INVESTIGATING POSSIBLE IMPACT OF UPSTREAM DEVELOPMENT SCENARIOS ON THE FLOW REGIME AND SALINITY INTRUSION IN THE DRY SEASON IN THE MEKONG DELTA, VIETNAM

MINISTRY OF EDUCATION AND TRAININGVIETNAM ACADEMY FOR WATER RESOURCES SOUTHERN INSTITUTE OF WATER RESOURCES RESEARCH ------TO QUANG ------TOAN INVESTIGATING POSSIBLE IMPACT OF UPS

MINISTRY OF EDUCATION AND TRAINING

VIETNAM ACADEMY FOR WATER RESOURCES

SOUTHERN INSTITUTE OF WATER RESOURCES RESEARCH

- -TO QUANG - -TOAN

INVESTIGATING POSSIBLE IMPACT OF UPSTREAM DEVELOPMENT SCENARIOS ON THE FLOW REGIME AND SALINITY INTRUSION IN THE DRY SEASON IN THE

MEKONG DELTA, VIETNAM

Major: Water Resources Engineering Code : 62 58 02 12

SUMMARY OF DOCTORIAL THESIS IN ENGINEERING

HOCHIMINH CITY - 2015

The research has been accomplished at:

Southern Institute of Water Resources Research

Supervisor: Prof Dr Tang Duc Thang

Examiner 1: Assoc Prof Dr Le Van Nghi

Examiner 2: Assoc Prof Dr Nguyen Ba Quy

Examiner 3: Assoc Prof Dr Huynh Thanh Son

This thesis to be defended at the committee of doctorial thesis examiners, at:

Southern Institute of Water Resources Research

658 Vo Van Kiet Blvd., Ward 01, District 5, Hochiminh city

at 08:00AM, Date 24thJanuary 2015

This thesis can be found at:

- Vietnam National Library

- Library of Vietnam Academy for Water Resources

- Library of Southern Institute of Water Resources Research

INTRODUCTION 0.1 THE URGENCY OF THE THESIS

The Mekong Delta plays a very important role in social and economic development in Vietnam, especially for food security It has been developing very fast, in 1985 total food production achieved 6.3 million tons, in 2011 it achieved 23.4 million tons, contributing more than 50% of food production of the whole country, 90% of exported rice production More than 70% of exported aquaculture products and about 55% of exported fruit come from the delta

Sustainable development of the Mekong Delta has been threatened by development in the upstream which changes the flow into the plain in both flood season and dry season, especially a change in the salinity intrusion in dry season resulting in a change in the source of water which affects people’s livelihood, agricultural production (crop pattern, area, yield and production), aquaculture products and other activities

In the past time, there were a lot of researches on salinity intrusion in Mekong Delta in which they concentrated mainly on monitoring and evaluating the changes of salinity intrusion according

to hydrological and meteorological conditions; calculation for water resources planning, systematic design and water resources management These activities had important contributions to irrigational development in the Mekong Delta, preventing and controlling saline water and reserving fresh water for social and economic development

Most calculations of salinity intrusion in the country are based

on design probability standards (flow, tide, water use) or on typical years, therefore, they are still limited very much, the impacts from the upstream to the Mekong Delta have not been considered in immediate, short-term or long-term cases One of reasons leading to the above-mentioned shortcomings is a lack of tools to evaluate these impacts

Recently the researches of International Mekong River Commission have taken into account the upstream development, their impacts in a ranger of typical hydrological conditions were evaluated, However, these are only the initial researches which have just evaluated the overview of the influence of the upstream development, especially not yet evaluated the different aspects of hydroelectric development, not yet evaluated in detail the influence

of the development of every country on a change in the flow and salinity intrusion in Mekong Delta For that very reason, the reliability of the results of calculation and evaluation of these researches are still much limited In addition, solutions adjusting to a change in the upstream in Mekong Delta have not been cared considerably

The above-mentioned analyses show the sustainable development of economy and society in Mekong Delta requires more adequate researches on the upstream, especially on a change in the flow by the impacts of agricultural and hydroelectric development as

a basis for proposing solutions adapting to changes These are reasons for the research of this thesis topic

0.2 PURPOSE OF THESIS

The purpose of the thesis topic is to advance reliably scientific evaluations on the capacity of water source in dry season and the salinity intrusion change in Mekong Delta for the target of sustainable agricultural development in the context of (hydroelectric and agricultural) development in the upstream in the future

0.3 OBJECT, SCOPE AND AIM OF RESEARCH

Research objects: Reservoirs, hydroelectric reservoirs on the

basin and irrigational system in the upstream of Mekong River The system of irrigational structures in Mekong Delta: salinity intrusion prevention and irrigation culverts; the river systems, irrigating and draining canals; the system of dike and embankment

Scope: Regarding space: research topic on the basin of

Mekong River Regarding research problems: impacts on the flow in

dry season on Mekong Delta according to the scenarios of development in the upstream which are limited to hydroelectric and agricultural development including Chinese hydroelectricity and the hydroelectricity of main tributaries in the downstream as proposed plan In Mekong Delta, restriction to the research is a change in the flow into the plain and a change in the development of salinity intrusion due to upstream development The boundary of sea tide is taken in the same condition as it was in 2005, this is considered as a typical year near to the present conditions (which have been chosen

by many recent researches) Regarding adaptation solutions, the main interest in this thesis is water resources solutions for preventing salinity intrusion and guaranteeing the source of water

The aim of research is to evaluate hydrological changes of historical flow (past to present) and near future (by hydroelectric and agricultural development in the upstream) and their impact, from that point, orientation and adaptation (irrigational) solutions are proposed for agricultural development production in Mekong Delta

0.4 PRACTICAL AND SCIENTIFIC SIGNIFICANCE

 Scientific significance

The scientific significance of the research is to solve the outstanding problems scientifically for sustainable agricultural development in the Mekong Delta A set of tools is set up for scientific research and water management supporting to agricultural production, which help to forecast the flow of dry season and salinity intrusion

 Practical significance

The thesis has practical significance for the work of planning, research concerning water resources and environmental protection, serving practically agricultural production (forecasting salinity intrusion, seasonal arrangement, water management), helping to make relevant decisions A set of tools is applied to forecast salinity intrusion in severe drought years 2010 and 2013

0.5 STRUCTURE OF THESIS

The thesis is presented in 140 pages including 28 figures, 34 tables and interpretational pages The main contents of the thesis

include 3 main chapters and conclusion Chapter1: Overview of

research problems: Mekong river basin, existed related researches

and identified the contents of the research; Chapter 2: Research on

the impacts of the abilities of the upstream development on the flow

regime into Mekong Delta; Chapter 3: Research on the impacts of

the abilities of the upstream development on the flow and salinity intrusion in Mekong Delta and adaptation solutions; Conclusion and recommendation of the thesis: Some main results have newness and the recommendations of the thesis have been advanced

CHAPTER 1 OVERVIEW OF RESEARCH PROBLEMS: MEKONG RIVER BASIN, RELATED EXISTING RESEARCHES AND THE IDENTIFIED CONTENTS OF THE RESEARCH

1.1 OVERVIEW OF MEKONG RIVER BASIN

territories of 6 countries: China, Myanmar, Laos, Thailand, Cambodia and Vietnam (see Table 1.1) The river has total length of main stream of more than 4,800 km in which the part of river through 2 upstream countries is about 2,100 km long The upstream

of Mekong Delta is the basin from China and extended to Kratie (the starting point of Mekong Delta) The upstream of Mekong Delta of Vietnam is understood as the basin from China spreading to the border of Vietnam and Cambodia

Tonle Sap in Cambodia is considered as a natural lake which plays a very important role in regulating the flow into the downstream of the plain in both flood and dry season Every year the

which about 50% water discharge is obtained thanks to regulation from the flood flow of Mekong River

Table 1.1: Area and contribution of flow from countries

% compared with the area of the basin

% compared with the area

of the country

% contribution

(Source : International Mekong River Commission - MRC, 2003)

1.2 STATUS QUO, DEVELOPMENT ABILITIES IN THE MEKONG RIVER BASIN AND MAJOR CONCERN IN MEKONG DELTA

There is a very huge potentiality of land which has ability to adjust to agricultural development in the upstream with total area of

4 downstream countries of 29.8 million hectares which concentrate mainly in Thailand (12.2 million hectares) Cambodia (11.2 million hectares), Laos (2.7 million hectares) the remainder is in Vietnam At present the only a small part of land resources of the basin are exploited, mainly in rainy season, accounting for about 11-17% adjustable land in every country In condition of the year 2000, the irrigated area in dry season in Thailand only achieved about 160,000 hectares, Laos 130,000 hectares and Cambodia 250,000 hectares (according to MRC, 2002) To increase the cultivated area in upstream countries, the largest limitation is difficulties in water source, investing and building an irrigational system is very costly

due to difficulties in terrain and geology, the area is crumbled because it is separated by terrain

According to the development plan of the upstream countries until 2020, agricultural area in Thailand can come to 3 million hectares, the cultivated area in Cambodia is 2.5 million hectares and

in Laos is 0.5 million hectares In near future, hydroelectric development with total active volume of reservoirs comes to

In the present condition, there are few cultivated areas in the upstream, however, salinity intrusion in Mekong Delta has happened complexly, increasing development in the upstream and building dams can cause unfavorable impacts on the delta and increase salinity intrusion threatening stable development in the Mekong Delta This is considered as great interest in Mekong Delta in the future

1.3 RELATED EXISTING RESEARCHES, LITTLE MENTIONED PROBLEMS AND THE IDENTIFIED RESEARCH CONTENTS OF THE THESIS

The researches of international organizations, especially the researches of MRC in the Basin Development Programme (BDP), only advance a significant increase in discharge in the scenarios of the upstream development [54], [55] and [77] Few researches mention or have not yet analyzed abnormal operation capacity at hydroelectric works One still pays little attention to the evaluation of salinity intrusion change due to model limitation

Domestic researchs on salinity intrusion in Mekong Delta and development in the upstream have been mentioned [3], [4], [16] … there were few specific or sketchy researches not including the upstream [9], [13], [24]-[28], [33] The majority of researches take discharge at Kratie by design frequency standards or by typical years This leads to limitations which are (1) Impractical evaluation

of the influence of salinity intrusion by design probability standards; (ii) Inadequate evaluation of impacts of upstream development on

Mekong Delta ; (iii) Not paying much attention to adaptation solutions to developments in the upstream ; (iv) Reliability of calculated results is still a problem

RESEARCH CONTENTS OF THE THESIS

1) Research on actual state and development abilities in the Mekong River basin, research on flow regime into Mekong Delta from historical data to indicate opportunities and challenges due to hydrological change of water flow into Mekong Delta ;

2) Research on the change in flow discharge of dry season on Mekong River due to upstream development and its influence

on the flow and salinity intrusion on the Mekong Delta ;

3) Proposing water resources solutions in Mekong Delta to prevent salinity intrusion and adaptation to development ability in the upstream

CHAPTER 2 RESEARCH ON THE IMPACT OF UPSTREAM

DEVELOPMENT ABILITIES ON FLOW REGIME INTO

MEKONG DELTA

This chapter presents the author’s researches on the basis of inheriting a set of DSF tools with improvements of the existing applications (of IQQM) and replacing ISIS model with MIKE 11 model, building models with data updated by scenarios to obtain tools for the research of thesis topic Research on hydrological regime of historical flow into Mekong Delta to get evaluational analyses of changes in the past due to the impact of developments in the upstream by different periods (3 periods) as a basis for evaluating changes due to development in the upstream in the future Scenarios

of upstream development have been built on development levels in the upstream (high or low), interest in influences by the field (agriculture, hydroelectricity), by the space (area, country, territoty) The development tool of the thesis has been applied to simulate, analyze and evaluate the impact by developments in the upstream on the change in the flow into Mekong Delta

2.1 DEVELOPING TOOLS FOR THE RESEARCH OF THE THESIS

The research has inherited the Decision Support Framework (DSF), a set of tools helping to make decisions of MRC, making good the shortcomings of the existing models, replacing and building the models of more reliability Diagram of tools for the research of the thesis is advanced in Figure 2.1

Figure 2.1: Diagram of tools for the research of the thesis and connections of models to simulate the upstream development scenarios

SWAT model simulates the flow from rain, applied in the upstream of Mekong Delta of Vietnam, using the updated results of MRC

IQQM model simulates the water balance in the basin, permitting to simulate irrigational developments for agriculture, reservoirs, hydroelectric reservoirs, water supply … There are 3 sets

of models applied to 3 areas:

i) The model is applied to the upstream of Mekong Delta, its symbol is IQQM-T, there are 7 models built, they are IQQM-T.1 to IQQM-T.7;

Parac el islands Quần đảo Trường Sa East sea

500 0 500 Kilo m e ter s

S N

E W

Zoning models application

ii) The model is applied to the part of Mekong Delta of Cambodia, its symbol is IQQM-C, there are 3 models built, they are IQQM-C.1 to IQQM-C.3;

iii) The model in Mekong Delta of Vietnam, its symbol is IQQM-ĐB, there are 5 models built, they are IQQM-ĐB.1

to IQQM-ĐB.5

The limitations of IQQM models overcome by the author are: cropping patern and cultivated area, dividing cultivated area to limit partial concentration of water demand; agricultural and hydroelectric data are updated according to construction scenarios In addition, the author has set up hydroelectric operation scenarios by abilities in which operation can really happen (retaining water early, retaining water late, retaining water abnormally due to construction, maintenance and overcoming problem …operation to satisfy the requirements for power load and day-night peak coverage operation)

MIKE11 hydrodynamic model is substituted for IQQM model

on main stream to simulate by a movement process of water flow to the downstream; simultaneously substituted for ISIS model on the delta area to overcome some shortcomings of this model

Specifically MIKE11-DC model is built by the author (Figure

hydroelectricity on the main stream to overcome limitations of IQQM model ISIS limit to salinity intrusion results is replaced by MIKE11 model, MIKE11-ĐB model (Figure 2.6) at the Southern Institute of Water Resources Research was applied in the past years, the author improved, upgraded, calibrated and validated well, built scenarios in the thesis topic

MIKE11-DC model:

- Source: Built by the author

- Upper boundary: Chiang Saen

- Lower boundary: Kratie

- Other boundaries: 30 tributaries on the basin

- Section: Data source from MRC’s navigation project

- Calibration and validation: for the years 2000, 1998 guaranteeing reliability

- Application: Hydraulic simulation on the main stream

of Mekong river; hydroelectric operation scenarios.

Figure 2.5: MIKE11-DC model is applied to Mekong main stream

MIKE11-ĐB model :

- Source: SIWRR, the author is a key participant

- Upper boundary: Kratie

- Lower boundary: sea boundary

- Other boundaries: in Cambodia; Saigon, Dongnai and Vaico river boundaries; irrigation boundaries; basin entry boundary from rain

- Terrain, section, works: are updated continuously

- Calibration & validation: for the years 2000, 2001, 2005 Guaranteeing reliability

- Application: Hydraulic simulation and salinity intrusion in Mekong Delta according to upstream

development scenarios Figure 2.6:MIKE11-ĐB: Hydraulic and saline intrusion model in MD

Nam Theun

Se Ba

ng Fai

Nam Kam

Nam Mun + Nam Chi

Ú

Ú

Ú Ú Ú

Mü ThuËn T©n Ch©u

$ Calibration station forn MRC source

Ú Rainfall, Q & H calibration stations

% Flow boundaries

$ W level boundaries

S N

W

Legends MIKE11-§B Model

2.2 RESEARCH ON HYDROLOGICAL REGIME OF FLOW INTO MEKONG DELTA BASED ON HISTORICAL DATA

2.2.1 Data base, concepts and division of analytical periods

Data of water level and discharge at Kratie from 1924 to 2012 were gathered from the source of the Mekong River Commission Hydrological parameters were analyzed according to 3 development periods in the basin: 1) Before 1960 (mainly agriculture); 2) From

1961 to 2000 (few more irrigation reservoirs, hydroelectric reservoirs

on the basin); 3) 2001 to 2012 (more hydroelectric reservoirs in China, Laos and Central Highland of Vietnam)

2.2.2 Analysis of average annual flow change and according to hydrological year

Average discharge of many years at Kratie was about 13,920

year was quite stable, the averages of many years vary about

compared with the period of 1961 to 2000 From 1924 to 2012 average different value of average discharge in dry season between

2.2.4 Analysis of flow change between months of dry season according to periods

The research indicated that there was a considerable increase

in the flow in dry season by the periods after 1960 as compared with previous periods due to regulation impact of reservoirs on the basin

2000 as compared with period before 1960

Table 2.6: Comparison of average discharge change of months of dry season between periods

No

Period A change in average discharge of periods in

months (m3/s) After Before Dec Jan Feb Mar Apr May

2.2.5 Research on a change in average flow regime of months of

dry season according to periods

 Analysis of flow ratio in dry season as compared with the flow of hydrographical year

Using balanced calculation methods according to water rate distributed in the year, take the rate of % the flow of every month of dry season or the whole dry season as compared with average discharge according to hydrological year in each year then take this average rate by the period, the author has proved there is the regulation of flow increase of rainy season to dry season (Table 2.7) Table 2.7: Results of analysis and evaluation of regulation increase

of rainy season to dry season

No Period

Qmk/

Qntv (%)

α , Average of flow ratio of every month of dry season as compared with the flow of

hydrological year (%) Dec Jan Feb March April May

The flow of April in the period of 2001-2012 accounted for 1.68% of the flow of the year, much more increase as compared with that in the period 1924-1960 (1.16%)

 Analysis of flow change ratio of next month compared with previous month in dry season

The research has proved that the flow of months of dry season

in recent periods, especially from 2001 until now, has tended to go down slowly, horizontally and rise up slowly as compared with that

in the period before 1960 (going down quickly and rise up quickly) The droughtiest month moved up March

2.2.6 Analysis and evaluation of hydrological change of dry season by flow frequency

Discharge into Mekong Delta is corresponding to flow

considerably as compared with a possible impact due to an increase

in agricultural development or regulation of hydroelectricity For that very reason, calculating hydraulic design and water resources planning by the standard of design flow probability has not yet guaranteed reliability if one does not consider developments in the upstream

2.3 SETTING UP DEVELOPMENT SCENARIOS IN THE UPSTREAM IN THE FUTURE

2.3.1 The factors of upstream affect hydrological flow into Mekong Delta of Vietnam

The thesis has studied, analyzed and evaluated natural factors and impacts by humans which affect the change in flow into the Mekong Delta of Vietnam and define important factors: Building reservoirs, developing agriculture and shifting water in the basin; managing operation, and changing hydrometeorology

2.3.2 Basis for setting up development scenarios in the upstream

On the basis of the analyzed important factors (2.3.1.), based

on actual conditions on the basin, hydroelectric and agricultural