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Chapter 3: Bangkok’s Water System
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Waterway Network in the Lower Chao Phraya Basin
Basically, there are a couple of rivers which form a system of waterways in this region.
They run from the north to the Gulf of Thailand, and the Chao Phraya River is the main river that
cuts through the city of Bangkok. Surrounded as they were by the water, it was inevitable that the
Thais would excel as hydraulic engineers, modifying rivers and digging canals to serve
development needs. The thousands of kilometers of tiny waterways that thread through
Ayudhya’s (discussed in Chapter 1), and later Bangkok’s, suburbs, paralleling and intersecting
each other like rural roads, suggest a culture inveterate, untiring excavators. On the Chao
Phraya, the scope of their work expanded from the khlong lat short-cut canals of the Ayudhya
period to the grand chuam maenam canals of the early 19th century dug to convey soldiers or
goods, drain low areas, and facilitate provincial administration. By the 1830s, the cessation of
wars with neighboring countries and the rise of a new economic and political dynamism dictated a
need to improve internal communications by excavating metropolitan waterways and rural canals
to open up land for cultivation, to transport produce from the farms to Bangkok and other urban
centers, and to send goods to provincial towns.
Figure 3.1 Lower basin canals.
Source: Beek, Steve Van. The Chao Phya River in Transition. Singapore: Oxford, 1995 (122)
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Until the 19th century, construction of shortcuts and auxiliary canals had not significantly
altered the river’s basic structure. The driving force of canal construction was the attractive prices
offered in world sugar markets. Introduced into Thailand in 1809, sugar was identified by the
Bowring Threaty of 1855 as an export product with enormous potential.1 Between 1857 and
1868, four new chuam maenam canals (to connect one river to another) (Figure 3.1), initiated and
financed primarily by royalty, opened the Western Central Plains to sugarcane cultivation. In
1860, Khlong Mahasawat (17.1 kilometers long, 14.0 meters wide, and 3.0 meters deep) was dug
to link Bangkok with the Tha Chin River. Khlong Chedi Pucha, an extension of Mahasawat,
began at Tha Nam on the Tha Chin River and ran 11.2 kilometers to Wat Phra Ngam in Nakhon
Pathom.
Another set of canals was dug south of, and parallel to, Mahasawat-Chedi Pucha.
Damnoen Saduak, 21 kilometers long, linked the Tha Chin River at Bang Yang to the Mae Klong
River at Bang Nok Kwang. Dug between 1860 and 1868, it was financed primarily by sugar tax
revenues originally intended for construction of a royal palace at Phetchaburi. Khlong Phasi
Chareun (fruit of tax) (1866-72) was financed by the “opium tax farmer”, a private citizen who had
purchased a government concession to collect duties on opium production. The canal ran 15.5
kilometers from Khlong Bangkok Yai at Wat Pak Nam to Ban Don Kai Di in Samut Sakhon
province. Fourteen meters wide, it quickly became a major trading route between towns along
the Tha Chin River and Bangkok.
In the 1870s, King Chulalongkorn began modernizing Thailand’s administration and
economy. The river in this period was regarded as an engine for development. There were two
phases of canal digging in his reign. The first phase (1870-1910) created canals to transport
sugarcane between plantations in the west and Bangkok. The second (1886-1910) opened
forested land north-east of Bangkok to rice cultivation. Originally conceived to serve sugar-cane
interests, Khlong Sawat Premprachakon became a conduit aiding rice farmers. Completed in
1872, the 31.8-kilometer canal connecting Khlong Padung Krung Kasem and Khlong Kho via Don
Muang was the first to be surveyed with theodolites.
To aid new cultivators and to facilitate communication with eastern towns, Khlong
Nakhon Nuangket was dug in 1876-7. The 63.25-kilometer-long, 12-meter-wide canal from
Khlong San Sap to Khlong Tha Kai shortened the distance between Bangkok and Chachengsao.
The 28.7-kilometer Khlong Pravet Burirom (1878-80) also shortened the route between Bangkok
and Chachengsao, offering a southern alternative to Khlong Nakhon Nuangket. Beginning at
Khlong Prakanong, it ended at the western entrance to the 25-kilometer-long Khlong Tha Thua,
which intersected the Bangpakong River 16 kilometers below Chachengsao. Four secondary
arterials provided access to new farmland.
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Beginning in the 1870s and covering a period of twenty years, King Chulalongkorn
(Rama V) issued a series of royal decrees which dismantled and ultimately abolished the system
of corvee labor and dept slavery. This created a large manpower pool to clear and cultivate vast
new tracts of forestland in the lower valley, and endeavor which contributed to the expansion of
Thailand’s role as a major rice exporter. These initiatives shaped the next and most ambitious
phase of canal construction, the Rangsit Project.
Initiated in 1890, the Rangsit Project, Thailand’s first comprehensive irrigation program,
was designed to expand rice cultivation into virgin lower basin lands. Two grids totaling 1,600
kilometers of waterways were to be dug over a period of 25 years. The first was concentrated in
the Rangsit area 20 kilometers north-east of Bangkok; the second phase would open land on the
western side of the Chao Phraya near Supan Buri. Each canal differed from traditional channels
in having a set of gates at the junctions with rivers or larger canals. Each gate could be winched
up or down to control the level and flow of water.
As the complexity and scope of
the project required Western technology
and machinery, the Thai government
commissioned a specially formed Thai and
Italian joint venture to carry out the work.
The basic design was straightforward. A
main 12-meter-wide, 3-meter-deep eastwest canal (Khlong Rangsit) was dug as a
54.8-kilometer spine from the Chao
phraya River to Ongkharak where it joined
a series of canals that carried on to
Nakhon Nayok. Extending at right angles
north and south of the Rangsit were the
ribs: 42 sub-canals 6-10m wide and 1.5-
Figure 3.2 The Rangsit Project.
Source: Beek, Steve Van. The Chao Phya River in
Transition. Singapore: Oxford, 1995 (124)
2.5 meters deep. The 13 longest subcanals were spaced 2.5 kilometers apart and ran north 21.5 kilometers from Khlong Rangsit to a
parallel canal, Khlong Raphipat. A second set of canals was dug from Khlong rangsit to Khlong
Hok Wa, 12 kilometers south of and parallel to Khlong Rangsit. Other canals extended south
from Khlong Hok Wa or ran east-west to connect some of the north-south canals. Engineers
used mechanical shovels mounted on railcars or on barges; in difficult areas, they employed
Chinese laborers. By 1900, nearly 80,000 hectares had been cleared; by the completion of the
company’s activities, 200,000-240,000 hectares had been brought under cultivation.
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Flood Protection System
Figure 3.3 Flooding in Bangkok.
Source: Jumsai, Sumet. NAGA: Cultural Origins in Siam and the West Pacific. Singapore: Oxford, 1988 (170)
Bangkok receives water from three primary sources: rain, north water, and backwater
from the south due to the sea level. These sources contribute to the flooding problem in the city
every year. After a couple hours of heavy rain, several roads look pretty much like canals packed
with paralyzed cars. In many houses, beside cars, small boats are prepared in their garages as
optional vehicles even though these houses are located far away from the water. Land
subsidence has exacerbated the problem, rendering portions of the city lower than the river itself.
At present, the city is partially protected by embankments raised by the Bangkok Metropolitan
Administration (BMA) on riverside streets. Water which overflows these barriers is removed by
large mechanical pumps and returned to the main river. Recent proposals have ranged from
construction of gigantic polders akin to those in Netherlands, to a system of dikes and pumps, to
large suburban reservoirs to store flood water for use during the dry season. Many streets were
to be raised to keep water out of one side, which would fire up a dispute between people who live
within and who live outside the flood protection area because the difference between being
flooded and no flooded is just a distance across a street. Each scheme requires a substantial
investment and the creation of a comprehensive water management master plan.2
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In the 1990s, the Royal Irrigation Department (RID), supported by the present King
Bhumiphol (Rama IX) and the BMA, launched a set of flood protection projects aimed on
comprehensive controlling the water input sources that could harm the city of Bangkok. The
whole system was scheduled to be complete by the year 2004 and it was promised to be the
ultimate system that would provide long-term flood protection for Bangkok.
The system was designed to correspond to the natural flow of water where most canals
feed water to the rivers which play a role as main arteries flowing southward and finally out to the
sea. Thus, the water circulation of the city’s canals tends to flow southward or any direction as
far as it could contribute to the collective flow of the whole system. In order to keep Bangkok’s
streets constantly dry, the new system would require major waterways, including the Chao
Phraya River, to have their banks raised and water gates (equipped with heavy electric pumps)
built at several junctions, to prevent floods caused by both rainfall in the city and water flowing
into the city from adjacent areas. It would also require the waterways to be frequently dredged
and maintained so they could carry water at their full capacity.
Figure 3.4 Small water gate separating a city canal from the Chao Phraya River.
As a complement to the system, a large area to the south of the city was to be sought for
detaining rapid water coming into the city during wet seasons. Therefore, the king initiated a
project called Gam Ling (Monkey’s Cheek Project), which would define some areas near or in
Bangkok for regulating rapid water pouring from the north and preventing backwater from the
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south—the Gulf of Thailand. Preferably, the detention areas should already be flood plains,
lakes, or swamps which already exist so that they would not affect people living in the vicinity.
The mechanism of Gam Ling is that whenever water level increases, the water would be
transferred (by gravity flow or electric pumps if necessary) through designated waterways to large
suburban reservoirs to the south, and if the sea level is lower than that in the reservoirs, the water
gates would allow water to naturally flow into the sea. On the other hand, if the sea level is higher
than the water level in the reservoirs, all the water gates would be closed to prevent seawater and
the water in the reservoirs would be drawn out by the use of electrical machinery. By this way the
reservoirs would always be ready to receive rapid water from the north that otherwise would flood
the city.3 This system not only prevents floods but also helps improving water quality in the inner
city since it keeps water in the urban channels circulated while flushing polluted water out to the
sea. However, it would be another false investment if people do not realize the importance of
water resources. A serious action must be taken to stop wastewater as well as garbage arbitrary
dumping into waterways from household and industrial activities.
After all, people who live outside the flood protection area will have to suffer the truth that
there is no way to avoid the floods unless they learn to adapt themselves to the kind of watery
environment.
The Sinking City
Historically, the delta’s high water table ensured a wealth of aquifers in the claysandwiched layers of sand. Located a dozen meters below ground, the layers brimmed with
water year-round and were replenished by surface water during wet seasons. In 1920s, residents
began boring deep wells and lining them with pipe. As factories were established, they, too,
tapped the aquifers, withdrawing plentiful amounts of water, reducing their dependence on
surface water from rivers and canals. In 1954, the Metropolitan Waterworks Authority (MWA)
began pumping groundwater to augment its surface water supplies. Initially, it withdrew about
8,000 cubic meters per day but by 1982 the daily total had risen to 447,000 cubic meters. In
addition, hotels, factories, and housing estates were drawing about 944,000 cubic meters per
day.
To supplement water supply in the city and suburban areas outside the piping system,
the Department of Mineral Resources (DMR) created the National Potable Water Scheme and by
September 1985 had drilled 22,361 wells nation-wide, bringing the total for the country to 50,00060,000 wells. Pumps extracted approximately 880 million cubic meters of ground water each
year, with about 475 million cubic meters consumed by domestic and industrial users. As the city
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has grown, however, the sheer numbers of people have created dual but related problems. First,
the aquifers have been seriously depleted, some to the point of extinction. Secondly, as a
consequently of the first, the drained aquifers can no longer support the weight of the soils above
them. As a result, between 1930 and 1990, Bangkok sank 1.7 meters; 80-85 centimeters of that
fall occurred between 1978 and 1990.
The first sign of land subsidence appeared in the 1960s but by the 1970s it was reaching
alarming proportions. Sidewalks were separating from buildings and bridges from their
approaches. An Asian Institute of Technology study in 1978 revealed that in most areas of
Bangkok, land was subsiding at a rate of more than 5 centimeters per year and in some places
was sinking 10 centimeters per year. By the 1980s, the suburban rate of decline equaled that of
the inner city. Moreover, the subsidence in the metropolitan area and the eastern suburbs
created a bowl. Trapped water could not drain over the bowl’s lip and into the sea without
extensive pumping.
To halt the subsidence, the government in 1977 passed the Groundwater Act banning the
drilling of more wells. It also attempted to reduce the volume of water drawn from existing wells,
but it took several years before the subsidence rate slowed. In addition, the MWA announced it
would halt its water pumping by 1987 and support enforcement of the Act. Despite its resolution,
it not only failed to cease pumping but in times of surface water shortage has increased the
volume it extracts. For example, in November 1993, it announced it would pump 100,000 cubic
meters of water per day to make up for shortfalls in tap water production, and the DMR would be
asked to provide another 100,000 cubic meters in the same manner. In January 1994, the DMR
announced it would bore 300 new wells.
Today, the situation has grown to serious proportions. According to the DMR in 1990,
1.2-1.4 million cubic meters of water per day were being extracted from 9,000 wells in the
Bangkok Metropolitan Region. More than 80 per cent of this total was consumed by the private
sector, mainly factories and housing estates. These figures, however, were based on known
wells. As the upper aquifers have been drained, it has been necessary to bore even deeper.
Whereas in 1968 the water table lay 12 meters below central Bangkok and 4 meters below the
eastern suburbs, by 1993, it was necessary to drill 100-600 meters in central Bangkok to reach
water.
Since 1989, the subsidence rate in central and northern Bangkok has slowed to 1.5
centimeters per year as the upper aquifers have collapsed. In the eastern suburbs, it had been
reduced 7.0 centimeters per year, although by that time the area around Ramkamheang
University had sunk to 30-40 centimeters below sea level. The city continues to sink, abetting
flooding and salinization, contaminating the aquifers, and necessitating substantial expenditure by
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the public and private sectors to repair damage to infrastructure, including roads and
underground piping systems.
More unsetting is the scenario predicted for the future if Bangkok continues to sink (Map
14). Studies in 1990 found that the sea had been rising 1.0-1.2 millimeters per year for the past
200 years. Global warming could raise sea level by 1.0-1.5 meters over the next 100 years. By
the end of the 21st century, an accelerating rise caused by climate change combined with
continuing land subsidence could see the creation of an enormous bay which would submerge
Bangkok in a salt sea extending from Thonburi to the Hua Mak area and from the present Gulf (of
Thailand) to Bang Khen near Don Muang Airport. Changing weather patterns would also subject
Thailand to tropical storms of the magnitude of those which strike the Philippines and Hong Kong
each year.4
st
Figure 3.5 The lower basin as it may look at the end of the 21 century.
Source: Beek, Steve Van. The Chao Phya River in Transition. Singapore:
Oxford, 1995 (166)
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Two related catastrophic events are occurring simultaneously. Delta growth is slowing
because sediments which would normally build it are trapped behind dams, while other sediments
flow into the river-bottom cavities created by the dredgers and never reach the sea. Without the
flow of aggregate into the Gulf, and with the destruction of mangroves which would buffer the
shore from waves, oceanic forces erode the sea-shore faster than river-borne sediments can
build it up. As has occurred in Taiwan, the vital margin between sea and land may simply
disappear without expensive remedial measures such as placing thousands of concrete blocks on
the shoreline to soften the wave action. The rise in sea level will eventually eliminate the need for
such measures.
1
Beek, Steve Van. The Chao Phya River in Transition. Singapore: Oxford, 1995 (121-123)
Beek, Steve Van. The Chao Phya River in Transition. Singapore: Oxford, 1995 (167)
"Drainage System" 6 Oct. 2000. Online. Internet. 6 Oct 2000. Available http://www.rid.go.th/kk-34.htm
4
Beek, Steve Van. The Chao Phya River in Transition. Singapore: Oxford, 1995 (164)
2
3