Thailand Northeast Rainfed Agricultural Development Project
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Thailand Northeast Rainfed Agricultural Development Project (493-0308) Supplemental Analysis to the Project Paper March, 1981 Northeast Rainfed Agricultural Development Project Supplemental Analyses to the Project Paper Annex V Technical Analyses V. Introduction V.A. Extension Support V.B. Social Support V.C. Cropping Systems V.D. Other Farming Systems V.E. Soil and Land V.F. Water Resources V.G. Demonstration and Research V.H. Resources Inventory V.I. Economic Studies V.J. Engineering Feasibility Annex VI Economic Analysis Annex VII Social Soundness Analysis Annex VIII Administrative Analysis I0 ANNEX V-i ANNE): V - Introduction Technical Analysis-l/ 1. Area and Population The Northeast of Thailand has an area of about 167,308 Km. bounded by the Mekong River on the North and East, the Phanom Dongrak escarpment on the South, and the Phetchabun ridge on the West. It comprises 16 provinces listed in alphabetical order as follows: Buri Ram, Chaiyaphum, Kalasin, Khon Kaen, Loei, Maha Sarak-ham, Nakhon Phanom, Nakhon Ratchasima, Nong Khai, Roi Et, Sakon Nakhon, Si Sa Ket, Surin, Ubon Ratchathani, Udon Thani, and Yasothon. A map of the Northeast is shown in the Project Paper. The region has a population of about 14 million which constitutes about one third of the population of the country. l/ Information in this section was freely borrowed from: (i) Water for the Northeast: Drought Analysis Part I: Rainfall Analysis. Prepared by the Asian Institute of Technology and published by the Water Resources Planning Subcommittee, National Economic and Social Development Board, Kingdom of Thailand, Bangkok 1978. (2) Report No. 1, Seasonality and Intensity of Rainfall in Northeastern Thailand by Frank Nicholls, Damrong Charoensook, Ittipon Padungwit, Anuri Chintakananda and Suparn Chamswasdi. Published by the Applied Science Research Corporation of Thailand, Bangkok 1967. (3) Northeast Rainfed Agricultural Development Project - An Opportunity Framework. Published by the Regional Planning and Development Project, Universit of Wisconsin under Contract No. AID/DSA-C-0060. Madibon 1979. (4) Village Level Study for Northeast Rainfed Agricultural Development Project by Damrong Thanee and Pit Sompong, Ramkhamhaeng University, Bangkok, Thailand, 1980. ANNEX V-2 2. Physical Features a. Topography Except for the hilly areas along the southern and western boundaries of the region and South of Udon Thani and Sakon Nakhon, the Northeast consists mostly of a very flat plain or plateau tilted gently towards the southeastern corner. The western edae of the plain at the foot of the Phetchabun mountains hL. an elevation of about 200 m. Along the Mekong River:, the ulevation for the most part is less than 150 m. In the South, the general elevation is 500 m., the highest peak being Khao Laen with an elevation of 1,328 m. b. Drainage Two main rivers, namely the Mun and the Chi Rivers, drain about four-fifths of the total area. The Mun River originates near Nakhon Ratchsima (Korat) and flows eastwards through Ubon Ratchthani to the Mekong River, draining the northern slopes of the Phanom Dongrak mountains. The Chi River drains all the western portion of the plain and most of the interior flowing southeast to reach the Mun River near Ubon Ratchathani. The combined drainage area of the two rivers is 125,500 Km.2 The northern and eastern fringes of the region are drained by several small rivers such as the Luang, Songkhram and Kham. All these rivers eventually flow into the Mekong River. c. Geological Structure The Northeast of Thailand is structurally unique in that it is located at the centre of a series of concentric mountain folds that encircle Burma, Thailand, Malaysia, Indonesia and Philippines. Except for a few small outcrops of balsalt in the South and limestone and igneous rocks along the North-South trending ridge between Loei and Udon, the region is made up of a series of fine arained sandstones and shale beds over lain in valley deprr sions by alluvium and river terrace deposits. The upper strata are most important from the water balance standpoint. Over a large portion of the region embracing Khon Kaen, Kalasin, Ubon Ratchathani, Surin, ANNEX V-3 Nakhon Ratchasima, and Chaiyaphum provinces, the near surface rocks are fine to medium grained sandstones, tan to pinkish-red in colour, interbedded with mottled purple and grey fine sandy shale. This formation is also found in some parts of the Udon Thani and Nong Khai provinces. In almost the rest of the region, in a strip of 10 to 15 Km. wide, the surface rocks are massive with fine to coarse grained sandstones, some conglomeritic, with a variety of colours and interbedded with shale. The sandstones in the upper strate, being least consolidated, are highly pervious. d. Soils Soils of the Northeast have been differentiated intol/ broad groups based on soil landscape relationships as follows:-/ (1) Soils Occurring on Flood Plains: Soils on this landform consist of very deep, well drained and poorly drained soils developed from recent alluvium. Soils occupying natural river levies are well drained, medium textured soils. They are usually used for garden crops. Soils in river basins are poorly drained, fine textured and are used for rice cultivation. The soils developed on this type of landform generally fall in the great groups Ustifluvents and Tropaquepts according to the U.S. Soil Taxonomy classification system. (2) Soils Occurring on Low Terraces: These soils have variable characteristics such as soil depth, texture, and salinity. They are moderately to poorly drained and are extensively used for rice production. they are classified in the great soil groups: Paleaquults, Plinthaquults, Natraqualfts, Halaquepts, and Dystropepts. (3) Soils Occupying Midd3e-High Terrace: Soils developed on this type of landform are composed of soils that have varied diagnostic characteristics which include color, soil, depth, and texture, All are well drained and are usually devoted to upland crop production or forests. These soils are classified as: Paleustults, Phinthustults, Haplustults, Haplustox, Rhodustults, Dystropepts, and Quartzipsamments. (4) Soils Occurring on Erosion Surfaces: Soils occurring on this landform are also variable in texture, colojr, soil reaction, soil depth, etc. These differences in properties occur primarily because of differences in parent materials. The soils occur mainly in the southern and western part of the region. They are generally heavier textured than soils of the middle to high terraces, These soils are classified as Paleustults and Haplustuits. I/ Unpublished (Memo , no date, no Athor. Supplied by Dr. Wanee Sanphantharak, Department f L.nd De'e_:zzmsnz, J jy 19"9. ANNEX V-4 '51 Soils Occupying Hilly Areas: These soils occur on hilly and mountainous areas and are usually included in mapping units as "slope complex soils". 3. Meteorological Factors a. Climate The climate of the Northeast is seasonal in nature. The Southwest Monsoon, caused by low pressure over Central Asia, brings heavy rainfall to the whole region. Beginning with the month of April, the precipitation increases steadily as the wet season progresses until the maximum monthly rain fall is reached, which normally occurs in September. This is accompanied with a slight rise in humidity and a simultaneous decrease in temperature and radiation, The average wind velocity during the wet season remains fairly steady at about 5 Km. per hour. Precipitation decreases rapidly in late October or early November. Even though occasional tropical storms with heavy rainfalls do occur along the Vietnamese Coast durL±g these two months, these weaken rapidly as they penetrate inland. The reverse airstream, the Northeast Monsoon, starts in December. The temperature falls to a minimum in December or January, then rises rapidly at first and then more gradually until it reaches a maximum in April. During this period, the weather is hot and dry moderated slightly by light breezes, cool nights and very occasional light showers. b. Rainfall Rainfall distribution dur.ng the rainy season of April through October has a bimodal tendency which is more pro nounced in the North and Northeastern provinces. The more pronounced bimodal pattern in these provinces is a result of higher rainfall in the early part of the season and these same provinces usually have the highest total rainfall. Total annual rainfall varies from about 1,100 mm. in Chaiyaphum and Nakhon Ratchasima provinces to more than 1,800 mr. in parts of Nong Khai and Nakhon Phanom provinces. Rainfall is generally quite variab.e from year to year.* Early season rainfall tends to be variable both in timing and amount. Heavy late season rainfall almost always occurs but 7 ANNEX V-5 the peak period can vary by a month cr so in timing and the sharpness of the peak also varies frcm year to year. C. Evaporati.on Evaporati6on in the Nzrtheast varies geographically as well as seasonally. The ridges of high evaporation extend through Nakhon Ratchasima, Khon Kaen and Udon Thani, with a trough to the west embracing Phetchabun and Loci, and a shallower depression centered in Sakon Nakhon. For Class A. pan evaporation, the higher annual values are found at Udon Thani, Khon Kaen and Ubon Ratchathani with values of 2,315 mm., 2,244 mm., and 2,339 mm., respectively, A typical value of pan evaporation in the western trough at Loei is 1,590 mm. per year. Around Nakhon Phanom and Sakon Nakhon, Class A. pan evaporation amounts to about 1,800 mm. per year. The seasonal variation is regular in transition from minimum values in September - October to maximum values in March - April. d. Temperature The temperature in the Northeast is lowest in December - January with a mean monthly temperature of about 22.5 0 C. The mean temperature then gradually increases until it reaches a maximum of 300 C in April. e. Humidity The humidity of the region varies according to the trend of the monsoons, with a mean relative humidity reaching a minimum of around 60 percent in March and rising to a maximum of about 80 percent in August or September.