By Le Thanh Binh
HO CHI MINH CITY | 28 March 2024 (IDN)—The Mekong Delta region in South Vietnam is a major food production base for the country. Approximately two million hectares of land are allocated for rice and fruit farming, and about a third of this land is regularly affected by drought and salinity during the dry season.
The Ministry of Agriculture and Rural Development is urgently adjusting the operation mechanism of irrigation works in the Mekong Delta, shifting from saltwater prevention to freshwater regulation for rice production.
Facing the challenge of declining freshwater sources, the agricultural sector is promoting water-saving irrigation programs for drought-resistant crops. The goal by 2025 is to have 700,000-800,000 hectares nationwide practicing water-saving irrigation.
Salinity Could Appear Earlier
Analyzing the saltwater intrusion situation during the 2023-2024 dry season, the latest water forecast by the Southern Institute of Water Resources Science for the Mekong Delta region indicates that the water levels flowing into the Mekong Delta at Tonle Sap and Kratie station in upstream in Cambodia, are lower than the dry seasons of 2017-2018 and 2022-2023.
Due to the limited water supply to the Mekong Delta in the 2023-2024 dry season, combined with the influence of El Niño, the possibility of salinity intrusion in the 2024 dry season is higher than the average of many years.
The Southern Institute of Water Resources Science also predicts that salinity may appear earlier and deeper than the average of many years. From February to March, salinity increases significantly, limiting water availability for irrigation in production areas located 50-65 km from the coast. Therefore, localities in the Mekong Delta need to operate salt control structures effectively to store water for agricultural production.
By the end of January, upstream areas of the Mekong Delta, including An Giang, Dong Thap, upper Long An, Kien Giang, and Can Tho City, had ensured water supply for agricultural production.
In mid-January, areas in the middle of the Mekong Delta with salinity levels of 4 g/l are most affected at river mouths—about 30-45 km from the coast. For coastal areas, water sources are currently sufficient, but freshwater reserves and enhanced monitoring of salinity levels are needed to ensure production during dry months.
Proactive Solutions in the Mekong Delta
Therefore, the Mekong Delta region needs to proactively develop suitable solutions to cope with and prevent salinity intrusion based on the conditions of each area.
Salinity intrusion may also occur unusually in coastal areas, affecting water sources and irrigation systems such as Go Cong, Northern Ben Tre, Tra Vinh coastal areas, and the Long Phu-Tiep Nhut system. Localities should prepare response plans and proper water storage before saltwater intrusion, especially in fruit tree cultivation areas in Chau Thanh, Cho Lach, Northern Mo Cay, Southern Mo Cay Districts of Ben Tre Province, and Ke Sach District of Soc Trang Province.
Based on these assessments, in addition to urgently dredging irrigation channels, localities in the Mekong Delta are actively operating irrigation works according to the actual water source situation.
The Irrigation Company of Soc Trang Province has deployed staff to monitor the sluices 24/7 to extract freshwater into the internal canal timely. Simultaneously, maintenance, repairs, and upgrades to the sluice system across the province are being carried out to ensure no saltwater leakage during saltwater intrusion in the Bassac River and My Thanh River. The irrigation canal system is dredged to serve freshwater storage, benefiting farmers and supporting agricultural production.
Currently, Soc Trang Province has 635 sluices, 1,000 km of canals, and 95 km of coastal dikes. In reality, this irrigation system does not fully meet the production requirements in the province.
Recently, the Ministry of Agriculture and Rural Development has approved an investment in a sluice system along the National Highway South of the Bassac River from Mop Canal to the long sluice systems of An Lac Commune, Ke Sach District. Once completed, this irrigation system is expected to effectively control water sources and ensure the success of fruit tree cultivation in Soc Trang Province.
Emphasize preventive factors
According to the National Meteorological and Hydrological Forecasting Center, during the dry season of 2023-2024, there is little possibility of off-season rainfall. Temperatures are expected to be higher than the average of many years, ranging from 0.5 to 1.5 degrees Celsius. This poses a risk of increased evaporation, raising the demand for water for crops and livestock.
The water supply to the Mekong Delta in the dry season of 2023-2024 is expected to be deficient by 10-15% compared to the average of many years. Freshwater availability is challenging from the beginning of the dry season, especially in coastal areas and areas far from the main stream of the Mekong River.
Currently, the atmospheric and oceanic conditions are in an El Niño phase. From February to April 2024, El Niño is expected to persist with a probability exceeding 90%. From late January to April 2024, the total flow on the Mekong River downstream and in the Mekong Delta will decrease by 5 – 10% below the average of many years. The water level in the Mekong River changes slowly, with a declining trend.
According to Le Xuan Hien, Director of the Meteorological and Hydrological Station of Kien Giang Province, the salinity intrusion during the 2023-2024 dry season on the Cai Lon and Cai Be rivers occurred earlier than average by about 10-15 days. Currently, the highest salinity level at Go Quao Station (35 km from the coast) is 2.7‰, higher than the average of many years by about 1‰, and higher than the same period in 2023 by about 2.5‰.
Off-season rainfall, coupled with intense sunlight and high temperatures, is scarce during the dry season, leading to increased evaporation and higher salinity levels than the average of many years.
For agricultural production, it is essential to have a suitable production plan, select crops and livestock that use less freshwater, and plan to prevent forest fires during the peak months of the dry season (March-April).
Historical experiences from previous drought and salinity intrusion events show that preventive measures must be implemented early and prioritized. These measures should be applied vigorously yet flexibly, tailored to the specific conditions of each locality.
In Kien Giang Province, the agricultural sector has taken proactive measures since the beginning of the dry season, including operating sluices reasonably to prevent salinity, retaining freshwater, and ensuring a water supply for agricultural production.
Simultaneously, 27 out of 58 embankments to prevent salinity were newly constructed or reinforced according to the seasonal schedule to protect fruit tree cultivation areas and the winter-spring rice crop in 2023-2024, ensuring freshwater for both production and daily life for the region inside the embankments of the U Minh Thuong National Park buffer zone.
Hien advised that small islands and coastal areas in the Mekong Delta need to proactively store domestic water and have a supplementary plan for domestic water supply for residents. [IDN-InDepthNews]
Photo: Vietnamese farms grow a variety of food. The picture was taken in 2009 before water salination problems and droughts crept in. Credit: Dennis Jarvis, CC BY-SA 2.0
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