Investigation on the upgrade
of landuse in irrigation project area using satellite image data in
Thailand
Kiyoshi Torli*, Tomoyuki Mase*, Masami Iwasaki**Takashi Hosh***, Prasert Millintangul*** and Prapant Svetanant**** *Dept. of Agric Eng. Kyoto Univ. Kyoto, Japan 606-1 **Dept. of Agric. Eng. Tottori University, Torroti, Japan 680-00 ***Dept. of Comp. & Inform. Sci., Ibaragi University, Mito, Japan 316-00 ****Hydrology Division, R.I.D Ministry of Agriculture, Bangkok, Thailand 10300 *****Faculty of Economics, Chulalongkorn University, Bangkok, Thailand 100500 Abstract In the big irrigation project area which implemented by Thai government for long time in the vicinity of Bangkok Metropolis, a large scale of Industrial estates and residential land were constructed, and expanding their area rapidly. About landuse in agricultural side, intensive agriculture for example orchard, fruit plant, vegetable farm, fish ponds became to be observed instead of former paddy rice field. We would like to discuss the upgrade of landuse in the irrigation project area using satellite image and by field survey in the point of water management system in Rangsit project in Thailand. 1. Introduction Outskirts of Bangkok, Thailand is being developed rapidly now and a sudden change in land use of this area is occurring. This change seems to center around Rangsit irrigation area extending in the east side of the central Chaophraya plain. In view of in landuse change in the aspect of agriculture, rice growing in the dry season has been introduced to the single corp paddy rice in the rainy season and, further, transfiguration to more profitable agriculture such as vegetable and fruit cultivation has been accomplished. In search of profit efficiency, fish ponds in inland and shrimp farms in coastal area have also become popular. A stable supply and enlarged volume of irrigation water including water supplied by Rangsit irrigation project seem to e the explosive power for upgrading of landuse. When we consider agricultural and social developments in developing countries in future, it is highly imaginable that this area in Thailand will be a model for developmental process. In the present study, we analyze the state of upgrading of landuse of Rangsit area and Sait Prakah district located downstream using satellite image data by field survey to assess the agricultural water management system comprehensively. 2. Development process in Ransit area Rangsit Irrigation Project area in the northeast of Bangkok is about 200,000 ha and it is most deltts-like area among chaophraya delts. Its 80% is between 1.5 and 2.5m above sea level and the whole area is extremely flat. This area used to be in the state of flood in the rainy season due to rainfall and inflow of water from the surrounding areas. In the dry season, the whole surface was dried up transfiguring into the earth spreading with cracks. In other words, this area presented the sight of a gigantic lake with the show surface under water in the rainy season and the sight clay desert being dried up in the dry season and these scenes were repeated over and over in the half year cycles. Today, the area has been turned into an extremely artificial space with highly dense canal networks. These canals were excavated in 1880s by siam canal arrangement of the canals consists of about 20 straight canals of 20-30 km lengths running from south to north at about 2-km intervals. Apart from these, some canals were constructed from east to west crossing perpendicularly to the previous ones. By the combination of these canals, this area is covered by a complete canal network. The space with a half year cycle of complete submerging and complete drying in Rangsit area, which is typical of a monsoon delta, was extremely unfit for human living. When the whole 200,000 ha land of Rangsit sank under water, it must have been difficult to make a living space for men there. On the other hand, in the state of dry season, it must have been more unfit as it was impossible to ensure drinking was when the whole 200,000 ha area was cracked and became a dry clay board without a river in Rangsit area was a space refusing human survival. Excavation of canal networks was the most effective means of improving environment of severe nature such as this. The canals with sufficient depth should have enough water even in the dry season. Living water can be secured with this, and construction of dikes with the dug earth should provide high places for residential area which is not flooded during the rainy season. Development of Rangsit area had been implemented using such a measure. At present, it is quire obvious at stepping into Rangsit area that all the houses were built along the canals excavated as such. 3. Water resources and upgrading of landuse In the mid 19th century, cash crop farm became popular in the areas of tropical rain forest climate and rice demand in these areas increased rapidly. Sugarcane cultivation in Java Island and cultivation of rubber in Malay peninsula were started in the end of 19th century and expanded their cultivation areas in the early 20th century. Corresponding to these trends, paddy field in Rangsit area gradually expanded to supply rice t these areas as food and rapidly popularized between the late 19th to the early 20th centuries when canals were excavated for rice transportation and living. As a result, export of Thai rice was increased and the country grew into the largest rice export country from the end of the Second World War to 1960s. Chaophraya delta was called the rice bowl of the world. As long as rice was the only and profitable product of the delta, all the construction works were carried out for building irrigation and drainage facilities with the aim of infrastructure improvement for rice growing. History of the delta development will be given in the following.
In the coastal area along the Chaophraya east bank, National Route 3 runs 2 - 3km inside the coast and this is playing the role of preventing sea water intrusion. At the river mount, gates were installed to prevent salt water from entering inland. Thus, it is planned to store fresh water flowing from upstream Rangsit area as much as possible before escaping to the sea so that it can be utilized for paddy field and dish breeding. According to the survey by Takaya and Kaida et.al in 1979 single crop-paddy field during the rainy season occupied the majority at that time and natural khlongs from 6 to 7 -m to 30 m wide were present at about 1 km intervals and houses were standing along these khlongs with ponds dug behind the houses for water intake. Generally, the hoses were built on the ground formed by heaping the earth from digging ponds and they were surrounded by coconut palms and bamboo arranged as windbreaks. 5. Analysis of satellite images We have examined the general trend that upgrading of landuse occurs accompanying a stable water supply and ensured water resources in Rangsit area. Here we proceed our analysis selecting 2 study areas; one is situated north of Don Muan International Airport along Rangsit canal and the other is Samut Prakan area where industrial estates are being constructed in a belt between Bangkok Pattaya highway and the coastal line.
6. Concluding remarks Rangsit irrigation project area was once a typical monsoon delta. In other worlds, the ground was flooded over the whole area in the rainy season while it was dried upto the water less state in the dry season. In such an area, stable and abundant irrigation water supply was facilitated gradually starting with construction of canal networks followed by South Pasak project, Greater Chaophraya project and construction of Phumpol and Sirikit dams. Accompanying these projects, agriculture in this area has developed to cultivation of more profitable products from single crop rice growing in the rainy season to two crop rice growing and to fruit gardens. With upgrading of landuse, water demand has grown further. Exploit of water resources had expanded selectivity of landuse and has shown a tendency of shifting to more profitable landuse. Construction of industrial estates and population increase accompanying it resulted in further rise of water demand in rangsit, area. As present there is a plan to introduce water from Ing and Kok rivers in the basin of Mekhon river to Sirikit dam and we could like to observe Ransit area where further change is expected using satellite images. Finally, satellite image processing in the present study was conducted under proram Developments with permission of Data Processing Center, Kyoto University, and Mos-1 image data was distributed specially for research purpose from the National space development agency of Japan. Landsat 5TM image data was supplied by the National Research Council or Thailand with special consideration. A part of this study was included in General Research (A) (Represented by Prof. Masahil Tanaka, Mie University) sponsored by the Scientific Research Fund of Ministry of Education. We express our gratitude for all who are concerned. References
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