Salinity intrusion and adaptation solutions assessing the transformation from rice paddies to shrimp farming as an approach to cope with salinity intrusion in ben tre province, vietnam

a Salinity intrusion and adaptation solutions: Assessing the transformation from rice paddies to shrimp farming to adapt to increasing saline intrusion in the Vietnamese Ben Tre provinc

SALINITY INTRUSION AND

ADAPTATION SOLUTIONS

Assessing the transformation from rice to shrimp

as an approach to cope with salinity intrusion in

a

Salinity intrusion and adaptation solutions:

Assessing the transformation from rice paddies to shrimp farming to adapt to increasing saline

intrusion in the Vietnamese Ben Tre province

Name: Pham Dang Manh Hong Luan

Department: Environmental System Analysis Group

Wageningen University and Research

dr AR (Andre) van Amstel Environmental System Analysis Group Department of Environmental Science

dr Ngo Thi Phuong Lan

University of Social Science and Humanities

Environmental System Analysis MSc Environmental Sciences Wageningen University and Research

Table of contents

List of tables i 

List of figures ii 

Acknowledgement iii 

Summary iv 

I  PROBLEM FORMULATION 1 

1.1  Introduction on study area 1 

1.1.1  Natural characteristics of Ben Tre province 1 

1.1.2  Socio-economic characteristics of Ben Tre province 2 

1.2  Problem statement 4 

1.2.1  Salinity intrusion in Ben Tre province 4 

1.2.2  Rice farming – a precarious livelihood 5 

1.3  Research objectives 7 

1.4  Conceptual framework 7 

1.5  Research questions 8 

1.6  Outline of the report 8 

II  METHODOLOGY 10 

2.2  Multi-criteria analysis (MCA) 10 

2.3  Literature study 12 

2.4  Data collection and field survey 12 

2.5  GIS 14 

III  HISTORY OF RICE INTENSIFICATION AND SHRIMP FARMING IN BEN TRE PROVINCE 17 

3.2  Rice expansion period from 1975 to 1990 17 

3.2  Rice intensification from 1990 to 2000 17 

3.3  Period 2000-2010 17 

3.4  Planning for rice and shrimp farming from 2010 to 2020 18 

IV  SHRIMP FARMING 22 

4.1  Type of shrimp farming 22 

4.2  Mono-shrimp cultivation 24 

4.3  Rice-shrimp rotation system 26 

V  RESULTS 28 

5.1  Level of salinity intrusion in Ben Tre province 28 

5.1.1  Selection of scenarios 30 

5.1.2  Extent of salinity intrusion 30 

5.2  Areas for rice-to-shrimp transformation 32 

5.3  Impact assessment of the rice-to-shrimp transformation 34 

5.3.1  Food security 34 

5.3.2  Economic development 35 

5.3.3  Environmental sustainability 36 

5.4  Optimal solution for the area 42 

VI  DISCUSSION 46 

6.1  The extent of salinity intrusion in Ben Tre province 46 

6.2  Area for rice-shrimp transformation 46 

6.3  Impacts implied in the rice-shrimp transformation 46 

6.4  Optimal solution for the area 47 

VII  CONCLUSION 49 

References 50 

Appendices 54 

i

Table I.1: Gross output (billions VND) of cultivation at current prices (2015) by crop groups 3 

Table I.2: Gross output (billion VND) of aquaculture at current price (year 2015) 4 

Table II.1: Goals, criteria and indicators for criteria applied in the research 10 

Table II.2: List of scenarios of development and its weight to goals 11 

Table II.3: Source of data for scoring in MCA 12 

Table II.4: Primary data to be collected 14 

Table III.1: Area (ha) for rice farming landuse and cumulative area of rice crop in 3 seasons paddy by district in 2010 (Ben Tre SO, 2015) 20 

Table IV.1: Shrimp species nurtured in the studied area and their favorable range of salinity level 23  Table V.1: Scenarios in the study on salinity intrusion (Toan, 2014) 29 

Table V.2: Salinity levels of water and their suitable use 30 

Table V.3: Original scores of criteria and their normalized values 40 

List of figures

Figure I.1: Map of Ben Tre province 1 

Figure I.2: Gross output (billion VND) at current price by economic sectors from 2010 to 2015 3 

Figure I.3: Monthly consumption of rice and meat of an individual in Vietnam from 2002 to 2012 5 

Figure I.4: Seasonal calendar in the Mekong Delta and the periods of saline- intrusion- related events 6 

Figure I.5: Conceptual framework 7 

Figure II.1: Map of survey area 13 

Figure II.2: Flowchart describing GIS application in the research 15 

Figure III.1: Map of rice farming activity in 2010 19 

Figure III.2: Landuse map of Ben Tre province in 2010 19 

Figure III.3: Map of landuse planning of Ben Tre province to 2020 21 

Figure IV.1: Shrimp production (tons) by district from 2010 to 2015 22 

Figure IV.2: Extensive shrimp pond in Ben Tre province 25 

Figure IV.3: Intensive mono-shrimp culture in Ben Tre province 26 

Figure IV.4: Rice-shrimp field in Ben Tre 27 

Figure V.1: Average salinity level in dry seasons in condition 2005 31 

Figure V.2: Area (ha) by district under different duration (days) of impact by salinity level 4ppt 32 

Figure V.3: Map of duration (days) of salinity level 4ppt in the condition 2005 32 

Figure V.4: Map of duration of salinity level 4ppt affecting rice crops 33 

Figure V.5: Map of rice-shrimp transformation in 2020 34 

Figure V.6: Food security scores of three options of land-use 43 

Figure V.7: Economic development scores of the three options of land-use 43 

Figure V.8: Environmental sustainability scores of the three options of land-use 44 

Figure V.9: Graphs illustrating scores of mono rice farming with respect to three criteria (on the left) and the its final scores in each scenario of development (on the right) 45 

Figure V.10: Graphs illustrating scores of intensive shrimp farming with respect to three criteria (on the left) and the its final scores in each scenario of development (on the right) 45 

Figure V.11: Graphs illustrating scores of rice-shrimp farming with respect to three criteria (on the left) and the its final scores in each scenario of development (on the right) 45 

iii

Acknowledgement

The idea for this thesis came from my experience of more than two years working as a researcher in Center of Water Management and Climate Change (WACC) whose duty mainly focuses on natural changes and social dynamics in the Mekong Delta It was also inspired by my special love for the Mekong Delta, the land of prosperity but can still preserve its idyll

I would like to express my gratitude to Wageningen University and Environmental System Analysis group for creating opportunity for me to do this research I also want to send my gratitude to Dr Andre van Amstel of Wageningen University and Dr Ngo Thi Phuong Lan of University of Social Science and Humanities for supervising me in this research

I would like to thank Sub-Institute of Hydrometeorology and Climate Change (SIHYMECC), especially Mr Tran Tuan Hoang, head of Hydrological department and Mr Truong Hoai Thanh, expert of Meteorological department for allowing me to work part-time in the office, supporting me in modelling job, and sharing precious data and information I also would like to thank Dr To Quang Toan, expert of Southern Institute of Water Resources Research (SIWRR) for sharing the result of his research on salinity intrusion in the Mekong Delta

Lastly, I would like to send great gratitude to Mr Dinh Quang Toan, lecturer of the University Thu Dau Mot, Binh Duong and Mr Pham Van Luan, lecturer and head of Ben Tre Young Creative Group

of Ben Tre University for giving enormous support in my field trip in Ben Tre province Without their great help in making contact with local government, the field trip could have never been done

Summary

Ben Tre is a coastal province in the Mekong Delta of Vietnam As a coastal province, it is frequently under the impact of saline intrusion, especially in the dry season The impacts of saline intrusion cause severe problems to freshwater livelihoods in the area Rice farming; in specific, is the most vulnerable freshwater livelihood in the condition of saline intrusion due to its heavy reliance on the availability of freshwater Rice farming in the Mekong Delta is also notorious for its low profit, trapping rice farmers in poverty Therefore, the research aims to assess the transformation from rice to shrimp cultivation to cope with increased saline intrusion in Ben Tre province and find the optimal solution Output from model of saline intrusion taken from previous study was applied to analyze the extent of salinity intrusion in Ben Tre province The model outputs were then overlaid with a land-use map planning to 2020 and rice-crop calendar to identify areas where rice was feasibly transformed to shrimp Impacts of the rice-shrimp transformation were then assessed In this research, the impacts on food security, economic development and the environment were considered Groups of criteria for these three dimensions and their indicators were identified using literature review Data for the impact assessment came from the field survey and partly from available literature Lastly, a multi-criteria analysis (MCA) was then applied to compare different land-use options such as 3-season mono-rice fields, 3-season industrial shrimp farming and the rice-shrimp rotation farming The application of MCA is to find the optimal option between the three options Results pointed out that any adopted land-use option implies substantial trade-offs between food-security target, economic development and the environment The research also showed that the rice-shrimp rotation model is the optimal option for the region thanks to its capability of reconciling the conflicting interests on food security, better income and environmental sustainability

1

1.1 Introduction on study area

1.1.1 Natural characteristics of Ben Tre province

Figure I.1 shows the map of the Vietnamese Ben Tre province It is is one of thirteen provinces of the Mekong Delta and locates in the coastal area of this delta Its northern side borders the Tien Giang province and the western and southern side borders the Vinh Long province Its eastern side borders the South China sea (or the East Sea in Vietnam’s naming system) through three estuaries Dai, Ham Luong and Co Chien The whole province is subdivided into nine administrative units including one city and eight districts Ben Tre city is the administrative, economic and cultural center of the Ben Tre province Seven other districts include Chau Thanh, Binh Dai, Giong Trom, Cho Lach, Thanh Phu,

Mo Cay Bac, Mo Cay Nam and Ba Tri

The Mekong river after entering Vietnam’s territory, separates into two main branches including Tien and Hau river Geographically, Ben Tre province is the most downstream area of Tien river Tien river is then divided into four main tributaries including Tien, Ba Lai, Ham Luong and Co Chien river These tributaries help form the shape of Ben Tre province which is similar to an alluvial fan With the existence of these main rivers running through the whole province, geomorphologically, Ben Tre is separated into three peninsulas including An Hoa, Bao and Minh

The geographic coordinates of the whole Ben Tre province are 9048’ to 11020’ North and 105057’ to

106048’ East

Figure I.1: Map of Ben Tre province

(www.bentretourist.vn)

About topography, Ben Tre province has characteristics of flat topography of the river delta formed

by deposition of sediments of the Mekong river The whole province can be topographically divided into three zones (MONRE, 2010) including:

• Zone of low elevation: elevation is lower than 1m This area includes newly formed peninsulas, tidal areas and mangrove areas It is usually flooded by tide;

• Zone of average elevation: elevation ranges from 1 to 2m This is the dominant topography in Ben Tre province which occupies up to 90% area of the whole province; and

• Zone of high elevation: this zone includes coastal sand dunes and high areas along main rivers

in the North West side of the province

About hydrology, Ben Tre province’s hydrological system is characterized by dense channel network with overall length of up to 6000 km Besides 4 main rivers including Tien, Co Chien, Ham Luong and Ba Lai, there are about 60 other small rivers and channels (MONRE, 2010) The flow of this dense channel network is driven mainly by flow from Tien river and tidal regime of the South China sea (ibid) In addition, the tidal regime in coastal area of the province follows semi-diurnal pattern with two high tides and two low tides each day Water level in high tide is normally 2.5-3m higher than in ebb tide in days with high tides, and the difference is approximately 1m in days with low tides (MONRE, 2011)

About climate, Ben Tre can be distinctively separated into 2 seasons The rainy season lasts from May

to November, the dry season, on the other hand, lasts from December to April next year The yearly average precipitation in the province is from 1,200 to 1,600 mm (MONRE, 2011) Precipitation in rainy season takes up to 90-95% of the yearly rainfall in the province On the contrary, in dry season, especially in January, February and March, there are only 1 or 2 rainy days and the rainfall in dry season only takes 1.5 to 6% of the total yearly rainfall (ibid)

1.1.2 Socio-economic characteristics of Ben Tre province

Ben Tre province has many geographic advantages for socio-economic development Being located at the most downstream area of the Mekong Delta with dense river network and only 86km away from

Ho Chi Minh city, the socio-economic center of the South, Ben Tre can easily integrate its economy with other regions in the Mekong Delta and the South Eastern part of Vietnam (Ben Tre DONRE, 2008)

According to Ben Tre SO (2015); in 2010, agriculture, forestry and aquaculture continues to be the main economic sector in the province with the largest contribution to the economy’s GDP In specific, these sectors account for nearly 45% of the province’s gross output in 2010 (ibid) In recent years; however, industrial and service sector have been developing sharply as shown in Figure I.2 to replace agriculture, forestry and fishing in the contribution to the province’s gross output

3

Figure I.2: Gross output (billion VND) at current price by economic sectors from 2010 to 2015

(Ben Tre SO, 2015)

Table I.1 shows the contribution of each type of crops to agricultural sector Cereal crops (mostly rice) are the most important annual crops contributing 1,501billions VND to gross product in 2015 (Ben Tre SO, 2015)

Table I.1: Gross output (billions VND) of cultivation at current prices (2015) by crop groups

(Ben Tre SO, 2015)

Annual crops Perennial crops Year Total Total Cereal Vegetable,

bean and flowers

Annual industrial crop

Total Fruit

crop

Perennial industrial crop

Aquaculture is another main economic activity in Ben Tre province Aquaculture activities involving farming rapidly expanded in the period 2001-2005 due to brackish-water shrimp farming program (Ben Tre DARD, 2010) As being shown in Table I.5; in 2010, the gross output of aquaculture is 6,717 billions VND and the number kept increasing to 7,383 billion VND in 2015 (Ben Tre SO, 2015)

Table I.2: Gross output (billion VND) of aquaculture at current price (year 2015)

(Ben Tre SO, 2015)

Year 2010 2011 2012 2013 2014 Prel 2015 Gross

output 6,717 9,147 8,629 9,818 11,547 9,491

1.2 Problem statement

1.2.1 Salinity intrusion in Ben Tre province

Similar to other downstream provinces in the Mekong Delta of Vietnam, salinity level in Ben Tre province is a function of many variables including the flow from the upstream part of the Mekong Delta, the effects of tidal regime of the East Sea, water storage in Tonle Sap (Cambodia) and in river

or canal system and the hydrological structures in the area (Nhan et al., 2007) With its low elevation compared to average sea level and being under the strong impacts of tidal regime of the East sea, salinity intrusion is very severe, especially in dry season (MONRE, 2011)

The salinity level in Ben Tre province is always tightly connected with tidal regime of the East Sea Salinity normally fluctuates accordingly with the tidal pattern of the East Sea Salinity is also greatly influenced by flow from the upstream of the Mekong Delta In flooded season, salinity boundary is pushed seawards However, in coastal areas, salinity level is never lower than 2ppt The highest salinity level usually occurs in April, the last month of dry season when there is least freshwater from Tien river (MONRE, 2011; My et al., 2006) The occurrence of ‘Chuong’ wind which pushes tidal flows further inlands in the dry season exacerbates the salinity intrusion in the province (MONRE, 2011)

Salinity level also varies in different rivers in Ben Tre Salinity intrusion in Ba Lai is the most severe, (i.e salinity goes furthest inland) It is because the upstream flow is too little to push back salinity Ham Luong is the river with the least impacts of salinity intrusion in Ben Tre mostly because of its flow which is the highest among four main rivers in the province Salinity is also higher in channels compared to in river because there is no upstream flow entering channels to dilute the salinity in water (MONRE, 2011)

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In the Mekong Delta, even though there are few researches that directly explore the linkage between rice farming and poverty, there are many expert opinions recently about this issue According to Vo Tong Xuan, leading expert in agriculture, using rough estimations, with the price of rice today of about 4,300 VND/kg, individual farmers with small-size farms only benefit about 300-400 VND/kg because they have to pay a higher cost of production compared to those in collectives or with large-size farms (Phan Chu, 2016)

b) Rice farming susceptible to salinity intrusion

Rice farming, especially in the coastal area, is always under the risk of negative impacts by salinity intrusion In the coastal Mekong Delta, areas with three seasons of rice are vulnerable the most because there will be one season in the dry period, when the areas are heavily affected by high salinity level

Figure I.4: Seasonal calendar in the Mekong Delta and the periods of saline- intrusion- related events

(Nhan, et al., 2011) The Winter-Spring season of rice in the Mekong Delta is normally started from the end of November

to Febuary in the irrigated area, e.g area without threat of salinity intrusion thanks to irrigational system In the coastal zone, shift of crop calendar had to be conducted to avoid rice cultivation in dry season normally lasting from the end of November till April However, climate change along with higher sea level can induce salinity stress on the agriculture activity (Wassmann et al., 2009) Climate change also cause abnormality in rainfall pattern, which in turn can cause drought, making it easier for saline water to intrude deeper inland (Nhan et al., 2011) It was estimated by Nhan et al (2012) that during the peak of dry season, salinity level of 5ppt can go up to 40-50km inland through main rivers

of salinity level, many rice fields were dead before farmers could harvest

The latest drought event in 2016 clearly showed the immense impacts of salinity intrusion on rice production in the Mekong Delta In this historic drought-salinity intrusion, by mid-April, it was estimated that in the Mekong Delta, there were up to 224,552 ha of rice field affected by salinity intrusion (CGIAR, 2016) In Ben Tre alone, 8,668 out of 11,200 ha of cultivated rice field was affected by salinity This accounted up to 77.4% of total area of rice fields Giong Trom district with 2,600 ha of sow rice field also suffered heavy loss in this incident with up to 1,000 ha (approximately 38%) lost completely (Giang Son, 2016) The damage reflected by rice yield was estimated from 50%

to complete loss (CIGAR,2016)

1.3 Research objectives

The current salinity condition in Ben Tre province and its expected trend in the future necessitate an urgent solution There are many options available for the area Among of those, changing of land-use patterns from freshwater-dependent land-use types to other types that favor saline environment is a promising adaptation solution The transformation from rice to shrimp farming; in specific, is the most desired possibility in the area This transformation, however, is considered debatable because it meets some opposition from the government for jeopardizing the possibility of national food security, which was proposed to maintain the productivity of rice cultivation The transformation also implies many environmental as well as socio-economic impacts, demanding a thorough understanding before being brought into practice Therefore, the research aims to assess the possible impacts of this transformation from rice to shrimp and find the optimal solution

1.4 Conceptual framework

Figure I.5: Conceptual framework

Figure I.5 visualizes the conceptual framework for the research Under the pressure of salinity intrusion, the transformation from rice to shrimp farming is a promising adaptive approach This

transformation; however, implies within it the trade-off between three aspects including food security, economic development and environmental sustainability In specific, there would be great loss to food security due to the transformation of rice paddies to shrimp farms as an exchange for better economic condition of farmers This transformation; however, also means huge environmental impacts because

of the environment cost of shrimp farming

1.5 Research questions

The research will target four main research questions:

1 How is the level of salinity intrusion in Ben Tre province ?

a What is the spatial extent of salinity intrusion in Ben Tre province ?

b What is the temporal extent of salinity intrusion in Ben Tre province ?

2 What is the area suitable for the rice-to-shrimp transformation ?

3 What are the possible impacts of changing from rice to shrimp ?

a What are the impacts of the transformation from rice to shrimp on food security situation in Ben Tre province ?

b What are the economic impacts of rice-shrimp transformation ?

c What are the environmental cost of this transformation ?

4 What solution is optimal for the area ?

1.6 Outline of the report

The report includes seven chapters The first chapter is the introduction part describing the studied area, the problem statement explaining explicitly the problems the area is facing, the research objectives, the conceptual framework for this study, and lastly the research questions

The second chapter is about the methodology used to address research questions in the first chapter The chapter describes in detail the techniques as well as tools and input data utilized in each method Four research methods including Multi-criteria analysis, literature study, data collection and field survey and geographic information system approach are discussed explicitly four separate sections The third chapter provides information the history of rice farming and shrimp farming in the studied region The purpose of this chapter is to briefly describe the success of rice farming in the Mekong region, turning Vietnam not only into a highly food-secured country but also one of the top rice-exporters of the world This success; however, implicitly put constraints on any innovative attempt to help agricultural sector in Vietnam cope with growing pressures from the environment such as salinity intrusion The chapter also shortly introduces about arrival of shrimp farming in the Mekong Delta and its equally important role to rice farming in Ben Tre province as reflected in the current land-use map 2010 and the land-use map planning to 2020 Lastly, the chapter provides information on land-use allocation planning to 2020 in the area, which later serves as input to the analysis of the possibilities and impacts of the transformation from rice to shrimp to cope with salinity intrusion The fourth chapter of the report provides insights into shrimp farming in the Mekong Delta region The chapter specifically discuss two distinctive types of shrimp farming including the intensive

9

shrimp farming and the rice-shrimp rotation farming with the aim to introduce about two water-dependent livelihoods which can be good substitutes to rice farming in the condition of salinity intrusion

brackish-The fifth chapter presents the results of the research This chapter includes four sections presenting the answers to the four research questions The first section of the chapter will discuss the extent of salinity intrusion in Ben Tre province using available outputs from modelling The second section will present the finding of areas where there should be transformation from rice to shrimp The third section will present the possible impacts of this transformation and lastly, the fourth section will discuss the optimal option of land-use for the area

The sixth chapter discusses the results of the research in the order of research questions Critical assessment on the result will be conducted The last chapter is the conclusion which summarizes the objectives that the research addresses

II METHODOLOGY

2.2 Multi-criteria analysis (MCA)

MCA is applied to address research question fourth The application of MCA is to assess alternatives

of land-use under different perspectives The advantage of MCA over other assessment tools is that it allows the assimilation of different criteria whether they are qualitative or quantitative Another advantage of MCA is that it allows the assignment of importance level or hierarchy to criteria (Mendoza et al., 2006)

The study applies the set of criteria in previous studies on assessing scenarios of land-use allocation

In their study on optimizing land-use allocation for the Mekong delta area, Trung et al (2006) suggested that economic development, social security and environmental sustainability should be used

in assessing scenarios of land-use allocation In this study, food security is used in place of social security as a criteria because the food security is still a main focus in any policies targeting land-use allocation in Vietnam Table II.1 shows list of criteria and their indicators used in this study

Table II.1: Goals, criteria and indicators for criteria applied in the research

Economic development

Profitability when crop wins Benefit to cost ratio in case of crop

succeeds Profitability when crop fails Benefit to cost ratio in case of crop

fails Job opportunity Labor days (labor days/year)

Environmental sustainability Environmental impact

Salinization cost (VND/year) Sedimentation by frequency of pond dredging (times/year)

Sedimentation by amount of industrial feed (kg/year)

Fertilizer application (kg/ha/ season)

Pesticide application (kg /ha/ year) Area irreversibly adjusted (hectares) Freshwater demand (m3/ha/year)

The food security criteria is measured by the production of rice It is an important criteria for any land use allocation decision in the Mekong Delta because it has a long history of being the top concern by the government

11

Socio-economic criteria include the benefit to cost ratio of rice and shrimp farming and their job opportunities Besides the possible profit that can be generated from options of land-use, the risk adhered to them will also be considered In the research, risk will be evaluated using the the ratio of benefit and cost in case of crop loss

Environmental criteria reflect the level of impact that rice and shrimp farming activities can induce on the environment The criteria will be evaluated by the volume of agro-chemical applied in each type

of farming Three other indicators of environmental impacts are also considered including salinization cost, terrain adjustment and freshwater usage

Table II.2: List of scenarios of development and its weight to goals Criteria

Economic development

Environmental sustainability

Table II.2 includes weights assigned to criteria in this study The weights are assigned differently in each goal or scenario of development The values of weights are taken from the study by Trung et al (2006) In their study on analyzing land-use planning approaches in the coastal Mekong Delta, Trung

et al (2006) applied FAO-MCE method to generate land-use scenarios The step involved decision makers into the process of identifying indicators and their level of importance The result from this step is a list of scenarios or goals for land-use planning; in each scenario, weights for criteria were defined as level of priority

In this study, nine scenarios or goals of development will be analyzed including one scenario of balance in which all goals have the same weight, two scenarios of food security in which weights for the goal food security are 0.7 and 0.5, two scenarios of economic development in which weights for the goal economic development are 0.7 and 0.5, two scenarios of environmental sustainability in which weights for the goal environmental sustainability are 0.7 and 0.5 and lastly two scenarios with equal priority levels on economic development and environmental sustainability and less or no concern about food security The values of weights are picked up on referencing to the work by Trung

et al (2006) More than one weight for each goal are chosen to analyze the sensitivity of the result to different weights

2.3 Literature study

Literature study is applied to address the research question one and three About the first research question on level of salinity intrusion, the research refers to the study by Toan (2014) on possible impacts of upstream development on hydrological regime and salinity intrusion in the Mekong Delta using modelling approach Two indicators of salinity intrusion including spatial distribution of salinity level and duration of salinity level 4ppt are extracted from the study to analyze the spatial and temporal extent of salinity intrusion in the region

The study also refers to the work by Trung et al (2006) on developing land-use approaches in the Mekong Delta Information taken from the research includes set of criteria, their indicators and their weights to compare different scenarios of land-use allocation

Lastly, literature study is to find out relevant information on the practice of rice and shrimp farming in the area Google scholar searching engine is utilized to find scientific papers with necessary information The search is applied with keywords ‘shrimp farming’, ‘rice farming’ and ‘Mekong Delta’ Available reports on environmental and social impact assessment of each type of rice, shrimp and rice-shrimp farming are the main target of this search These information is used to fill in the values of criteria in MCA which data gathered from field survey cannot cover In specific, criteria that will be scored using data from available reports and articles are production of rice, job opportunity, salinization impact, pesticide and fertilizer application and freshwater demand Sources for these

criteria are mentioned in Table II

Table II.3: Source of data for scoring in MCA

2.4 Data collection and field survey

Data collection and field survey are applied to address research questions one, two and three In this study, a wide range of data will be collected including data from doing interviews in field survey and data from available sources Data from doing interviews in field survey or primary data is collected using questionnaire instrument The field survey will focus on shrimp farming activity in the research area Two specific types of shrimp farming are to be considered including the mono intensive shrimp

Food security Rice yield Ben Tre DARD, 2010

Economic development Labor days Vu et al., 2014

Environmental sustainability Salinization cost Be et al., 1999

Fertilizer application Huan et al., 2005 Freshwater demand To, 2015

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farming and the rice-shrimp rotation models Stratified sampling technique using local knowledge of studied area is used to identify sampling area Figure II.1 depicts the sampling area In this study, two wards My An and An Thanh of Thanh Phu province are chosen to do the field survey because in these two wards, shrimp farming is the dominant activities and there is a mix of intensive shrimp farming and rice-shrimp rotation model These two wards are also areas where there used to be a transformation from rice farming to shrimp farming Random sampling technique is then applied in the field trip to find participants for interviews Total sampling size is thirty two in which there are sixteen interviews with intensive shrimp farmers and sixteen interviews with farmers doing rice-shrimp rotation models Because the survey targets two distinctive groups of farmers, two questionnaires with different formats are needed Interviews are in form of semi-structure interview with questionnaires including open-ended questions Questions mainly focused on capital investment, farming practice and lastly productivity of two types of shrimp farming in the condition of crop win and crop loss The two version of questionnaires are included in Appendices two and three Information taken from the field survey is listed in Table II.4

Figure II.1: Map of survey area

Secondary data collected are maps of current land-use and land-use planning in the province to 2020 and other layers of maps including administrative and hydrological maps

Application of agro-chemicals

2.5 GIS

GIS is applied to address the first, second and third research question The workflow of using GIS in the research is depicted in Figure II.2 All of GIS operations applied in the study are conducted using software ArcMap of ESRI

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he

id

with base layers to create maps depicting the spatial and temporal extent of salinity intrusion in Ben Tre province

For the second research question about the area where the transformation from rice to shrimp farming can happen, the layer of rice paddies in 2020 and layer of duration of salinity level 4ppt are used as inputs Each parcel of layer of rice paddies in land-use planning map to 2020 is updated with information of duration of salinity level 4ppt from layer of duration of salinity level 4ppt using Zonal Statistics tool of ArcGIS The rice parcels with updated information on number of days under the impact of salinity level 4ppt are then separated into rice parcels that should be transformed to shrimp farming area and those should not by comparing to rice crop calendar by Nhan et al (2011) mentioned in Figure I.4 The query tool Select by Attribute of ArcMap is used in this step, for rice parcels lying in saline-water zone, the query condition is duration of 4.00 ppt salinity level more than

60 days; on the other hands, for those rice parcels lying the fresh-water zone, the query condition is duration of salinity level 4.00 ppt more than 30 days

For the third research question, the Summarize tool of ArcMap is used to calculate area of shrimp transformation The calculated area is utilized directly as value for the indicator Terrain adjustment mentioned in Table II.1 Another indicator that needs inputs from GIS is the Salinization cost To generate value for this indicator; firstly, the spatial query Select By Location of ArcMap is used to select rice parcels lying in range of 10m away from transformed rice paddies identified in the second research question The Summarize tool of ArcMap is then used to calculate total area of these selected rice parcels which is used as input to calculate salinization cost afterwards

3.2 Rice expansion period from 1975 to 1990

According to Garschagen et al., 2011, on facing the threat of the collapse of the centrally-controlled economy due to low productivity of industrial and agricultural activities, in the late 1970s, Vietnamese government started a reform in economic sector, shifting from state-controlled economy

to a market-oriented economy This transformation really kicked in from December 1986 with Renovation policy (Doi Moi), which encouraged economic activities in private sector (ibid) In this period, the ‘rice-first’ policy along with the construction of irrigation system lead to the expansion of rice farming of approximately 85,000 ha yearly Besides, cultivation of traditional long-growth rice varieties a year was also substituted by cultivation of two or three crops of high-yield rice varieties (Garschagen et al., 2012) As a result, Vietnam had shifted from rice-importing to rice-exporting

country (Renaud et al., 2015).Rice intensification from 1990 to 2000

This is the period of further rice intensification in which rice cultivation was perceived as the top priority Farmers in this period could intensify their rice production thanks to the further development

of the hydraulic infrastructure serving drainage, irrigational and salinity control purposes More rice crops a year can be cultivated as a result, leading to higher area of cultivated rice land even though the area for rice cultivation purpose did not change This intensification in term of seasons allowed farming not only for subsistence but also for exporting (Garschagen et al., 2012)

3.3 Period 2000-2010

The governmental policy of agricultural diversification since 2000 drastically transformed the picture

of the province’s landuse In specific, the Decree No 09/2000/NQ-CP announced on 15th of June,

2000 encouraged farmers to diversify their livelihoods for better incomes Many farmers had changed their economic activities from rice to aquaculture, fruticulture or mixed farming practices Aquaculture was preferable among many possibilities because it can generate huge profit for farmers

It was also noted by Nhan et al (2007,2008) that the focus on aquaculture was due to the observation

of the success of pioneers in this sector (Garschagen et al., 2012) The booming of aquaculture activities in the area could also be considered as a result of a paradigm shift in agricultural practices towards adaptive approaches, i.e living or farming in flooding and saline environment rather than the

old-fashioned control approaches in earlier years (Garschagen et al., 2012) Shrimp farming is the most dominant activity in the salinated zone in Ben Tre province This zone includes wards approximately 26km away from the shoreline in Binh Dai district, wards from the shoreline to Thanh Phu town in Thanh Phu district and 3 coastal wards in Ba Tri district

However, the diversification policy in this period did not mean that farmer could apply any type of economic activities on their land parcels In fact, the government still hold some restrictions towards landuse categories in a spatial entity The enforcement was to ensure the production targets for certain crops and in reality, the farmers are not allowed to change to a crop that is completely different to the assigned one The assignment of crop types for each area was based on physical condition (including soil, water quality and irrigational system) and national target of food security, market availability and the prospect of profit

3.4 Planning for rice and shrimp farming from 2010 to 2020

In 2010, two patterns of rice crop were applied in Ben Tre province including monoculture and polyculture pattern as shown in Figure III.1 The mono-rice farming mostly concentrated in Ba Tri district, while in Binh Dai and Thanh Phu district, the polyculture or rice-shrimp rotation system in specific is more dominant Ba Tri is also the biggest rice bowl in the whole province with up to 39,332 ha of 3-season planted rice field; in which, areas of Winter-Spring, Summer-Autumn and Winter rice crop are 12,772; 12,032 and 14,528 ha respectively (Ben Tre SO, 2015) Ba Tri is also the leading district in term of area of land-use for rice cultivation purpose according to land-use map of Ben Tre province in 2010 as shown in Figure III.2 and Table III.1

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Figure III.1: Map of rice farming activity in 2010

(Mekong River Commission, 2010)

Figure III.2: Landuse map of Ben Tre province in 2010

(Ben Tre DONRE, 2006)

Table III.1: Area (ha) for rice farming landuse and cumulative area of rice crop in 3 seasons paddy

by district in 2010 (Ben Tre SO, 2015)

District

Total area for rice farming

Total planted area in 3 seasons

Winter-Spring Summer-Autumn Winter

Ba Tri, Giong Trom and wards to the West of Thanh Phu continues to be area specialized for rice cultivation In case of Thanh Phu district, channel system to provide freshwater will be enhanced to support rice farming in the area Also in the East of Thanh Phu, system of rice-shrimp rotation will be developed In the Western wards of Binh Dai district, mixed system of rice and vegetables will be implemented (ibid)

For aquaculture, in 2020, area for aquaculture in general will be maintained at 47,000 ha; in which, area for freshwater aquaculture is 8,400 ha Saline-water aquaculture, whose area is up to 38,600 ha, will still play the dominant role in the province’s aquaculture sector Brackish-water farming

identifies shrimp farming the key activity The area for freshwater shrimp (Macrobrachium

rosenbergii) will be 3,080 ha and the area for saline-water shrimp will be 32,200 ha; in which Tiger

shrimp (Penaeus monodon) is the main species, the other saline shrimp is White shrimp (Lipopenaeus

vannamei) White shrimp is currently considered a potential species in the province and the area for

White shrimp cultivation is expected to 1,400 ha in 2020 The remaining aquaculture land is for

cultivation of clam (Meretrix lyrata) (5,550 ha), crabs (850 ha) and other species

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Figure III.3: Map of landuse planning of Ben Tre province to 2020

(Ben Tre DARD, 2010)

IV SHRIMP FARMING

Shrimp farming started to prosper in Vietnam since the end of 1990s with the increasing demand for shrimp internationally and the encouragement from government’s aquaculture development (Lebel et al., 2002) Since then, the area of shrimp farming increase continuously to reach the number of 546,757 ha in 2003 Mekong Delta is the area with the highest area for shrimp farming, taking up 90% brackish shrimp farming, mostly in the coastal area (Anh et al., 2010) In Ben Tre province alone, area

for shrimp farming is 38,098 ha in 2015 with total production of 52,303 tons (Ben Tre SO, 2015)

Brackish shrimp farming in Ben Tre province is mainly distributed in the coastal area to take advantage of year-round high salinity level

In Ben Tre province, Binh Dai is the leading district in shrimp industry, whose total production is 22,374 tons in 2015 Shrimp production increased sharply in Thanh Phu district from 6,636 tons in

2010 to 16,184 tons in 2015 The productions of shrimps from 2010 to 2015 in each district are shown

in Figure IV.1

Figure IV.1: Shrimp production (tons) by district from 2010 to 2015

(Ben Tre SO, 2015)

4.1 Type of shrimp farming

There are many models of shrimp farming have been applied in Ben Tre province ranging from mono-shrimp culture models including extensive, improved-extensive, semi-intensive, intensive farm

to shrimp-rice rotation farm and ecological or shrimp-mangrove farm The defining differences between these models are shrimp fry density, pond size, labor demand, requirement of capital investment (Anh et al., 2010) Even though these models of shrimp farming co-exist in the area but it has been noted that there is a trend of shifting from traditional extensive shrimp farming to improved extensive and intensive farms (ibid) This also implies the transition from shrimp farming on large ponds relying on natural stock of shrimp to smaller ponds relying on artificial sources of stock

Cho Lach South Mo

Cay

North Mo Cay

Giong Trom Binh Dai Ba Tri Thanh Phu

2010 2012 2013 2014 2015

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The dominant type of shrimp that being reared in the Mekong Delta and Ben Tre province is Tiger

shrimp (Penaeus monodon) (MARD, 2009) In recent years, White-leg shrimp (Litopenaus

vannamei) has been introduced into shrimp farming sector in the area as a substitution to Tiger shrimp

with hope to reduce the environmental impacts of this shrimp However, Tiger shrimp is still considered preferable species by farmers because of its value on international market (Wyban, 2007;

Mishra et al., 2008; Anh et al., 2010) Giant freshwater prawn (Macrobrachium rosenbergii) is

another species of shrimp that is being cultivated in the area This type of shrimp is considered a good species for the shrimp industry, especially for area with brackish or freshwater for its tolerance of lower salinity level (Phuong et al., 2002; Yen et al., 2008) Shrimp species and their favorable range

of salinity are mentioned in Table IV.1

Table IV.1: Shrimp species nurtured in the studied area and their favorable range of salinity level

Species

Salinity tolerance (ppt)

Optimal salinity level for growth (ppt)

Singh, 1980

Shrimp cultivation was proved to bring about huge profit to local farmer compared with rice farming (Be et al., 1999) There were many studies in the Mekong Delta that confirms this fact A study conducted in Long An and Ca Mau province is a good example According to the survey in the study, income from shrimp farming is 32-34 times income from rice (Lan, 2014) Another good example is the study conducted in Soc Trang and Bac Lieu province in which Be et al (2003) stated that farmers that grow shrimp have higher income than those who live on rice farming

The research only focuses on the monoculture shrimp farming and shrimp-rice models The defining difference between these two models is that the monoculture shrimp farming can bring about huge profit but it can cause detrimental effects on the environment; on the other hands, the rice-shrimp system brings about less profit; however, it is less harmful to the environment and therefor, more sustainable

Intensive shrimp farming is also characterized by high density of shrimp stock Fries that are put into intensive ponds come from artificial sources (Business, 2003) Fry density is recommended to be 20-

50 fries per square meter for ponds with depth of 1.2 meters For other ponds with higher depth and aeration system, fries can be reared with higher density of 30-40 fries per square meter It was also recommended that fries should not be reared at density of more than 50 fries per square meter (MF, 2007) However, Lebel et al (2002) noticed that there were farms in Vietnam that used a shockingly high rate of stock of up to 150 fries per square meter

Different to extensive system which relies totally on natural source of stock and feed, intensive shrimp involve commercial sources of stock and feed (Joffre et al., 2009) Farming is completely mono-culture with shrimp is the only species that been reared Farmers can choose to Tiger shrimp or White-leg shrimp depending on the value of them on the market

In coastal area where impact of high salinity level is year-round, there are usually 2 seasons of shrimp crops a year Typical duration for one crop season in intensive system is 100-120 days (Anh et al., 2010) The first shrimp crop normally start from November and end at the end of March next year After that there will be 1 month for pond treatment before the next crop starting from May to October

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There are also areas that apply intensified pattern with three crop seasons The first season starts from November and end in February The second season starts from April to June and the last season starts from July to October Between these seasons there are also vacant time for pond recovery (Tu et al., 2014)

Rate of water exchange of intensive shrimp farm is the highest in all forms of shrimp farm system (Van Khang, 2008) Rate of water exchange increases over growth period and with the level of intensification (Hopkins et al., 1993) It is also stated by Anh and colleagues (2010) that water exchange should be conducted every 10 days relying on the season and water quality When one season is finished, an enormous amount of polluted water will be discharged into the surrounding environment This discharge and exchange water is flushed directly into nearby canals, causing pollution in this water body

Sediment from shrimp ponds is another environmental threat After one season is finished, the sediment collected from the bottom of shrimp pond will be removed to prepare for the next season This sediment cannot serve as fertilizer for agriculture activities because it is low in organic content and high in salinity (Dierberg et al., 1996) In a good management system, normally, this sediment will be collected instead of dumping directly into the canals

Figure IV.2: Extensive shrimp pond in Ben Tre province

Figure IV.3: Intensive mono-shrimp culture in Ben Tre province 4.3 Rice-shrimp rotation system

The rice-shrimp system like in Figure IV.4 has been introduced into the Mekong Delta in the response

to the call for a more suitable farming system in area frequently affected by salinity intrusion The area is characterized by one season of high salinity level or dry season and one season of low salinity level or wet season (Brennan et al., 2008) Joffre et al (2009) also stated that rice-shrimp system is suitable for the area with around six and half months of freshwater

There are generally two crop patterns of rice-shrimp in the Mekong Delta The first one is the one shrimp – one rice pattern and the other is two shrimp – one rice In the former, shrimp crop usually starts from January and end in August, after harvesting shrimp, ponds will be treated and rice is then cultivated from September and harvested in December or January (Tu et al., 2014; AMDI, 2016) Rice seed to be applied in this system is normally local traditional rice with longer growth period of about

120 days (AMDI, 2016) Type of shrimp to be reared in one shrimp – one rice system is typically

Tiger shrimp (Penaeus monodon) or in some cases, White leg shrimp (Litopenaeus vannamei) Fry

density is normally ranging from 8-17 fries per square meter (ibid)

In the two shrimp – one rice system, the dominant type of shrimp to be cultured is White leg shrimp

(Litopenaeus vannamei) White leg shrimp is preferable in this system because of its shorter period of

growth, normally ranging only from 60-90 days compared with Tiger shrimp with longer growth period of 100-120 days (AMDI, 2016) Thanks to this shorter period of growth of White shrimp, two shrimp crops can be done from starting from January and ending in July (ibid)

The rice-shrimp system is expected to be more environmentally friendly and sustainable than monoculture rice or shrimp system (Tran, 1994) In specific, the siltation as remnant after shrimp crop can make the soil fertile for rice cultivation (Tran, 1994; Lan, 2011) Therefore, less fertilizer has to

27

be applied on rice crop However, according to Be et al (1999), similar to intensive shrimp farming, the system also implies many environmental costs Among of those, exacerbation of salinity intrusion and the environmental impacts of disposal of sediment from the field are the most detrimental About the impact of salinity, it has been proved that there are impacts of leaching or overflowing saline water from shrimp pond to nearby rice fields The direct disposal of sediment from ponds to the canals; on the other hands, can cause water pollution, bringing about serious problems to downstream area (ibid)

Figure IV.4: Rice-shrimp field in Ben Tre