Proposal for reservoir operation plan during extreme rain and flood

TP - The Ministry of Natural Resources and Environment has requested the Ministry of Industry and Trade, the Ministry of Agriculture and Rural Development, and local authorities to urge reservoir owners to develop reservoir operation plans based on extreme rainfall and flood scenarios.

According to the National Center for Meteorological and Hydrological Forecasting, the weather and climate developments in Vietnam from now until the end of the year will be very complex and unpredictable. After Super Typhoon Yagi made a direct landfall in the North, the East Sea may experience 1-2 typhoons in September, concentrated in the last 10 days of the month, potentially affecting the North and North Central regions. In addition, due to the influence of La Nina, the Central region is likely to experience a series of storms and floods in the last months of the year, peaking in October and November.

In the context of potentially facing extreme rainfall and flooding situations in the coming period, especially the risk of successive storms and floods in Central Vietnam, the Ministry of Natural Resources and Environment stated that it will conduct a comprehensive review and adjustment of inter-reservoir operating procedures based on updated calculations and a thorough and comprehensive consideration of unusual and emergency situations and climate change scenarios. When conditions permit, the operating procedures will be adjusted to a real-time approach.

Enhancing flood mitigation capabilities for downstream areas.

In addition, research and propose a plan to utilize a portion of the flood control capacity above the normal water level of large, important reservoirs to enhance flood control and reduction capabilities for downstream areas in emergency and unusual situations.

The Ministry of Natural Resources and Environment is conducting a comprehensive review and adjustment of the inter-reservoir management process based on updated information on unusual and emergency situations and climate change scenarios.

The Ministry of Natural Resources and Environment also recommended that the Ministry of Industry and Trade, the Ministry of Agriculture and Rural Development, and local authorities urge relevant agencies and reservoir owners to strictly and fully implement the regulations of the Inter-Reservoir Operation Procedure on river basins, and to implement reservoir monitoring and information reporting in accordance with the law on water resources. They also recommended reviewing reservoir operation plans with extreme rainfall and flood scenarios, especially in the Central region, where there are warnings of potential heavy rainfall and a late end to the flood season in October and November due to the influence of the La Nina phenomenon.

Previously, due to the impact of heavy rain from the circulation of Typhoon YAGI, followed by the tropical convergence zone and cyclones developing over land, water levels on many rivers and streams in Northern Vietnam rose rapidly. Flooding at the Thac Ba hydroelectric reservoir reached historical levels, threatening the safety of the dam.

The Thac Ba hydroelectric reservoir was surveyed and designed between 1959 and 1961. Due to limited hydrological data on flow rates at that time, the spillway was designed with a maximum discharge capacity of only 3,230 m³/s. In reality, the maximum inflow into the Thac Ba reservoir reached 5,620 m³/s at 9:00 AM on September 10th, exceeding the design flood peak by 0.01% (5,100 m³/s) and far exceeding the maximum discharge capacity by 74%.

According to operating procedures, when the water level of Thac Ba Lake reaches 59.60m, it will switch to a special operating mode to ensure dam safety. In reality, from 5 PM on September 10th, the water level of Thac Ba Lake reached 59.62m and switched to a special operating mode, then reached its highest level of 59.84m at 5 AM on September 11th. The worst-case scenario was considered if the water level reached 61m, but fortunately, heavy rain subsided afterwards, causing the flood inflow into the lake to decrease.

NGUYEN HOAI

Source: https://tienphong.vn/kien-nghi-len-phuong-an-van-hanh-ho-chua-khi-mua-lu-cuc-doan-post1673419.tpo