Loophole in compliance with flood discharge
According to the Department of Agriculture and Environment (NN&MT) of Lam Dong province, Binh Thuan Irrigation Works Exploitation One Member Limited Liability Company is the unit managing and operating Song Quao reservoir. Recently, this unit has reported and explained the operation of the reservoir during the floods in early December.
The Department of Agriculture and Environment said that current legal regulations require reservoir operators to notify local authorities to disseminate to people in downstream areas and relevant agencies before discharging floodwater, with a minimum notification time of 4 hours.
This is a mandatory requirement to create conditions for localities to proactively implement plans to prevent, relocate people and protect property.
Through practical understanding, it shows that from November 24, Lam Dong Provincial People's Committee issued document No. 7747 on proactively responding to tropical depressions near the East Sea, requesting irrigation reservoir owners to strengthen monitoring of weather developments and floods.
In which, deploy plans to ensure project safety, flood prevention capacity and strictly implement reservoir operation procedures, especially in emergency flood discharge situations.
On November 26, the Provincial People's Committee continued to issue document No. 7956 on responding to storm No. 15 (Koto), emphasizing the requirement to focus on reservoir operation, ensuring project safety and downstream areas.
However, by November 29th, the operation unit of Song Quao reservoir had notified downstream localities about flood discharge from 7 am on November 30th with an initial flow rate of 15 m3/s.
After that, announce adjustments to gradually increase discharge flow according to rain and flood dien bien: At 0:00 on December 2nd, it increased to 40 m3/s; at 0:00 on December 3rd, it increased to 80 m3/s.
At 4:30 PM on December 3rd, the company continued to send notices to the Civil Defense Command at all levels on the expected increase in overflow flow to 100 m3/s at 7:00 PM on the same day. Also on the evening of December 3rd, overflow flow was increased to 150 m3/s.
From 1:43 AM to 5:34 AM on December 4th, Song Quao reservoir had 3 more adjustments to increase discharge flow, the highest level increased to 500 m3/s.
Many subjective causes
Explaining the cause of serious flooding in the downstream area, the Department of Agriculture and Environment assessed that there are both objective and subjective factors. Objectively, the old Binh Thuan area often had to store water at reservoirs at the end of the rainy season (early November) to serve drought prevention and control.
However, in 2025, the weather dien bien cuc doan, heavy rain appeared late and rush in a short time, causing the amount of water flowing into the reservoir to increase suddenly, exceeding the designed regulation capacity.
Subjectively, weather forecasts and floods at some times are not close to reality. Specifically, on December 1st, meteorological forecasts showed that on December 3rd - 4th, the common rainfall in Lam Dong was only from 10 - 30mm.
However, in reality, on December 3rd, extreme rain occurred, in some places the rainfall exceeded 460mm, many times higher than forecast. Thereby, causing difficulties for calculating the amount of water flowing to the reservoir and building appropriate flood discharge plans.
The operating process is also one of the subjective reasons. According to the Department of Agriculture and Environment, the operating process of irrigation reservoirs only stipulates the highest water level during the flood season. In arid areas like old Binh Thuan, irrigation reservoirs are allowed to store the highest water to normal water levels from October.
Faced with the current climate change situation, it is necessary to adjust the highest water levels before floods and supplement the lowest flood reception levels for irrigation reservoirs to suit the actual situation.
Also according to the Department of Agriculture and Rural Development, the flood prevention capacity of some reservoirs is not suitable for the characteristics of the basin. Song Quao Lake has a large basin and a large slope, but the reservoir's flood prevention capacity is not commensurate.
In addition, there is also the reason that there is no effective warning system for the downstream area. The downstream area does not have an early, automatic, direct warning system to people via loudspeakers, warning messages via SMS, Zalo when there is heavy rain in the basin.
Especially in basins without flood regulation works, because in river branches without reservoirs, water will flow downstream faster than in river branches with regulating reservoirs.
The flood drainage capacity in the downstream area is also a subjective cause. Because all flood drainage lines in the downstream area have not been renovated to ensure flood drainage according to the designed flow of the project.
The current situation of low-lying riverside areas with residential areas and production areas. Besides, there is the situation of people encroaching on land to build works, narrowing the flow, limiting drainage capacity, and increasing flooding levels...
Communes and wards in the downstream area of Song Quao lake were heavily damaged after the flood in early December and the flood in late October and early November.
Ham Thang ward in the flood in early December had 2,800 houses heavily flooded, 2 houses completely collapsed, agricultural area flooded is about 521ha. Estimated total damage is about 120 billion VND.
Ham Thuan Bac commune (from October 26 to December 4) had 7 houses collapsed, agricultural area damaged more than 2,029ha, more than 10,000 livestock swept away and died. Estimated total damage is about 50 billion VND.
Ham Thuan commune (from October 26th to December 4th) has nearly 1,500 houses and 1,813ha of agricultural area flooded. The number of floating livestock missing and dead is 5,134. Estimated total damage is about 50 billion VND.
In addition, communes such as Ham Liem commune: flooded 400 houses, 1 death; flooded 250ha of crops of all kinds. Hong Son commune: flooded 600 houses, flooded about 784 ha of crops of all kinds; damaged 8,520 livestock and poultry.
