Adaptive irrigation: A long-term solution

The Mekong Delta is facing three major challenges: upstream Mekong River impacts, impacts of the sea, and internal challenges. These are serious factors, and external factors are nearly uncontrollable and require a scientific and proactive approach, while internal challenges demand long-term adaptive responses.

Three major challenges

From the upstream, the construction of reservoirs and the intensifying use of water have altered the flow regime to the Mekong Delta, causing a severe decline in silt load. This directly impacts alluvial deposition and ecological stability. However, there are also positive aspects, including reducing floods in the upper regions, increasing dry-season flows, and partly mitigating saltwater intrusion along the coast.

From the sea, the gradual rise in average sea level over time has made flooding and saltwater intrusion increasingly complex. Meanwhile, the delta itself is under heavy pressure from land subsidence, averaging 1–3 cm/year, far exceeding the rate of sea-level rise. As a result, the Mekong Delta is sinking rapidly, creating the risk of widespread and prolonged inundation, which is emerging as the greatest long-term challenge in the future.

According to MSc Tran Minh Tuan, Director of the Center of Water Supply and Irrigated Agriculture Research (Southern Institute of Water Resources Research—SIWRR), the combined impact of these three factors has been posing a series of serious challenges, such as water security, large-scale flooding, and delta degradation (riverbank and coastal erosion, terrain lowering). In this context, there ca be no strategic direction but controlled adaptation, meaning proactive planning of production and development based on water availability. For sustainable development, the Mekong Delta requires proactive irrigation models tailored to each ecological region: brackish-water aquaculture in coastal areas, fruit farming, and rice cultivation.

In coastal zones, in the dry season with freshwater shortages, rice is heavily affected by saltwater intrusion. The SIWRR has proposed a "two-in-one" infrastructure system, including sluices to control salinity and pumping stations to store freshwater during low tide. Pumping stations such as Xuan Hoa (former Tien Giang), Ba Xam (Can Tho), and Cay Gao–Rach Dao (Tay Ninh) have already proven effective. At the same time, the multifunctional canal model (saltwater–freshwater alternating) is being applied in many areas, helping farmers to remain flexible in their production.

The shrimp–rice model is one of the successful adaptation solutions. Its cultivated area has expanded nearly fivefold over the past decade, reaching 170,000 hectares by 2024. However, the model’s stability still depends on hydrological conditions each year. To reduce risks, the SIWRR has recommended investment in large-scale irrigation structure clusters for saline–freshwater control in the North Ca Mau, Southeast Ca Mau, and Bac Lieu–Ca Mau areas during the 2026–2030 period.

For fruits, decentralized freshwater storage is considered the key solution. The Institute, in collaboration with the Department of Irrigation Works Management and Construction, has issued the Handbook on Decentralized Water Storage and Efficient Irrigation Techniques to guide farmers in managing specific crops, especially during the saline dry season.

In floodplain areas, irrigation systems are being studied with a focus on the rational use of land and water under conditions of reduced flooding, ensuring both agricultural production and ecological sustainability.

Salinity control, freshwater storage, and flood regulation

According to MSc Tran Minh Tuan, three core solutions are essential to ensuring water security for the delta, including saltwater intrusion control, multi-level freshwater storage, and reasonable in-delta flood regulation.

Among these, salinity control is pivotal, protecting freshwater sources from contamination. Freshwater storage needs to be implemented on large and household scales, forming an interconnected network. In particular, salinity forecasting across multiple time horizons will provide effective support for the operation of irrigation works.

Regarding floods, irrigation system design perspectives are shifting as major floods become increasingly rare. Irrigation structures are no longer built solely for flood control but also for multifunctional purposes such as regulating water for agriculture, aquaculture, domestic water supply, and waterway transport. Rotational flood regulation within enclosed fields is also being researched to adapt to the new conditions.

The Director of the Center of Water Supply and Irrigated Agriculture Research further noted that the Mekong Delta has two particularly sensitive zones: deep-flood areas and coastal regions. In floodplains, the reduced frequency of major floods has created opportunities for year-round cultivation and production model diversification. Therefore, irrigation systems must be designed to be flexible and multifunctional, ensuring both water supply and drainage for year-round production.

Irrigation is not only water control structures but also a critical link in the chain of sustainable agricultural livelihoods in the Mekong Delta. When irrigation systems can proactively regulate appropriate water regimes, farmers can confidently produce, shift production models flexibly, and reduce risks from natural disasters.

"Ensuring water security means ensuring the survival of the Mekong Delta. Adaptive irrigation is the most long-term and sustainable solution, especially in the face of climate change," affirmed MSc Tran Minh Tuan.

To achieve this, irrigation works must not only control salinity, store freshwater, and regulate in-delta floods, but also contribute to stabilizing livelihoods, helping people to remain committed to the delta. Conversely, production activities must also be aligned with the capacity of irrigation systems. For instance, the shrimp–rice model is only sustainable when supported by proactive irrigation systems capable of regulating water regimes to meet production needs and reduce dependence on natural conditions.

"Water security, therefore, depends largely on irrigation. Particularly in coastal areas, irrigation works serve as the strongest ‘shield’ against saltwater intrusion. At the same time, irrigation helps redistribute freshwater resources among regions, contributing to ensuring overall water security for the entire delta," emphasized MSc Tran Minh Tuan.

The models currently under research and implementation demonstrate the ability of "smart coexistence" with drought, salinity, flooding, and land subsidence. At the same time, combining structural and non-structural works, from forecasting and production planning to livelihood transition, is the long-term solution.