Saltwater intrusion in the Mekong Delta is increasingly severe and unusual

On April 25, reporting on the prevention and control of drought and saltwater intrusion in the Mekong Delta, the Department of Irrigation (Ministry of Agriculture and Rural Development) cited data from the International Mekong River Commission for Before 2012, the impact from the upstream to the area is still small, the flow is close to natural laws.

But by 2024, countries have built 128 lakes (13 lakes on the main stream, 115 lakes on tributaries) with a capacity of about 88 billion m3, expected to increase to 90-95 billion m3 by 2030 and will reach 120 billion m3. billion m3 when completing 231 lakes according to the planning period 2040-2060.

In the future, when upstream countries complete reservoirs as planned, with rising sea levels, climate change, lowering of river beds, saltwater intrusion will tend to be more severe and unusual. The level of penetration deep into the mainland is generally 5-7 km higher than the average for many years; Serious droughts and saltwater intrusions such as the dry season of 2015-2016 and 2019-2020 appear more frequently.

Saltwater intrusion tends to affect freshwater sources in the Mekong Delta 1-1.5 months earlier than before. Before 2012, salinity usually came from February to April, with peak salinity at the end of March-April, which is the month with the lowest flow. Currently, in years when the upstream flow is low, salinity intrusion appears from the end of December last year, with salinity peaking in February or early March.

From April 2024 until now, saltwater intrusion in coastal areas has increased, and at some times salinity levels have increased dramatically. As on April 18-22, at Cai Tu bridge (Cai Lon river) salinity was more than 3-4 g/liter, at Bac Hong Dan more than 10 g/liter, affecting water collection for agricultural production in the provinces. Kien Giang, Hau Giang, Bac Lieu, Soc Trang.

The Department of Irrigation explains that the cause of the above situation is that the upstream water source to the Mekong Delta in April 2024 was low, combined with prolonged heat and high water evaporation. Localities simultaneously planted summer-autumn crops, causing the water level in the fields to drop rapidly.

In addition, the work to demarcate internal water sources has not been completed, and salt water from the East Sea through the Quan Lo – Phung Hiep irrigation system serving aquaculture for Bac Lieu province has increased the salinity of water resources of Bac Lieu province. Cai Lon – Cai Be system.

In general, compared to the historical saltwater intrusion events of 2015-2016 and 2019-2020, the salinity boundary depth of 4 g/liter of the 2023-2024 saltwater intrusion period is lower. However, due to a lack of rainfall, especially in many places there has been no rain for a whole month, combined with continuous heat has increased the impact in some localities, especially Ca Mau.

According to statistics, up to now the Mekong Delta has about 1,580 hectares of rice (1,530 hectares in Soc Trang, 50 hectares in Ben Tre), 4,640 hectares of lemon and other fruit trees in Long An that are at risk of reduced productivity. 43 hectares of rice in Soc Trang province were completely lost. About 73,900 households (2.1% of rural households) suffer from water shortages concentrated in seven provinces of Long An, Ben Tre, Kien Giang, Tra Vinh, Soc Trang, Bac Lieu and Ca Mau, lower than last year. 2019-2020 (96,000 households).

Depleted water sources have caused land subsidence, landslides along canals, ditches, and combined roads along canal banks in freshwater areas in Ca Mau and Kien Giang. In total, there were 901 subsidence and landslide points with a total length of 23.4 km (Ca Mau 601 points, 15.9 km long; Kien Giang 310 points, 7.5 km long).

It is forecasted that in the Mekong River estuary region, from May, saltwater intrusion will decrease, no longer affecting water sources for agricultural production from the beginning of June. In the Vam Co River area, saltwater intrusion will tend to increase. , is likely to reach its highest peak on April 23-27 or May 6-10 and remain at a high level until the end of May. From the end of June, drought and salinity decrease rapidly.

Viet An