Development of Methodologies for Land Degradation Assessment Applird to Land Use Planning in Thailand

International Institute for Geo-Information Science and Earth Observation

PILOT AREA II

Land degradation due to drought and salinity is crucial for agricultural development in Nong Suang, Nakorn Ratcha Sima Province. Crop yields have not only decreased substantially in the recent past but the area affected by salinity has also increased which is threat to agricultural development. The area affected by salinity extends between 101o 45/ and 101o 59/ longitudes and between 15o 1/ and 15o 15/ latitudes and covers 750 sq.km of surface area. The area is characterised by tropical monsoon climate, with an average summer temperature of 40 degrees Celsius and average winter temperature of 10 degrees Celsius. Annual average rainfall is 1,000 mm, most of which falls during rainy season.

Area is characterised by gently undulating to nearly level topography consisting of low and high alluvial terraces in some part of the area. Land use is paddy rice and cassava. Due to drought and salinity many agricultural areas have been abandoned. Salinity problem is in the magnitude of 25dS/m. Average ground water table is 50 cm in rainy season.

Figure 1 : Pilot area 2 Nong Suang, Nakorn Ratcha Sima Province

Climate

Northeast Thailand has two main climatic seasons, the dry season, which occur from November to April. Its climate is influenced by the dry winter monsoon coming from China, while the rainy season occur from May until October, with it’s hot wet climate generated by both the maritime monsoon passing over the Indian ocean, and the Typhoons of south China.

Soil climatic conditions: Moncharoen (1964) describe the dominant soil temperature regime is “Ustic” in the upland, while the “Aquic” regime dominants the low area.

Figure 2 : annual rainfall (1952-2001)

Geology

The geological settings in northeast Thailand according to [12] is composed from:

Precambrian massif underlain the whole plateau.

Mesozoic sedimentary rocks and sediments cover the massif base rock, which is called

Korat group. This group contains a Varity of sedimentary rocks like sandstone, siltstone, shale and conglomerate. Ward and Bunnag classified the Korat group into six formations, while Gardner et al 1967 gave the name “MahaSarakham” for the salt bearing formation), According to Imaizumi et al.(2002) the “MahaSarakham formation is composed of clay stone, shale, inter- bedded with two or three layers of evaporates (halite, gypsum, anhydrite, carnallite, and sylvite) varying in thickness from 10 to 170 m. Figure 3. shows stone units map of Nakorn Ratchsima Provice

Table 1 : the classification of Korat group

Age	:	Formation
Quaternary	:	Unnamed
Teriary	:	Maha Sarakham

Cretaceous

Upper

Khok Kruat

Lower

Phu Phan

Jurassic

Upper

Sao Khu

Middle

Phra Wihan

Lower

Phu Kradung

Triassic Middle - Upper

Rhaetian Norian

Nam Phong

Carnian Ladinian

Hui Hin Lat

The main source of soil Salinisation in northeast region is the geological formation, which includes the salt rock as part of its composition.
Generally causes of Salinisation can be summarized in to two main groups:

Natural Causes: The variation in ground water pizometeric pressures, which force the water to raise to the surface throw the existing faults.

Human influence: the salt mining industry is well known in the area since a long time ago, the human efforts to pump saline ground water to the surface as part of salt making industry, ion has a contribution to the rate, and spread of Salinisation.

Both of the previous reasons had influence from the local geology. Solving the problem of Salinisation in the northeast Thailand depends more in understanding the natural setting more and especially focusing on the nature reaction to local communities activities.

Pkd	Greyish black limestone, shale, fossiled chert, sandstone: Permian	Jbk	Purplish silt stone, greenish sandstone, clay stone and conglomerate: Jurassic
Pn	Greyish black limestone, taff, hornfels, chert, quartzite: Pemian	Jpp	Greyish white sandstone, siltstone, grey or brown shale: Jurassic - Cretaceous
Ppa	Sahle, sanstone, limestone, hornfels: Permian	Jpw	Thick white, pink and grey Quatz sandstone, siltstone, mudstone: Jurassic- Cretaceous
Ps	Limestone, volcanic limestone, sandstone, chert, basalt: Permian	Jsk	Greyish red, purplish red Silt stone, sandstone, shale: Jurassic- Cretaceous
Qa	Alluvium, sand & pebble sediment in flood plain: Quarternary	Ktms	Reddish brown siltstone, clay stone with rock salt and potassium : Cretaceous-tertiary
Qt	Terrace sediment, pebbles, silt, clay: Quarternary	Kk	Brown sanstone, siltstone and shale: Cretaceous
Trhl	Conglomerate, shale, siltstone, greywacke, limestone: Triassic	Kkk	Lime texture siltstone, sandstone and shale, conglomerate: Cretaceous
Trht	Mudstone, silica mudstone, sandstone, shale: Triassic	Kpp	Thick white sandstone, siltstone, small conglomerate: Cretaceous
Trs	Shale, sandstone, conglomerate: Triassic	Ptrku	Unidentified volcanic rock, rhyorite, andesite, taff, aggromerate, volcanic breccia: Permian- Triassic
bs	Basalt, olivine basalt: Quarternary	PTrp	Diorite, hornblende diorite: Permian-Triassic
	Water bady

Figure 3 : Stones units map of Nakorn Rachsima

Source: Department of Mineral Resources

Development of Methodologies for
Land Degradation Assessment Applied to
Land Use Planning in Thailand

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