Thailand

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Geography, climate and population

Geography

Thailand covers an area of 513 120 km2 and is located in the southeastern region of the continent of Asia (Table 1). Its immediate neighbours are Myanmar to the north and the northwest, Lao People’s Democratic Republic to the northeast, Cambodia to the east and Malaysia to the south. The water bodies that skirt Thailand are the Mekong River in the east that forms Thailand’s natural boundary with Laos, the Gulf of Thailand to the southeast and the Indian Ocean and the Andaman Sea to the southwest.

Administratively, the country is divided into 76 changwats (provinces), 4 regions and the Bangkok Metropolitan area. The four regions correspond approximately to the physiographical regions of Thailand: the northern region is mountainous with forests; the northeast is dry and consists of a plateau which borders the Mekong River; the central region is an extensive plain subject to flooding; and the southern part consists of a peninsula.

About 26.79 million ha are considered as cultivable which represents 52 percent of the country area. In 2008, the cultivated area was estimated at 18.85 million ha. Of this total, 15.20 million were under annual crops (mainly paddy rice) and the remaining 3.65 million ha were under permanent crops.

Climate

The climate is mainly governed by the alternation between the southwest monsoon, which brings heavy rainfalls (May-October), and the northeast monsoon, which is comparatively dry and cool (October-February). The transitional period (March-April) is characterized by heavy thunderstorms.

The average annual rainfall is estimated at 1 622 mm. It ranges from 1 100 mm in the central plain and the northeast of the country to 4 000 mm in the southern peninsula near the Andaman Sea.

Population

The total population was estimated at 67.4 million inhabitants in 2008 (66.8 percent rural, while in 1998 69.2 percent was rural). During the period 1998-2008 the annual population growth rate was estimated at 0.93 percent. The population density is about 131 inhabitants/km2.

In 2008, 98 percent of the population had access to improved water sources (99 and 98 percent in urban and rural areas respectively). Sanitation coverage accounted for 96 percent (95 and 96 percent in urban and rural areas respectively).

Economy, agriculture and food security

In 2009, Thailand’s GDP was $US263 772 million of which agriculture sector accounted for 12 percent (Table 1).

In 2008, the total economically active population is 38.7 million, or slightly more than 57 percent of the total population. The economically active population in agriculture is estimated at 19.4 million (50.1 percent of total active population) of which 45.3 percent is female.

According to FAO, Thailand’s yearly hungry people reduce from 16.8 million (30 percent of total population) during 1990-92, to 13.8 million (23 percent) during 1995-97, and 13.4 million (21 percent) during 2001-03.

In 2003, food exports account for 24.6 million and food imports account for 8.4 million tons.

Water resources and use

Water resources

Thailand can be divided into seven river basins, but in the literature it is generally divided into 25 sub-basins. Figure 1 and Table 2 and show the location and the characteristics of the 25 major river sub-basins and indicate the total surface water resource of the country, 213.35 km3/year. Aquifer recharge from rainfall is estimated at 41.90 km3/year (about 5-6 percent of the total precipitation). Approximately 30.70 km3/year are estimated to return to the river system (overlap). The total internal water resources of Thailand are therefore estimated at 224.55 km3/year.

Thailand shares three major river systems with its neighbours: the Mekong River forms the border with Lao People’s Democratic Republic in the north and east (about 18 percent of the total Mekong catchment area is located in Thailand), the Salween River is on the northwestern border with Myanmar, and the Kolok River is on the southern border with Malaysia. This last river, originating in Thailand and then bordering between Thailand and Malaysia, is very short with a total length of just over 100 km. The Mekong and Salween rivers constitute an additional external resource for Thailand, which has been estimated at half the discharge of the rivers, but from which the contribution of the country to these rivers has to be deducted. This gives a total of 199.9 km3/year, which is equal to 100.0 (=200.0/2, or half the Salween discharge) - 8.156 (contribution of Thailand to Salween in the border reach) + 162.225 (324.45/2, or half the Mekong discharge) - 51.9 (contribution of Thailand to Mekong in the border reach).

By adding the internal and external resources together, the total renewable water resource are estimated at approximately 427 km3/year (Table 3).

Total exploitable water is estimated at 125.98 km3/year, consisting of 75.64 km3/year regular renewable surface water, 27.34 km3/year irregular renewable surface water and 23.00 km3/year regular renewable groundwater.

Total large dam capacity is estimated at 68.28 km3 in 2007, which is about 32 percent of the annual runoff. However, a lot of dams have been over-designed compared with the annual recharge obtainable. There are four categories of dams in Thailand:

  • Large dams with hydropower component are built by the Electricity Generating Authority of Thailand (EGAT), the Royal Irrigation Department (RID) or the Department of Energy Development and Promotion and managed by the EGAT. Their total capacity is estimated at 62.87 km3. All these dams are multipurpose dams, and the irrigation component receives priority over the other components.
  • Large dams without hydropower, and therefore mainly destined for irrigation, are operated by the RID. Their total capacity was estimated at 5.41 km3 in 2003.
  • Medium dams, similar to large dams with no hydropower, are also under RID. Reasons for not classifying these as large dams are: (i) to avoid environmental assessment, and (ii) to shorten budget processing and construction times to cope with high priority areas.
  • Small dams used to be under RID, but are now under local governments. Most of these small dams are for domestic and subsistence irrigation purposes.

There are five dams with a capacity of more than 5 km3: Srinagarind (17.75 km3), Bhumipol (13.46 km3), Sirikit (9.51 km3), Vaijiralongkorn (8.86 km3) and Rat Cha Prapa (5.64 km3).

There are 5 main dams on the Mekong River basin in Thailand, the Sirindhorn (1 966 million m3), Chulabhorn (188 million m3), Ubol Ratana (2 264 million m3), Pak Mun (114 million m3) and Lam Ta Khong (310 million m3).

Water use

In 2007, total water withdrawal was estimated at 57.3 km3, of which 90.4 percent was for agricultural purposes, 4.8 percent for municipal and 4.8 percent for industrial purposes (Table 3 and Figure 2). In 1990, total water withdrawal was estimated at 33.1 km3, of which 91 percent was for agricultural purposes, 5 percent for municipal use and 4 percent for industrial use. Of the total withdrawal of 57.3 km3, 82.9 percent was surface water and 17.1 percent was groundwater (Figure 3).

Wastewater treatment is not common. Industrial wastewater is generally discharged into rivers and canals. About 2 191 million m3 of wastewater were produced in 2003. In 2007, some 523 million m3 of wastewater were treated. Numerous wastewater treatment projects are being developed in the Bangkok metropolitan area. There is no reuse of treated wastewater in Thailand.

International water issues

In general, Thailand’s international water issues stem from the country’s thirst for water, hydroelectricity, and utilization of coastal areas. The main issues include:

  • The Mekong River Treaty (1995): This is a treaty between Thailand, Lao People’s Democratic Republic, Vietnam and Cambodia. The treaty specifies how cooperation and conflict resolution among the countries involved should be done, but does not propose any sharing of water between the riparian countries.
  • Myanmar: There are a number of planned and under-construction dams both inside Myanmar and on the border that international NGOs question because of their environmental consequences. No agreements have been signed on the Salween River.
  • Lao People’s Democratic Republic: Issues are similar to Myanmar but include existing dams that supply electricity to Thailand.
  • Cambodia: Issues are similar to Myanmar but include natural resources in coastal areas.

Irrigation and drainage development

Evolution of irrigation development

Irrigation through river diversion and from reservoirs started in the north seven centuries ago. In modern times, canal construction for irrigation started at the beginning of the last century, in parallel with the creation of the RID. The aim was to maintain water in canals for irrigation and navigation, and to drain paddy fields during periods of flooding. Irrigation has traditionally been supplementary irrigation for the wet season. It is only recently that schemes have been designed for dry season irrigation.

The irrigation potential for the wet season can be roughly estimated at 12.2 million ha, considering both soil and water availability but excluding basin transfers (WB, 1985). New estimates consider that irrigation potential accounts for 9.5 million ha (Thai Hydrologist Assembly, 2007).

In 2007, the area equipped for wet season irrigation was estimated at 6 414 800 ha. In 2005, the regional distribution of irrigated area in the wet season was 54 percent in the central plain, 18 percent in the north, 14 percent in the northeast and 14 percent in the south. In 1995, the area equipped for wet season irrigation was estimated at 5 003 724 ha, of which 47 percent in the central plain, 24 percent in the north, 19 percent in the northeast and 10 percent in the south.

In 2007, the area actually irrigated was estimated at 5 089 914 ha, or 79 percent of the equipped area (Table 4).

Surface irrigation is the only technology used in the schemes. Sprinkler and localized irrigation are at an experimental stage only on fruit trees. Generally surface water is used, accounting for 90.9 percent of the total area equipped for irrigation (Figure 4).

Early systems were designed to operate at full capacity only in the wet season. The canal capacities and control regulators are inadequate for the increasing demand for dry season irrigation. Furthermore, irrigation water demand has to compete with demand from other sectors. This becomes a sensitive issue during the dry season. A certain flow of water must be maintained for navigation, to prevent saltwater intrusion, and to supply water for domestic and industrial purposes in the Bangkok area. In the dry season, water resources can no longer meet the increasing water demand from all sectors, and particularly from the irrigation subsector which needs to withdraw more and more water because of the development of dry season irrigation. This water competition has led to poor agricultural performance in recent dry seasons.

Dry season irrigation is practiced on 60 percent of the equipped area. In 1994, dry season irrigation was practiced on 18 percent of the equipped area.

Small-scale projects are those which can be completed within one year and without land compensation. The schemes which cannot be completed within one year or which need land compensation are considered medium-scale. Schemes are classed as large-scale if there is a storage capacity of more than 100 million m3 or if they can irrigate at least 80 000 rais (12 800 ha). Irrigated areas can be divided into the three categories as follows (Figure 5):

  • There were 83 large-scale projects under the Royal Irrigation Department (RID) and operational by the year 2002 with a combined storage volume of 6 662 million m3. In 2007, the total command area was estimated at 2.7 million ha. Water management in these projects is the responsibility of RID and water user groups.
  • There were 607 medium-scale projects by the year 2002 with a combined storage volume of 3 191 million m3. In 2007, the total command area was 898 880 ha. Water management in these projects is also the responsibility of RID and water user groups.
  • There were 10 606 small-scale projects by the year 2002 with a combined storage volume of 2 110 million m3. In 2007, the total benefit area was estimated at 2.4 million ha. Water management in these projects is the responsibility of local governments and water user groups.

By the year 1999, there were 1 985 pumping projects. Essentially these are small-scale projects with electrical pumping from nearby waterways. In 2007, their combined command area is 460 000 ha, mainly in the northeast and north. Water management in these projects is the responsibility of RID and water user groups. In the near future, management responsibility will be transferred to Local Governments.

Role of irrigation in agricultural production, the economy and society

In 2007, total harvested irrigated cropped area was estimated at 7 387 072 ha. Rice accounts for 6 268 080 ha (2 327 158 ha first season rice and 3 940 922 ha second season rice), or 84.9 percent of the harvested irrigated copped area, vegetables represent 83 421 ha (1.1 percent), other annual crops (tobacco, cotton, etc.) 37 396 ha (0.5 percent), sugarcane 256 016 ha (3.5 percent) and other perennial crops 742 159 ha (10.1 percent) (Table 4 and Figure 6). There are also 233 033 ha of fish ponds irrigated, not taken into account in the total, because it is not a crop.

Irrigation development costs area US$3 647/ha as follows: construction of head work US$2 187/ha, conveyance system US$860/ha, field system US$600/ha and maintenance cost US$33/ha per year.

Poverty is observed to be concentrated in non-irrigated areas (or rainfed areas).

Status and evolution of drainage systems

Because of the low-lying topography, about 26 500 km2 or 18 percent of the country is inundated during monsoon season each year. During severe floods the affected area may exceed 53 000 km2 or 37 percent of the country and in extreme events like 1998 flood about 66 percent of the country is inundated. Floods are caused by overspills from main rivers and their distributaries, overspills from tributaries and by direct rainfall. Flood control works can reduce floods from the first two, but only drainage can have any effect on the latter two. The basic benefit of drainage is water control – supply as well as removal. The particular benefits can be: i) potential increase in cropped area through earlier drainage; ii) higher yields from transplanted Aman rice through early planting; iii) crop diversification in the wet season through better drainage; and iv) more control over crop calendars and patterns through control of the water regime.

In 1964, a master plan for water resources development was developed. This envisaged the development of 58 flood protection and drainage projects covering about 5.8 million ha of land. Three types of polders were envisaged: gravity drainage, tidal sluice drainage and pump drainage.

Flood control and drainage projects have accounted for about half of the funds spent on water development projects since 1960. They include:

  • Large-scale projects such as the Coastal Embankment Project (949 000 ha), the Manu River Project (22 500 ha), the Teesta Right Embankment (39 000 ha), the Ganges-Kobadak Project (141 600 ha), the Brahmaputra Right Flood Embankment (226 000 ha), the Chandpur Irrigation Project (54 000 ha), and the Chalan Beel Project (125 000 ha);
  • Medium-scale projects such as the Sada-Bagda, Chenchuri Beel and Bamal-Salimpur-Kulabasukhali projects implemented under the Drainage and Flood Control Projects (DFC I to DFC IV) and financed by the World Bank. These projects typically cover areas of 10 000 30 000 ha and involve flood control and drainage with limited irrigation development;
  • Small-scale projects such as those implemented under the Early Implemented Project, the Small-scale Irrigation Project and the Small-scale Drainage and Flood Control Project.

During the National Water Plan Phase I and Phase II period (1986-1991) the Master Plan Organization (MPO) made comprehensive assessment of the ongoing water resources development projects (large-scale irrigation projects, flood control and drainage (FCD) projects, and flood control, drainage and irrigation (FCDI) projects. It was envisaged that the performance of FCD and FCDI projects need to be improved under the NWP. The main emphasis of the FCD projects under this NWP strategy would be on gravity drainage schemes in shallow to medium flooded areas, and submersible embankments in deeply flooded areas. After 1991, FCD projects were implemented under the Flood Action Plan (FAP) by the MoWR. This was a comprehensive plan for the progressive reduction in floods from major rivers in association with improved drainage systems. Under the existing Five Year Plan (Planning Commission, 2009), the Government has approved 12 FC and FCD investment projects in the current Annual Development Programme (ADP) (2009-2010).

In 1993, the total area of wetlands was 3.14 million ha, of which 1.55 million ha were cultivated and 1.38million ha were drained through surface drains. In 1992, the average cost of drainage development was US$192/ha.

Different types of floods occur in Bangladesh. Of the total cropped area, about 1.32 million ha are severely flood-prone and 5.05 million ha are moderately flood-prone. The flood protected area in 1990 was estimated at 4.20 million ha.

Water management, policies and legislation related to water use in agriculture

Institutions

In total 31 ministerial departments under 10 ministries, 1 independent agency and 6 national committees are involved in water resources development, with responsibilities for water policy, irrigation, domestic and/or industrial water supply, fisheries, flood alleviation, hydropower generation, navigation or water quality.

The National Water Resources Committee (NWRC), under the Office of the Prime Minister, is responsible for setting a policy to develop water resources throughout the country.

In general, the Ministry of Natural Resources and Environment (MONRE) is responsible for policy planning while the Ministry of Agriculture and Cooperatives (MOAC) is responsible for implementation.

The National Economic and Social Development Board is responsible for economic planning.

The Department of Groundwater Resources, under the MONRE, monitors groundwater resources, while surface water monitoring is mainly carried out by the Department of Water Resources, and the Royal Irrigation Department, which has its own network.

Many departments or agencies are involved in water supply for domestic or industrial purposes. The main one is the Metropolitan (or Provincial, outside Bangkok) Waterworks Authority. Wastewater treatment and water quality are mainly the responsibility of the Ministry of National Resource and Environment.

Large dams are operated either by RID or by the Electricity Generating Authority of Thailand (EGAT), while small dams have been developed by the Land Development Department or the Department of Water Resources.

The Harbour Department is in charge of protecting inland waterways, and of issuing licenses for navigation.

Irrigation is managed by the RID for public schemes, or by the Department of Water Resources. The RID is the supervising agency for private irrigation.

Water management

Within the irrigation areas there are 4 levels of water user organizations as follows:

  • Water User Group (WUG): These are the smallest groups, responsible for one tertiary irrigation canal. In 2004, there are 14 930 WUG with 358 846 farmer members.
  • Integrated Water Users Group (IWUG): This is integration of many WUG to cover one level up of irrigation canals, the secondary canals. In 2004, there are 410 IWUG with 234 203 farmer members.
  • Water Users Association (WUA): This is an IWUG with legal recognition. In 2004, there are 40 WUA with 17 575 farmer members. IWUG is not profit oriented.
  • Water Users Cooperative (WUC): This is the cooperative form of a WUA. In 2004, there are 83 WUC with 53 158 farmer members. WUC is business-oriented.

Participatory irrigation management (PIM) and cost sharing in water management are encouraged in all the RID irrigation areas but not widespread.

Policies and legislation

By 2025, Thailand is projected to have sufficient water of good quality for all users through efficient management, organization and a legal system to ensure the equitable and sustainable use of its water resources with due consideration to the quality of life and participation of all stakeholders.

Thailand’s nine-point National Water Policy and Vision, as set forth by RID, details how this will be implemented:

  • Accelerate promulgation of a Draft Water Act as the framework for national water management by reviewing the draft and implementing all necessary steps to make it effective, including reviewing existing laws and regulations;
  • Create water management organizations both at national and river basin level with supportive legislation. The national organization is responsible for formulating national policies, monitoring and coordinating activities to fulfill the policies. The river basin organizations are responsible for preparing water management plans through a participatory approach;
  • Emphasize suitable and equitable water allocation for all water use sectors and fulfill basic water requirements in agriculture and domestic uses, to be achieved by establishing efficient and sustainable individual river basin water use priorities under clear water allocation criteria, incorporating beneficiary cost-sharing based on the ability to pay and the level of services used;
  • Formulate clear directions for raw water provision and development compatible with basin potentials and demand, ensuring suitable quality while conserving natural resources and maintaining the environment;
  • Provide and develop raw water sources for farmers extensively and equitably in response to water demand for sustainable agriculture and domestic uses, similar to deliveries of other basic governmental infrastructure services;

Most laws related to water management are outdated. All existing laws are focused on individual aspect of water management and none on a holistic view (IWRM). There is no law specifying water rights. At present there exists a draft Water Law which specifies water rights, river basin organizations and national apex body for water management. This draft passed the cabinet in June 2007, waiting for approval from the parliament. Earlier versions of this law have been at this stage before but failed to pass.

Environment and health

In 2004, surface water quality classified as “good”, “fair” and “poor” accounted for 48 percent, 32 percent and 20 percent respectively. The classification is done by analyzing water quality of samples taken from natural waterways throughout the country. The overall situation improved compared to the previous year. Critical areas are: lower Chao Phraya in central Thailand and Lower Lam Takong in northeast Thailand. In regional terms, good (surface water quality) and improving are the North, Northeast and South, while the Central is good with mixed improvement, and the East is fair and stable.

In 1999, in the northeast of the country, 10 percent of the irrigated land was affected by salt. The presence of the salt bearing nature of the soil parent material has been identified as the primary cause for this. Other activities, such as irrigation, could be classed as secondary causes for accelerating this locally. Many programmes have been launched in order to correctly manage cash crops and paddy on saline soils. Salinization is now reported to be affecting large areas in the coastal parts of the central plain.

Bangkok faces problems of both too much and too little water. Flooding occurs frequently in the wet season due to low average elevation, high tides and inadequate drainage. The Metropolitan Waterworks Authority is unable to supply water to meet all domestic and industrial demand. As a result, in the outskirts of Bangkok, private and industrial abstraction of groundwater exceeds the safe yield of the aquifer. This accelerates the rate of land subsidence (5-10 cm/year), which in turn aggravates the problem of flooding. Indeed, subsidence has caused some parts of the drainage systems to be below the normal water level and has thus rendered them ineffective.

The minimal discharge to maintain a water level of 1.7 m for navigation (this means 300 m3/s released in the navigation channel from Nakhon Sawan to the Chao Phraya dam, and 80 m3/s downstream of the dam) cannot be maintained due to large amounts of water diverted from the river for dry season irrigation in the northern and central regions. This reduced the volume of inland waterway transport fivefold between 1978 and 1990. The volumes of water released by the Bhumipol and Sirikit dams are increasingly important to prevent saltwater intrusion, even if they do not meet the navigation demand.

Leptospirosis seems to prevail in flood-prone and irrigation areas, but is under control. There are no clear impacts (positive or negative) of irrigation on health. This is probably due to the complicated interaction among socio-economic factors and land use changes. People whose paddy is in irrigation areas are better off economically than those in rainfed areas and hence can afford better health care. Changes in land use transform remote irrigation areas into suburban areas with reasonable road access. Poverty is less in irrigation areas than in rainfed areas.

During the period 1984-2007 Thailand has 317 513 cases of HIV, resulting in 87 643 deaths. Most HIV cases occur in the services and agriculture sectors with age ranges from 25 to 34 years.

In 1999, the main the water-borne diseases were acute diarrhoea (affecting 1.48 percent of the population) dysentery (0.14 percent) and enteric fever (0.03 percent). Malaria, as a water related disease, affected 0.12 percent of the population.

The area salinized by irrigation was estimated at 100 000 ha in 1993.

Irrigation water quality has deteriorated in some locations due to pollution of from agrochemicals, industrial waste and other sources. Arsenic contamination of groundwater, particularly water from STW and HTW within 59 out of 64 districts of the country, has been reported in many government and donor agency documents (GoB, UNICEF, WB, FAO). The arsenic concentration has been found maximum within the upper 50 m depth of aquifers in most regions of the country (Water Aid, 2000). In many places concentration of iron and arsenic in irrigation water has gone beyond the limit of safe water quality standards of Bangladesh and WHO. Some diseases and health hazards like arsenicosis, blindness, physical disability, occur due to arsenic toxicity to human body (RDA, 2001). Throughout the country, about 1.44 million tubewells (STWS and HTWs have been affected by arsenic contamination and about 30 million people are exposed to arsenic toxicity (Ahmed, 2007).

In some parts of the country, particularly the Barind Tracts within the NW region, there are already symptoms of deterioration in the natural hydrological regime, water quality effects on soils and growth of agricultural crops, health hazards and effects on the flora and fauna due to decline of groundwater levels. Therefore, careful consideration should be given to these environmental issues in order to harness the beneficial uses of irrigation water comprising both surface water and groundwater resources.

Prospects for agricultural water management

Water management in agriculture is said to have to focus on improving water use efficiency. Reasons for this are: (i) the trend indicates that Thailand’s water shortage is emerging; (ii) the agriculture sector consumes the largest proportion of water.

Improving agricultural water use efficiency must be done through IWRM and must be river basin oriented. To do so, organization and institutional tools must be in place. Organization tools include River Basin Organizations, Apex body and line agencies. Institutional tools include laws, policy and strategies.

In tandem with improving agricultural water use efficiency, the farmers should move from traditional agriculture to modern agriculture, making use of high technology such as precise water control.

Main sources of information

Center for Agricultural Statistics, Ministry of Agriculture and Cooperatives. 2006. Agricultural statistics of Thailand, crop year 2005/06. Bangkok.

ESCAP [United Nations Economic and Social Commission for Asia and the Pacific]. 1991. Assessment of water resources and water demand by users sectors in Thailand. New York, USA.

FAO. 1999. Irrigation in Asia in figures. FAO Water Report No. 18. Rome.

Hydrologist Assembly. 2006. Hydrologist Assembly, 11th Year Volume 10-2006 .Bangkok

National Economic and Social Development Board, Office of the Prime Minister. 2001. The ninth national economic and social development plan 2002-2006. Bangkok.

National Economic and Social Development Board, Office of the Prime Minister. 2006. The tenth national economic and social development plan 2007-2011. Bangkok.

National Statistical Office, Office of the Prime Minister. 2006. Statistical yearbook of Thailand. Bangkok.

Thai Hydrologist Assembly. 2007. Journal of Hydrologist Assembly.

WB [World Bank]. 1985. Options and Investments priorities in irrigation development.