THE ZONING AND CALCULATION OF AREAS ENDURED THE EFFECTS OF CLIMATE CHANGE IN THE LOWER MEKONG RIVER DELTA Presented by Bao Thanh Authors: Bao Thanh, Nguyen Thi Phuong, Bui Chi Nam, Tran Tuan Hoang SUB – INSTITUTE OF HYDROMETEOROLOGY AND ENVIRONMENT OF SOUTH VIETNAM Ha Noi, September 2012 ASIA GEOSPATIAL FORUM 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 In this study, LMRD is divided into six sub-regions: West of Hau River, Long Xuyen Quadrangle, Between of Tien- Hau River, Dong Thap Muoi (Plain of Reeds), East Coast, Ca Mau Peninsula

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 rice- growing 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....APPROACH

Six sub-regions, survey locations in LMRD

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 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 seaAPPROACH

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).APPROACH

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.

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 Details of the yield reduction for the 6 sub-regions are shown in the table below: RESULTS RICE YIELD

Decrease of rice yield (in kg/ha and %) in the sub-regions according to B2 scenarios

2 - 3% 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 % and the highest 30% compared to the base time. RESULTS RICE YIELD

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 INUNDATION AREA

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 RESULTS SALTWATER INTRUSION

Salinity area of LMRD in 2020, 2050 By 2020, rice area remains only % compared to now. By 2050, rice area remains only % compared to now. By 2100, rice area remains only % compared to now. RESULTS INUNDATION AREA

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 DROUGHT INDEX

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 km 2 (near 34% of LMRD area). The second large area endured the effects of both the 6.16%-frequency drought and salinity intrusion with 9660 km 2 (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 km 2, 180 km 2 and 229 km 2 (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 km 2 (near 27% of LMRD area). The second large area endured the effects of both the 6.16%-frequency drought and salinity intrusion with 9507 km 2 (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 km 2, 898 km 2 and 579 km 2 (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 km 2 (near 27% of LMRD area). The second large area endured 3 effects of inundation, salinity and 6.16%-frequency drought is 5573 km 2 (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 km 2, 5573 km 2 and 2848 km 2 (total occupied 31.92% of LMRD area). RESULTS THE COMBINATION OF FACTORS

RESULTS

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 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. CONCLUSION

Thanks for your attention