MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT THUY LOI UNIVERSITY LƢƠNG NGỌC CHUNG STUDY ON THE IDENTIFICATION OF THE MINIMUM FLOW FOR SUSTAINABLE WATER RESOURCES MANAGEMENT IN DOWNSTREAM OF THE MA RIVER Major : Water resources engineering Code : 9-58-02-12 SUMMARY OF PHD DISSERTATION HANOI, 2018 The product was completed in Thuy Loi University 1: Assoc.Prof Dr Trần Viết Ổn Doctorial advisor: 2: Dr Lê Viết Sơn Reviewer 01: Reviewer 02: Reviewer 03: The dissertation was defended against the dissertation review board at Room 5K1 of Water Resources University Dated 2018 The dissertation can be found at: - National Library - Library of Thuy Loi University INTRODUCTION The neccessity of the dessertation topic Ma River is critically important to our country, with profuse water resources, contributing significantly to the socio-economic development of the basin At the moment, the Ma river resources are being exploited and used for a variety of purposes, which have altered the natural flow regime during the dry season resulting in negative impacts on the exploitation capacity, water use and aquatic ecosystems, especially in the downstream area of the Ma river According to monitoring data gathered at the hydrological stations, it is shown that the water level in the dry season reached a much lower level compared to the average of multiple years (0.8÷1.4m) Changes in the flow regime on the Ma River have direct and indirect adverse effects on the water environment and ecological characteristics of the river Therefore, to balance and harmonize the river flow regime to ensure the its functions to serve socio-economic development and sustain aquatic ecosystems of the river is very necessary On the other hand, Article of Decree 120/2008/NĐ-CP on river basin management stipulates: "For each river, it is necessary to regulate, allocate water resources, maintain a minimum flow" To date, no research has quantified the amount of water needed to harmonize the demand for water between socio-economic development and ecological environment protection in the downstream of Ma River In order to contribute to the development of a long-term strategy for the sustainable management of water resources in the lower Ma River, it is necessary to conduct a thorough and in-depth study on the scientific basis and methodology for determining the minimum flow in order (1) to meet the minimum water requirement of water users and (2) to meet the water demand to maintain the environmental flow to sustain the aquatic ecosystem in the basin river With the above issues, the dessertation on "Study on the identification of the minimum flow for sustainable water resources management in downstream of the Ma River" is very necessary and urgent for sustainable exploitation and management of water resources in the lower Ma River Study objectives The study objectives of this dessertation include: - To study and develop a scientific basis for determining the minimum flow in the downstream of Ma River to meet the minimum water demand of water users and maintain the aquatic ecosystems in the downstream of the Ma river - To study and propose solutions to maintain the minimum flow to ensure the sustainable development of water resources in the downstream of the Ma river Subjects and scope of the study 3.1 Study subjects: Minimum flow in the dry season (from January to May), downstream area of the Ma River 3.2 Scope of the study: The Ma River Basin, (1) focuses on the lower Ma river mainstream from Cam Thuy to the estuaries, (2) in the dry season, (3) the dissertation focuses on the minimum flow requirements to serve socio-economic development (people's life, industry, agriculture, navigation) and maintain the aquatic ecosystem In particular, at the current time, water quality in the Ma river meets the requirements of the water use purposes Therefore, in this study, water quality is considered stable and upto the quality standards to maintain aquatic ecosystems and ensure water supply to sectors Study approaches and methodologies 4.1 Study approaches: (i) Systematic approach: From From theoretical study to to practical application, from the overall solutions to the specific solutions; (ii) Inheritance Approach: Data are inherited from previous studies and researches 4.2 Study methodologies: Inheritance method; Method of surveying, measuring the field, sampling analysis in the laboratory; Statistical analysis method; Mathematical modeling; Comparative analysis method Scientific and practical significance of the study 5.1 Scientific significance: Improve the scientific basis for the identification of minimum flows taking into account all hydrological, hydraulic, ecological, and water demand factors for key water users Using ecological analysis methods (water environment conditions to meet the requirements of maintaining some key fish populations) is one of the important scientific contributions of the dessertation 5.2 Practical significance: The dissertation identifies the minimum flow of the lower Ma River as a scientific and practical basis for the management of water resources on the Ma River in a sustainable manner, meeting the requirements of the socio-economic sectors New findings of the dessertation: a Identification of the minimum flow for the downstream of the Ma River on the basis of identification and quantification of dominant factors including hydrological, hydraulic and ecological regimes, in which a ecological model based on indicator species is successfully applied b Identification of ecological indicator species of aquatic ecosystem in the downstream of the Ma river, including: 1) Cyprinus carpio (Chep fish), 2) Cranoglanis henrici (Nganh fish), 3) Chelon subviridis (Doi Dat fish), 4) Eleotris fusca (Bong Moi fish), 5) Glossogobius giuris (Bong Cat Toi fish) Dessertation contents: Excluding the introduction, conclusion and recommendation parts, the dessertation include 03 chapters: Chapter 1: Overview of minimum flow and related studies; Chapter 2: Subjects and methods in studying the minimum flow; Chapter 3: Study results and discussion CHAPTER OVERVIEW OF THE MINIMUM FLOW AND RELATED STUDIES 1.1 Overview of the study of the minimum flow, environmental flow in river basins 1.1.1 Definitions of the minimum flow and environmental flow Decree No 120/2008 / ND-CP dated December 2008 by the Government on river basin management defines "the minimum flow as the lowest flow necessary to maintain a river or river section, ensuring the normal development of aquatic ecosystems and ensuring the minimum level for the exploitation and use of water resources by water users according to the priority order identified in the river basin planning” There are also many definitions of environmental flows of some organizations by the International Union for Conservation of Nature (IUCN), the World Bank (WB), International rivers, International network of global environmental flows and some authors such as Dyson, Bergkamp, Scanlon etc In general, the different definitions of "the environmental flow" share some similarities: all emphasize the maintenance of the ecosystems However, in these definitions, there is no component mentioning the flow for other water use needs and serving the socio-economic development From an overall perspective, the "minimum flow" is more comprehensive when regarding the water users and the "minimum flow" can be considered to include the environmental flow and the flow for minimum water use needs of key users Therefore, the study in this dessertation on the "minimum flow" consists of two components: (1) ecological environmental flow, (2) flow for minimum water use needs 1.1.2 The role of the minimum flow The environmental flow is considered to be part of the minimum flow Therefore, the role of minimum flow includes the role of a environmental flow, which is essential for the health of any river The lack of minimum flow can put the existence of ecosystems, people, and the economy at risk In the context of integrated water resources management, minimum flow requirements are a trade agreement among water users In order to facilitate the analysis of the trade agreement, minimum flow must be ensured on the basis of equality and harmony between the interests of different users and the aquatic ecosystem 1.1.3 Overview of the minimum flow studies components of the minimum flow: (1) flow for the ecological environment and (2) flow for water use demands The flow regime calculation for river basins, water balance calculations, hydrological calculations, etc., is an integral part of the study of minimum flows or environmental flows Hydrological and hydraulic models are chosen based on the purpose and content of the study and data availability In order to evaluate the flow regime in the downstream part of the river basin, it is neccesary to calculate in the long run (5 years, 10 years, 20 years or more), so studies commonly use hydraulic models for simulation, calculation and evaluation There are many models that can be used for calculating the flow regime in the downstream in the dry season such as VRSARP, HEC-RAS, MIKE11 models and other models In the three models of VRSARP, HEC-RAS, MIKE11, each has different advantages and disadvantages, but the MIKE 11 model is one of the most widely used models in Vietnam and the dessertatopm selects this model to calculation of flow regime in the downstream Ma river In the world, the studies of environmental flows have grown steadily since the 1990s when a number of important studies emerged, focusing on natural flow regime and restoration of the flow The main methods are as follows: (1) Hydrological methods: Low and high flows will depend on the time and period, used widely in the North and Central America and are considered a simple, quick and least costly method to provide information on flow level thresholds; (2) Hydraulic assessment methods, also known as habitat maintenance methods or geometric hydraulic methods, show the relationship between depth and flow, and direct and indirect impacts of the flow to aquatic species, hydraulic methods depend much on the morphology of the river so it is not suitable for tributaries; (3) habitat simulation methods for the preservation of previously selected representative species taking into account the comprehensive linkages among hydrological, hydraulic, and biological elements; (4) General method and expert: This method is first developed and used in Australia and South Africa, recently expanded to England This is a complex, time-consuming and costly method Evaluating studies in the world, it can be seen that environmental flows are applied according to the requirements and depending on the characteristics of each river basin as well as the ecological characteristics of the river basin With such different requirements, the studies have approaches that are tailored to the specific requirements of each river basin Thus, the dessertation inherits similarities and provides the most appropriate approach applicable to the Ma River basin in Vietnam In Vietnam there are a number of related studies that need to be mentioned, namely Nguyen Thi Kim Dung's proposed minimum flow of components (1) river maintenance flow, (2) flow for demand ecological water, and (3) minimum flow for water users in Vu Gia - Thu Bon river; Study of Doan Thi Tuyet Nga on environmental flows on the Day River from Hat Mon to Ba Tha, including analyses of hydrological data and water quality data; study on impacts of low flow to agriculture and aquaculture in lowland areas of Ca river and Ma river by Nguyen Quang Trung Although studies have yielded the results of environmental flow or minimum flow for river basins, due to limited ecological data, they cannot quantify the specific level of the environmental flow or minimum flow and lack practicality 1.2 Overview on the Ma River Basin 1.2.1 Introduction Ma river basin covers an area of 28,490 km2, the mainstream is 512 km long, with large tributaries such as Chu river, Buoi river and two distributaries: Lèn river and Lach Truong river The Ma river basin is distributed in Laos and Vietnam On the territory of Vietnam, the basin area is 17,690 km2, of which the lower part is 8,503 km2 concentrated mainly in the province of Thanh Hoa This river has profuse water resources and flows across the mountainous terrain, hills, plain and coastal plain (1) The mountainous areas of the Ma River have the potential to build integrated hydraulic facilities and hydropower cascades; (2) the midland has great potential for developing industrial crops and specialty trees; (3) coastal and delta areas cover only 8.25% of the whole basin area, but are the main economic development centers of the basin, suitable for intensive farming and aquaculture development, fisheries, industrial development and marine economic services 1.2.2 The current status of socio-economic development in Ma River Basin The economy in the Ma River basin is shifting dramatically towards industrialization and modernization and has formed many industrial parks and economic zones such as Nghi Son economic zone, industrial zone in Thanh Hoa city By 2015, the population in the entire basin is approximately million people, unevenly distributed: sparsely populated in the upland areas and densely populated in urban areas The average population density is 197 people/km2 Population is concentrated in rural areas, accounting for 90%; and 10% in the urban areas The economic structure in the basin is as follows: Agriculture - Forestry - Fishery 42.58%, Industry 27.22%, Construction Service 30.2% 1.2.3 The current status of environment and ecology in the downstream of Ma river basin The survey shows that the water environment in the lower part of Ma River is good, most of the water quality indicators are within the allowable limit of A 2, indicating the diluting and self-cleaning capacity of the Ma River is good In the lower part of the Ma River, 747 species under 493 genus have been identified, 218 groups of creatures including 153 species of floating plants, 232 species of vascular plants, 71 species of zooplankton, 40 species soft shell, 48 crustaceans and 203 species of fish 1.2.4 History of water resources exploitation and use in the Ma river Water resources of the Ma River have been and will be exploited for livelihood activities of the people The exploitation of water resources has been promoted effectively, typically Cua Dat - Bai Thuong system, Hoang Khanh pump station, Nam Song Ma pump station with an increasing amount of exploitation from 50 m3/s (before 1950), reaching at 277 m3/s at the current time 1.3 Research orientation and issues to be solved The dissertation focuses on the following issues: (i) Assessment of current issues related to water resources exploitation on the Ma River; (ii) Identification of specific species of aquatic ecosystems and determination of water levels and flow rates in the Ma River; (iii) Application of simulation model to calculate the flow in the downstream of Ma River to meet the water demand for socioeconomic development in the basin; (iv) Proposal of the minimum flow and overall solutions to maintain minimum flow with structural diagrams as Fig 1.5 Figure 1.5: Structure of the minimum flow 1.4 Conclusion of Chapter 1: The dissertation studies the minimum flow with two components: (1) The ecological environment flow and (2) the flow for minimum water needs of water users Determining the minimum flow in the downstream of the Ma River is a multi-purpose problem to meet the human and ecological requirements in the context of current water conditions requires further studies on factors determining the flow of water on the Ma River, development of a methodology and tools to determine the minimum flow to ensure the sustainable development of the river The study selects MIKE11 hydraulic model, RHYHABSIM ecological model to determine the minimum flow for downstream of Ma River Figure 2.5: Changes in the riverbed elevation across the Ma River from 2008 - 2013 - The Ma River from Cam Thuy to Hau has a downward trend, with a common lowering level reaching over 1m, some river beds are lowered to over 3m, especially at the bottom elevation The river is lowered to 5,08m - On the Chu river, the level of erosion lowered the river bed from the Bai Dai dam to the Giang intersection; the erosion was highest in the upper part of Giang Giang junction, from 1.69 to 3.33m Many locations have a tendency of accretion 2.1.5 Effects of the factors The analysis shows that changes in the flow regime on the Ma River before the operation of reservoirs (1980÷2009) and after the operation (2010÷2015) are as follows: - In Chu river, at Cua Dat hydrological station, due to the influence of the regulation of Hua Na and Cua Dat reservoirs leading to higher fluctuation in the smallest daily flow rate and the smallest daily water level, from 3÷5m3/s, in the period before the smallest lake at the station is about 20m3/s + On Ma river (in Ly Nhan): Average water level and water level in 2010÷2015 period, are lower than in the period of 1980÷2009 from 0.9÷1.0m Meanwhile, the average daily water level and the upstream water level (in Cam Thuy) in the period 2010÷2015 are higher than in the period 1980÷2009 and the 11 flow at Cam Thuy station during the dry season also changed not much in two periods This shows the clear impact of low level depression on the lower Ma river mainstream in 2010 to 2015 - On the Chu river (at Xuan Khanh station): The average water level and water level in the reservoir period (2010÷2015) are lower than before the lake 30÷50 cm, although from 2010÷2015 The dry season has been improved thanks to the regulation of Cua Dat Lake upstream Impacts of low flow in the lower part of the Ma River: Saline intrusion deeper, lowering water levels directly affecting river basins, altering ecological habitat aquatic life 2.2 Developing the methodology to calculate the minimum flow in the downstream of the Ma river 2.2.1 Methodology to calculate the minimum flow The minimum flow can be considered as the “environmental flow” plus the “demand for water uses in the calculated river sections” (at the minimum level) QTT = ∑(QMT,ST, QKTSD) (2-1) In which: QKTSD: is the flow to ensure the socio-economic activities, in this study including: water supply for domestic use, industrial production, agricultural production and navigation QKTSD consists of components: (i) Consumed environmental flow (Qmtth): is the flow that is exploited from the Ma river for water supply in domestic uses, industrial and agricultural productions; (2) Non-consumed environmental flow (Qmtkth): is the flow which is not consumed during the exploitation, such as in navigation - QMT,ST: is the flow to ensure the normal operation and development of the ecosystem and is the non-consumed environmental flow From the characteristics of the consumed environmental flow and nonconsumed environmental flow, the formula 2-1 is summarized as: QTT = ∑(Qmtkth+Qmtth) (2-2) 12 In which: Qmtkth is the non-consumed environmental flow, is the total value to ensure the development of the aqua ecosystems, river health, river landscape and navigation Within the scope of this study, the non-consumed environmental flow consists of 02 parts: (1) flow for navigation and (2) flow for the ecosystem Therefore: Qmtkth = ∑ (Qstts, Qgt) (2-3) In which: + Qstts is the the flow for the aquatic ecosystem + Qgt is the flow for navigation To identify the minimum flow in the downstream of the Ma river, in this study, the PhD candidate selected combined methods, including: (i) Field survey and measurement methods; (ii) statistical analysis method; (iii) Hydrodynamic modeling; (iv) ecological modeling; (v) Comparative analysis Figure 2.21: Steps in calculating the minimum flow 13 2.2.2 Numerical modelling to simulate and calculate the flow regime a Method to identify the water demands at intake nodes along the river The Ma river basin is divided into water supply areas In the upper reaches of the Ma River to Cam Thuy, the upstream of the Chu River to Cua Dat, the upstream of the Buoi River to Thach Quang, the water supply is mainly from dams on small tributaries One of the factors influencing the flow regime in the downstream of the Ma River is the exploitation and use of water from water supply facilities directly on Ma River, Chu River and other rivers Therefore, the identification of water demand for the downstream Ma River in this study focuses on the identification of water demand at the direct water intake locations in the river The method is as follows: (i) Investigation and identification of actual exploitation demand from 2010÷2015; (ii) Determining the water demand at the downstream points of the Ma River Under the current conditions of water resources are seriously degraded, the water supply works in difficult water conditions, the ability to meet the water demand of irrigation works has also approached minimum water requirements Therefore, in the dessertation, the actual volume of water extracted from 2010÷2015 is the minimum amount of water for the water demand of the industries b Modeling simulation method for flow regime calculation on the Ma river Hydraulic models are used to calculate and simulate the flow patterns in the dry season in the past, as a basis for analysis and determination of flow for navigation demand, minimum flow for the environment ecological and selective minimum flow appropriate for river sections, as well as proposed minimum flow maintenance solutions The MIKE 11 model used in the study looks at all components of the wave equation and solves the equation of momentum and momentum equations (St Venant equations) c Modeling simulation method for ecological flow calculation The study use the RHYHABSIM (River HYdraulic HABITAT SIMULATION) model to predict flow conditions and flow variation affect the habitat available 14 to some fish species RHYHABSIM uses a combination of hydraulic modeling to predict flow conditions (depth, velocity) and ecological models to predict the flow fluctuations of the available habitat to aquatic species Fish habitat prediction is quantified using the Weighted Usable Area (WUA) index, where the suitability of the habitat with the assessed organism is determined A combination of data on the quantity and relative quality of available habitats at a given flow is used to calculate the WUA The WUA represents an area of suitable habitat for each length or depth of flow (m2 / m) The study uses the RHYHABSIM model to establish a minimum ecological flow limit for the Ma River This process uses the results of the MIKE11 hydrodynamic model to determine the minimum ecological flow required to help balance the exploitation of water The process consists of two steps: - Determine the point at which the habitat of the selected aquatic species diminishes considerably due to the decrease in flow That point is called the inflection point on the curve × environment response flow (WUA); - Determine the baseline and assess the habitat relative to that flow, which is usually the lowest annual average flow (MALF) 2.2.3 Surveying, measuring and analyzing methods in laboratory In the surveyed areas (KS), the study performs such tasks as: collecting aquatic organisms; collecting water quality samples; accurately measuring some environmental factors; photograph, observing, and recording natural conditions, and hydrolizing the survey stations of the Ma River Basin, measurement, experiment with water samples, aquatic creatures, interviews with local people and records of all field data recorded on sampling forms including floating organisms, benthic animals, fish 15 Figure 2.27: Map of survey sites, collecting aquatic species downstream of Ma river The survey results show that in the area there are 203 fish species belonging to 144 genera, 54 families, 12 families in the downstream area of the Ma river with the dominant codfish in all taxa Based on the results of the analysis and assessment of the ecosystem status on the Ma River, five fish species have been identified as ecological indicators for assessing aquatic ecosystems on the Ma River, including: 1) Cyprinus carpio, 2) Cranoglanis henrici, 3) Chelon subviridis, 4) Eleotris fusca, 5) Glossogobius giuris 2.3 Hydraulic modeling for the dry season in the Ma river network 2.3.1 River network map Ma River is a complete river system, so when studying hydrographic and hydrographic modes downstream, it is necessary to consider the entire river 16 network The river network includes hydropower calculations covering the entire main stream and main tributaries of the central and downstream areas of the Ma River basin, including the Ma River, Buoi River, Chu River, Lung River, Van Newspaper, Lach Truong River, De Canal Figure 2.27: Hydraulic diagram of Ma river network used for calculation 2.3.2 Input data and calculation boundaries Use of data related to: (i) Riverbed terrain; (ii) Hydrological documents; Water works along the river 2.3.3 Simulation, calibration and validation of the model a Simulation To determine hydraulic model parameters and salinity intrusion in the dry season for downstream Ma River, this study selected the period from 17 ÷ 30/03/2010 to calculate the simulation for the hydraulic problem exhaustion – salinity This is the time of a tidal in the dry season, with relatively complete and synchronous observation data Results of water level, maximum and minimum saline concentration simulations and actual measurements at some 17 locations on Ma River were also determined b Calculation and validation To validate the hydraulic model of the dry season for the downstream of Ma River, in this study, the period from 10 to 22 March 2015 was used to calculate the model test, which is the time of one tide in the dry season and new data will be measured in 2015 The results of validation and measurement at some locations on the Ma River have also been determined The simulation results and validation of the hydraulic model of the dry season in Ma river downstream showed that: (1) The results of the simulation of the exhausted hydraulic regime at checkpoints with monitoring data for the results water level, calculated salinity and the actual value of the difference is not significant; water level process, the salinity in the dry period in 2010 between the calculation and the relative measure of relative suitability; (2) The results of the model validation are quite consistent with the survey, so the set of parameters used in the hydraulic model accurately reflects the hydraulic regime in the dry season of the Ma river network, with sufficient credibility to carry out the hydrometric-salinity calculations for other cases in this study 2.4 Establishment of ecological models downstream of Ma River 2.4.1 Input and calculation boundaries Input data for the simulation of the model includes two groups of data: field survey data and a series of multi-year records on river flow When surveying, the parameters representing each section of the river sections in hydraulic and habitat of the indicator species were collected - Hydrological data - hydraulic, topography, including survey data in three river sections on the Ma river mainstream, such as hydrological data, terrain and base - Environmental ecological data including species of fish identified as ecological indicators for assessment of aquatic ecosystems on the Ma River 2.4.2 Assessment of the suitability of species for environmental conditions Assessment and analysis of habitat adaptation characteristics of selected species 18 under hydraulic conditions, and the substrate characteristics are shown in Figure 2.36 A Cyprinus carpio (Linnaeus, 1758) B Cranoglanis henrici (Vaillant, 1893) C Chelon subviridis (Valenciennes, 1836) D Eleotris fusca (Forster, 1801) E Glossogobius giuris (Hamilton, 1822) Figure 2.36: Adaptability of fish species under different habitat conditions 2.5 Conclusion of Chapter Chapter has identified the factors that influence flow regime in downstream Ma River, including natural factors and socio-economic activities In particular, 19 socio-economic activities are the main factors influencing the downstream flow, especially the change of navigation in recent years, which led to the lowering of the Ma River The operation of the waterway works along the river, causing salinity intrusion into the inland and affecting the habitat of aquatic species downstream Ma River Five species of ecological indicators have been identified to assess aquatic ecosystems on the Ma River as a basis for the identification of ecological environment flows CHAPTER STUDY RESULTS AND DISCUSSION 3.1 Calculating the minimum flow in downstream of the Ma river 3.1.1 Identify the control points for the minimum flow Minimum river flow through the control point is "The lowest flow necessary to maintain the river or river section to ensure the normal development of aquatic ecosystems and to ensure minimum levels of activity Exploitation and use of water resources of water users." Control points for river sections are defined as follows: - Section (DKS 1): From Cam Thuy hydrological station to Vinh Khang intersection, control point at Ly Nhan hydrological station - Section (DKS 2): From Vinh Khang junction to Bong junction, checkpoint at Thet Thon (about 3km far from Vinh Khang intersection) - Section 3: From Bong junction to Giang intersection, control point at downstream of Hoang Khanh pump station (2.2 km from Bong crossroad) 3.1.2 Results of hydrographical calculation of dry season in Ma river By analyzing the results of the case of dry season flow (average dry season, average dry season, mean monthly dry season and the lowest flow), the years from 1980 to 2015 show: For 35 years in 1999, the frequency of cases reviewed at Cam Thuy hydrological station is 99%; the worst stage in the chain since 1989÷1999; The highest flow period in the dry season is from 2000÷2009; In 20 the period from 1980÷1988 and 2010÷2015 the flow in the dry season is at average level 3.1.3 Identification of the water flow to meet the water demands in river sections Based on the water flow of the water source exploitation projects along Ma River to determine the flow of water needed for the needs of the users of the river sections downstream Ma river as Table 3.5 Table 3.5 Flow rate to meet the water demands in river sections Qmax Qmin Section River (m3/s) (m3/s) Section 1: Cẩm Thủy ÷ Intersection Vĩnh Khang Mã 15.55 11.55 Section 2: Intersection Vĩnh Khang ÷ Bơng Mã 4.72 4.72 Section 3: Intersection Bơng ÷ Intersection Giàng Mã 14.49 8.89 Section 4: Intersection Giàng ÷ Hồng Long Mã 1.25 1.25 Qaver (m3/s) 14.17 4.72 12.06 1.25 3.1.4 Identification of non-consumed environmental flow Non-consumed environmental flows include: (1) flow for navigation needs and (2) flow for ecological environment Based on input data, the ecological model RHYHABSIM has constructed ecological curves that correlate the habitat assessed on the WUA values of fish species on the Ma River as shown in Figure 3.7, thereby identifying be flow for ecological environment Based on the results of the two above flow components, the study identified the inevitable environmental flows for the river sections in the lower Ma river mainstream as follows: Table 3.15 Non-consumed environmental flow in river sections Section Level Control location Qmtkth (m3/s) Section No reference ĐKS 51.0 Section IV ĐKS 49.0 Section III ĐKS 61.0 21 Section Section Q (m3/s) Q (m3/s) Section Q (m3/s) Figure 3.7: Correlation between habitat assessment on WUA values of fish species on Ma River 3.1.5 Determination of minimum flow in downstream of Ma river Based on the results of the calculation of the wastewater flow and the nondrainage environmental flow of the river sections, it is determined The results of minimum flow of river sections are as follows: Table 3.16 Minimum flow of river sections downstream Ma river Qmtkth Qmtth Qtt River section Location River (m3/s) (m3/s (m3/s) Section ĐKS Mã 51.0 14.17 65.17 Section ĐKS Mã 49.0 4.72 53.72 Section ĐKS Mã 61.0 12.06 73.06 3.2 Analysis of the suitability of the minimum flow The results of the minimum flow calculation according to the method chosen by the dessertation are in line with actual flows from 1980÷2015 The method of 22 selection of the dessertation has basically considered the full composition of the minimum flow, more scientifically comprehensive 3.3 Solutions to maintain the minimum flow in the downstream of the Ma river 3.3.1 Reservoir operation solution Operate reservoirs in accordance with Operational Procedure 214/QĐ-TTg; Operate the reservoirs according to Operation procedure 214/QĐ-TTg, Cua Dat canal to replace irrigation pumping stations along Ma river with the flow of 15.42 m3/s: in both cases, calculate the lowest flow for the year with the lowest flow ever occurring on the Ma River (1999, frequency is approximately 99%), the flow on Ma River can meet the minimum flow requirements set for river sections downstream of Ma River When Cua Dat, Hua Na and Trung Son reservoirs increase the flow in the dry season, the saline concentration can be reduced so that the pumping stations from Giàng to Ham Dragon bridge can take advantage of the water supply for agriculture Thus, when the solution to maintain the minimum flow on the river downstream of Ma River has been identified, the requirement for waterway transportation is also guaranteed for the worst case in 1999 3.3.2 Proposed management solutions In order to maintain the minimum flow, the study suggests a number of management options as follows: (1) Management of discharge to avoid changing the status of water quality in Ma River; (2) strict management of the Ma river will ensure that the river bed is not lowered due to economic activities in the basin; (3) Study of low flow forecast for Ma river basin as the basis for operating reservoirs in the dry season; (4) Rational crop restructuring for drought years based on baseline dry run forecast of Ma river basin 3.4 Conclusion for Chapter Chapter defines the minimum flow for river sections based on two criteria: ensuring adequate water supply for all sectors (domestic, industrial, agricultural and navigation) and ensuring the environment ecosystem 23 CONCLUSION AND RECOMMENDATIONS Conclusion: The dessertation has identified a change in hydrological regime in the lower part of Ma River, in which the most prominent is the lowering of water level in recent years This lowering has many causes such as decreased flow, overexploitation and lowering of conduction The decline in flow has impacted on the activities of river basins and the ecological environment in the study area The study has identified the minimum flow for river sections: From Cam Thuy hydrological station to Vinh Khang crossroad is 65.17 m3/s, from the Vinh Khang crossroad to the Bong crossroad is 53.72 m3/s , from the Bong junction to Giang intersection is 73.06 m3/s Minimum flow is required to meet the demand of domestic water, industry, agriculture, navigation and ensure the development of aquatic ecosystems On the other hand, the proposed minimum flow corresponds to the actual flow of past years in the Ma River Recommendation: It is necessary to expand the calculation and determine the flow in other river branches such as Chu river and Buoi river 24 PUBLICATIONS Lương Ngọc Chung, Bùi Nam Sách, 2018, Xác định dòng chảy tối thiểu giải pháp trì dịng chảy tối thiểu hạ du sơng Mã, Tạp chí Nơng nghiệp Phát triển Nông thôn, số 12, tháng 6/2018, ISSN 1859-4581 Lương Ngọc Chung, Trần Viết Ổn, 2018, Ứng dụng mô hình thủy lực chiều đánh giá xu biến động dịng chảy kiệt lưu vực sơng Mã, Tạp chí Khoa học Thủy lợi Môi trường, Số 60, 3/2018, Tr 41-47, ISSN 18593941 Luong Ngoc Chung, Nguyen Thi Kim Cuc, Trieu Anh Ngoc, Nguyen Thanh Nam, Le Viet Sơn, Tran Viet On, 2017, Required flows for aquatic ecosystems in Ma River, Vietnam, International Journal of Environment, Agriculture and Biotechnology (IJEAB), Vol-2, Issue-6, 3068-3077, November 2017, ISSN: 2456-1878 Lương Ngọc Chung, 2017, Nguy xảy hạn hán, thiếu nước hạ du sông Mã, Hội nghị Khoa học Thủy lợi toàn quốc năm 2017, Tr 41-43 Lương Ngọc Chung, 2016, Suy giảm dòng chảy kiệt tác động đến khai thác sử dụng nước môi trường vùng hạ du lưu vực sông Mã, Tạp chí Nơng nghiệp Phát triển Nơng thơn, 1/2016, Tr 53-60, ISSN 1859-4581 25 ... shifting dramatically towards industrialization and modernization and has formed many industrial parks and economic zones such as Nghi Son economic zone, industrial zone in Thanh Hoa city By 2015, the... Operate reservoirs in accordance with Operational Procedure 214/QĐ-TTg; Operate the reservoirs according to Operation procedure 214/QĐ-TTg, Cua Dat canal to replace irrigation pumping stations... agricultural production and navigation QKTSD consists of components: (i) Consumed environmental flow (Qmtth): is the flow that is exploited from the Ma river for water supply in domestic uses, industrial