Introduction

With its long coastline and low topography, the Mekong Delta in Vietnam has been facing some of the worst impacts of climate change. Seawater intrusion has been expanding in the 13 provinces of the delta in recent years, threatening its hugely productive rice fields and fruit and vegetable gardens. [1]

The Mekong Delta has a low terrain, with a coastline stretching over 600 kilometers, is criss-crossed by an intricate river network that is over 5,000 kilometers in length and ranging from several tens of meters to several kilometers in width. The shape of the delta is influenced by the deep-sea tides from the eastern and western seas of Vietnam. Seawater intrusion has resulted in salinization of about 500,000 hectares around the coastal areas. The seawater mainly intrudes into the canals and river systems during the dry season when rainfall and water levels are low (January to May). The saltwater then seeps into the groundwater and the soil destroying agricultural production.[2]

Covering about 12 per cent of the country’s total land area with 21 per cent of its population, the delta produced 24.3 million tons of rice or 56 per cent of the Vietnam’s total rice production in the year 2012.[3] Given the delta’s contribution to the national economy, economic losses caused by salt water intrusion can be significant. In 2015, losses were estimated at US$45 million or 1.5 per cent of the annual rice production in the Mekong Delta. The Government of Vietnam has built dykes and sluice gates to control seawater intrusion into the coastal provinces.[4] But despite these infrastructure efforts, the Ministry of Agriculture and Rural Development reported that (2011)[5], out of 650,000 ha of rice grown in the lower delta, annually about 100,000 ha of rice is at risk to salinity intrusion. This situation is more severe when there is water scarcity after the end of the rainy season.

Along with climate risks, the delta is also facing fluctuating water levels due to the many dams being built upstream in the Mekong River that further worsen salinity intrusion especially in the dry season when the river flows are lower.

Seawater intrusion in the Mekong Delta

According to recent data [6], salinity intrusion has increased the salt content of water in the delta’s intricate system of rivers and irrigation canals. Salinity (4g/l) expanded through the Tien and Hau Rivers by up to 45- 65 km and 55-60 km, respectively, considered to be the most extensive salinity intrusion in the last 90 years.[7]

In early 2016, saltwater intrusion appeared two months earlier than usual, and spread more widely and deeply into the major tributary rivers of the Mekong River in the western area, including the Tien, Hau, Vam Co and Cai Lon Rivers.

In some areas, saltwater intruded as much as 90 km inland and was measured at 20-30 km deeper than in previous years. The salinity rates were measured at 8-9% in some of the river estuaries. The Hau and Tien Rivers, the main source of freshwater in the region, have become unusable for irrigation with salinity levels in excess of 5%, way above the usual level of 1-2% in December. The residents in An Bien, An Minh and Kien Luong districts in Kien Giang province have reported facing tremendous difficulties caused by the shortage of potable water. In many areas, people have to drill wells up to 90 meters in depth to get groundwater. In Ben Tre Province, 160 out of 164 communes lack freshwater for domestic use. They save freshwater in different ways such as bathing with alum water before using a little amount of rainwater stored from the previous rainy season.

The delta provinces of Kien Giang, Soc Trang, Bac Lieu and Ca Mau are the hardest hit by saltwater intrusion. The rice farmers in Kien Luong, An Bien, An Minh, Vinh Thuan and U Minh Thuong districts have tried hard to save their standing rice crop but failed. A rice farmer, Mr. Nguyen Van Phuong in Ca Chanh hamlet, Phong Dong commune, Vinh Thuan district lost his entire rice field due to a shortage of fresh water.

Losing their yields: Farmers in Cu Lao Dung district, Soc Trang province

In Cu Lao Dung district of Soc Trang province, approximately 31,000 hectares of rice fields, upland gardens, fruit orchards and shrimp farms have been damaged affecting 24,000 hectares of rice and sugarcane cultivation and more than 23,000 farming families. In this district, sugarcane is the main income for farming households.

Mr. Nguyen Van A, in Binh Thanh A hamlet, My Chanh commune, has been cultivating sugarcane for more than 20 years. He said that he lost his entire sugarcane field of 0.5 hectares in 2015 due to saltwater intrusion.

Usually sugarcane planting starts in February and is harvested in February of the next year. In 2015, saltwater started seeping in from November destroying many sugarcane fields. Moreover, of the little sugarcane crop that survived, the plants were stunted in growth affecting the quality of the yield and making it difficult to sell. Farmers also had to pay more money for electricity as they add to pump groundwater to use in their fields. Faced with mounting crop losses, many farmers had to borrow money at high interest rates and fell further into poverty. As crops are damaged and farmers lose income, the younger people are beginning to migrate out of the rural areas to find work, splintering families as older parents or young children are left behind at home while their parents have moved away.

References

[1] Hook, J., Novak, S., Johnston, R. (2003). Social Atlas of the Lower Mekong Basin. Mekong River Commission, Phnom Penh. ISSN: 1727-1800.
[2] A-T. Le, C. Suppakorn, “Climate change in the Mekong River Delta and key concerns on future climate threats”. Paper submitted to DRAGON Asia Summit, Siem Riep, Cambodia (2009).
[3] GSO (General Statistical Office) (2013). Statistical Yearbook 2012. Statistical Publishing House, Hanoi, Vietnam.
[4] Binh N. T. (2010). Vulnerability and Adaptation to Salinity Intrusion in the Coastal Province of Tra Vinh, Vietnam. In: Setiadi, N., Birkmann, J., Buckle, P. (Eds) Disaster Risk Reduction and Climate Change Adaptation: Case Studies from South and Southeast Asia. SOURCE Publication Series of United Nations University, Institute for Environment and Human Security, No. 14/2010, 32-39pp.
[5] MARD (Ministry of Agriculture and Rural Development) Rice Production Evaluation for 2010 and Work Plan for 2011 for the Southern Vietnam. Agricultural Publishing House, 129- 146pp.
[6] DWRM. 2016a. Summary of water sources, drought and salinity intrusion updated on 15 April 2016. Department of Water Resources Management. Ministry of Agriculture and Rural Development. URL: http://www.tongcucthuyloi.gov.vn/Tin-tuc-Sukien/catid/79/item/2702/tong-hop-tinh-hinh-nguon-nuoc–han-han–xam-nhap-m. Accessed date: 15 April 2016.
[7] DWRM. 2016b. Salinity intrusion in the Mekong River Delta (2015-2016), drought in the Central and Central Highlands regions and solutions. Department of Water Resources Management. Ministry of Agriculture and Rural Development. URL: http://www.tongcucthuyloi.gov.vn/Tin-tuc-Su-kien/Tin-tuc-su-kien-tonghop/catid/12/item/2670/xam-nhap-man-vung-dong-bang-song-cuu-long–2015–. Accessed date: 25 May 2016.