State of water : Thailand
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State of water environmental issues

The Kingdom of Thailand covers a land area of 513,115 square kilometers. The country extends 1,500 km from north to south and 800 km from east to west. The golden axe shape both the South China Sea and the Indian Ocean. Thailand is bordered by Malaysia in the south, the Union of Myanmar in the west and northwest, the Loa People’s Democratic republic to the northeast, and Cambodia to the southwest. As reported in 1999, the estimated population was about 62 million with a growth rate of 0.32 percent. The urban population was approximately 12 million with high density in the capital and the regional centers.

Thailand can be divided into four main geographical regions: the North, the Central Plains, the Northeast, and the South. The North is mainly mountainous which serves as the origin of four major rivers (Ping, Wang, Yom, and Nan) which converge to become the Chao Phraya River, the lifeline of the Central Plain. The whole region lies above 200 m elevations. The Northeast occupies one-third of the country’s total land area and is the most populous and lowest income region. The Northeast is a dry plateau at 100 to 200 m elevations. Large parts of this region regularly experience standing with periods of floods and alternating with periods of drought. Saline soils are also the major problem of this region. As a result, the productivity of the land is generally low.

Based on geographical characteristics, Thailand can be divided into 25 river basins. The average of annual rainfall for the country is about 1,700 mm. The total annual rainfall of all river basins is about 800,000 million m³ of which 75 % of the amount is lost through evaporation, evatranspiration and the remaining 25 % (200,000 million m³) is in streams, rivers, and reservoirs (see Table 1). Thus, the available water quantity was about 3,300 m³/ capita/year (Office of National Water Resources Committee, 2000).

Table 1: Watershed Areas and Annual Runoff of the Major River Basin in Thailand
Basin No River Basin Name No Watershed area
Annual run-off
[million m³.]
1 Part of Salawin 17,920.19 8,156
2 Part of Mekong 57,422.07 15,800
3 Kok 7,895.38 5,119
4 Chi 49,476.58 8,035
5 Mun 69,700.44 21,767
6 Ping 33,891.71 6,686
7 Wang 10,790.74 1,429
8 Yom 23,615.59 1,430
9 Nan 34,330.16 9,518
10 Lower Chao Phraya 20,125.25 4,925
11 Sakae Krang 5,191.43 519
12 Pasak 16,292.24 2,708
13 Tha Chin 13,681.24 2,815
14 Mae Klong 30,863.76 12,943
15 Prachinburi 10,481.32 4,502
16 Bang Pakong 7,978.15 4,900
17 Part of Tonle Sap 4,149.97 1,193
18 East Coast Gulf 13,829.72 25,960
19 Phetchaburi 5,602.91 1,140
20 West Coast-Gulf 6,745.33 1,013
21 Peninsular-East Coast 26,352.78 35,624
22 Tapi 12,224.53 17,380
23 Thale Sap Songkhla 8,494.97 7,301
24 Pattani 3,857.82 3,024
25 Peninsular-West Coast 21,172.25 9,918
Total 512,065.81 214,128
Sources: Office of the National Water Resources Committee (2000)

For water quality the results water quality monitoring program showed that most receiving waters were still compiled with the water quality standards and guidelines. However, rivers in populated areas were polluted due to the discharges of wastewater from various point sources. Thus, mitigation measures such as construction of wastewater treatment plants, hazardous waste treatment, agricultural waste management, industrial waste control, and management of other pollution sources are required.


  • Office of National Water Resources Committee. 2000. National Water Vision: A Case Study of Thailand.
  • Simachaya, W. “Water Quality Management in Thailand”.

Water Quality Situations

Like many countries in Asia, increasing population, economical, agricultural and industrial expansion in Thailand are the major causes of water quality in various water sources, including surface water, ground water and sea water to be deteriorated. High loading of pollutants from human activities beyond the water resource carrying capacity can contribute to degradation of water quality in the country.

In general, the water quality of water resources in Thailand is in fair condition with a significant trend of improvement. However, the surface water quality of major rivers, lower Chao Praya, Tha Chin, Lam Takhong and Songkhla Lake, particularly in the areas where receiving pollutants discharged from industrial, agricultural or populated areas. Similarly, the coastal water in the Inner Gulf and certain highly populated areas of the Outer Gulf of Thailand are in poor quality, particularly in the areas into which four main rivers flowing (Mae Klong, Tha Chin, Chao Phraya and Bang Pakong Rivers). Despite the currently good condition of the coastal water quality, high levels of significant pollutants are closely monitored in many densely-populated and/or tourist areas of the Andaman Sea.

Surface Waters

In 2003, Pollution Control Department (PCD) monitored the quality of 49 rivers and 4 lakes in Thailand. Finding revealed that 68% water bodies surveyed were suitable for agriculture and general consumption (“good” and “moderate” quality) Only less than 40% of Thailand’s surface waters were in poor or very poor quality. According to the survey of major rivers and lakes by PCD, no surface water was categorized as “very good” quality (extra clean water which is suitable for aquatic animals and human consumption after normal treatment), and the surface water quality appeared to be slightly worse than that of last year in terms of dissolved oxygen (DO) and total coliform bacteria (TCB) indicators.

Surface water quality varies widely in the different regions in Thailand. Water quality studies by the PCD revealed that surface water monitored in the Northern Central and Southern regions appear to have poor quality; while water in the Eastern region was fair. Compared to the other regions, the rivers and lakes monitored in the Northeastern region had good quality surface water.

In terms of DO, surface water in the Northern regions rank the best, approximately 6 mg/L, followed by the Northeastern region with DO concentration around 4 mg/L. The Central, Eastern and Central regions rank the lowest, about 2 mg/L. The highest concentration of TCB, among surface waters monitored, is found in the Central region with concentration of TCB higher than 4000MPN/100ml, while the surface water in the other regions have relatively lower TCB levels.

Coastal Water

During 2003, PCD has set up 240 monitoring stations in 23 provinces along the 2,600 km coastline and significant islands. In 2003, monitoring results showed that coastal water of 68% of the stations were in “very good” and “good” quality, while 30% of the stations were in “fair” and only 3% were in “poor” quality. Compared to the data in the past, the coastal water quality has been significantly deteriorated, specifically in the areas into which the 4 main rivers flowing. The concerned pollutants are DO and TCB.

Water quality in the Inner Gulf of Thailand, into which four main rivers and several canals discharged, revealed high concentration of domestic pollutants. Very low DO level (0.3, 1.8-3.5 mg/L) were found in the areas of Khlong 12 Thanwa, Mae Khlong and Tha Chin, respectively. Additionally, TCB and certain heavy metal level appeared to be higher than allowable standards in the same area. Moreover, at Bang Pakong areas the total suspended solid (TSS) appeared to be high.

The Western Seaboard, areas of tourist attraction sites, tiger shrimp and oyster culture, generally appeared to have “good” water quality. However, TCB levels in some particular areas where domestic wastewater discharged into the sea without treatment exceeded the Standard. Water quality in most areas of the Eastern Seaboard was in “good” condition, except for high levels of and Total Suspended Solid (TSS) and TCB at the areas of Lam Chabang Port, Map Ta Phut Industrial Estate. Despite the rapid growth, the overall coastal water quality in the Andaman Sea were still in very “good” condition, except for the few areas revealed slightly concerns of DO and TCB levels.

Recently, PCD has established the Environmental Quality Index for Tourist Beach and Islands to evaluate environmental conditions suitable for tourists. PCD conducted excessive survey throughout since 2003 for coastal water quality, amount of solid waste found on beaches, land use, conditions of sand dune, erosions and coral reef. Results from the survey shown the environmental quality was in “good” condition with a slight improvement in some areas such as Jom Tien, La Mai, Pa Thong and Loh Dalam Beahces.

Ground Water

Ground water is mainly recharged by rainfall and seepage streams. Aquifers yield a large amount of water throughout Thailand, with the exception of the Eastern region. The largest source of groundwater is found in the Lower Central Plain, particularly in Bangkok Metropolitan Region (BMR) and surrounding provinces, and is being used to meet the growing water demand.* Unlike the other regions, some ground water extraction data is available for the central region.

Agricultural run-off, coastal aquaculture, industrial effluents and domestic sewage are responsible for the pollution of groundwater in Thailand. Also, the lack of an appropriate pricing policy is leading to over-exploitation of groundwater beyond sustainable yield levels. There is limited information on groundwater extraction rates, or the extent of contamination at the national level.

* Water demand doubled between 1980 and 1990 to reach a daily amount of about 43,000 million cubic meters, and it is growing at the rate of 10 percent annually. Demand is projected to continue roughly doubling each decade for at least the next twenty years.

Reference: “Thailand State of Environment: The Decade of 1990’s”
  “State of Water Pollution 2003”


Thailand Water Quality for 2003