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

Header Page of 89 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 Footer Page of 89 Header Page of 89 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 Footer Page of 89 Header Page of 89 -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 Footer Page of 89 Header Page of 89 -2- 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 Footer Page of 89 Header Page of 89 -3- 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 Footer Page of 89 Header Page of 89 -4- 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 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 Footer Page of 89 Header Page of 89 -5- 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 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 Footer Page of 89 Header Page of 89 -6- 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 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 Footer Page of 89 Header Page of 89 -7- 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 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 Footer Page of 89 Header Page 10 of 89 -8- 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 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 QuÇn ®¶o Hoµng 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-§B 500 Parac el islands QuÇn ®¶o Tr­êng 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; Footer Page 10 of 89 Header Page 17 of 89 2.4 - 15 - 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 Footer Page 17 of 89 Header Page 18 of 89 - 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 Footer Page 18 of 89 Header Page 19 of 89 - 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 Footer Page 19 of 89 Header Page 20 of 89 - 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) Footer Page 20 of 89 Header Page 21 of 89 - 19 - Table 3.4: The distance of salinity intrusion in some upstream development scenarios Scenario Tien River Hau River L(km) + increase;–decrease L(km) + increase;–decrease KBH-1 44.4 0.0 45.5 0.0 KBH-6 39.9 -4.5 39.2 -6.3 KBH-7 44.4 0.0 45.5 0.0 KBH-8 49.8 5.4 51.7 6.2 Unfathomable impacts cause a disadvantage for the flow change and the development of salinity intrusion in Mekong Delta evaluated such as (i) Reservoirs retaining water early can make longstanding salinity last month and affect Summer-Autumn rice; (ii) Reservoirs retaining water late can make salinity appear early (from to months), which affects Summer-Spring rice crop; (iii) Reservoirs retaining water abnormally or operating according to the requirements for load (an increase in capacity with a long time) can make saline development change suddenly, which is very unfavorable for taking fresh water Area affected by salinity intrusion with concentration in selected scenarios 1800 Area (1000ha) 1600 1400 1200 1000 800 600 400 200 > 4g/l KBH-0 KBH-3 0.2-2g/l KBH-6 KBH-8 KBH-9 0.2-2g/l KBH-0 475.20 KBH-3 437.31 KBH-6 430.92 KBH-8 471.78 2-4g/l 704.22 619.36 607.70 714.03 KBH-9 447.19 640.44 > 4g/l 1587.88 1530.65 1515.10 1607.28 1556.00 Figure 3.6: A change in the area of salinity intrusion is corresponding to salinity concentration according to some scenarios 3.3 A CHANGE IN SALINITY INTRUSION ACCORDING TO UPSTREAM DEVELOPMENT SCENARIOS AND A CHANGE IN LAND USE ON MEKONG DELTA Footer Page 21 of 89 Header Page 22 of 89 - 20 - 3.3.1 Scenarios and description of simulated scenarios MIKE11-ĐB model is used and simulated for the established scenarios of KBHN-0 to KBHN-10 3.3.2 Indicators of analysis and evaluation of results Table 3.5: Indicators of analysis and evaluation of impact rate changing discharge into Mekong Delta by upstream development scenarios Positive influence: Discharge increase > a change in discharge levels (m3/s) Very Good Positive good (TT) (T) (TTT) 489 337 Negative influence: discharge decrease >= a change in discharge levels (m3/s) Very Bad Negative bad (XX) (X) (XXX) -489 -337 No Month January February 320 221 -320 -221 March 278 191 -278 -191 April 349 240 -349 -240 In which: the each following indicator means the difference are higher or smaller the ‘threshold’ - ‘Very good’ indicator  QP50% - QP85%; ‘Very bad’ ≤ QP85% QP50%; - ‘Good’ indicator  QP50% - QP75%; ‘Bad’ ≤ QP75% - QP50%; - ‘Positive’ or ‘Negative’ indicator: Q increases or decreases 3.3.3 Results of simulation, analysis and evaluation By advancing indicators to evaluate the impact rate which changes the flow into Mekong Delta such as Table 3.5, limits of boundary conditions have been eliminated and quantified reliably the impact rate of upstream development scenarios Results show that in the case of hydroelectric increase with reasonable operation and agricultural development increase, most water discharge into Mekong Delta is still at ‘Very good’ level, so the existing irrigation system can prevent salinity intrusion better as compared with baseline scenario However, increasing agricultural development, Footer Page 22 of 89 Header Page 23 of 89 - 21 - intervening in Tonle Sap or operating water retention … will have a ‘Very bad’ impact Salinity intrusion development according to upstream development scenarios in combination with a change in land use in the Mekong Delta of Vietnam is also similar to scenarios corresponding to status quo of agricultural cultivation in 2005 analyzed in section 3.2, which means that this change in water use in the Mekong Delta of Vietnam by land use change is not a main solution The thesis has studied and made the relationship between salinity concentration at stations Dai Ngai (Hau river), Tra Vinh (Co Chien river) and Son Doc (Ham Luong river) corresponding to the discharge into Mekong Delta of Vietnam and indicated difference between them 3.4 SATIFACTION ABILITY OF THE EXISTING WATER RESOURCES WORKS AND SOME MAIN SOLUTIONS TO ADAPT WITH THE UPSTREAM DEVELOPMENT SCENARIOS 3.4.1 Evaluating the satisfaction ability of the existing water resources works with the upstream development scenarios The results of salinity intrusion simulation according to the upstream development scenarios show in normal operation conditions of hydroelectric works, salinity intrusion tends to decrease significantly due to an increase in regulation discharge from reservoirs However, in the conditions of unfavorable hydrological year (droughty year) an increase in water use for agricultural development in the upstream makes salinity intrusion penetrate more deeply as compared with it in the present The irrigational systems of Go Cong, North Ben Tre, South Mang Thit, Ca Mau peninsular (QLPH and Soc Trang) and Western coast meet with difficulties in water source because salinity intrusion affects water intake or reduces ability to take water 3.4.2 Some solutions in Mekong Delta of Vietnam to adapt with the upstream development scenarios Footer Page 23 of 89 Header Page 24 of 89 - 22 - Structural solutions: The thesis has advanced some solutions to every existing irrigational system combined with large sluices solutions (Ham Luong, Vam Co, Cai Lon, Cai Be), dredging axis canals or supplementing sluices for every system Especially proposing active solutions to water and operating the system effectively such as combining small projects into larger systems to guarantee water source (Go Cong+Bao Dinh, Ba Lai+Nam Ben Tre, Tiep Nhat+QLPH …), building electric pump stations, the alternative of active on-off operation of sluice gates (electric motor …) to guarantee for water, water storage or drain to wash the system; solutions to the establishment of automatic monitoring systems, updating information on water to take initiative in operation Non-structural solutions: The thesis has advanced some solutions such as strengthening the work of forecast, warning; building the operation schedule of works; studying and setting up the water management boards with a large scale not limited by provincial boundary (institution, law); seasonal transfer and changing land use to adapt with changes in salinity intrusion and water source 3.5 CONCLUSION OF CHAPTER Chapter has quantified adequately the impacts according to the upstream development scenarios on changes in the flow and the development of salinity intrusion on the Mekong delta including both positive impacts and negative impacts Detail the impacts due to hydroelectric development; due to agricultural development in the upper countries or according to the area Indicate opportunities for increasing water source as well as unfathomable impacts and obtain adaptation solutions to upstream developments CONCLUSION AND RECOMMENDATION CONCLUSION The thesis has solved some shortcomings discovered in relevant researches such as indicating unreliability in planning and design solutions according to design probability standard 4.1 Footer Page 24 of 89 Header Page 25 of 89 - 23 - corresponding to discharge into Mekong Delta at Kratie and advancing adaptation solutions to the possible impacts due to development in the upstream At the same time, solving shortcomings scientifically (reliability of calculation results) thanks to tool improvement and approach methods has indicated unfavorable impacts which previous researches have not yet had such as (i) Discharge reduction at the beginning of rainy season and at the end of dry season (due to early or late water retention) makes salinity appear early or end late; (ii) Clarification such as the impact of Chinese hydroelectricity which does not increase completely and regularly the discharge into the downstream but it still has unfavorable impacts when water is retained abnormally or capacity increase is operated; (iii) The impact can be caused by an increase in agricultural area in Cambodia … Analyzing a sequence of historical data has helped to understand the law of the flow change in dry season and changes in recent time have helped to forecast the longterm flow in dry season and salinity intrusion Some new main results which the thesis has achieved as advanced below:  Regarding the development of tool set of the thesis topic 1) The thesis has inherited the DSF, a set of tools for making decision by International Mekong River Commission, overcoming shortcomings and developing newly as indicated in Chapter 2, simultaneously building scenarios and simulation models Apply this tool set to simulate, analyze and indicate unfavorable impacts on the flow change and salinity intrusion in Mekong Delta according to development scenarios in the upstream The results of the thesis and the updated data base set have created a set of knowledge base (data base and model tools) of Mekong River basin, which permits to apply in scientific research and production service in Mekong Delta such as annual salinity intrusion forecast; water resources protection, management and planning, supporting to agricultural, irrigational development, aquaculture and environmental protection Footer Page 25 of 89 Header Page 26 of 89  - 24 - Regarding changes in the flow into Mekong Delta (at Kratie) from a new research of the thesis with a sequence of historical data from 1924 to 2012 2) The thesis has analyzed and evaluated the flow changes in dry season into Mekong Delta from a sequence of historical data from 1924 to 2012 and quantified the flow changes of the months in dry season according to periods, proving this increase due to the regulation impacts of reservoirs on the basin from rainy season to dry season, simultaneously indicating changes have happened in the process of the flow in dry season in recent years These results have been used as a basis for comparing, evaluating the reliability of the simulated results of models of the thesis (explaining the abnormal increase and decrease of the flow in recent years) and forecasting the future, which helps to advance the process of salinity intrusion forecast in Mekong Delta with specific products that are a set of tools having ability to forecast long-term salinity intrusion directly from the beginning of dry season with quite high reliability as applied effectively in heavily droughty years 2010 and 2013 3) The thesis has also indicated that the flow in Mekong River is quite stable, difference between discharge corresponding to probability of 85% used for design or planning as compared with discharge corresponding to probability of 50% in droughty months (Table 2.9) is smaller considerably as compared with regulation ability of hydroelectric reservoirs or an increase in irrigation use in the upstream This conclusion also explains why irrigational systems are designed with high guarantee level but meet with difficulties in water supply and salinity intrusion prevention every time dry season arrives The thesis has built the evaluation indicators of impact rates of upstream scenarios on a change in the flow into the Mekong Delta (Table 3.5) based on the analytical results of difference in discharge according to probability  Regarding the impact of upstream development scenarios on changes in the flow into Mekong Delta Footer Page 26 of 89 Header Page 27 of 89 - 25 - 4) The thesis has proved that the impact of upstream development scenarios can increase discharge into Mekong Delta as evaluated in related researches of MRC in [54], [55] and [77], however, it only happens with the cases of normal operation of hydroelectric reservoirs At the same time it has indicated anxiety due to an increase in agricultural development in Cambodia and a change in water quality when an increase in water use in the direction of upstream can surpass 30% water potentiality in months of dry season (Table 2.19), at that time water environment pollution can happen although discharge into Mekong Delta still increases more due to the regulation of hydroelectric reservoirs 5) The thesis has studied the scenarios of hydroelectric operation and indicated disadvantages in a change in the flow into Mekong Delta due to the impact of developments in the upstream: (i) An increase in capacity of Chinese hydroelectricity can make 30-40% of the number of years have months of the flow into downstream descend (such as 2010 and 2013); (ii) Abnormal operation at Chinese hydroelectricity can change considerably hydrological regime of the flow into the Mekong delta, turning the flow of dry season in normal hydrological year into droughty year or the year of much water; (iii) Early water retention operation can make the flow into Mekong Delta decrease at the beginning of rainy season, or late water retention will decrease the flow at the beginning of dry season and it will be very unfavorable for main rice crops; (iv) Day-night peak coverage operation at large hydroelectric reservoirs in the scope of distance of 300-700 km for Mekong Delta of Vietnam will be able to affect a change in salinity intrusion on the Mekong Delta  Regarding changes in the flow, salinity intrusion and adaptation solutions in Mekong Delta of Vietnam 6) The thesis has indicated that regulation impact of hydroelectric reservoirs has partially limited salinity intrusion increase in Mekong Delta in past time due to a change in the flow in droughty months When an increase in the regulation of hydroelectric reservoirs in the Footer Page 27 of 89 Header Page 28 of 89 - 26 - future can decrease salinity intrusion on the Mekong Delta; pushing salinity come near river mouths: Tien River (receding 4.5 km); Hau River (receding 6.3 km) However, very unfavorable impacts are still always implicit in the cases of hydroelectric operation: (i) reservoirs retaining water early can make long-standing salinity last, which affects Summer-Autumn rice; (ii) reservoirs retaining water late can make salinity appear early (1 to months), which affects WinterSpring rice crops; reservoirs retaining water abnormally or operation according to the requirements for load (capacity increase) can make saline development change suddenly 7) The thesis has indicated that the system of the existing irrigational works can operate more effectively on condition that regulation discharge into downstream is increased but cultivated area is still maintained as it is now, however, it is difficult to satisfy in cases that hydroelectric operation causes unfavorable impacts for Mekong Delta and main solutions have been proposed in order to adjust actively to unfavorable conditions, especially strengthening observation and forecast; taking initiative in sluice gates on-off operation (by electric motor); supplementing pump stations to make the best of opportunities for fresh water in the condition of dry season in which salinity changes through time Associate projects to strengthen ability to guarantee water source and raise the capacity of water management units 4.2 RECOMMENDATION 1) Continuing to perfect and develop a set of tools, building newly scenarios with updated data of upstream development, reservoir operation … can happen in the future (due to time limit this research has not yet implemented) 2) Continuing to work out fully the evaluations of the law of the flow in dry season in years in succession and the flow in corresponding flood season to serve the work of the flow forecast of dry season and long and short term salinity intrusion forecast 3) Clarifying more the investment itinerary in large water resources works in Mekong Delta, large main stream sluice gates Footer Page 28 of 89 Header Page 29 of 89 - 27 - The research has indicated these structures are really necessary when subjective impact in the upstream changes the flow into Mekong Delta LIST WORKS OF AUTHOR HAVE BEEN PUBLISHED INSIDE COUNTRY To Quang Toan, Le Sam (2007), “Past changes in water demand evaluated for the Mekong Delta of Vietnam from 1985 to 2000’, Technological & Scientific results collection in 2006-2007, Southern Institute of Water resources research, Agriculture Publishing House, pages 115-123 Nguyen An Nien, To Quang Toan (2007), “Another method for deriving governing equations for one dimensional hydraulic problem in open channels”, Technological & Scientific results collection in 2006-2007, Southern Institute of Water resources research, Agriculture Publishing House, pages 464-473 To Quang Toan, Tang Duc Thang and Pham Duc Nghia (2008), “Initial investigating on acid water movement at the early rainy season in the Plain of Reeds”, Technological & Scientific results collection in 2008, Southern Institute of Water resources research, Agriculture Publishing House, pages 409-419 To Quang Toan, Trinh Thi Long and Vu Nguyen Hoang Giang (2009), “Surface water resources assessment of Thi Vai river basin and its environmental issues”, Technological & Scientific results collection in 2009, Southern Institute of Water resources research, Agriculture Publishing House, pages 76-85 To Quang Toan, Nguyen Quang Kim and Tang Duc Thang (2009), “Assessment of variation of Mekong river flow at Kratie for different upstream development scenarios”, Technological & Scientific results collection in 2009, Southern Institute of Water resources research, pages 115-123 To Quang Toan, Nguyen Quang Kim et al (2009), “Assessment of water requirement changes for upstream development scenarios compared to 2000 baseline condition”, Environmental & Irrigational Technical Science Magazine No 24/3-2009, Hanoi Water Resources University, pages 16-22 Footer Page 29 of 89 Header Page 30 of 89 - 28 - To Quang Toan, Nguyen Quang Kim et al (2009), “Assessment of variation of Mekong flow at Kratie for different upstream development scenarios”, Environmental & Irrigational Technical Science Magazine No 24/3-2009, Hanoi Water Resources University, pages 7-15 To Quang Toan, Tang Duc Thang (2010), “Tidal inundation change due to sea water level rise in the Mekong Delta according to climate change scenarios and its possible impact to biosphere reservation area of Ca Mau peninsula Technological & Scientific results collection in 2010, Southern Institute of Water resources research, Agriculture Publishing House, pages 25-33; Report collection at Scientific seminar in Ca Mau in 2010 on ‘Conserving the values of biosphere reserve and supporting inhabitants of coastal area of Ca Mau province in the face of climate change’, Department of Science and Technology of Ca Mau province, pages 101-108 To Quang Toan, Tang Duc Thang, et al (2010), “Point of view and proposed measures for floods and tidal inundation adaptation for the Mekong Delta in climate change conditions”, Technological & Scientific results collection in 2010, Southern Institute of Water resources research, Agriculture Publishing House, pages 34-42 10 To Quang Toan, Tang Duc Thang (2011), “Inundation by floods and sea level rise in Mekong Delta in the context of climate change and some adaptation solutions”, Irrigational Technological Science Magazine – No 4/10-2011, Vietnam Academy for Water resources, pages 2-7 Footer Page 30 of 89 Header Page 31 of 89 11.To Quang Toan and Tang Duc Thang (2013), “Evaluation of the hydrological change of Mekong river flow to the deltaic area based on the historical data at Kratie station from 1924 to 2012”, Science and technology for water resources Journal – No 19/122013, Vietnam Academy for Water Resources, pp 17-23 LIST WORKS OF AUTHOR HAVE BEEN PUBLISHED INTERNATIONAL 12.To Quang Toan (2006), “Past changes in water demand evaluated for the Mekong delta of Viet Nam from 1985 to 2000”, Proceedings of the 2nd symposium on sustainable development of the Mekong river basin, Phnom Penh – Cambodia 13.To Quang Toan (2006), “Water resources management in the Mekong basin: modelling and evaluation of floods, droughts and salinity intrusion”, Proceedings of the International Symposium on Prediction of Rice Production Variation in East and Southeast Asia under Global Warming, INAES, Tsukuba, Japan 14.To Quang Toan et al (2008), “An investigation for acid water spreading on the canal systems at the early stage of rainy season in the Plain of Reeds”, Proceedings of the 3th international workshop on the sucstainable development of the Mekong basin, Khonkhaen, Thailand 15.To Quang Toan and Nguyen Quang Kim (2010), “The impact of upstream development scenarios to downstream saline water intrusion in the Mekong delta”, Proceedings of the Large Dams workshop, Hanoi, Viet Nam 16.To Quang Toan, Tang Duc Thang and Nguyen Anh Duc (2010), “Impact of climate change and sea water level rise to the innundation condition in the Mekong delta”, Proceedings of the 8th Annual Mekong floods forum, Vientiane, Lao PDR, pp 374379 17.To Quang Toan, Tang Duc Thang (2014), “Evaluation of the hydrological change of Mekong river flow to the Deltaic area based on the historical data at Kratie station from 1924 to 2012”, Proceedings of the 19th IAHR-ADP 2014 congress, Thuyloi University, Hanoi, Section – Sustainable water resources Footer Page 31 of 89 ... law of the flow in dry season in years in succession and the flow in corresponding flood season to serve the work of the flow forecast of dry season and long and short term salinity intrusion forecast... 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. .. 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