Reservoir safety concerns during storm season

(Baonghean) - Reservoir safety is an issue of particular concern to the public, especially in times of complex weather conditions like today. Nghe An Newspaper reporters had a conversation with comrade Pham Huu Van - Deputy Head of the Irrigation Sub-Department about this issue.

- Dear comrade, currently the whole province has over 625 reservoirs, the characteristics of Nghe An reservoirs are that most of them have been in use for a long time, from 30 to 40 years, with some reservoirs built over 50 years ago. Could you give more specific information?

- That's right. The whole province has over 625 reservoirs. These are the "famous" reservoirs with a capacity of 1 million m3 or more that are in the industry's planning. Specifically, the number of reservoirs corresponding to the designed flood level with a capacity of over 1 million m3 is 88 (of which: From 1 to under 10 million m3: 80 reservoirs; from 10 million m3 or more, there are 8 reservoirs). The number of reservoirs with a dam height of 10 m or more is 121.

The reservoirs invested in and built by the State are surveyed and designed according to the old standard process, most of the flood prevention levels are calculated with short hydrological documents, single flood models, and low previous design frequencies from P = 5-10%. The reservoirs built by the State and the people often lack hydrological documents, or must be calculated using the correlation method with low accuracy. Even many reservoirs built by the people themselves (usually with a capacity of 0.1 to less than 1 million m3) do not have a design survey.

Comrade Pham Huu Van - Deputy Head of Irrigation Sub-Department

Meanwhile, the construction of the project items is not synchronized and using many different technical means; most of the construction is done manually, with poor compaction, and many lakes do not have their foundations treated in the stream bed. Some lakes are built high to prevent floods by building the dam slope, reducing the width of the dam surface and not ensuring the cross-section according to technical standards.

The water intake is mainly made of prefabricated concrete pipes, the sluice gates are mostly flat and not watertight. There are still many lakes using overflows, the process of using them is deeply eroded, reducing the effective capacity of the lake.

- In fact, the spillways of many projects are temporary and do not have enough width to discharge floodwaters. Many dams do not have management roads or have poor quality roads that do not meet the requirements for emergency response when an incident occurs... On the other hand, the construction time is so long that it is probably no longer suitable for the current weather conditions?

- I can summarize the safety assessment of Nghe An reservoirs as follows: Reservoirs with a storage capacity of 10 million m3 or more can ensure safety at a flood frequency of 0.5 - 1%; Reservoirs with a storage capacity of 2 to 10 million m3 or more can ensure safety at a flood frequency of 1 - 2%; The remaining small reservoirs can only ensure a flood frequency of 5-10% (old design standards) and some reservoirs are even lower (mainly built and managed by people). In case of heavy rain and floods, water can overflow the dam surface and cause the dam to break.

Xuan Duong Lake in Dien Phu, Dien Chau has just been upgraded to ensure safety against 1% frequency floods.

- It is known that currently over 80% of the reservoirs are full of water, the rest are at over 70% capacity. At this water level, do the reservoirs need to be discharged?

- Up to this point, through inspection and assessment, all reservoirs in the area are safe. However, in the face of the flood situation, the Provincial People's Committee has a plan to organize reservoir safety inspections, based on the actual situation to operate water discharge to prevent floods, ensure the safety of dams and downstream of irrigation and hydroelectric reservoirs, especially reservoirs that are full or nearly full of water, and weak dams...

- The issue that people are also very concerned about is the water level of Vuc Mau reservoir. A few days ago, the Project's Flood Control Steering Committee also planned to release floodwaters?

- It is true that there was a plan to discharge floodwaters, but then based on the actual situation, the discharge did not take place, but only the spillway was discharged to ensure that the water level in the lake reached the 21m elevation according to the process. Currently, Vuc Mau Lake has a flood discharge scenario according to the unfavorable options established by the Institute of Water Resources. However, for Vuc Mau Lake, we also propose that the Government and the Ministry of Agriculture and Rural Development allow the establishment of a project and provide funding to expand the Hoang Mai River to ensure flood drainage when Vuc Mau Lake opens all 5 spillways. At the same time, we propose that local authorities at all levels annually develop and deploy flood and storm prevention drills in the downstream areas of dams, especially large reservoirs such as Vuc Mau Lake...

- In the context of limited budget, investment in construction projects is always difficult. It is known that for weak projects, the World Bank has a funding program to upgrade, but what about small lakes managed by localities?

- With the attention of the Provincial People's Committee, the Ministry of Agriculture and Rural Development, and the Government, Nghe An has received a capital funding program from the World Bank (WB) to repair 27 reservoirs in the province. These are weak projects that need to be upgraded soon. However, there are still some small reservoirs in the localities that are leaking and seeping, which poses a high risk of unsafety. We recommend that the People's Committees of communes and districts use irrigation fees and local budgets to repair the projects to ensure safety during the rainy season as well as meet the water supply needs for production and people's lives.

Thank you very much for this conversation!

Thu Huyen(Perform)