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 24th January 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 -1INTRODUCTION 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 -2Recently 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 -3dry 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 -40.5 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 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 OVERVIEW OF RESEARCH PROBLEMS: MEKONG RIVER BASIN, RELATED EXISTING RESEARCHES AND THE IDENTIFIED CONTENTS OF THE RESEARCH 1.1 OVERVIEW OF MEKONG RIVER BASIN Mekong River basin has total area of 795,000 km2 and annual total flow of approximately 475 billion m3, flowing through the territories of 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 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 lake supplies to the downstream about 40-80 billion m3 water in -5which 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 No Name of country Area in the basin (Km2) China Myanmar Laos Thailand Cambodia Vietnam Total area: 165,000 24,000 202,000 184,000 155,000 65,000 795,000 % compared with the area of the basin 21 25 22 20 100 % compared with the area of the country 97 36 86 20 Total flow: % contribution of flow 16 35 18 18 11 475 km3 (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 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 -6due 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 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 approximately 50 billion m3 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 -7Mekong 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 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 -82.1 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 N W E S RESEARCH MODELLING TOOLS Zoning models application SWAT Model MIKE11-DC MIKE11-§B China Knowledge base SWAT & IQQM-T SWAT & IQQM-C IQQM-DB IQQM Model Myanmar Vietnam â Hµ Néi Lao PDR MIKE11 Model MIKE11-DC Vientiane â MikeToGIS SWAT & IQQM-T Parac el Islands Quần đảo Hoàng Sa Thailands Tools for analysis Bangkok â SWAT&IQQM-C East sea Cambodia Times series Spatial data Phnom Penh â MIKE11-§B West sea IQQM-ĐB 500 Parac el islands Quần đảo Trường Sa 500 Kilo m e ter s 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 sets of models applied to areas: i) The model is applied to the upstream of Mekong Delta, its symbol is IQQM-T, there are models built, they are IQQM-T.1 to IQQM-T.7; - 15 2.4 RESEARCH ON THE EVALUATION OF WATER DEMAND CHANGE IN THE UPSTREAM AND THE FLOW INTO MEKONG DELTA ACCORDING TO UPSTREAM DEVELOPMENT SCENARIOS 2.4.1 Scenarios and simulated methods scenarios of KBT0-KBT8 are simulated with the case of normal operation of hydroelectricity The case of abnormal water retention operation at Chinese hydroelectricity is considered at KBT9 (water retention in a short period of 10 days/month) In addition, there are still very many different scenarios which can happen to hydroelectric operation analyzed and calculated such as: - Water retention operation : retaining water early or late ; - Peak coverage operation satisfies the requirements for electrical load ; - Day-night electrical peak coverage operation (simulated by Mike11-DC) Scenarios are simulated, corresponding to sequence of hydrometeorological times series from 1985 to 2000, eliminating the results of 1985 (eliminating the error of the first year) 2.4.2 Indicators and result evaluation methods Analytical indicators are built to evaluate adequately the impacts by a change in water demand and discharge into Mekong Delta according to countries, according to many years; according to months; the largest month; the droughtiest month; comparing the allocation of water use between countries; the used water ratio as compared with water potentiality; compared with baseline scenarios 2.4.3 Results of simulation, analysis and evaluation The research indicates that hydroelectric development in the upstream in the case of normal operation increases the flow in dry season, even highly agricultural development, the flow in dry season can increase 300-800m3/s, the droughtiest month also achieves more than 2,200 m3/s higher as compared with a necessary level to maintain saline boundary reasonably High agriculture scenarios with no additional hydroelectricity, the flow of the droughtiest month only - 16 still has 1298 m3/s, therefore, agricultural development in the upstream is anxiety Abnormal water retention operation (KBT-9) according to periods of unfathomable impacts can change the flow in dry season in these periods of the year of much water into droughty year and vice versa (droughty year changing into the year of much water) Early or late water retention operation makes the flow into the Mekong Delta reduce at the beginning of rainy season or the beginning of dry season, therefore, it can affect main rice crops Winter-Spring and Summer-Autumn Peak coverage operation at Chinese hydroelectricity satisfies the requirements for load at the level of 60% capacity (VH60) which can make 30%-40% of the number of years that reservoirs lose regulation ability because their water lowers to dead water level (Table 2.21) Day-night peak coverage operation can affect the downstream within a distance of 300-700km from dam site Table 2.21: Satisfaction ability of Nuozhadu hydropower dam according to operation scenarios No Operation Scheme The number of appearance years achieves in total 16 simulated years 60% 70% 80% To Overflow NWL Whi Whi Whi DWL exist 0 0 15 VH70 VH60 4 VH50 16 16 16 15 14 VH50CN 16 16 15 15 12 VH45 16 16 16 15 15 VH5045 16 16 16 16 15 VH5147 16 16 16 15 15 VH5147T 16 16 16 15 14 Where: Whi: Active volume; NWL: Normal water level; DWL: Dead water level - 17 2.5 CONCLUSION OF CHAPTER The author has set up a set of tools for the research and applied it to simulate the impacts of the upstream development scenarios on the changes in the flow into Mekong Delta; and indicated opportunities and challenges for the Mekong Delta of Vietnam in the future, especially opportunities of the regulation of flow increase by regulation operation of hydroelectric works as well as unfathomable impacts which it can conduct (abnormal water retention, early water retention, late water retention …) are clarified Anxiety for an increase in water use for agricultural development in the upstream and especially in Cambodia is clarified The laws of changes in the flow in dry season are also clarified and have helped to forecast the flow of dry season and salinity intrusion serving production opportunely CHAPTER RESEARCH ON THE IMPACTS OF UPSTREAM DEVELOPMENT ABILITIES ON THE FLOW AND SALINITY INTRUSION IN MEKONG DELTA OF VIETNAM AND ADAPTATION SOLUTIONS This chapter presents the established scenarios to evaluate the impacts of upstream development abilities on the changes in the flow and salinity intrusion in Mekong Delta in which changes in land use in the Mekong Delta of Vietnam are considered : (i) Status quo of land use in 2005; (ii) A change in land use in the future as expected Applying tools developed in Chapter to simulate the established scenarios; analyzing and evaluating the flow changes and salinity intrusion in the Mekong Delta; evaluating satisfaction ability of irrigational structures for salinity intrusion prevention, water supply and proposing adaptation solutions in Mekong Delta - 18 3.1 SETTING UP SCENARIOS IN MEKONG DELTA IN THE CONTEXT OF UPSTREAM DEVELOPMENT The research has set up 10 scenarios for Mekong Delta (KBH0 to KBH-9) which are the combination of the corresponding upstream scenarios (KBH-0 to KBH-9) associated with status quo of land use in 2005 in Mekong Delta of Vietnam Similarly, the research has also set up 11 scenarios for Mekong Delta which are the combination of upstream scenarios associated with the expected land use in the future in Mekong Delta of Vietnam, they are symbolized by KBHN-0 to KBHN-10 KBHN-10 is a scenario which intervenes in the Tonle Sap by a barrage at Prekdam 3.2 A CHANGE IN SALINITY INTRUSION ACCORDING TO UPSTREAM DEVELOPMENT SCENARIOS AND STATUS QUO OF LAND USE IN MEKONG DELTA 3.2.1 Scenarios and description of simulated scenarios MIKE11-ĐB model is used and simulated for the established scenarios from KBH-0 to KBH-9 3.2.2 Indicators of analysis and evaluation of results Many analytical details are considered: salinity intrusion by the space (area, zone); influence time (early, late appearance, saline concentration is maintained at a high level); by the distance from river mouth; increase, decrease as compared with baseline scenarios 3.2.3 Results of simulation, analysis and evaluation The map of salinity intrusion concentration and duration has been set up, changes in salinity intrusion by the area and by the distance on the main stream have been analyzed and quantified The results show positive impacts due to increase regulation of hydroelectric reservoirs such as the area of saline influence of 4g/l which decreases more than 57 thousand hectares according to KBH3 as compared with KBH-0 Salinity is pushed back 6.3km on Hau River in KBH-6 (as compared with background scenarios) ... 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... stream of more than 4,800 km in which the part of river through 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... tu key participant Kratie flow boundary init Prek Te g Ch - Upper boundary: Kratie Stun Prek Chhlong - Lower boundary: sea boundary Stung Baribo - Other boundaries: in Cambodia; Saigon, Dongnai