In August and September 2022, the operation and management units of hydropower reservoirs in the Vu Gia River basin will discharge more water in a bid to ensure adequate water supply for the daily lives, and production activities, across Da Nang, especially on the upcoming holiday for National Day (September 2).

Dawaco is in rush to build the raw water pumping station on the upstream of the An Trach Dam to ensure the ability to overcome the flood from late August, 2022. Photo: HOANG HIEP

At the same time, the units are urgently taking drastic solutions to guarantee sufficient water supply for the city in 2023 - the year when El Nino phenomenon is forecasted to return, causing hot and dry weather conditions.

Hydropower plants increase water discharges to push salinity

Since early this year, hydropower plants in the Vu Gia - Thu Bon river basin have been mobilized to generate electricity by discharging water to downstream areas due to a lot of rain in the Vu Gia - Thu Bon river basin and difficulties facing coal-fired power plants and gas turbines. A large volume of water discharged from hydroelectric reservoirs, rivers and streams, has helped push the salinity out of the Cam Le River.

Therefore, except for March 7 and the period from March 23 - 30, 2022, when the high salinity level recorded at the Cau Do (Red Bridge) Water Supply Plant’s raw water intake on the Cam Le River, during this year's dry season, the raw water supply to the Cau Do Water Supply Plant is almost free from saline intrusion.

Especially, during periods of peak summer hot and tourist season in Da Nang, hydropower plants are mobilised to generate more electricity, so the water reserve is large. Therefore, the Da Nang Water Supply Company (Dawaco) directly takes fresh water in the Cam Le River in service of production activities and daily lives of local residents.

As noted by our reporter, on the afternoon of August 1, the water level of the Yen and La Tho rivers was 0.65m higher than the overflow threshold at the dams of An Trach, Ha Thanh, and Bau Nit, helping the Cau Do Water Supply Plant’s raw water intake on the Cam Le River be almost free from salinity.

Meanwhile, the water level in the A Vuong hydropower reservoir was 26m and 16m higher than the dead water level and the prescribed minimum water level respectively.

The water level in the Dak Mi 4 reservoir was 5.5m higher than dead water level and 1m higher than the regulated minimum water level, and that in the Song Bung 4 reservoir was 8m and 3m higher than the dead water level and the prescribed minimum water level respectively.

Thus, in August 2022, hydropower reservoirs on the upstream of the Vu Gia River will all have to discharge water to the downstream areas with a large volume, and the time of day water discharge may be longer to ensure flood control. The volume of discharged water can completely push salinity out of the Cam Le River.

Director of the Song Bung Hydropower Company Le Dinh Ban informed that, in June and July, the two Song Bung 4 and Song Bung 2 reservoirs were alternately repaired, so they generated electricity through water discharge in moderate level.

Currently, there is still much water in the two hydroelectric reservoirs compared to last year, so the company is actively running generators through water discharge to lower the water level at the two reservoirs to ensure their safe operation during the upcoming flood season.

Deputy General Director of the A Vuong Hydropower JSC Ngo Xuan The said that the water level in the hydropower reservoir is still high, so during the rest of the dry season and the beginning of the flood season as well, there will be a lot of fresh water. Therefore, Dawaco will not have to build any dams and reduce the cost of pumping fresh water while still ensuring the adequate water supply for production and daily activities in the city.

Currently, the water level in the A Vuong hydropower reservoir is at a high level. so the reservoir will increase water discharge during the end of the dry season in order to push saline water at the Cau Do Water Plant. Photo: HOANG HIEP

Urgent preparedness and response to El Nino

El Nino is forecasted to come in 2023, so the management and operation units of hydropower reservoirs in the Vu Gia river basin are on track to prepare necessary conditions to ensure safe reservoir operation, effectively reduce floods for the downstream areas and store water at the end of the flood season in accordance with the process in order to meet the requirements of electricity generation and water supply for downstream areas.

To effectively exploit water sources discharged from reservoirs, Dawaco is in rush to implement a project to increase the daily capacity of An Trach anti-salinity pumping station from 210,000m³ to 420,000m³. The project is expected to be completed in the first quarter of 2023.

Dawaco General Director Ho Minh Nam informed construction units poured concrete over the wall of the pumping station on August 3. By late August, the concrete pouring of the pump station’s wall will rise above the ground, ensuring the ability to overcome floods for this work item.

As for raw water pipe line with 7,397m in length and 1.2m in diameter, more than 50% of the length of the pipeline has been installed.

Reporting by HOANG HIEP - Translating by M.DUNG