CC BY
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LONG AN IN THE CONTEXT OF CLIMATE CHANGE IN THE MEKONG DELTA
Nguyen Minh Nguyet
Nguyen Minh Nguyet - Graduate Student, ANTHROPOLOGY FACULTY, Deputy Director, INTERNATIONAL COOPERATION OFFICE, VNU UNIVERSITY OF SOCIAL SCIENCES AND HUMANITIES, HANOI, SOCIALIST REPUBLIC OF VIETNAM
Abstract: Long An is a province with a critical function for national food security and a strategic significance due to its geographical location as a gateway between the Southeast and Southwest provinces of Vietnam. Despite the lack of an internal sea, being located near one, it has abundant seafood resources. However, Long An's geographic location is also a disadvantage. Long An's water is heavily influenced by salinity due to its low and flat topography, which is subjected to the effects of ocean tides (acidification in the upper section, salinization in the lower section). The process of saltwater intrusion in Long An is becoming increasingly intense, primarily due to climate change and increased sea levels. As a result, one of the most fundamental solutions is to use irrigation to proactively provide water for agricultural output rather than relying on increasingly depleted and saline groundwater. With results from field trips and the analysis of relevant data, the article aims to provide an overview of the natural and agricultural features and the irrigation system of Long An in the past and present, as well as advice on irrigation projects intended for providing locally appropriate solutions in light of climate change in the entire Mekong Delta.
Keywords: natural characteristics, agricultural production, irrigation, climate change.
LONG AN В КОНТЕКСТЕ ИЗМЕНЕНИЯ КЛИМАТА В ДЕЛЬТЕ МЕКОНГА
Нгуен Минь Нгует
Нгуен Минь Нгует - аспирант, факультет антропологии, заместитель директора, Офис международного сотрудничества, ВНУ Социально-гуманитарный университет, г. Ханой, Социалистическая Республика Вьетнам
Аннотация: Лонг Ан — провинция, играющая важную роль в обеспечении национальной продовольственной безопасности и имеющая стратегическое значение благодаря своему географическому положению в качестве ворот между юго-восточной и юго-западной провинциями Вьетнама. Несмотря на отсутствие внутреннего моря, находясь рядом с ним, она обладает богатыми запасами морепродуктов. Однако географическое положение Лонг Ана также является недостатком. Вода Лонг-Ан сильно подвержена солености из-за ее низкого и плоского рельефа, который подвержен воздействию океанских приливов (закисление в верхней части, засоление в нижней части). Процесс проникновения соленых вод в Лонг Ан становится все более интенсивным, в первую очередь из-за изменения климата и повышения уровня моря. В результате одним из наиболее фундаментальных решений является использование орошения для активного обеспечения водой сельскохозяйственного производства, а не полагаться на все более истощающиеся и засоленные грунтовые воды. На основе результатов полевых поездок и анализа соответствующих данных цель статьи состоит в том, чтобы предоставить обзор природных и сельскохозяйственных особенностей и ирригационной системы Лонг Ан в прошлом и настоящем, а также рекомендации по ирригационным проектам, предназначенным для обеспечения местных условий. решения в свете изменения климата во всей дельте Меконга.
Ключевые слова: природные особенности, сельскохозяйственное производство, орошение, изменение климата.
Long An is located in the wetlands of Dong Thap Muoi, yet it is still considered a thirsty land in Vietnam's Southwest region from a geo-historical perspective. Drought and seawater intrusion become more intense during the dry season, affecting agricultural production and local people's lives for several months every year. Canal irrigation systems have made a substantial contribution to the growth of agricultural productivity and the creation of stable water sources for the local population. However, in today's context of increasingly complex climate change, rather than relying solely on construction-based solutions such as building canals to trap water for deacidification and desalization, which are too drastic and can disrupt the region's topographical structure, adaptive and flexible solutions are required to not only achieve the goal of economic growth but also to ensure ecosystem conservation and resilience.
In this article, the natural and hydrological characteristics of the Long An region are first described, followed by the process of establishing of a canal system there. The article's next section discusses the effects of climate change on agricultural activities and said canal system, before offering recommendations for the region's future agricultural and irrigation development projects.
1. Long An from a geohistorical standpoint
Long An was an important part of the Funan-Chenla empire in ancient times. The territory of Long An belonged to Gia Dinh court when Nguyen Huu Canh was dispatched to explore Southern Vietnam. Cochinchina was divided into 21 provinces during the French colonial period, and Long An encompassed the Tan An and Cho Lon provinces [9, p. 90]. Long An was formed on October 22, 1956, when the Republic of Vietnam merged the provinces of Cho Lon and Tan An, with Tan An as the provincial headquarters. It combined with Kien Tuong and two districts Duc Hoa and Duc Hue of Hau Nghia province in 1976 to create a new Long An province [9, p. 100].
Long An is situated in the Mekong Delta, at the crossroads of Vietnam's Southeast and Southwest regions. It shares borders with Tay Ninh province, Ho Chi Minh City, and Cambodia's Svay Rieng to the north. It is bordered on the south and southwest by the provinces of Tien Giang and Dong Thap, and on the east and northeast by Ho Chi Minh City. Long An shares a border with Cambodia's Prey Veng to the west. The city of Tan An, the town of Kien Tuong, and the districts of Ben Luc, Can Duoc, Can Giuoc, Chau Thanh, Duc Hoa, Duc Hue, Moc Hoa, and Tan Hung, Tan Thanh, Tan Tru, Thanh Hoa, Thu Thua, and Vinh Hung are among the 15 district-level administrative divisions of the province [3].
Despite its location in the Mekong River Delta, Long An is a transitional area between Vietnam's Southeast and Southwest regions, therefore its terrain is formed to be lower from northeast to southwest and has a variety of ecological characteristics. This location has both the high and low topography of ancient and modern alluvial deposits. A huge seaward flatland with high and low giong ("rising alluvial sands") interspersed across the province, as well as various coastal marshes, swamps, and marshy glades, can be found in the vast Dong Thap Muoi area. "Mosquitoes sing like flutes, and leeches abound like pancakes" there (local idiom). Although the land of Long An is large, stretching from the banks of the Soai Rap river to the Vietnam-Cambodia border, the majority of it is acidic soil, accounting for 46% of the natural area, compared to 15% in the Mekong Delta and 70% in the Dong Thap Muoi region. The South China Sea (East Sea in Vietnam) intrudes into Long An via the Soai Rap estuary, which is triggered by the semidiurnal tidal cycle. Saltwater intrusion occurs at a rate of 2 to 4 grams/liter from January to June [3].
Long An has a typical sub-equatorial monsoon tropical climate, with varying heat and humidity and plenty of sunshine. The average monthly temperature is between 27.2 and 27.7 degrees C. This is a very advantageous element that allows year-round intensive cropping. The Northeast monsoon, which lasts from November to April, and the Southwest one, which lasts from May to October, are the two prevailing monsoons. The Southwest Monsoon transports a large amount of water vapor, which can easily result in rain. The northeast wind, termed "wicked wind" by locals, surges in the coastal area during the northeast monsoon season. In the late afternoon and at night, the wind blows from the sea inland. It runs parallel to the main river tributaries, forcing saline water to flow into the rivers and inland, especially between February and May, when water demand is high.
2. Long An, a thirsty land amongst wetlands
The average annual rainfall in much of the Long An area is classed as low in the south, ranging from 1,600 to 1,740 mm/year, compared to roughly 1,800 mm/year in Southern Vietnam [2, p. 33]. The Southern climate, which includes Long An, has a seasonal rain distribution. Rainfall is concentrated in the rainy season, accounting for 70 to 80 percent of the total annual quantity, with the wettest months being September and October. Excess water overflows the surface of the mound area due to the severity of heavy rain, causing soil erosion. Rain, along with floods and high tides, inundates the fields in lowland locations. Since Long An lacks fresh water, farming activities rely on water acquired from strong rains, particularly in the districts south of National Highway 1. The rainy season is thus a time of high productivity; yet, protracted droughts (locally known as "Ba CMn droughts") are common due to weather variations, resulting in precarious crop productivity and low efficacy. To fix the problem, technical solutions such as active irrigation must be promoted.
Two huge rivers, Vam Co Dong (East Vam Co) and Vam Co Tay (West Vam Co), run through Long An. The two rivers unite into a 40-kilometer-long stream before entering the Soai Rap estuary, and they are both designated as Vam Co. The third river, Can Giuoc, is essential in terms of waterway transit, connecting Ho Chi Minh City to the Mekong Delta's rich region, despite being shorter and narrower than the two preceding rivers. Long An, similar to the rest of the Southern region, has a network of natural canals such as Cai Cai, Cai Co, and Long Khot, as well as a system of interlaced canals connecting rivers and areas, forming a regionwide system of extremely convenient waterways, to the point where people can travel everywhere by boat without ever setting foot on land.
The flood season in Long An begins in late August and lasts until December in the province's West-Northwest section. The more south - southeastward one goes, the later the flood season arrives and the less severe the floods are. Every year, enormous floods from the Mekong enter Dong Thap Muoi and Vam Co Tay, causing the water levels in the former to be consistently higher than the latter, which are also regularly higher than the Vam Co Dong River. The floods can be said to shift from Vam Co Tay to Vam Co Dong.
In the dry season, the hydrological patterns in the province are primarily controlled by the tides of the South China Sea and the flows of Tien River during the dry season. The main water source of Vam Co Tay is replenished by water from the Tien River during the dry season through the main canal lines connecting two rivers such as Cai Co - Long Khot, Tan Thanh - Lo Gach, Hong Ngu, Dong Tien - Duong Van Duong, An Phong - My Hoa - Bac Dong, and Nguyen Van Tiep -Bac Dong. The upstream rivers and streams on Vam Co Dong are depleted during the dry season. Because the Vam Co Dong River's fundamental flows are so low, saltwater intrusion is particularly severe, reaching even Go Dau Ha in April. Salinity is pushed back to Xuan Khanh thanks to regulated water supplies from Dau Tieng reservoir, and enough water is replenished to irrigate around 21,500 hectares in Duc Hoa, Duc Hue, and a northern section of Ben Luc district [6, p. 18].
While Long An has a large network of rivers and canals, it has comparatively few lakes and ponds. Small-sized ponds are generally dug to breed fish and store fresh water.
Long An has two-thirds of its natural area in the Dong Thap Muoi wetlands, resulting in a marsh expanse of thousands of hectares. These marshes are submerged to a depth of 40 cm to 50 cm all year, resulting in dense vegetation. The wetlands help to store water during the rainy season, but because the water cannot drain, they are saturated at length, causing alum to collect. Long An has more than 200,000 hectares of alum-infested land, accounting for 46.4 percent of the natural area (69.8% of the acid sulphate soil area in Dong Thap Muoi and 15.3 percent of the acid sulphate soil area in the Mekong delta), with Bac Dong and Bo Bo - Mo Vet being two "concentrated" areas of this soil [6, p. 18]. Rainwater washes the topsoil and then flows into canals and rivers, acidifying the water when the rainy season arrives. June and possibly July are the most acidic months, depending on whether the rainy season arrives early or late. This is referred to as a period of "greater amount of alum" by locals. This amount of alum has had a significant impact on the water quality of Long An's rivers and canals.
Aside from the extremely alum-contaminated lowlands, Long An's soil is quite saline, despite the lack of a sea. The estuary land has a flat topography and minor height above water level due to its connection to the ocean through enormous estuaries; its water is heavily influenced by tides and sea water. The tides penetrate further into infield canals during the dry season, carrying a substantial amount of salt, triggering soil and water salinization. At the end of the dry season and the beginning of the rainy season, salt levels in the Vam Co Tay and Vam Co Dong rivers reach a maximum of 4g/liter [10]. The "wicked wind," which blows from the sea inland in conjunction with river tributary flows, pushes seawater further into the fields during the dry season.
Long An has a considerable water supply thanks to the yearly rainfall and the volume of water in the river network. Water quality and irregular water distribution throughout the year, on the other hand, are two key roadblocks to water resource development. In direct contrast to the rainy season, which lasts from May to October on the solar calendar and produces about 90% of the total rainfall for the year, the dry season, which lasts from November to April, is when there are water deficits. The dry season is not conducive to agricultural production, particularly for short-term crops. The fields are parched due to water shortages, and farmers cannot obtain water to cultivate their farms due to low river water levels.
Long An also possesses excellent groundwater resources, the majority of which are found between 50 and 400 meters underground. According to studies of several wells drilled locally, groundwater is quite abundant in Duc Hoa, Duc Hue, Moc Hoa, and Tan An [9, p. 111]. However, due to acidification and salinization, the quality of these sources is variable and relatively low.
It can be seen that while Long An does not lack rainfall, river water, or groundwater, it is nonetheless a province with significant fresh water scarcity due to low water quality, and the cultivated land is primarily reliant on rainwater. If there is a prevalent misconception that Southern Vietnam is a place where people "don't have to work as hard to make money" since the land is blessed by nature, this is not the case in Long An. Long An does not receive nearly as much of the fertile alluvium as the Mekong River brings to Vinh Long, Sa Dec, Can Tho, and My Tho. "Acidification in the upper section, salinization in the lower section" is the most obvious characteristic of the soil and water resources in Long An, with acidic soil covering two-thirds of the natural area in Dong Thap Muoi, and soil salinity spanning tens of kilometers of the area from the Soai Rap estuary to the mainland.
Long An is often referred to as a "thirsty region" in hydrology studies, as it is one of the five western provinces that frequently experience severe drought during the dry season. Saltwater intrusion is particularly harsh there, according to the Long An Department of Agriculture and Rural Development (2017). Salinity levels in the main rivers tended to rise faster than in 2016. In Duc Hoa, it is observed that withering and dying vegetables and rice are extremely common throughout the dry season. Despite the fact that drought and salinity are present in many districts of Long An, there have been no detailed figures on the harm caused by these factors.
Saltwater intrusion not only affects output but also poses problems for the daily lives of people of Long An. Canals with no water supply gradually dry up, develop cracks, and leave just a few puddles of water. "In various residences, ponds, lakes, tanks, and water reservoirs are also gradually inert under extreme drought," according to the Illustrated newspaper of Ethnic groups and Mountainous Areas (2020) [5]. People in the lower communes of Long An are in desperate straits because they must buy fresh water brought by barges and tank trucks at exorbitant prices, sometimes up to 200,000 VND/m3. Due to uneven roads, water transportation also confronts numerous barriers and takes a long time, bringing significant disruption to people's life.
3. Long An's Irrigation Development History
The canal system at Long An was mentioned as an integral part of the interwoven canal network throughout the six provinces of Southern Vietnam in recorded texts about the region. It acted as an arc that surrounded Ho Chi Minh City, stretching from the Vietnam-Cambodia border to the mouth of the Soai Rap river, and was a province with a large area of agricultural land in the Mekong Delta, a key rice granary of the country. The canal system in Long An played a significant role in the province's socio-economic infrastructure development and the wholistic development of the region.
Long An has a lot of acid sulfate soil and saline soil, as previously indicated. As a result, digging a canal is necessary in order to plant rice. The formation and development of the canal system in Long An is linked to the history of land exploitation, beginning with the powerful migrations carried out by the Nguyen lords at the end of the 17th century, particularly when Nguyen Huu Canh was ordered by Lord Nguyen Phuc Chu to go to the south to stabilize the political situation and establish an administrative apparatus in 1698. Several disagreements and disputes between the Nguyen court and Chenla and Siam kingdoms were reported during this time. The Cochinchinese government had to mobilize troops several times to safeguard the exiled people and preserve territory security. The navy performed the most crucial role during such mobilizations, and their swift marches via the canal system enabled to transport reinforcements to the outlying
border districts. The land in the south was fertile, the fields were plentiful, and rice was grown not just for home consumption but also for sale throughout the Inner Circuit [9]. Because production had progressed and goods were available, commerce with other regions and countries became unavoidable. The canal system of Long An also helped to build arterial roadways that connected key ports like My Tho, Bai Xau, and Ha Tien with the Ben Nghe - Saigon hub. Canal dredging shaped waterways for military and commercial purposes throughout the reign of the Nguyen lords and kings.
After seizing the Southwest region in 1867, the French quickly developed technical infrastructure to support their colonial exploitation, which began with the theft of rice and other natural resources in this vast land for exportation. The French built canals in the Mekong Delta to reap colonial profits, develop transportation, and keep order and peace in the occupied areas since "security went hand in hand with transportation" [7, p. 161). The policy was to dredge canals as soon as a piece of land was taken to shorten the critical waterway from Saigon to the Southwestern area, particularly in the two provinces of Cho Lon and Tan An (present-day Long An). Despite their failure to totally conquer Cochinchina, the French colonialists dug and dredged various old canals with strategic locations in the area [8, p. 78]. The French colonists regained certain uninhabited areas in order to enhance rice cultivation and export. As for the low-lying basin of Dong Thap Muoi, water sources were stagnant throughout the year. As a result, irrigation was required to begin the reclamation of this area, which included building drainage canals to drain water from the Tien River to remove alum that had accumulated over time. The French were heavily involved in dredging canals in the Mekong Delta, particularly in Long An, to implement irrigation and trade projects, even if only for military and imperial exploitation.
Long An's geopolitical position influenced the implementation of state programs, particularly the development of irrigation projects, during the Republic of Vietnam's period. The implementation of political and economic policies, including the expansion of the irrigation system with US assistance, was not only for the purpose of agro-economic development, but also greatly contributed to the process of pacification and gaining popular support during President Ngo Dinh Diem's rule. Because of the Southern region's geographical isolation, irrigation, particularly the canal system, significantly impacted geopolitics and people's lives. President Ngo Dinh Diem's rule came to an end after a coup in November 1963. Along with the political unrest, the economy of South Vietnam stalled at this time, and irrigation projects failed.
Following its liberation in 1975, and with a general aim of converting all remaining arable land in the Mekong Delta into highly productive rice fields, the state pursued large-scale natural resource exploitation in Dong Thap Muoi in the 1980s. Irrigation operations began with dredging canals to remove alum and deacidify the soil in lowlands, with slogans like "pour tons of water into the fields," "squeeze the soil to produce water," and "make our own rainfall." According to the design, the entire Dong Thap Muoi would be covered by a complex system of interlaced canals, each 500 meters apart from the next, forming the area of Miet Kinh. The dredging and maintenance of used canals that had been filled up after the war, as well as the digging of new canals, were merged into a master plan. The activities were guided by the united efforts of the State and the people, as well as close coordination between the central and local plans.
4. Problems confronting Long An in light of the current climate change
There is no questioning the advantages that Long An's irrigation system has provided in recent years. The canal network, for example, helped to renovate a wide area of acidic and saline soil, improve crop production, and transform Vietnam from a food-shortage country to the world's second-largest rice exporter in the 1990s.
However, the growth of the canal system, particularly during the post-1975 Dong Thap Muoi Exploitation Program, which aimed to increase the density of canals in the region, has created a slew of issues, with increasingly visible negative consequences. The salt marshes in the Mekong Delta, especially the Dong Thap Muoi salt marsh, have received significant impacts in recent decades. Many new canals have been created, built canals dredged, and the network of subsidiary canals becomes increasingly thick, triggering flood diversion in these places. Because a huge amount of fresh water from the Tien River has migrated into the canals, saltwater intrusion in the estuaries is becoming increasingly intense. Since then, the river's water flows have been steadily decreasing, particularly during the dry season, and there is insufficient fresh water to prevent saltwater encroachment. Given the effects of climate change, this process becomes much more ferocious. In recent years, the Mekong Delta has experienced a number of several severe consequences as a result of this phenomenon, which has significantly affected people's daily life throughout the eastern coastline region. In the Mekong River basin, the intense El Nino phenomenon in 2015-2016 resulted in record low rainfall, causing severe drought and saltwater intrusion regionwide [1, p. 88].
It's worth noting that irrigation engineers in the Mekong Delta still plan irrigation systems using the Red River Delta's water treatment principles, so the irrigation efforts in Long An follow a fairly traditional pattern of adopting techniques from outside the region (brought in from the North) without taking into account the fact that the people of the Mekong Delta have been dealing with floods for hundreds of years. While the Red River Delta's water treatment principle of building solid dikes along the riverbank to prevent floods and digging canals to direct water to crops during the dry season has proven to be effective, its application in the Mekong Delta must be reconsidered because each area has unique characteristics. With their inherent low-lying terrain, the Dong Thap Muoi and Long Xuyen Quadrangles play an important role in the hydrological management of the entire Mekong Delta. These areas absorb a considerable volume of flood water, alluvium, and aquatic resources during the flood season, which serves to reduce flooding in downstream areas. Flood water from these low-lying areas replenish river flows during the dry season, helping to regulate salinity distribution among coastal provinces. These areas can limit agricultural activities and create a slew of other problems. Still, they also provide a lot of benefits for fisheries, increase soil fertility, and keep the environment clean. As a result, solutions for this problem
should be synchronized and capable of improving human adaptability to actual natural events, taking into account the unique natural characteristics of the Mekong Delta, including Long An, as well as the current impacts of climate change on the entire region.
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