Thailand

Area equipped for irrigation per province in year 2007 was derived from then country questionnaire used as base for the AQUASTAT country profile [TH01]. Area equipped for irrigation per province added up to 6 414 880 ha as shown in the table below, also downloadable as Thailand irrigation areas in PDF or Thailand irrigation areas in Excel.

Digital maps of irrigated areas (polygon dataset) and irrigation projects (point dataset) were used as compiled by the Mekong River Commission [TH02]. However, these inventories covered only the part of the country that belongs to the Mekong river watershed. In the other part of the country two similar datasets provided by the remote sensing department of FAO were used ([TH03]; [TH04]). In general, the point dataset was used for small schemes (fewer than 1 000 ha) while the polygon dataset was used for large schemes (more than 1 000 ha). Exceptions had to be made in cases where schemes were available only in the polygon dataset or only in the point dataset. In addition, irrigated area was assigned to agricultural land as taken from a digital land-cover map [TH05] using the priorities shown in Table 1.

In the wet season, the whole irrigated area is irrigated by using surface water resources. In the dry season, a second or third rice crop can be cultivated if the water supply is ensured. This is often realized by private shallow tube wells, resulting in dry season paddy areas that are larger nowadays than the potential area estimated before based on available (surface) water resources [TH06]. Total area planted with a second rice crop was 495 712 ha in year 1994 and increased to 1 584 446 ha in year 2006 [TH07]. Detailed statistics on the area irrigated with groundwater were not available but it was reported that almost all farmers in the Phitsanulok irrigation project (104 000 ha) have access to groundwater extracted by tube wells [TH08]. Another area for which groundwater irrigation was reported is the Sukhotai irrigation project [TH09]. It was assumed therefore that the area irrigated with groundwater in the Phitsanulok and Sukhotai provinces is similar to the area planted with a second rice crop in season 2006, while for all the other provinces area irrigated with groundwater was set to 50 percent of the reported increase of the area planted with a second rice crop within the period 1994-2006. Total area equipped for irrigation with groundwater computed that way was 481 063 ha. Area actually irrigated in year 2007 was reported at 5 059 914 ha [TH01].

References

[TH01]: FAO. 2012. AQUASTAT country profile of Thailand, version 2010. FAO, Rome, Italy.
[TH02]: Mekong River Commission Secretariat. 2003. People and the environment atlas of the Lower Mekong Basin. CD-ROM, Phnom Penh.
[TH03]: FAO. 2004. Dataset irr-area, provided by FAO ASIACOVER project.
[TH04]: FAO. 2004. Dataset irr-proj, provided by FAO ASIACOVER project.
[TH05]: FAO. 2004. Dataset landuse, provided by FAO ASIACOVER project.
[TH06]: Wongprasittiporn, C. 2005. Large rice-based irrigation systems in Thailand. In: Proceedings of the regional workshop on the future of large rice-based irrigation systems in Southeast Asia held in Ho Chi Minh City, Viet Nam, October 26-28, 2005. RAP Publication 2007/28, FAO, Rome, Italy, 136-140, http://www.fao.org/docrep/010/ai408e/ai408e00.htm, 28/08/2009.
[TH07]: FAO. 2008. Regional data exchange system (RDES) on food and agricultural statistics in Asia and the Pacific. FAO Regional Office for Asia and the Pacific, Bangkok, Thailand, http://faorap-apcas.org/index.htm, 28/08/2009.
[TH08]: IPTRID. 2003. The irrigation challenge - increasing irrigation contribution to food security through higher water productivity from canal irrigation systems. IPTRID Issues Paper 4, IPTRID Secretariat, FAO, Rome, Italy, http://www.fao.org/docrep/006/Y4854E/y4854e00.htm#Contents, 28/08/2009.
[TH09]: FAO. 1999. Irrigation in Asia in figures. Water Report 18, FAO, Rome, Italy.