition
A2 Scenario
Bg
250
At
307
Bg
357
Bg
379-2
(a)
-13.6
-10.3
-6.0
-2.1
(b)
3.5
4.5
4.0
1.9
(c)
-0.4
1.7
3.4
2.2
B2 Scenario
(a)
-6.2
-5.1
-1.8
-0.5
(b)
6.5
4.9
4.5
1.5
(c)
1.9
2.0
3.3
2.4
4. CONCLUSION
SDSM 4.2 was used to downscale the future
weather conditions in Kurunegala District, Sri
Lanka, up to 2090 under the emission scenarios A2
and B2 published by the IPCC.
DSSAT 4.5 was used to model four rice varieties
(including both short term and long term rice
varieties) that are cultivated in Kurunegala district,
Sri Lanka.
Simulations were carried out under three different
conditions to examine the effect of atmospheric
CO2 concentration and daily maximum temperature
on the dry season rice yield as,
a. Present level of CO2 concentration with
future temperatures
b. Present temperature with future CO2
concentrations
c. Future CO2 concentrations with future
temperatures
The results under condition (a) indicate that the rice
yields would decrease due to expected trend of
temperature increase in the future. The condition
(b) shows that future rice yields would increase due
to the high concentration of atmospheric CO2. The
condition (c), under the effect of both CO2
concentration and daily maximum temperature,
shows that rice yields would increase at a lesser
rate than the condition (b) except the rice variety
Bg 379-2.
Therefore in order to meet the future rice
requirement of the country, it is timely need to
introduce suitable adaption measures. The
following potential adaptation measures against
climate change impacts could be suggested
however, there effect need to be verified.
 Adjustments in planting date
 Introduce temperature tolerant rice
varieties

- 34 -
SAITM Research Symposium on Engineering Advancements
(SAITM – RSEA 2012)
5. REFERENCES
[1]. S. Sriyananda, “Drought attack - lives and
livelihood in peril”, SUNDAY OBSERVER, 28
March 2004,
http://www.sundayobserver.lk/2004/03/28/fea06.ht
ml
[2]. R.L. Wilby and C.W. Dawson, User manual of
Statistical Downscaling Model, 2007.
[3]. G. Hoogenboom, J.W. Jones, P.W. Wilkens,
C.H. Porter, K.J. Boote, L.A. Hunt, U. Singh, J.L.
Lizaso, J.W. White, O. Uryasev, F.S. Royce, R.
Ogoshi, A.J. Gijsman, and G.Y. Tsuji, Decision
Support System for Agrotechnology Transfer
(DSSAT) Version 4.5, University of Hawaii,
Honolulu, Hawaii, 2010.
[4]. IPCC, Climate Change 2001: The Scientific
Basis. Contribution of Working Group I to the
Third Assessment Report of the Intergovernmental
Panel on Climate Change [Houghton, J.T.,Y. Ding,
D.J. Griggs, M. Noguer, P.J. van der Linden, X.
Dai, K. Maskell, and C.A. Johnson (eds.)].
Cambridge University Press, Cambridge, United
Kingdom and New York, NY, USA, 881pp., 2001.
[5]. W.A.J.M. De Costa, “Prediction of the effects
of elevated CO2 and temperature on irrigated rice
yields in the low-country dry zone of Sri Lanka
using a process-based simulation model”, Journal
of the National Science Foundation of Sri Lanka,
165-184 pp, Vol. 28(3), 2000.
[6]. S. Yoshida, Fundamentals of Rice Crop
Science, The International Rice Research Institute,
Manila, 1981.
[7]. M.L. Parry, C. Rosenzweig, A. Iglesias, M.
Livermore and G. Fischer, “Effects of climate
change on global food production under SRES
emissions and socio-economic scenarios”, Global
Environmental Change, Vol. 14., 2004.
[8]. D. Subrahmanyam, R. Rao, P.M.V. Reddy and
S.R. Voleti, “Climate Change and its Impact on
Rice”, Rice Knowledge Management Portal
(RKMP), Hyderabad, 2010.
[9]. J.E. Sheehy, F.P.L. Mitchell and B. Anaida,
“Decline in rice grain yields with temperature:
Models and correlations can give different
estimates” Field Crops Research, Vol. 98, Manila,
2006.