History

The Rama VI Barrage holds the distinction of being Thailand’s first diversion dam, marking a milestone in the country’s pursuit of modern irrigation. The idea of developing an organized irrigation system in the lower Chao Phraya basin dates back to 1902 during King Rama V’s reign. At that time, the Ministry of Agriculture engaged Dutch hydraulic expert Mr. J. Homan van der Heide to study the region and propose a comprehensive irrigation plan. His report, presented in June 1903 as “The General Report on Irrigation and Drainage in the Lower Menam Valley,” recommended large-scale interventions. However, due to financial limitations, the Thai government did not implement these plans. Despite this, Mr. Heide later became the first director general of the newly established Canal Department (Krom Klong), overseeing improvements and maintenance of the extensive canal network in areas like Rangsit.

During the reign of King Rama VI, Thailand faced severe droughts that threatened rice cultivation, prompting renewed focus on irrigation development. Recognizing the urgency, the King enlisted British engineer Sir Thomas Ward to review previous plans and recommend practical solutions. Sir Thomas Ward proposed implementing five smaller irrigation schemes instead of a single large-scale project. The Tha Luang scheme, chosen as the first of these, involved constructing a diversion dam on the Pasak River to irrigate roughly 680,000 Rai (108,800 hectares). This initiative laid the foundation for the South Pasak, Northern Rangsit, and South Rangsit irrigation projects and ultimately led to the commencement of construction for the Rama VI Barrage in 1915.

Structure Details

Construction of the Rama VI Barrage officially began in 1916 and was completed in 1924, making it the first modern water diversion structure in Thailand. The barrage is a substantial engineering feat featuring six large sluice channels, each 12.5 meters wide, equipped with vertical lift steel gates 7.50 meters in height. These gates were custom-manufactured in Scotland and shipped to Thailand, while smaller gates and auxiliary components were produced locally. The project faced challenges due to World War I, including delays in gate deliveries and funding shortages, which were alleviated through special assistance from King Rama VI’s central funds.

The barrage has a maximum flood discharge capacity of 1,800 cubic meters per second and can divert water at a rate of 100 cubic meters per second into the Rapeepat main canal. From there, a network of 360 kilometers of canals distributes water to irrigate 10,800 hectares across the South Pasak, Northern Rangsit, and Southern irrigation projects. Remarkably, despite the technical challenges, wartime interruptions, and the labor-intensive construction process that relied entirely on Thai workers, the structure remains in excellent condition nearly a century after its completion.

Benefits

Since its completion, the Rama VI Barrage has played a critical role in stabilizing agricultural production within its command area. By ensuring a reliable water supply, the barrage has mitigated the impacts of drought on rice cultivation, contributing significantly to food security and the livelihoods of local farmers. Its diversion capacity supports large-scale irrigation projects, enhancing the efficiency and reach of Thailand’s water management systems.

Beyond agriculture, the barrage represents a historic achievement in Thai engineering and modern water infrastructure development. Its enduring functionality exemplifies the successful integration of international engineering expertise with local labor and resources. Even today, the Rama VI Barrage continues to be a vital component of Thailand’s irrigation network, providing a model for subsequent water diversion projects and serving as a symbol of the country’s commitment to sustainable water resource management.