Exploitation combined with subsidence require adaptive water management Mekong Delta

Published: 24 October 2019

Agricultural areas devoted to rice crops have transformed Vietnam into one of the world’s leading rice producers, while aquaculture and fruit growing are also found in the Mekong Delta. This delta covers roughly 40,000 km2 and is home to more than 18 million people. More than three quarters of the delta’s population depend on agriculture for their livelihoods, while the average farm is only 1.2 hectares (0.012 km2). Freshwater availability during periods of drought like the severe drought of 2016, prolonged dry seasons and changing environmental conditions are some of the many challenges these farmers face.

Drought, salinization and subsidence

Prolonged periods of drought have forced farmers to increase their use of valuable deep groundwater. Delta-wide challenges that have been attributed to the overexploitation of groundwater include increased salinity in the freshwater system due to saltwater intrusion and landsubsidence on the scale of the entire delta. With the Mekong Delta’s highest point only 80 cm above sea level, subsidence is an additional challenge when outlining adaptive measures.

The rise in sea level

Recent climate-change reports show scientifically based scenarios include conservative estimation of sea level rise of over half a meter by the end of the century. Combined with the sinking delta, the livelihoods of the inhabitants of the Mekong Delta will be threatened. Doing nothing is not an option.

Time to act together

The initial call to action of the Netherlands Enterprise Agency (RVO) resulted in the drawing up of sustainable adaption and mitigation plans for the Mekong Delta that focus on farm-scale water storage. Deltares, Royal HaskoningDHV, WUR, Nelen & Schuurmans and local climate and water authorities, including the Center of Water Management and Climate Change (WACC) and the Division for Water Resources Planning and Investigation for the South of Vietnam, were invited to create an integrated approach that would improve and optimize freshwater availability in Ben Tre and Tra Vinh provinces.

Investigating and developing adaptive water management

The FAME project (Freshwater Availability in the Mekong Delta) program includes scoping, piloting and opportunity mapping phases. It aims to (i) collect hydrogeological data that can be used in the selection of possible shallow Aquifer Storage and Recovery (ASR) locations; (ii) create an overview of potential ASR technologies for the farm-scale storage of freshwater; (iii) monitor the surface and subsurface at viable locations; (iv) assess the potential for upgrading existing systems that are congruent with water security and sustainable water-use practices; and (v) provide recommendations for upscaling potential ASR measures across the Mekong Delta using lessons learned from the pilot locations.

Exporting the aquifer storage and recharging pilots

ASR systems have been tested and applied in the Netherlands and other countries like Australia, Israel and the USA. This technique allows suitable rain- and surface water to be infiltrated or injected into the subsoil and stored for use in times of freshwater shortage. Rainwater run-off to the sea is thus avoided and precious freshwater can be stored safely in the subsoil. These efforts will reduce the salinization of the subsoil and inland water systems as well as provide a water-management framework in which water resources are managed in a sustainable manner. By addressing these topics localized water quality and quantity problems in the catchment areas of the Ben Tre and Tra Vinh provinces can be managed. Farmers will then have access to enough clean water in dry periods and will be able to grow their crops without depleting deep aquifers or increasing land subsidence.

Guaranteeing continuity

The FAME project is based on a continuing partnership and knowledge exchange between European project partners and Vietnamese authorities, professionals and local communities. Workshops will help water managers and other local actors to detect, understand and analyze the water-supply versus demand paradigm and realize how it can affect their farming operations.

Follow the FAME project here