The French began building canals and draining lands in the Mekong delta as Vietnam had fertile land which was suitable for rice production and plantation crops. For the constant supply of natural resources and other essential goods colonies used to annex other countries and the custom was followed by French also. To increase cultivation in Vietnam the French started to expand its territories and began building canals and draining lands in the Mekong delta. The vast system of irrigation workscanals and earthworks-built with forced labour, increased the production of rice cultivation went up from 274,000 hectares in 1873 to 1.1 million hectares in 1900 and 2.2 million in 1930. By 1931, Vietnam became the third largest exporter of rice in the world. This was the main reason for French to build canals and draining lands.