Chương III Thông tư 03/2024/TT-BTNMT: Xác định, điều chỉnh dòng chảy tối thiểu

Chapter III

DETERMINATION AND ADJUSTMENT OF MINIMUM FLOWS

Article 15. Requirements for minimum flow values

1. Minimum flow on rivers, streams and downstream of dams and reservoirs has a value in the range from the smallest monthly flow rate to the average flow rate of 3 months with smallest flow rates (m³/s).

In case a value different from the abovementioned value is required, the regulations set out in clause 4 Article 24 of the Law on Water Resources shall be relied on to determine the minimum flow value at each location but the maximum increase must not exceed the average flow in the dry season and must be within the actual capacity of the water source and the regulation and operation capacity of a dam or reservoir; the maximum reduction must not exceed 50% of the smallest monthly flow rate but water supply safety, social security, environmental and aquatic ecosystem protection must be assured.

2. According to the required values of minimum flows on rivers, streams and downstream of dams and reservoirs specified in clause 1 of this Article, the determination of minimum flows shall comprehensively and fully rely on the principles and bases specified in clauses 3 and 4 Article 24 of the Law on Natural Resources to select an appropriate minimum flow value for each location.

3. Depending on the requirements regarding water exploitation and use regimes and regulation and operation capacity of dams, reservoirs and capacity of regulation structures, the minimum flow value at each location may be considered and determined corresponding to each period and time of year.

The minimum flow at each location must meet the requirements for regime and period of using water downstream, ensuring systematicity within the same river and stream system.

4. Regarding structures serving salinity and flooding prevention and dams in coastal estuaries, the competent authority that confirms the registration and licensing of surface water exploitation shall decide the necessity of maintaining the minimum flow.

Article 16. Locations at which minimum flows are determined

1. For rivers and streams:

a) Locations at which minimum flows are determined on a river or stream shall be determined at one or more locations. To be specific: location(s) on the river or stream before merging into another river or stream; location(s) at hydrological stations and water resources monitoring stations;

b) In addition to the locations specified in point a of this clause, in the case where the specific requirement for flow is laid down to facilitate water exploitation and use; cultural, sports and tourism activities; to prevent water source degradation, restore water sources, protect aquatic ecosystems, conserve biodiversity and economically valuable aquatic species on one or more segments of the river or stream, the competent water resources authorities specified in clauses 6 and 7 Article 24 of the Law on Water Resources shall consider and decide to additionally select location(s) at which minimum flows are determined.

2. For dams and reservoirs:

a) Locations at which minimum flows of downstream of a dam or reservoir are determined shall be determined right behind the dam;

b) For the dam or reservoir for which a water exploitation plan is tailored resulting in interrupting the flow of a river or stream, depending on the size and regulation capacity of the reservoir, degree of impact of the structure, requirements for flow regime on the river or stream and requirements for exploitation and use of water downstream of the dam or reservoir, in addition to the location(s) specified in point a of this clause, consider determining the minimum flow at a location right behind the work item intended for returning flow to the river or stream;

c) For a dam or reservoir on a river or stream with a water exploitation scale subject to registration and licensing of water resource exploitation according to regulations of law on water resources, arrange the work items for discharging the minimum flow which have full capacity for discharge to meet the requirements specified in clause 1 Article 15 of this Circular, except where the dam or reservoir has been put into operation and the work items for discharging the minimum flow fail to be adjusted or added.

Article 17. Methods for calculating flow characteristics in service of determination of minimum flows

1. The flow characteristics calculated at each location at which minimum flow is determined include:

a) Distribution of annual flow by months;

b) Annual flow characteristics;

c) Characteristics of flow in dry season (minimum monthly flow, average flow of the month with smallest flow, average flow of 3 months with and average flow in dry season).

2. Based on existing hydro-meteorological monitoring data and characteristics of the basin, the flow characteristics shall be determined using one of the following methods:

a) In the case where a hydrological station or water resources monitoring station or annual or multi-year regulating reservoir (hereinafter referred to as “hydrological monitoring station”) along a river or stream has a series of hydrological monitoring data obtained over the last 20 years or more and the difference in the basin area of the hydrological station and that at the location at which minimum flow is determined does not exceed 10%, the correlation (between annual rainfall and basin area) with flow data of the hydrological monitoring station may be used for determination;

b) In the case where a hydrological monitoring station along a river or stream has a series of hydrological monitoring data obtained over the last 20 years or more but the difference in the basin area of the hydrological station and that at the location at which minimum flow is determined exceeds 10% or the series of hydrological monitoring data is obtained in less than 20 years or there is not a hydrological monitoring data along the river or stream, any of the following methods may be considered and selected:

Regionalisation method regarding the hydrological station with a series of data obtained over the last 20 years or more if the area of one basin does not exceed five (05) times the area of another basin and the two basins are similar in terms of basic conditions for forming flow and synchronization of flow fluctuations.

Correlation between annual rainfall and annual flow.

Hydrological and hydraulic modelling method.

Other methods appropriate to the hydrological characteristics and hydrometeorological data and conditions of a region.

3. If there are multiple locations at which minimum flow is determined adopting various methods on the same system of rivers or streams, values of the flow characteristics may be considered and adjusted to ensure the systemacity.

4. For a dam or reservoir on a river or stream subject to registration of water exploitation according to regulations of law on water resources, in addition to the methods specified in clause 2 of this Article, the correlation (by the ratio of basin area) with the flow data of the hydrological station or correlation with the minimum flow value of another dam or reservoir licensed in the same river basin or operating data of a structure may be used to determine the minimum flow value.

Article 18. Requirements for information, data and results of determination of minimum flows

1. Information and data used to assess and determine a minimum flow must be reliable and consistent with the applied method.

Where hydrological monitoring data has been affected by the regulation by water regulation and water transfer works on rivers and streams, the data must be restored before being used for calculation and assessment.

2. The results of calculation of flow characteristics and selection of minimum flow value at each location must be justified and explicitly explained in terms of the satisfaction of the requirements specified in Article 15 of this Circular and the following contents:

a) Location selection;

b) Selection of calculation method;

c) Fulfillment of requirements for water exploitation and use in terms of flow, water level and spatial flow regime and the regulation capacity of a dam or and reservoir.

3. Results of determination of minimum flow on a river or stream must be consolidated, included in a diagram and list which primarily contains the following information:

a) Name of the river or stream in the river basin;

b) Location at which minimum flow is determined: coordinates, administrative location;

c) Minimum flow value

4. For a dam or reservoir, the minimum flow value downstream of the dam or reservoir is specified in the surface water exploitation permit or certificate of registration of surface water exploitation containing information about location (coordinates, administrative location), minimum flow value.

Article 19. Approval and announcement of minimum flows

1. Where the determination of minimum flows is covered by the comprehensive inter-provincial river basin planning or provincial planning, the announcement of minimum flows shall be part of the procedures for approving and announcing planning.

2. Where the Ministry of Natural Resources and Environment or provincial People’s Committee determines and announces minimum flows as prescribed in clauses 6 and 7 Article 24 of the Law on Natural Resources, the approval and announcement of minimum flows shall be carried out as follows:

a) For rivers and streams:

The Ministry of Natural Resources and Environment shall direct the Department of Water Resources Management to carry out survey and assessment, and collect comments on minimum flows on inter-provincial and transboundary rivers and streams (within Vietnamese territory) from the Ministry of Industry and Trade, Ministry of Agriculture and Rural Development, Ministry of Transport, Ministry of Construction, Ministry of Culture, Sports and Tourism, provincial People’s Committee, river basin organization (if any) and related agencies and units.

On the basis of those comments, the Department of Water Resources Management shall consolidate, receive and respond to them, complete and submit the application to the Minister of Natural Resources and Environment for consideration, approval and announcement of minimum flows.

The provincial People’s Committee shall direct the Department of Natural Resources and Environment to carry out survey and assessment, and collect comments on minimum flows on intra-provincial and transboundary rivers and streams from the Department of Industry and Trade, Department of Agriculture and Rural Development, Department of Transport, Department of Construction, Department of Culture, Sports and Tourism and related provincial departments and local authorities; consolidate comments of Departments and agencies and send them to the Ministry of Natural Resources and Environment (through the Department of Water Resources Management) to obtain its comments.

On the basis of those comments, the Department of Natural Resources and Environment shall consolidate, receive and respond to them, complete and submit the application to the provincial People’s Committee for consideration, approval and announcement of minimum flows.

The dossier for collection of comments includes a draft approval decision enclosed with a list of minimum flows on rivers and streams, a report on explanation for determination of minimum flows and minimum flow diagrams of rivers and streams.

Within 14 days from the date of approving minimum flows on rivers and streams, the Ministry of Natural Resources and Environment or provincial People’s Committee shall, within their power, announce and post the decision to approve minimum flows on the web portal of the Ministry of Natural Resources and Environment or provincial People’s Committee;

b) For dams and reservoirs:

Owners of dams, reservoirs or organizations and individuals managing and operating dams and reservoirs shall propose the values of minimum flows downstream of dams and reservoirs that they invest in, construct, manage and operate in the registration form or the application for issuance of permit for surface water exploitation according to regulations of law on water resources, which are approved by the competent authority in point b clause 6 and point b clause 7 Article 24 of the Law on Water Resources in the permit for exploitation and use of surface water or certificate of registration of surface water exploitation and use.

Every 6 months, the Ministry of Natural Resources and Environment or provincial People’s Committee shall, within their power, direct the aggregation of the approved values of minimum flows downstream of dams and reservoirs to issue an announcement decision and post it on the web portal of the Ministry of Natural Resources and Environment or provincial People’s Committee.

Article 20. Review and adjustment of minimum flows

1. The review and adjustment of minimum flows shall comply with the regulations set out in clause 9 Article 24 of the Law on Water Resources. Any authority having the power to approve minimum flows shall decide the review and adjustment thereof.

2. Owners of dams, reservoirs or organizations and individuals managing and operating dams and reservoirs prescribed in point b clause 1 Article 24 of the Law on Water Resources shall propose the values of minimum flows downstream of dams and reservoirs in the registration form or the application for issuance or adjustment of permit for surface water exploitation and submit it to the competent authority in point b clause 6 and point b clause 7 Article 24 of the Law on Water Resources for consideration and approval in the course of certification or permit issuance.

3. The adjustment of minimum flows shall be made in the same manner as the determination, approval and announcement of minimum flows as specified in this Circular.