Ensuring dam safety during flood season

(Baonghean) - The Northern Irrigation System (located in Yen Thanh, Dien Chau, Do Luong districts) has over 17 large reservoirs managed by the Northern Irrigation Company Limited, and over 250 small dams managed by localities. Currently, only a few large reservoirs have been upgraded, the rest are severely degraded, posing a risk of being unsafe during the flood season.

Ready "4 on the spot"

Following the forest road, we arrived at Ve Vung reservoir, Dong Thanh commune - Yen Thanh. This reservoir was built in 1973, in 1978 the dam body broke causing serious consequences, in 2007 it was invested in repairing and upgrading with the dam body height of 16.4 m, the upstream roof was paved with dry stone. The basin area of ​​the reservoir is up to 37 km2, the storage capacity is nearly 20 million m3 of water. Although upgraded, Ve Vung dam is not safe, the reason is that in the basin of Ve Vung reservoir there are more than 40 small reservoirs in Kim Thanh, Tay Thanh, Quang Thanh communes that have been degraded for a long time, heavy rains if these reservoirs break in succession will pour water causing the risk of breaking the Ve Vung dam body.

At Thi Long dam (Quang Nhan hamlet, Quang Thanh commune, Yen Thanh) - a small reservoir located in the basin of Ve Vung lake, the water is full, the banks are thin. Mr. Tran Van Ky - Quang Nhan hamlet chief, who has been assigned by the commune to manage the lake for more than 5 years, shared: "I mainly rent it to raise fish and am responsible for releasing water to irrigate rice fields for the people. During the rainy and flood season, managing the lake is very difficult, because the lake is degraded, there is no professional level, I only know how to mobilize people to contribute bamboo poles to prevent dam breakage". In Quang Thanh commune, there are currently 31 small reservoirs located in the basin of Ve Vung lake, of which 4 have just been upgraded, the rest are mostly degraded. Mr. Hoang Van Bay - Chairman of Quang Thanh commune People's Committee admitted that the commune has too many small dams, mainly upgraded and repaired by the hamlets themselves, so most of the dams are degraded, during the rainy and flood season, 3-4 small dams often break. This year, since the beginning of the season, there has been a lot of rain, so most of the reservoirs are full of water. If the rain continues, the risk of small dams breaking will be very high. To deal with the above situation, the commune can only mobilize people to be on duty, prepare some bamboo poles, and prepare a plan to evacuate people.

Faced with the above situation, to ensure the safety of Ve Vung reservoir, Yen Thanh District People's Committee has issued a Decision to establish a Steering Committee for Flood and Storm Prevention and Control of Ve Vung reservoir, headed by Mr. Thai Van Thanh - Chairman of Dong Thanh Commune People's Committee. The core standing force is the staff of Ve Vung reservoir cluster with 12 people taking turns on duty 24/24 hours, monitoring, reporting on the project, and handling technical incidents of the project. Regarding the technical plan for the proposed situation, if there is heavy rain exceeding the design frequency, the plan to discharge water through the spillway will be implemented. In addition to 30 m3 of rubble and over 30 m3 of sand prepared by Yen Thanh Irrigation Enterprise, Dong Thanh commune has mobilized people to contribute over 1,000 sacks, straw and over 400 bamboo trees, when necessary, over 1,000 people can be mobilized to handle the incident.

Don Hung Reservoir (Hung Thanh Commune - Yen Thanh) was built in 1973, in 1978 a 120 meter dam broke. According to observations, we saw that the dam body sank in many places, causing cracks in the breakwater. The upstream rock slope sank 15-20 cm, the dam body and dam slope were leaking in many places. Le Thanh Hai - Head of Don Hung Reservoir Cluster said: Don Hung Reservoir is currently the weakest reservoir, with a high risk of dam breakage, so the Cluster always improves management; construction maintenance, and paving of peeling stone on the downstream slope. During heavy rains, 5 officers are on duty 24/24 hours to measure and monitor, collect meteorological and hydrological factors in the reservoir basin, seepage and water leakage through the dam body, dam foundation, dam shoulder, cracking and landslides at the dam body. In 2014, the reservoir expanded the auxiliary spillway to 20 meters wide. The cluster actively checks the extrusion circuit through the dam body, water leakage due to termites, and increases water discharge through the main spillway and emergency spillway.

According to Mr. Ho Ngoc Mai - Director of Bac Irrigation LLC, the company manages 17 reservoirs, 4 of which have been upgraded, the remaining reservoirs are weak. To ensure the safety of reservoirs during the flood season, the company has implemented "4 on-site" work such as strengthening the PCBL steering committee, preparing basic materials at the foot of the reservoir... For level I alarm, the permanent units at the construction site check every 3 hours on the dam line to detect leaks, seepage, subsidence, termite nests and organize treatment. For level II alarm, the forces check 24/24h, mobilize reserve materials to the foot of the construction site at vulnerable places. Mobilize local shock forces on-site to the construction site and deploy soil to prevent overflow, landslides, and waves. Emergency alarm, high concentration on preventing water from overflowing the dam, choosing a location to lower the water level in the lake according to technical plan, using soil sacks to prevent overflowing the dam crest, preventing waves from damaging the upstream slope, evacuating people downstream to safety.

Actively upgrading small dams

Faced with the situation of weak dams, some districts have made efforts to upgrade and maintain small reservoirs. At Khe May reservoir in Quynh Tan commune, which was previously in a state of serious degradation, in 2012, Quynh Luu district People's Committee implemented the upgrade of Khe May dam with a total value of over 17.8 billion VND. In difficult conditions of lack of capital, the district People's Committee has only disbursed 10 billion VND, the district has encouraged the construction unit to continue the construction, up to this point the reservoir has completed over 90% of the volume. We were present at the construction site when the workers were actively completing the public road item, Ms. Nguyen Thi Mau - project commander said: The dam body is 480 m long, 8 meters high, poured with reinforced concrete upstream roof. Up to this point, Quynh Luu has completed the construction of 6 reservoirs managed by the locality, continuing to construct Khe Sau and Khe Binh reservoirs in Quynh Chau commune, Thung Da reservoir in Quynh Thang...

Reservoir embankment of Quynh Chau commune (Quynh Luu).

Do Luong district is also simultaneously implementing the construction of 6 reservoirs including Khe Chuoi lake and Quan Dong lake in Dai Son commune, Bau Nai lake in My Son, Phu Cuong lake in Dang Son, Khe Mai lake in Giang Son. According to Mr. Tran Doan Hung - Head of Do Luong Agriculture Department, some construction units have made efforts to invest capital to ensure the progress of the flood-proofing, the District People's Committee has urged the completion of important items such as culverts and spillways for unfinished dams before the flood season. For Yen Thanh district, up to this point, more than 10 small reservoirs have been upgraded, the district is implementing the construction of 7 reservoirs and is trying to complete them before the flood season.

Mr. Nguyen Truong Thanh - Deputy Head of the Irrigation Department said: The whole province has 625 large and small reservoirs, while the number of upgraded dams only accounts for less than 15%. Regarding reservoir management, there are currently 2 models. The model managed by LLCs is quite effective, because the dam management staff are all trained in basic professional skills, and some large dams have been upgraded. As for local reservoirs, the communes mainly assign them to cooperatives and individuals to manage, because they have not been trained in reservoir management, they mainly discharge water for rice irrigation, and there is no operating procedure, so it is very confusing when an incident occurs. To minimize the damage caused by floods, localities need to further strengthen the direction of not storing water in reservoirs beyond the level prescribed by competent state management agencies. During the flood season, reservoirs are responsible for flood regulation. The operation of water storage and flood discharge must prioritize dam safety, flood control and reservoir water storage according to the project's tasks. Develop a plan to prevent and control floods for downstream areas in case of emergency flood discharge and dam breakage before water storage. It is necessary to organize training, retraining, and capacity building for reservoir management and operation forces.

Van Truong