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ASIA GEOSPATIAL FORUM 2012
THE ZONING AND CALCULATION OF AREAS
ENDURED THE EFFECTS OF CLIMATE CHANGE IN THE
LOWER MEKONG RIVER DELTA
Authors: Bao Thanh, Nguyen Thi Phuong, Bui Chi Nam, Tran Tuan Hoang
SUB – INSTITUTE OF HYDROMETEOROLOGY AND ENVIRONMENT OF SOUTH VIETNAM
Presented by Bao Thanh
Ha Noi, 17 - 19 September 2012
CONTENTS
Introduction
 Approach
 Results
 Conclusion

INTRODUCTION


In the Lower Mekong River Delta (LMRD), when climate
change, the average sea water level will rise, especially in
peak tidal water level will make the plain areas in the LMRD
flooded and salinity boundary will be pushed deeper into
inland. A significant portion of agricultural land in the coastal
areas would be inundated by sea level rise (SLR). A
consequence of drought is water shortage.
In order to develop properly an eco-agriculture structure
and ensure national food security, forecast information of
yield of rice production for each region and each province
is indispensable. It is more necessary to forecast the rice
yield in the context of fluctuated weather.
INTRODUCTION
The aim of this study is to research impacts of climate
change on rice production under the climate change
scenarios 2020, 2050, and 2100.
 In this study, LMRD is divided into six sub-regions: West
of Hau River, Long Xuyen Quadrangle, Between of TienHau River, Dong Thap Muoi (Plain of Reeds), East Coast,
Ca Mau Peninsula

APPROACH
Simulation of rice crop yield in the agro-ecological
sub-region
 The study have conducted investigations and
surveys of rice cultivation at 10 sampling locations in
the six sub-regions which represented for typical ricegrowing areas.


Data series (from 1989 to 2009) from meteorological
stations in the six sub-regions. Required data for the
model comprise of the maximum and minimum air
temperature, precipitation and solar radiation.
DSSAT Model simulates yield and seasonal
comparison with actual performance. Rice yield
simulation on the basis of the elements to make rice
yields as cultivation techniques, irrigation regimes,
fertilizer, seed, weather, season, land and soil....
Six sub-regions, survey locations in LMRD
APPROACH
Drought index calculation



For the frequency of droughts, the study applied the
Standardized Precipitation Index – SPI (McKee et al.
1995), and just used term frequency of occurrence
which was severe drought (SPI <-1.5).
A simple term frequency is the ratio of the month,
SPI <-1.5 on the total number of months in the
period 1979 to 2008.
SPI of Ca Mau station represent for the Ca Mau
Peninsula, SPI of Rach Gia station represents for
the Long Xuyen Quadrangle, West of Hau River and
the SPI of Can Tho station represents for Between
Tien - Hau River, Dong Thap Muoi, East Coast.
APPROACH
Inundation area
For zoning of inundation areas, study used data
released from the project "Building a basic database
of terrain hydrological information system for flood
prevention and socio-economic development of the
Cuu Long” implemented by the National Remote
Sensing Center .
 The criteria of selected floodplains in the LMRD
include:

◦ - The areas of lower elevation terrain 0.12 meter, 0.30 meter
and 0.75 meter according to the B2 scenario for 2020, 2050
and 2100
◦ - The coastal area.
◦ - The area is associated with the surface of rivers, lakes and
canals connecting to the sea
APPROACH
Saltwater intrusion
 For salinity, the study applied MIKE model to calculate
salinity intrusion.
 The upstream boundary are water levels at stations of
Tan Chau and Chau Doc,
 The estuary boundarie are water levels at 8 stations of
Cua Dai, Cua Tieu, Ba Lai, Ham Luong, Co Chien, Cung
Hau, Dinh An and Tran De.
 Data verification are the stations of My Thuan, My Hoa,
Nam Can, Ca Mau, Soc Trang (5 stations).
Network and cross sction of LMRD hydraulic model
RESULTS

To simulate effect of the rice yield caused by climate
change in the future, it is based on the average emission
scenarios (scenario B2 as recommended by the Ministry
of Natural Resources and Environment ). Below are the
B2 scenarios of the changes in temperature and rainfall in
LMRD.
RESULTS
RICE YIELD
Mức giàm năng suất lúa mô phỏng theo kịch bản B2 giai đoạn 2020,
%
2050 và 2100 tại đồng bằng sông Cửu Long
0.0
-5.0
-10.0
-15.0
-20.0
-25.0
2020
Hè Thu
2050
Đông Xuân
2100
Thu Đông
The reduction in rice yield simulation of LMRD under climate
The rice yield in LMRD is simulated by DSSAT model in
the timeline of 2020, 2050 and 2100. Details of the yield
reduction for the 6 sub-regions are shown in the table below:
Decrease of rice yield (in kg/ha and %) in the sub-regions according to B2 scenarios
RESULTS
RICE YIELD



To 2020: rice yield reduces not much with
average rate: 2 - 3% and the highest of 6.6%.
Especially, in Ca Mau Peninsula sub-region, yield
tends to increase 5 - 6%.
To 2050: rice yield decreases on average 6 - 9%
and the highest 15% compared to the base
time.
To 2100: the most decrease year for rice yield
with the average 16 - 21% and the highest 30%
compared to the base time.
RESULTS
INUNDATION AREA

For LMRD, the average sea level rises highly,
especially in peak tidal water level, will cause flooding
of lowland areas and deliver saltwater from sea to
inland. Saltwater boundaries will enter further to inland.
A significant portion of agricultural land in the coastal
lowlands would be flooded by sea level rise.
RESULTS
INUNDATION AREA
Inundated area of LMRD in 2050 and 2100
Rice area is quite large with the proportion up to 60% areas
of LMRD. It is supposed that rice area is permanently flooded.
If, sea levels is 12 cm, 30cm, 75cm, the flooded rice area is
1.4%, 6% and 38%, respectively.
RESULTS
SALTWATER INTRUSION

Saline rice area is simulated by climate change
impacts in the timeline as follows: 38% by 2020,
52.5% by 2050 and 83.2% by 2100.
RESULTS
INUNDATION AREA
Salinity area of LMRD in 2020, 2050



By 2020, rice area remains only 62 - 64% compared to now.
By 2050, rice area remains only 48 - 53% compared to now.
By 2100, rice area remains only 17 - 20% compared to now.
RESULTS
DROUGHT INDEX
The drought also leads to decline of rice yields due
to water shortage during rice growth period.
 In Ca Mau Peninsula, possibility of severe drought is
6.16%.
 Between the Tien - Hau River, Dong Thap Muoi,
East Coast have possibility of severe drought of
6.46%.
 Regions such as the Long Xuyen Quadrangle, West
of Hau River with possibility of severe drought is
4.49%

RESULTS
THE COMBINATION OF FACTORS

In 2020, in LMRD, there are 12 kinds of area endured
from 1 to 3 effects of inundation, salinity and drought
of 3 different frequencies.
The area endured the effect of 6.46%- frequency
drought is the largest with 12808 km2 (near 34% of
LMRD area).
The second large area endured the effects of
both the 6.16%-frequency drought and salinity
intrusion with 9660 km2 (over 25% of LMRD area).
The areas endured 3 effects of inundation,
salinity and drought of 3 different frequencies 4.49%,
6.16% and 6.46% respectively are 29 km2, 180 km2
and 229 km2 (total occupied 1.15% of LMRD area).
RESULTS
THE COMBINATION OF FACTORS
Rice areas and the impact of flooding. salinity. drought in 2020 scenarios
RESULTS
THE COMBINATION OF FACTORS

In 2050, the area endured only the effect of 6.46%frequency drought still is the largest with 10044 km2
(near 27% of LMRD area).
The second large area endured the effects of
both the 6.16%-frequency drought and salinity
intrusion with 9507 km2 (25% of LMRD area).
The areas endured 3 effects of inundation,
salinity and drought of 3 different frequencies 4.49%,
6.16% and 6.46% respectively are 426 km2, 898 km2
and 579 km2 (total occupied 5.04% of LMRD area).
RESULTS
THE COMBINATION OF FACTORS

In 2100, the area endured the effects of both 6.46%frequency drought and salinity intrusion is the largest
with 10068 km2 (near 27% of LMRD area).
The second large area endured 3 effects of
inundation, salinity and 6.16%-frequency drought is
5573 km2 (near 15% of LMRD area).
The areas endured 3 effects of inundation,
salinity and drought of 3 different frequencies 4.49%,
6.16% and 6.46% respectively are 3644 km2, 5573
km2 and 2848 km2 (total occupied 31.92% of LMRD
area).
RESULTS
THE COMBINATION
OF FACTORS
CONCLUSION
Results of the study show that the effects of climate
change on rice yield from weather, salinity, sea level
rise and drought factors are to reduce rice production
and the risk of narrowing the area of rice cultivation in
the LMRD.
 Rice yield is decreased significantly by climate change
impacts in different periods. Rice yield can decrease 6%
by 2020, 15% by 2050 and even 30% by 2100.
 The area of agricultural land, especially rice cultivated
land is decreasing by sea level rise, salinity intrusion
besides the reasons of urbanization and
industrialization.
 In summary, results provided a scientific basis for
agricultural development strategies in general and rice
production in particular so that ensure national food
security and give direction for adaptation measures in
the context of climate change.

Thanks for your attention