Circular No. 65/2017/TT-BTNMT on technical procedures for determining minimum flow rates in rivers and streams and establishing inter-reservoir operation procedures

CIRCULAR

Technical regulations for determining minimum flow on rivers and streams and establishing inter-reservoir operation procedures and constructing inter-reservoir operation procedures

---------------

Pursuant to the Law on Water Resources No. 17/2012/QH13 dated June 21, 2012;

Pursuant to Decree No. 36/2017/NĐ-CP dated April 4, 2017 of the Government stipulating the functions, tasks, powers, and organizational structure of the Ministry of Natural Resources and Environment;

Pursuant to Decree No. 201/2013/NĐ-CP dated November 27, 2013 of the Government detailing the implementation of certain provisions of the Law on Water Resources;

At the proposal of the Director of the Water Resources Management Department, the Head of the Science and Technology Department, and the Head of the Legal Department;

The Minister of Natural Resources and Environment promulgates this Circular stipulating technical regulations for determining minimum flow on rivers and streams without reservoirs or dams and constructing inter-reservoir operation procedures.

PART I

GENERAL PROVISIONS

Article 1. Scope of Regulation

This Circular stipulates technical regulations for determining, reviewing, and adjusting minimum flow on rivers and streams without reservoirs or dams, downstream of reservoirs or dams, and constructing, reviewing, and adjusting inter-reservoir operation procedures.

The establishment, review, approval, organization of implementation, acceptance, handover, and archiving of products, projects, and programs shall be carried out in accordance with current regulations.

Article 2. Applicability

This Circular applies to state agencies, organizations, and individuals involved in the work of determining, reviewing, and adjusting minimum flow on rivers and streams without reservoirs or dams, downstream of reservoirs or dams, and constructing, reviewing, and adjusting inter-reservoir operation procedures.

Chapter II

TECHNICAL REGULATIONS FOR DETERMINING MINIMUM FLOW ON RIVERS AND STREAMS WITHOUT RESERVOIRS OR DAMS

Article 3. Procedure for Determining Minimum Flow on Rivers and Streams Without Reservoirs or Dams

The determination of minimum flow on rivers and streams without reservoirs or dams shall follow the following procedure:

1. Prepare the project outline for determining minimum flow on rivers and streams without reservoirs or dams (hereinafter referred to as the project).

2. Collect, analyze, and process relevant information and data related to determining minimum flow on rivers and streams without reservoirs or dams.

3. Restore and extend flow data on river sections where minimum flow needs to be determined.

4. Conduct field surveys to delineate river and stream sections and determine minimum flow.

5. Survey and supplement information and data on water levels, flow rates, topography, cross-sections of rivers and streams, and water quality (if applicable) to determine minimum flow on rivers and streams without reservoirs or dams.

6. Summarize and process collected and surveyed information according to river and stream sections where minimum flow needs to be determined.

7. Analyze and identify river sections that need to maintain minimum flow and propose minimum flow rates.

8. Hold discussions and seek opinions from relevant authorities regarding minimum flow on rivers and streams without reservoirs or dams.

9. Compile and draft reports and proposals on minimum flow on rivers and streams without reservoirs or dams.

Article 4. Collection, Analysis, and Processing of Relevant Information and Data for Determining Minimum Flow on Rivers and Streams Without Reservoirs or Dams

1. Content of information and data to be collected includes:

a) Meteorological and hydrological data including humidity, evaporation, wind speed, temperature, rainfall in the river basin; daily average water level and flow rate data at operational hydrological stations in the river basin;

b) Information and data on basin characteristics including area, shape, topography, geology, soil, vegetation cover, river and stream network; river morphology, density of rivers and streams, elevation, slope... geological and hydrogeological maps at scales of 1:200,000 and 1:50,000 (if available), topographic maps at scale 1:50,000; river and stream cross-sections;

c) Data and information on saltwater intrusion including degree of saltwater intrusion, years of saltwater intrusion, salinity measurement data in the basin and losses caused by saltwater intrusion, water requirements to push back saltwater;

d) Statistical data on drought conditions in the specific basin including duration of drought in a year, drought years in the data series and losses caused by drought;

đ) Data and information on current status and planning for socio-economic development;

e) Data and information on planning for industries related to water extraction, use, and wastewater discharge into water sources;

g) Data and information on water quality along the length of the river and stream being evaluated; location, extent, scale, degree of water source pollution, and other changes in water quality over time;

h) Data and information on aquatic ecosystems specifically including aquatic ecosystems, major aquatic plants and animals;

i) Other relevant materials.

In case of review and adjustment: update information and data for calculating minimum flow from the date of publication until the review and adjustment.

2. Requirements for collected materials:

a) Must have clear origins, published or verified by authorized agencies or provided by the supplying agency;

b) Must ensure consistency with the project's objectives;

c) Must ensure continuity and synchronization between completed projects;

d) A time series of meteorological and hydrological data of at least the last 20 years.

3. Analysis and processing of collected information and data:

a) Create a list of collected information and data;

b) Identify missing information and data needed for evaluation purposes and to extend the flow data series;

c) If there is a hydrological station and flow data is less than 20 years, additional surveys or data extension are required;

d) If there is no hydrological station, select methods to restore flow data and specify data requirements for restoring flow data.

Article 5. Restoration and extension of flow data on river sections requiring determination of minimum flow

1. Methods for restoration and extension of flow data:

Based on existing data conditions, data provision services, and measurement capabilities, the restoration and extension of flow data shall be carried out according to one of the following methods:

a) Using correlation relationships in cases where flow data from hydrological stations upstream or downstream of the location requiring determination of minimum flow are available, provided that the observed data series at these hydrological stations are sufficiently long.

In cases where there are many rainfall measurement materials within the study watershed, if the relationship between annual rainfall and annual runoff is closely related, a correlation equation between annual rainfall and annual runoff may be established, and missing data may be supplemented using this equation.

b) Using the similar watershed method in cases where there are few hydrological observation materials or no data. The procedure for implementing the similar watershed method is as follows: Select a similar watershed with conditions such as climatic similarity; synchronous variation in flow over time (correlation during simultaneous measurement periods); uniformity in flow formation conditions, geology, soil, hydrogeology, forest cover ratio, wetland ratio, and land use conditions; absence of factors altering natural flow; area ratios not exceeding five times; average elevation differences between watersheds not exceeding 300 meters; investigate the synchronous changes in flow variations of one or more similar watersheds and the calculation watershed based on actual measured years, then select the watershed with longer and more synchronized observation periods as the similar watershed; establish a watershed correlation relationship; only use the correlation relationship to restore flow when the correlation coefficient is ≥ 0.8; use the correlation relationship to restore flow.

c) Using hydrological computational models: based on rainfall, evaporation, and watershed geomorphological and geological conditions, use mathematical models to extend and restore flow data from rainfall.

d) Using hydraulic models to calculate flow data series in cases where there are materials and data on topography, cross-sections, meteorology, and hydrology.

e) Using other methods (if applicable): as required by specific projects and approved by competent authorities.

2. Product requirements:

a) For correlation methods: a 20-year flow data series and a report explaining the calculations, calculation diagrams, and relevant charts (if applicable).

b) For the similar watershed method: a 20-year flow data series and reports explaining the calculation of flow data, calculation diagrams, and relevant charts.

c) For model methods: a hydrological or hydraulic model; a 20-year flow data series; a report on model verification and calibration; reports explaining the calculation of flow data, calculation diagrams, and relevant charts.

Article 6. Field investigation for river segmentation and determination of minimum flow

1. Content and objects of field investigation and survey:

a) Collecting additional materials from provincial departments and localities (district and commune levels). Collected materials must ensure consistency with project objectives and must be approved or verified by competent authorities from the providing agencies.

b) Investigating and collecting additional information on terrain characteristics, vegetation cover, riverbeds, soil types, economic and social development conditions.

c) Preliminarily segmenting rivers and streams requiring determination of minimum flow based on the following characteristics: different riverbank and riverbed terrain; sections of rivers and streams experiencing depletion and loss of flow; sections of rivers and streams with tributaries; sections of rivers and streams affected by pollution and water source degradation; sections of rivers and streams subject to sedimentation and erosion; sections of rivers and streams with hydrological monitoring stations and water resource facilities; sections of rivers affected by tides (if applicable); presence of inland waterway transportation; presence of distinctive aquatic ecosystems; facilities for water extraction and utilization; for tributaries and inflows into sections of rivers and streams requiring determination of minimum flow, collect information on flow and water extraction and utilization facilities.

d) Conducting detailed investigations at each section of rivers and streams requiring determination of minimum flow, including describing and collecting information on riverbank and riverbed terrain, types of bank and bed rock and soil, vegetation cover, estimated depth, width, flow rate, and direction of rivers and streams; occurrence time and status of depletion and loss of flow (inadequate for transportation, inadequate for water supply, no flow); information on depletion; information on water source pollution; locations and conditions of riverbed and bank erosion; information on sections of rivers affected by tides: highest and lowest tide impact locations (if applicable); locations, coordinates, current status, and operational conditions of hydrological monitoring stations and water resource facilities; information on waterways, navigation routes, and inland waterway traffic water levels; information on aquatic ecosystems (aquatic species, maintained water levels, maintained water volumes, etc.); information on water extraction and utilization facilities (coordinates, administrative locations, purposes of extraction, extraction rates, etc.), information on water quality (color, odor, pH, conductivity, salinity, etc.);

In cases of reviewing and adjusting minimum flow: collect, investigate, and supplement (if necessary), update information and materials on flow; monitor flow; extract, utilize water, and maintain minimum flow from the date of announcement until the review and adjustment.

đ) Conducting detailed investigations at tributaries and inflows into sections of rivers and streams requiring determination of minimum flow, including describing and collecting information such as estimated depth, width, flow rate, and direction of tributaries and inflows; locations, coordinates, current status, and operational conditions of hydrological monitoring stations and water resource facilities; information on water extraction and utilization facilities (coordinates, administrative locations, purposes of extraction, extraction rates, etc.); information on water quality (color, odor, pH, conductivity, salinity, etc.).

In cases of reviewing and adjusting the minimum flow: collect, supplement investigations (if necessary), and update information and documents on flows, flow monitoring, and water extraction and usage from the time of publication until the review and adjustment.

e) Propose points for hydrological measurements to serve the determination of the minimum flow.

2. Requirements for investigation work:

a) Collected information and documents must ensure consistency with the project's objectives and must be approved or verified by the competent authority from the providing agency.

b) Information obtained through interviews and descriptions must be fully, truthfully, and accurately recorded in the investigation form, field investigation logbook, or record book.

c) The field investigation logbook must record the purpose of the investigation before each journey, objects of investigation, types and quantities of investigated works, journey time; after each journey, the investigation team must compile the investigation information and record observations of that journey.

d) Investigation using forms for water resource exploitation and utilization works. The main content of the form is stipulated in Points d, đ Clause 1 of this Article. The information provider is management staff or individuals familiar with the works. The investigation method is recording in the investigation form or record book.

đ) Measure water quality indicators at the site for pH, conductivity, salinity using a multi-parameter meter, pH meter. The multi-parameter water quality meter must be installed before measurement. The accuracy requirement for measuring equipment is ≤ ± 5% of the measured value; during measurement, read the result three times and take the average data.

e) Measure coordinates using handheld GPS: handheld GPS coordinate measurement must comply with current technical regulations.

3. Products of field investigation work

a) Report on the results of field investigation, including main contents: content, volume of work performed; summary of investigation routes; preliminary assessment of topography; flow; water extraction and usage needs, drought and saltwater intrusion conditions in the watershed, water quality and aquatic ecosystem of river sections, rivers, streams;

b) Diagrams of actual investigation materials;

c) Summary tables and statistics of preliminary and detailed investigation results; statistics of water extraction and usage works;

d) Table of statistics of surveyed areas;

đ) Investigation forms, field investigation logbooks, and other investigation materials;

The content and format of records and descriptions in the logbook and on the field map must comply with current regulations on the establishment of original investigation and survey materials.

Article 7. Measurement and supplementation of information and data on water levels, flow rates, topography, river cross-sections, stream cross-sections, water quality (if applicable) to determine the minimum flow on rivers and streams without reservoirs or dams

1. Regarding hydrological measurement:

a) Hydrological measurement factors include: river cross-sections, stream cross-sections, flow rates, and water levels at river sections, rivers, and streams;

b) Measurement time: during the dry season;

c) Measurement frequency: hourly or daily according to the project's objectives;

d) Measurement period: within a day, quarter, or year according to the project's objectives;

đ) Measurement points: based on recommendations following detailed investigations at rivers and streams requiring determination of the minimum flow;

e) Hydrological measurement techniques for determining the minimum flow must comply with current regulations.

2. Purchase of meteorological, hydrological, topographic, river cross-section, stream cross-section, and water quality data from agencies authorized to provide such data according to their functions and responsibilities (if applicable).

Article 8. Compilation and processing of information collected and investigated according to river and stream sections for determining minimum flow

1. Compilation and processing of information collected and investigated according to river and stream sections with different topographical features, flow characteristics, water extraction and usage, and varying requirements for minimum flow.

2. Construction of a practical document diagram to determine minimum flow on rivers and streams without reservoirs or dams based on a 1:50,000 scale topographic map, including the following contents:

a) River and stream network, locations of areas experiencing depletion, loss of flow, erosion, landslides, water quality pollution, water extraction and usage facilities along the river and stream sections; flow monitoring stations;

b) Current land use and vegetation cover;

c) Detailed investigation points.

Article 9. Analysis to Determine River Sections Requiring Minimum Flow Maintenance and Propose Minimum Flow Levels

1. Analysis and evaluation of current water resource extraction and usage.

2. Determination of river sections requiring minimum flow maintenance.

3. Analysis and proposal of minimum flow levels to be maintained at river and stream sections, including:

a) Compilation of daily average flow data from the data series;

b) Calculation of daily average flow corresponding to frequencies of 80%, 85%, 90%, and 95%;

c) Determination of the daily average flow frequency curve over time corresponding to frequencies of 80%, 85%, 90%, and 95%;

d) Proposal of minimum flow levels to be maintained at river and stream sections.

4. Proposal of time periods for maintaining flow at river and stream sections requiring minimum flow maintenance.

5. Compilation and construction of diagrams of river and stream sections requiring minimum flow maintenance. The diagram will include the following key information:

a) Diagrams showing the minimum flow values for each river and stream section;

b) Locations of areas experiencing depletion, loss of flow, erosion, landslides, water quality pollution, major water extraction and usage facilities along the river and stream sections, and flow monitoring stations.

6. Workshop and solicitation of expert opinions

a) Preparation of materials and organization of the workshop (editing, duplicating materials, sending related materials for feedback). Solicit workshop opinions on the following contents: river and stream sections requiring determination of minimum flow; time periods for maintaining minimum flow; minimum flow levels on river and stream sections;

b) Organization of the workshop and solicitation of expert opinions.

7. Compilation, editing, and finalization of the explanation of minimum flow determination after the workshop and solicitation of expert opinions on the following contents:

a) River and stream sections requiring determination of minimum flow;

b) Time periods for maintaining minimum flow;

c) Minimum flow levels on river and stream sections.

8. Draft Decision approving the list of minimum flows on rivers and streams.

In cases of review and adjustment, it is necessary to update, analyze, and evaluate the maintenance of minimum flow from the date of publication until the review and adjustment, and propose adjusted minimum flow levels.

Article 10. Workshop and Solicitation of Opinions from Relevant Authorities on Minimum Flow on Rivers and Streams Without Reservoirs or Dams

Contents of the workshop and opinion solicitation work include: printing of materials; organizing the workshop; compiling and finalizing opinions and making revisions based on feedback regarding minimum flow on rivers and streams without reservoirs or dams.

Article 11. Compilation and construction of reports and draft documents on minimum flow rates for rivers and streams without reservoirs or dams

1. Specialized reports:

a) Report on the results of field investigations;

b) Report analyzing the identification of river and stream sections requiring maintenance of minimum flow rates;

c) Report analyzing time periods for maintaining minimum flow rates;

d) Report analyzing minimum flow rates for river and stream sections;

đ) Report on establishing models to restore flow data (if applicable);

e) Report on model validation for restoring flow data (if applicable);

g) Report evaluating the implementation of previously published minimum flow rates (in cases of adjustment or supplementation).

2. Project summary report:

The project summary report shall include the following main contents:

a) Analysis of basic factors affecting minimum flow rates such as topography, soil, vegetation cover, meteorology and hydrology, socio-economy, water extraction and utilization;

b) Evaluation of the implementation of initially published minimum flow rates (in cases of adjustment or supplementation);

c) Analysis identifying river and stream sections requiring maintenance of minimum flow rates;

d) Analysis of time periods for maintaining minimum flow rates;

đ) Analysis of minimum flow rates for river and stream sections.

3. Summary report on the implementation results of the project.

4. Draft Decision approving the list of minimum flow rates for rivers and streams.

Article 12. Documentation of products and results determining minimum flow rates for rivers and streams without reservoirs or dams

The documentation of products and results determining minimum flow rates for rivers and streams without reservoirs or dams, completed at the end of the fiscal year or the entire project, includes:

1. Project summary report.

2. Summary report on the implementation results of the project.

3. Draft Decision approving the list of minimum flow rates for rivers and streams.

4. Specialized reports as stipulated in Clause 1, Article 11 of this Circular.

5. Related diagrams and charts:

a) Diagrams of actual data for determining minimum flow rates for rivers and streams without reservoirs or dams based on topographic maps at a scale of 1:50,000;

b) Diagrams of river and stream sections requiring maintenance of minimum flow rates.

6. Data set:

a) Collected data;

b) Measured and surveyed data;

c) Analyzed data, tables, drawings, intermediate maps, models, and other relevant information and data related to the project content (if applicable).

7. CD containing all project products.

Chapter III

TECHNICAL REGULATIONS FOR DETERMINING MINIMUM FLOW RATES ON RIVERS AND STREAMS AFTER RESERVOIRS AND DAMS

Article 13. Procedure for determining minimum flow rates on rivers and streams after reservoirs and dams

Determination of minimum flow rates on rivers and streams after reservoirs and dams follows the procedure below:

1. Preparation of project and program outlines for determining minimum flow rates on rivers and streams after reservoirs and dams (hereinafter referred to as the project).

2. Collection, analysis, and processing of relevant documents and data for determining minimum flow rates on rivers and streams after reservoirs and dams.

3. Preliminary determination of the scope of impact of reservoirs and dams.

4. Field investigation within the affected area of reservoirs and dams.

5. Measurement and supplementation of information and data on water levels, flow rates, topography, cross-sections of rivers and streams, and water quality (if applicable) to determine minimum flow rates on rivers and streams after reservoirs and dams.

6. Compilation and processing of collected and investigated information within the affected area of reservoirs and dams.

7. Restoration and extension of flow data after reservoirs and dams.

8. Assessment of water level and flow rate changes over time.

9. Analysis and calculation of downstream water demand.

10. Analysis and proposal of minimum flow rates.

11. Workshop and solicitation of opinions from relevant agencies on minimum flow rates on rivers and streams after reservoirs and dams.

12. Compilation and construction of reports and draft documents on minimum flow rates for rivers and streams after reservoirs and dams.

Article 14. Collection, analysis, and processing of documents and data related to determining the minimum flow downstream of rivers and streams after reservoirs and dams

1. Content of information and data to be collected includes:

a) Documents collected in accordance with Clause 1 of Article 4 of this Circular;

b) Collecting data on the operation of reservoirs and dams: operational data of reservoirs and dams.

In case of review and adjustment, update information and data for calculating the minimum flow.

2. Requirements for documents collected in accordance with Clause 2 of Article 4 of this Circular.

3. Analysis and processing of information and data collected in accordance with Clause 3 of Article 4 of this Circular.

Article 15. Preliminary determination of the scope of impact of reservoirs and dams

Preliminarily determine the scope of impact of reservoirs and dams, including:

1. Upstream: determine up to the location of major works directly affecting the water source of the reservoirs and dams; determine water extraction and utilization facilities and direct tributaries of the reservoirs and dams.

2. Downstream of the reservoirs and dams: determine the scope of impact of the operation of the reservoirs and dams on water sources and water extraction and utilization objects downstream. Basis for determining the scope of impact of the reservoirs and dams on the downstream:

a) Based on the area downstream of the reservoirs and dams to the location of tributaries included in the list of inter-provincial river basins and intra-provincial river basins approved by competent state authorities;

b) Water extraction methods, water usage regimes, water usage capacity, and the role of the reservoir in regulating and supplying water to the downstream;

c) Water extraction methods, water usage regimes, and dependence on flow regime of water extraction facilities directly on the river downstream of the reservoirs and dams.

Article 16. Field investigation within the scope of impact of reservoirs and dams

1. Content, subjects of field investigation and survey:

a) Collecting additional materials from provincial departments and localities (district and commune levels). Collected materials must ensure consistency with project objectives and must be approved or verified by competent authorities from the providing agencies.

b) Conduct route investigations to collect additional information about topography, vegetation cover, buffer zones, rivers and streams, soil conditions, socio-economic development situation;

c) Preliminarily conduct route investigations to collect information within the affected scope of the reservoirs and dams: riverbank and riverbed topography downstream of the reservoirs and dams; within the reservoir and upstream of the reservoir; post-reservoir flow and upstream flow before the reservoirs and dams; flow monitoring stations; water resource extraction and utilization situation directly from the reservoir; upstream and downstream areas of the reservoirs and dams; for tributaries and inflows upstream and downstream of the reservoirs and dams, it is necessary to determine information about flow and water extraction and utilization facilities;

d) Detailed investigation at points within the affected scope to determine the minimum flow: describe riverbank and riverbed topography; type of bank and bed material; vegetation cover; estimate depth, width, flow rate, and direction of rivers and streams; collect information about drying up and loss of flow: occurrence time, condition of drying up and loss of flow (inadequate for transportation, inadequate for water supply, no flow); information about drying up; information about water pollution; position and condition of erosion of riverbanks and beds; position, coordinates, current status, and operation situation of hydrological and water resource monitoring stations; information about navigation channels and routes; information about aquatic ecosystems (aquatic species, maintenance water level, maintenance water volume,...); information about water extraction and utilization facilities (coordinates, administrative location, purpose of extraction, extraction flow rate, source of extraction,...); information about water quality (color, odor, pH, conductivity, salinity,...);

In case of review and adjustment, conduct investigations, update, and supplement information about topography, flow, flow monitoring; water extraction and utilization; maintaining the minimum flow from the date of announcement until the review and adjustment.

đ) Detailed investigation at tributaries and inflows within the affected scope, it is necessary to describe and collect information such as: estimate depth, width, flow rate, and direction of tributaries and inflows; position, coordinates, current status, and operation situation of hydrological and water resource monitoring stations; information about water extraction and utilization facilities (coordinates, administrative location, purpose of extraction, extraction flow rate,...); information about water quality (color, odor, pH, conductivity, salinity,...);

In case of review and adjustment, conduct investigations, update, and supplement information about flow, flow monitoring, and water extraction and utilization from the date of announcement until the review and adjustment.

e) Propose points for hydrological measurements to serve the determination of the minimum flow.

2. Requirements for investigation work:

a) Information and documents collected in accordance with Point a of Clause 2 of Article 6;

b) Information obtained through interviews and descriptions must be fully, truthfully, and accurately recorded in the investigation form, field investigation logbook, or record book.

c) The field investigation logbook must record the purpose of the investigation before each journey, the investigation subjects, types and quantities of investigated facilities, journey time; after each journey, the investigation team must compile the investigation information and record observations of that journey;

d) Investigation method using questionnaires for water extraction and utilization facilities. Main contents of the questionnaire as stipulated in Points d and đ of Clause 1 of this Article. Subjects filling out the investigation questionnaire: responsible managers of water extraction and utilization facilities. Investigation form is recording in the investigation questionnaire or logbook;

đ) Measure water quality indicators on-site in accordance with Point đ of Clause 2 of Article 6;

e) Measure coordinates using handheld GPS in accordance with Point e of Clause 2 of Article 6.

3. Products of investigation and survey work:

a) Report on the results of field investigation including main contents: content and volume of work performed; summary of investigation routes; preliminary assessment of topography; flow; current status of reservoirs and scope of impact, water extraction and utilization needs, drought and saltwater intrusion situations, water quality, and aquatic ecosystems downstream of the reservoir.

b) Diagrams of actual investigation materials;

c) Summary tables and statistics of preliminary and detailed investigation results; statistics of water extraction and usage works;

d) Table of statistics of surveyed areas;

đ) Investigation forms, field investigation logbooks, and other investigation materials;

The content and format of records and descriptions in the logbook and on the field map must comply with current regulations on the establishment of original investigation and survey materials.

Article 17. Surveying, supplementing information and data on water levels, flow rates, topography, river cross-sections, stream cross-sections, and water quality (if applicable) to serve the work of determining minimum flows downstream of reservoirs and dams.

1. Hydrological surveying:

a) Hydrological survey factors include: river cross-sections, stream cross-sections, flow rates, and water levels on rivers and streams;

b) Measurement time: during the dry season;

c) Measurement frequency: hourly or daily according to the project's objectives;

d) Measurement period: within a day, quarter, or year according to the project's objectives;

d) Survey points: according to proposals following detailed investigations at rivers and streams downstream of reservoirs and dams where minimum flows need to be determined;

e) Hydrological measurement techniques for determining the minimum flow must comply with current regulations.

2. Purchasing meteorological, hydrological, topographical, river cross-section, stream cross-section, and water quality data as stipulated in Clause 2, Article 7 of this Circular (if applicable).

Article 18. Consolidating and processing collected and investigated information within the scope of impact of reservoirs and dams

1. Preparing tables and data on water sources; exploitation and utilization of water:

a) Tables of water level and flow rate data over time;

b) List of water exploitation and utilization structures;

c) Compiling a list of requirements and periods of water usage for downstream users of reservoirs and dams;

d) Other data tables serving calculations and evaluations.

2. Developing a practical diagram to determine minimum flows downstream of reservoirs and dams at a scale of 1:50,000, including:

a) River and stream networks, reservoirs, and dams; locations of areas with low water levels, dry stretches, sedimentation, erosion, water pollution, and water exploitation and utilization structures;

b) Current land use and vegetation cover;

c) Detailed investigation points.

Article 19. Restoring and extending flow data downstream of reservoirs and dams

1. Methods for restoring and extending flow data as prescribed in Article 5 of this Circular.

2. In cases where cascading hydropower projects upstream have been put into operation, the flow to the lower cascading hydropower project can be calculated based on the operational data series of the upper cascading hydropower project.

Article 20. Evaluating changes in water levels and flow rates over time

1. Analyzing and calculating characteristics of flow at selected locations:

a) Average daily flow rate from the data series;

b) Average daily flow rate corresponding to frequencies of 80%, 85%, 90%, and 95%;

c) Other characteristics (water levels, flood flows, drought flows, monthly flow distribution throughout the year, etc.).

2. Evaluating water conditions at selected locations:

a) Determining the flow rate curve of average daily flow over time corresponding to frequencies of 80%, 85%, 90%, and 95%;

b) The Q (flow rate) x H (water level) curve over time;

c) Water source characteristics during different periods to determine minimum downstream flows from reservoirs;

3. Other evaluations.

4. In cases of review and adjustment, updating, analyzing, and evaluating changes in water conditions over time from when the minimum flow was announced until the review.

Article 21. Analyzing and Calculating Water Usage Requirements for Downstream Areas

1. Analyzing and assessing the current state of water exploitation and utilization by direct water extraction structures on rivers and stream sections.

2. Water usage requirements:

Analyzing and determining water usage requirements for various purposes in terms of flow rates, water levels, and extraction regimes (flood season, drought season, increased water usage period), including:

a) Domestic use;

b) Agricultural irrigation;

c) Aquaculture;

d) Industrial production;

đ) Waterway transportation;

e) Conservation of cultural and historical values, environmental improvement;

g) Ecosystems;

h) Other purposes.

3. Summarizing requirements and determining priority order for water usage needs.

4. Reservoir capacity to meet downstream water usage needs.

5. Assessing the impact of reservoir operation:

a) Analyzing the impact of upstream water exploitation and utilization structures on water levels and reservoir volume;

b) Analyzing and assessing the impact of reservoir and dam operational capacity on flow regimes; changes in water levels and flow rates downstream of the structure (daily, monthly, seasonal, annual, multi-year). For structures that interrupt natural river and stream flows, assess and forecast changes in water levels and flow rates on interrupted sections;

c) Analyzing and assessing the impact of reservoir and dam operational capacity on the methods and regimes of direct river water extraction structures and other water usage needs.

6. In cases of review and adjustment:

a) Reviewing and adjusting minimum flows downstream of reservoirs and dams is based on factors such as changes in the purpose and mission of the reservoirs and dams, changes in water sources, and downstream needs compared to the minimum flow announced since its announcement until the review and adjustment;

b) Conducting analysis, calculation, and updating of water usage requirements and prioritization for downstream areas.

Article 22. Analysis and Proposal for Minimum Flow Rates

1. Analysis and selection of flow rates to meet downstream needs of reservoirs and dams during different time periods and stages.

2. Analysis and determination of time periods to maintain minimum flow rates downstream.

3. Compilation and construction of river and stream diagrams downstream of reservoirs and dams that require maintenance of minimum flow rates. The diagram shall include the following key information:

a) A chart showing the minimum flow rate values for the river and stream areas downstream of the reservoirs and dams;

b) Locations of areas experiencing depletion, dry-up, erosion, landslides, water quality pollution, and major water extraction and utilization facilities within those river and stream areas.

4. Expert consultation meetings:

a) Preparation of materials and organization of the meeting (editing, duplicating materials, sending related materials for comments). Solicit opinions from the meeting on the following contents: downstream water usage requirements; priority order in water usage requirements; time periods to maintain minimum flow rates; minimum flow rates downstream of reservoirs and dams.

b) Organization of the workshop and solicitation of expert opinions.

5. Compilation, editing, and finalization of the explanation determining minimum flow rates after the meeting, incorporating expert opinions on the following contents: downstream water usage requirements; priority order in water usage requirements; time periods to maintain minimum flow rates; minimum flow rates downstream of reservoirs and dams.

6. Draft Decision approving the list of minimum flow rates on rivers and streams.

7. In cases of review and adjustment, implement the contents stipulated in Clauses 1 to 6 of this Article and analyze and evaluate the implementation of ensuring minimum flow rates from the date of announcement until the review and adjustment.

Article 23. Consultation Meetings and Solicitation of Opinions from Relevant Authorities on Minimum Flow Rates on Rivers and Streams Downstream of Reservoirs and Dams

Contents of consultation meetings and solicitation of opinions include: printing of materials; organizing meetings; compiling and summarizing opinions and making revisions according to the opinions provided regarding minimum flow rates on rivers and streams downstream of reservoirs and dams.

Article 24. Compilation and Construction of Reports and Drafts on Minimum Flow Rates on Rivers and Streams Downstream of Reservoirs and Dams

1. Specialized Reports

a) Report on the results of field investigations;

b) Report on the scope of impact of reservoirs and dams;

c) Report on the assessment of water source changes over time;

d) Report on analysis and calculation of water usage requirements for downstream areas;

đ) Report on analysis of time periods to maintain minimum flow rates;

e) Report on analysis of minimum flow rates downstream of reservoirs and dams;

g) Report on establishing models to restore flow data and complete missing data (if applicable);

h) Report on testing models to restore flow data and complete missing data (if applicable);

i) Report on analysis and evaluation of the implementation of ensuring minimum flow rates announced initially (in cases of adjustment and supplementation).

2. Project Summary Report

The project summary report shall include the following main contents:

a) Analysis of basic factors affecting minimum flow rates such as topography, soil, vegetation cover, meteorology and hydrology, socio-economy, water extraction and utilization;

b) Evaluation of the implementation of initially published minimum flow rates (in cases of adjustment or supplementation);

c) Analysis and determination of the scope of impact of reservoirs and dams;

d) Assessment of water source changes over time;

đ) Analysis and calculation of water usage requirements for downstream areas;

e) Analysis of time periods to maintain minimum flow rates;

g) Analysis of minimum flow rates on rivers and streams downstream of reservoirs and dams

3. Summary report on the implementation results of the project.

4. Draft Decision approving the list of minimum flow rates for rivers and streams.

Article 25. Documents for determining the minimum flow rate downstream of reservoirs and dams

The documents for determining the minimum flow rate downstream of reservoirs and dams at the end of the fiscal year or the completion of the entire project include:

1. Project summary report.

2. Summary report on the implementation results of the project.

3. Draft Decision approving the list of minimum flow rates for rivers and streams.

4. Special reports as prescribed in Clause 1, Article 24 of this Circular.

5. Related diagrams and charts

a) Diagrams of actual data to determine the minimum flow rate downstream of reservoirs and dams based on topographic maps at a scale of 1:50,000;

b) Diagrams of river and stream areas downstream of reservoirs and dams that need to maintain the minimum flow rate.

6. Database

a) Collected data;

b) Measured and surveyed data;

c) Analyzed data, tables, drawings, intermediate maps, models, and other relevant information and data related to the project content (if applicable).

7. CD containing all project products.

Chapter IV

TECHNICAL REGULATIONS FOR BUILDING OPERATING PROCEDURES OF INTERCONNECTED RESERVOIRS

Article 26. Procedure for building operating procedures of interconnected reservoirs

1. Drafting the project proposal and plan for building operating procedures of interconnected reservoirs (hereinafter referred to as the project).

2. Collecting and compiling information and data related to building operating procedures of interconnected reservoirs.

3. Analyzing and processing collected information and data related to building operating procedures of interconnected reservoirs.

4. Conducting supplementary field surveys for building operating procedures of interconnected reservoirs.

5. Surveying and supplementing meteorological, hydrological, topographical, and cross-sectional data of rivers (if applicable) to serve the construction of operating procedures of interconnected reservoirs.

6. Compiling and analyzing collected materials and survey results for building operating procedures of interconnected reservoirs.

7. Soliciting opinions from relevant agencies regarding monitoring stations.

8. Developing operational plans and establishing computational models for flood season operations of interconnected reservoirs.

9. Developing operational plans and establishing computational models for dry season operations of interconnected reservoirs.

10. Preparing the procedure.

11. Holding seminars and soliciting opinions from relevant agencies regarding the operating procedures of interconnected reservoirs.

12. Compiling and preparing reports and draft procedures for building operating procedures of interconnected reservoirs.

Article 27. Collection and compilation of information and data related to building operating procedures of interconnected reservoirs

1. Materials on flooding and drought conditions in the river system: determining the extent of flooding and drought as boundary conditions for setting up and running models, hydrology serving the construction of procedures; statistical data on losses caused by floods and droughts in the watershed.

2. Materials and data related to current socio-economic development status and future socio-economic development directions: socio-economic development strategies of localities in the watershed, planning and plans related to projects to be included in the interconnected reservoir procedures.

3. Materials on design and operation of reservoirs:

a) Design materials of reservoirs to be included in the operating procedures of interconnected reservoirs, including: location, scale, mission of the works, layout diagram of components; design parameters of the works including: reservoir characteristics (reservoir capacity, water level-volume relationship, area); flood discharge structures and water level relationships with discharge capacity of the structures, minimum flow discharge structures, hydropower plants (energy indicators, power generation capacity, turbine characteristics, operating mode, etc.);

b) Single-reservoir operating procedures of approved reservoirs and operational data of single reservoirs in recent years (five-year operational data for reservoirs with more than five years of operation) of reservoirs to be included in the operating procedures of interconnected reservoirs (during both flood and dry seasons);

c) Documents on: operational instructions; information provision for reservoir operation; coordination documents between management agencies and units;

d) In cases of review and adjustment without adding new reservoirs, collecting design information of reservoirs already included in the operating procedures of interconnected reservoirs as stipulated in Point a, Clause 3 of this Article; single-reservoir operating procedures of approved reservoirs and operational data of single reservoirs in recent years as stipulated in Point b, Clause 3 of this Article; issued interconnected reservoir operating procedures; operational data of facilities, facility operation reports according to the approved interconnected reservoir operating procedures in the past three years of hydropower plants included in the construction of interconnected reservoir operating procedures (during both flood and dry seasons); documents on: operational instructions; information provision for interconnected reservoir operation; coordination documents between management agencies and units of reservoirs in the procedures;

đ) In cases of review and adjustment with additional reservoirs: collecting design information of operated reservoirs according to interconnected reservoir operating procedures, reservoirs planned to be included in interconnected reservoir operating procedures as stipulated in Point a, Clause 3 of this Article; single-reservoir operating procedures of approved reservoirs and operational data of single reservoirs in recent years as stipulated in Point b, Clause 3 of this Article; issued interconnected reservoir operating procedures; operational data of facilities, facility operation reports according to the approved interconnected reservoir operating procedures in the past three years of hydropower plants included in the construction of interconnected reservoir operating procedures (during both flood and dry seasons); documents on: operational instructions; information provision for interconnected reservoir operation; coordination documents between management agencies and units of reservoirs in the procedures.

4. Materials on water intake structures potentially affected by reservoirs:

a) Design materials of water intake structures, including: location, scale, mission of the works, layout diagram of components; design parameters of components; operation mode of the works;

b) Actual operational data of water intake structures over the past five years, especially during urgent water usage periods.

5. Topographic materials:

a) Digital elevation model (DEM 30m x 30m): A digital elevation model (DEM 30m x 30m) allows determining the elevation of any point in the watershed, serving as base data for mathematical models;

b) Topographic maps at a scale of 1:50,000 comprising seven layers of data;

c) Topographic materials: longitudinal profiles, cross-sections, contour maps of rivers and streams in the watershed.

6. Materials on meteorological, hydrological, water resource monitoring stations, and reservoir operation monitoring stations:

a) List of meteorological, hydrological, water resource stations, and reservoir operation monitoring stations currently operating within the river basin; regulations on flood warning levels at hydrological and water resource stations;

b) Collection of meteorological, hydrological, and water resource data, including evaporation rates, wind speeds, rainfall; water level and flow rate data hourly and daily averages at meteorological, hydrological, and water resource stations currently operating within the river basin with a minimum requirement of 30 years;

c) In cases of review and adjustment without adding new reservoirs, collect data from meteorological, hydrological, and water resource stations as stipulated in Point a and Point b of Clause 6 of this Article; update meteorological, hydrological, and water resource data and water level and flow rate data at reservoir operation monitoring stations;

d) In cases of review and adjustment with the addition of new reservoirs, collect data from meteorological, hydrological, and water resource stations as stipulated in Point a and Point b of this Article; additional data from reservoir operation monitoring stations; update and supplement meteorological, hydrological, and water resource data; update water level and flow rate data at reservoir operation monitoring stations;

7. Water conservancy, hydropower, construction plans, and other related plans that have been implemented or approved by competent authorities;

8. Requirements for information and data collection:

a) Design data, operational procedures; hydrological measurement data from stations within the river basin; hydrological measurement data from reservoirs within the river basin are input data at calculation points in mathematical and hydrological models for developing inter-reservoir operation procedures;

b) Consistency of collected information and data: ensuring project objectives;

c) Collected documents must be approved by competent authorities or verified by the providing agencies;

Article 28. Analysis and processing of information and data related to the development of inter-reservoir operation procedures

1. Establish a list of collected information and data.

2. Analyze and process collected data when developing initial inter-reservoir operation procedures:

a) Analyze and assess the role and impact of each reservoir in flood prevention, ensuring safety of structures, and water regulation for downstream areas;

b) Rank the degree of influence of the reservoirs and preliminarily identify reservoirs to be included in the inter-reservoir operation procedures;

c) Preliminarily select hydrological and water resource stations for water source calculations;

d) Determine criteria for selecting reservoir operation monitoring stations and preliminarily determine the location of these stations;

đ) Analyze and preliminarily determine water usage needs, periods of water usage, requirements for water levels and flows at extraction and usage locations;

e) Preliminarily identify water extraction and usage locations on the river and develop a layout diagram of reservoirs, extraction and usage structures, and meteorological, hydrological, and water resource stations and operation monitoring stations;

g) Identify missing documentation lists, point out existing issues regarding water extraction and usage, water resource sharing, and water transfer between river basins;

3. Analyze and process collected data when reviewing and adjusting without adding new reservoirs:

a) Review and preliminarily evaluate the degree of impact and regulatory role of reservoirs already included in the inter-reservoir operation procedures;

b) Review existing issues with issued inter-reservoir operation procedures;

c) Analyze and assess the suitability of reservoir operation monitoring stations;

d) Review and update information and data from hydrological and water resource stations to serve water source calculations and reservoir operation monitoring stations for procedure operation and preliminarily select additional reservoir operation monitoring stations (if necessary);

đ) Review and determine water usage needs, periods of water usage, requirements for water levels and flows at extraction and usage locations;

e) Preliminarily identify water extraction and usage locations on the river and develop a layout diagram of reservoirs, extraction and usage structures, and meteorological, hydrological, and water resource stations and operation monitoring stations;

g) Identify missing documentation lists, point out newly arising issues regarding water extraction and usage, water resource sharing, and water transfer between river basins;

4. Analyze and process collected data when reviewing and adjusting with the addition of new reservoirs:

a) Analyze and process collected data when reviewing and adjusting with the addition of new reservoirs as stipulated in Clause 3 of this Article;

b) Analyze and assess the role and impact of proposed additional reservoirs in flood prevention, ensuring safety of structures, and dry season water regulation within the basin;

c) Rank the degree of influence and preliminarily select proposed additional reservoirs to be included in the inter-reservoir operation procedures;

d) Preliminarily select additional reservoir operation monitoring stations.

Article 29. Field investigation for supplementing the construction of inter-reservoir operation procedures

1. Content and objects of field investigation and survey:

a) Prepare materials to serve field surveys, including: a list of reservoirs and hydrological stations, water resources, operational monitoring during flood and drought seasons, accompanied by diagrams; anticipate materials to be collected locally (planning documents, water resource usage plans; water needs for various sectors; design documents, tasks, and actual operational data of reservoirs, water extraction and utilization facilities, etc.) and organize field trips.

b) Collect additional materials from departments, agencies, and localities (districts, communes). Collected materials must ensure consistency with the project's objectives; they must be approved or verified by competent authorities from the providing agencies.

c) Prepare information and materials to organize meetings with relevant localities.

d) Investigate at the reservoirs planned for inclusion in the inter-reservoir operation procedures, collecting information including: actual operational regimes of the reservoirs in recent years (five-year operational data for reservoirs with more than five years of operation); design documents of the reservoirs; single-reservoir operation procedures; operational conditions of the reservoirs in past years; current and past water supply situations.

đ) Investigate at hydrological stations, water resource stations, and reservoir operation monitoring stations, collecting information including: drought and flood conditions in the region corresponding to water levels and flows at hydrological stations, water resource stations, and reservoir operation monitoring stations; information on water extraction and utilization related to water levels and flows at hydrological stations, water resource stations, and reservoir operation monitoring stations; changes in water levels and flows at hydrological stations, water resource stations, and reservoir operation monitoring stations; information on the impact of upstream and downstream water extraction and utilization on water levels and flows at hydrological stations, water resource stations, and reservoir operation monitoring stations; information on river width; changes in riverbeds; flow transparency; issues regarding watershed water transfer affecting the livelihoods and socio-economic development of downstream areas.

e) Investigate at water extraction and utilization facilities on rivers, collecting information including: location, scale, mission, volume of water extracted, actual water usage at water extraction and utilization points on main river branches with reservoirs; water extraction regime, annual water extraction time; water level ensuring water extraction; design parameters of the facility; operation procedure (if available); information on water transfer, water resource sharing, and other relevant information in the affected watershed that impacts the livelihoods and socio-economic development of downstream areas.

g) Accurately determine positions and draw diagrams of river cross-sections requiring supplementary measurements (if necessary) to serve the establishment of calculation models.

h) In cases of review and adjustment without adding new reservoirs, collect, update, and supplement information as prescribed in Points d, đ, e Clause 1 of this Article, and investigate and collect supplementary information including: actual operational regimes of the reservoirs in recent years (three years) since the inter-reservoir operation procedures were implemented; operational conditions of the reservoirs in past years; current and past water supply situations.

i) In cases of review and adjustment with added reservoirs, collect, update, and supplement information as prescribed in Points d, đ, e, g Clause 1 of this Article, and investigate and collect supplementary information including: actual operational regimes of the reservoirs in recent years (three years) since the inter-reservoir operation procedures were implemented; operational conditions of the reservoirs in past years; current and past water supply situations; and information and data at the reservoirs planned for inclusion in the inter-reservoir operation procedures (actual operational regimes of the reservoirs in recent years (five-year operational data for reservoirs with more than five years of operation); design documents of the reservoirs; single-reservoir operation procedures; operational conditions of the reservoirs in past years; current and past water supply situations; at supplementary operation monitoring stations (water levels, flows); at additional water extraction and utilization facilities on rivers, including information on water usage purposes and water supply standards).

2. Requirements for investigation work:

a) Collected information and documents must ensure consistency with the project's objectives and must be approved or verified by the competent authority from the providing agency.

b) Information obtained through interviews and descriptions must be fully, truthfully, and accurately recorded in investigation forms, field investigation notebooks, or record books.

c) The field investigation logbook must record the purpose of the investigation before each journey, objects of investigation, types and quantities of investigated works, journey time; after each journey, the investigation team must compile the investigation information and record observations of that journey.

d) The method of using questionnaires for water resource extraction and utilization facilities. The main contents of the questionnaire are stipulated in Point e Clause 1 of this Article. The subjects filling out the questionnaire are those responsible for managing water extraction and utilization facilities. The form of investigation is recording in the questionnaire or record book.

đ) Measure coordinates using handheld GPS: handheld GPS coordinate measurement must comply with current technical regulations.

3. Products of field investigation work:

a) Report on field investigation results, including main contents: The report on field investigation results includes main contents such as the content and volume of work performed; summary of investigation routes; preliminary assessment of the current status of reservoirs, reservoir operation monitoring stations, water extraction and utilization needs, flooding and drought conditions downstream of reservoirs.

b) Diagram of actual investigation materials for constructing inter-reservoir operation procedures at a scale of 1:50,000, including: river and stream network, reservoirs, dams, culverts, water extraction and utilization facilities, meteorological and hydrological station network, locations of reservoir operation monitoring stations; land use and vegetation cover status; detailed investigation points.

c) Summary tables and statistics of preliminary and detailed investigation results; statistics of water extraction and usage works;

d) Table of statistics of surveyed areas;

đ) Investigation forms, field investigation logbooks, and other investigation materials;

Article 30. Surveying, supplementing information and data on meteorology, hydrology, topography, river cross-sections (if applicable) for the development of inter-reservoir operation procedures

1. Topographic surveying and river cross-section surveying in accordance with current regulations.

2. Purchasing meteorological, hydrological, and topographical data to serve the development of inter-reservoir operation procedures from agencies authorized to provide such data according to their functions and tasks (if applicable).

Article 31. Compilation and analysis of collected materials and investigations for the development of inter-reservoir operation procedures

1. Compilation and analysis of the current reservoir operation status:

a) In the case of developing the first inter-reservoir operation procedure: prepare a list of reservoirs; a list of operational data for each reservoir; preliminary analysis of the operating regime of the reservoir, including: power generation mode, agricultural water supply, domestic use, etc.; preliminary assessment of the ability to meet design tasks and other tasks arising during operation;

b) In the case of reviewing and adjusting without adding new reservoirs or adding new reservoirs, compile and analyze the current reservoir operation status in accordance with Point a Clause 1 of this Article. Additionally, conduct a preliminary assessment of the ability to meet flood prevention and downstream water supply tasks according to the existing inter-reservoir operation procedure; analyze the actual operation situation of reservoirs within the procedure since its issuance (during both flood and dry seasons); evaluate the coordination of operations among reservoirs in the watershed as stipulated in the inter-reservoir operation procedure (during both flood and dry seasons); analyze and assess the suitability of reservoir operations based on water level indicators at operational monitoring stations (during both flood and dry seasons); evaluate the end-of-flood season water storage capacity of reservoirs since the issuance of the inter-reservoir operation procedure; analyze and assess the suitability of regulations on reservoir water release during different water usage phases in relation to downstream requirements and inflow to the reservoir.

2. Compilation and analysis of the current status of water extraction and utilization facilities:

a) Prepare a list of water extraction and utilization facilities: facility name, location, coordinates; managing agency; operating unit; management type; facility type; source water name, river basin; extraction flow rate; extraction regime; extraction method; purpose of use; water usage period; water supply range; task and scale of the facility; water supply standards;

b) Preliminarily determine the current water usage status according to each water usage period.

3. Compilation of local requirements for flood prevention and water extraction and utilization.

4. Compilation, analysis, and evaluation of the current status of meteorological, hydrological, water resource stations, and reservoir operation monitoring stations:

a) In the case of developing the first inter-reservoir operation procedure: prepare a list of stations; a list of operational data for each station; analyze and evaluate the current monitoring regime and data of hydrological, water resource, and reservoir operation monitoring stations; select meteorological, hydrological, and water resource stations to serve water source calculations and reservoir operation monitoring stations for procedure operation and preparation for local opinions;

b) In the case of reviewing and adjusting without adding new reservoirs or adding new reservoirs, implement the provisions of Point a Clause 4 of this Article and conduct an analysis and evaluation of streamflow changes and flood conditions in the river basin since the issuance of the inter-reservoir operation procedure; analyze and evaluate streamflow changes and drought, saline intrusion conditions in the river basin since the issuance of the inter-reservoir operation procedure.

5. Determination of data requirements for calculating inter-reservoir operation scenarios:

a) Identify the data that need to be updated and supplemented to restore and extend water level and flow rate (Q, H) data;

b) Identify methods to synchronize data for calculation purposes, extend data, and restore water level and flow rate (Q, H) data;

c) Preliminarily determine the requirements for calculating water demand at operational monitoring stations during each period, the effective capacity of each reservoir, the amount of water generated in the watershed during the dry season, and calculate the required water levels of each reservoir during the 10-day period to determine the required water levels of each reservoir at the beginning of the dry season, during the dry season, in two cases: if the water source capacity and the reservoir capacity can meet the water demand of the downstream area throughout the dry season, it is necessary to calculate and determine the minimum water level of each reservoir to maintain at the beginning of each 10-day period, and if the water source capacity and the reservoir capacity cannot meet the water demand of the downstream area throughout the dry season, it is necessary to determine the priority period for reservoir water storage to increase water usage during the water usage period, while analyzing and determining the priority level for each purpose of use and determining the minimum water level of each reservoir to maintain at the beginning of each 10-day period.

6. Development of related diagrams:

a) Sketch the locations of meteorological, hydrological, and water resource stations;

b) Sketch the locations of water extraction and utilization facilities, reservoirs, and hydrological and water resource stations and reservoir operation monitoring stations.

Article 32. Soliciting opinions from relevant agencies on operation monitoring stations

1. In the case of establishing the first operation procedures for inter-reservoirs:

a) Prepare and compile documents to solicit opinions on operation monitoring stations;

b) Summarize and finalize based on feedback received.

2. In the case of reviewing and adjusting with additional reservoirs:

a) Prepare and compile documents to solicit opinions on additional operation monitoring stations.

b) Summarize and finalize based on feedback received.

Article 33. Developing operation plans and establishing computational models for inter-reservoir operations during flood season

1. Extending and restoring flow data:

a) Purpose: to extend and standardize data for developing inter-reservoir operation procedures;

b) Implement extension and restoration of data based on collected information and supplementary field surveys using models. Model establishment for extending and restoring data shall comply with current regulations and ensure project objectives.

2. Determining flood prevention requirements downstream.

3. Identifying operation monitoring stations for flood control:

a) Analyze and determine water levels and flows at operation monitoring stations for floods when such stations lack warning levels;

b) Determine water levels and flows at operation monitoring stations for decision-making on reservoir operations.

4. Studying, analyzing, and evaluating flood characteristics, rainfall-flood combinations, storms, and dangerous weather patterns within the watershed as a basis for management:

a) Statistically analyze the occurrence times of different-sized floods and their features;

b) Analyze flood characteristics, causes, and development processes of past floods; identify flood periods (if any);

c) Categorize rainfall amounts generating floods in the watershed;

d) Develop flood distribution charts according to rainfall categories over time;

đ) Analyze and determine the relationship between rainfall and floods according to rainfall categories in the watershed;

e) Calculate statistical features of floods at hydrological stations;

g) Calculate and establish statistical relationships of flood characteristics along the system and dam lines;

h) Calculate, determine, and evaluate flood combinations among river branches within the watershed (in cases involving two or more branches);

i) Calculate, determine, and evaluate flood combinations between upstream reservoirs and downstream areas;

k) Identify, evaluate, and select flood events and combinations for calculating operational plans for inter-reservoirs.

5. Study, determine, and select tide and flood flow combinations within the system (for watersheds affected by tides).

6. Identify conflicts in actual reservoir operations for flood reduction downstream:

a) Analyze the actual operation mode of reservoirs over the past five years to identify conflicts in flood reduction operations downstream;

b) Compare the actual operation of reservoirs over the past five years with local flood prevention requirements and provide initial assessments for the operation procedure.

7. Establish models for evaluation and forecasting:

Model establishment for evaluation and forecasting shall comply with current regulations and ensure project objectives.

a) Reservoir flood regulation model;

b) Flow calculation model for operation monitoring stations.

8. Develop operational plans for reservoirs during the flood season.

9. Analyze and propose operational plans to optimize flood reduction and power generation efficiency:

a) For the first establishment of inter-reservoir operation procedures: analyze and determine water release coordination among reservoirs to ensure water levels and flows at operation monitoring stations while achieving maximum power generation efficiency; determine the power loss of each reservoir under each plan compared to its original design; propose operational plans and analyze and evaluate the strengths and weaknesses of each plan;

b) For review and adjustment without adding new reservoirs, or with added reservoirs: follow the provisions of Point a Clause 9 of this Article and compare with existing inter-reservoir operation procedures, proposing adjustment plans.

10. Draft inter-reservoir operation procedures during the flood season (or adjustments and supplements in the case of reviews and adjustments).

11. Organize expert meetings to solicit opinions from relevant departments, localities, and reservoir management units:

a) Prepare documents and other preparations for the meeting (compile, duplicate documents, send related documents for soliciting opinions) on the contents stipulated in the flood season operation procedures;

b) Organize the meeting and solicit opinions;

c) Summarize and finalize based on opinions received, selecting inter-reservoir operation plans.

Article 34. Establishing operation plans and creating operational reservoir interconnection models during the dry season

1. Extending and restoring flow data:

a) Purpose: to extend and standardize data for developing inter-reservoir operation procedures;

b) Implementing the extension and restoration of data based on information collected from data collection, consolidation, processing, and supplementary field surveys using the data extension and restoration model.

The work of establishing the data extension and restoration model according to current regulations and ensuring the project's objectives.

2. Determining monitoring stations for operation during the critical period:

a) Considering the locations of hydrological, water resource stations, and reservoir operation monitoring stations;

b) Analyzing and building correlations between water levels and flows at hydrological, water resource stations, and reservoir operation monitoring stations with water extraction and usage points;

c) Analyzing and evaluating the assurance of water levels and flows for different purposes (agriculture, industry, domestic use...), which may require different operation monitoring stations for each water usage need.

3. Analyzing and assessing the determination of water demand and usage periods:

a) Accurately determining the location, scale of works, water level elevation, supply range, quantity of water extracted, actual water usage at water extraction and usage points on main rivers affected by the reservoir;

b) Determining the water usage period; evaluating and calculating water demand and determining requirements for water levels and flows at each water extraction and usage facility during each period;

c) Summarizing water demand and determining requirements for water levels and flows according to each usage period;

d) Identifying contradictions between actual reservoir operation and water usage needs: analyzing the actual operation mode of reservoirs over the past five years to identify contradictions in water resource sharing and usage due to the current operation mode of facilities; comparing the actual operation status of reservoirs over the past five years with local requirements for water usage downstream and making initial assessments in the operation process; proposing preliminary solutions to harmonize water usage needs;

đ) Completing calculation results regarding water usage requirements, water level, and flow requirements at hydrological, water resource stations, and reservoir operation monitoring stations according to each period.

4. Dividing operational periods for reservoirs:

Based on downstream water requirements, reservoir regulation capacity, and priority in water usage, dividing different operational periods:

a) Priority period for supplying domestic water;

b) Priority period for supplying agricultural water;

c) Priority period for supplying industrial water;

d) Priority period for ensuring minimum flow for inland navigation;

đ) Priority period for power generation.

5. Establishing models to evaluate and forecast

Model establishment for evaluation and forecasting shall comply with current regulations and ensure project objectives.

6. Establishing operation plans for inter-reservoir connections during the dry season.

7. Analyzing and proposing operation plans to ensure optimal water usage and power generation efficiency:

a) In the case of establishing the first inter-reservoir operation procedure: analyzing and determining the coordination of water release among reservoirs to ensure water levels and flows at monitoring stations while achieving the highest possible power generation efficiency; determining the power loss of each reservoir for each plan;

b) In the case of reviewing and adjusting without adding new reservoirs, adding new reservoirs, updating contents according to Point a Clause 7 of this Article and comparing with the previously issued inter-reservoir operation procedures, proposing adjustment plans.

8. Drafting the inter-reservoir operation procedure during the dry season.

9. Holding seminars and soliciting opinions from experts, relevant departments, localities, and reservoir management units:

a) Preparing materials and other preparations for the seminar (editing, duplicating materials, sending related materials for comments) on the content stipulated in the procedure during the dry season;

b) Organize the meeting and solicit opinions;

c) Summarizing and perfecting according to opinions, selecting inter-reservoir operation plans.

Article 35. Drafting the Operating Procedure

1. Compile the operating procedures for both flood season and dry season to establish the annual procedure (covering both flood and dry seasons).

2. Identify technical safety regulations for works, downstream safety, and general provisions to be included in the draft Operating Procedure.

3. Determine the responsibilities of relevant Ministries, sectors, People's Committees of provinces directly under the Central Government, and owners of related works; responsibilities for providing information and reports to be included in the draft Operating Procedure.

4. Prepare an explanatory report on the Operating Procedure.

Article 36. Workshop and Solicitation of Opinions from Relevant Agencies on the Inter-River Reservoir Operation Procedure

1. Prepare and compile documents for soliciting opinions.

2. Organize workshops and solicit opinions from relevant agencies.

3. Incorporate and synthesize technical explanations of opinions.

4. Prepare the draft Operating Procedure document incorporating revisions and amendments to send to relevant Ministries, sectors, provincial People's Committees, and related units to prepare for drafting team meetings.

5. Organize drafting team meetings (including relevant Ministries, sectors, provincial People's Committees, related units, and experts).

6. Incorporate technical opinions at the drafting team meeting, continue to perfect the draft Operating Procedure document for submission to competent authorities.

Article 37. Compilation and Construction of Reports and Drafts of the Inter-River Reservoir Operation Procedure

1. Special reports on the inter-river reservoir operation procedure during the flood season:

a) Report on determining requirements and criteria for flood prevention for downstream areas;

b) Report on researching, analyzing, and evaluating flood characteristics, rainfall-flood combinations, typhoons, and dangerous weather patterns in the river basin as a basis for management;

c) Report on researching and determining tidal and flood flow combinations in the system (for river basins affected by tides);

d) Report on analyzing and proposing optimal operation plans to reduce floods and improve power generation efficiency;

đ) Report on analyzing, constructing, and calculating inter-river reservoir operation plans to ensure downstream flood prevention, safety of works, and power generation efficiency;

e) Report on establishing models to extend, restore data, evaluate, and forecast;

g) Report on model verification;

h) Report on the implementation of regulations in the inter-river reservoir operation procedure during the flood season that have been issued (in cases of review and adjustment of the procedure).

2. Special reports on the inter-river reservoir operation procedure during the dry season:

a) Report on analyzing water demand;

b) Report on dividing operational periods for reservoirs;

c) Report on analyzing and proposing optimal operation plans for water use and power generation efficiency;

d) Report on researching, analyzing, constructing, and calculating inter-river reservoir operation plans to serve the construction of the inter-river reservoir operation procedure for regulating water in the dry season for downstream areas;

đ) Report on establishing models to extend, restore data, evaluate, and forecast;

e) Report on model verification;

g) Report on the implementation of regulations in the inter-river reservoir operation procedure during the dry season that have been issued (in cases of review and adjustment of the procedure).

3. Project summary report:

The project summary report includes the following main contents:

a) Analysis of factors affecting the inter-river reservoir operation procedure such as topography, soil, vegetation cover, meteorology and hydrology, socio-economy, reservoir systems, water extraction and utilization works;

b) Main contents when drafting the inter-river reservoir operation procedure during the flood season, including: determining requirements and criteria for flood prevention for downstream areas; requirements and criteria for selecting monitoring stations for reservoir operations during the flood season; research, analysis, and evaluation of flood characteristics, rainfall-flood combinations, typhoons, and dangerous weather patterns in the river basin as a basis for management; research and determination of tidal and flood flow combinations in the system (for river basins affected by tides); operation plans for inter-river reservoirs during the flood season; analysis and proposal of plans to ensure optimal operation for reducing floods for downstream areas and improving power generation efficiency; situation of implementing regulations in the inter-river reservoir operation procedure during the flood season that have been issued (in cases of review and adjustment of the procedure).

c) Main contents when drafting the inter-river reservoir operation procedure during the dry season, including: requirements and criteria for determining monitoring stations for reservoir operations during the dry season; analysis and determination of water demand; division of operational periods for reservoirs; operation plans for inter-river reservoirs during the dry season; analysis and proposal of plans to ensure optimal operation for water use and improving power generation efficiency; report on the implementation of regulations in the inter-river reservoir operation procedure during the dry season that have been issued (in cases of review and adjustment of the procedure).

4. Summary report on the results of the project implementation.

5. Draft of the inter-river reservoir operation procedure including the main contents:

a) General provisions;

b) Provisions for operating reservoirs during the flood season;

c) Provisions for operating reservoirs during the dry season;

d) Provisions on responsibilities, organization of reservoir operations, and provision of information and reports.

Article 38. Documents for the construction of inter-reservoir operation procedures

1. Draft of the inter-reservoir operation procedure.

2. Comprehensive report on the construction of the inter-reservoir operation procedure.

3. Summary report on the implementation results of the project.

4. Specialized reports as prescribed in Clause 1 and Clause 2, Article 37 of this Circular.

5. Related maps and diagrams

a) Map of actual data for constructing the inter-reservoir operation procedure based on a topographic map with a scale of 1:50,000;

b) Diagram of the location of meteorological, hydrological, water resource stations, reservoir operation monitoring stations, and water extraction and utilization facilities;

c) Rainfall level diagram.

6. Data set:

a) Collected data;

b) Measured and surveyed data;

c) Compiled and analyzed data, tables, drawings, intermediate maps, models, and other relevant information and data pertaining to the project content (if any).

7. CD containing all project products.

Chapter V

IMPLEMENTING PROVISIONS

Article 39. Implementation Organization

1. Ministries, ministerial-level agencies, government agencies, provincial People's Committees, city People's Committees under the central government, heads of units under the Ministry of Natural Resources and Environment, and related organizations and individuals are responsible for implementing this Circular.

2. The National Water Resources Management Agency is responsible for guiding and supervising the implementation of this Circular.

Article 40. Effective Date

1. This Circular takes effect from February 5, 2018.

2. During the implementation process, if there are difficulties or obstacles, it is requested that agencies, organizations, and individuals promptly reflect them to the Ministry of Natural Resources and Environment for study, amendment, and supplementation./.