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Thailand Irrigation
Thai farmers traditionally relied on rain and flood water for
crops, but the amount needed for rice cultivation was not always
received. By the mid-1800s, a number of canals had been
constructed in the central plain to carry floodwaters from the
Chao Phraya, and in the latter half of the century other canals
were dug. The canals did not form a controlled irrigation system,
however, but simply a distribution net, and whether additional
water could be made available depended on the level of the
rivers. Records covering almost a hundred years to 1930 showed
that in about one-third of the years water from the rivers was
insufficient, resulting in considerable crop losses. In 1902 the
government contracted with a Dutch expert to develop a controlled
irrigation plan for the entire country but failed to take further
action. Droughts in 1910 and 1911 led to renewed interest and the
hiring of a British irrigation specialist. Nevertheless, the
first irrigation project was not completed until 1922.
By 1938 about 440,000 hectares had been irrigated. Supply
problems held up projects during World War II, but work resumed
with renewed vigor in the late 1940s. By 1950 the irrigated area
totaled nearly 650,000 hectares. In 1950 Thailand secured the
first of a series of loans from the
World Bank (see Glossary) for
the construction of the vital Chainant Diversion Dam on the Chao
Phraya and a number of major canals. By 1960 over 1.5 million
hectares had been irrigated, almost entirely in the Center and in
the North.
Systematic development of the irrigation system began with
the First Economic Development Plan (1961-66) and was continued
in later plans. New assistance from the World Bank included
financing of the important multipurpose Phumiphon (Bhumibol) Dam
(completed in 1964) on the Mae Nam Ping and the Sirikit Dam
(completed in 1973) on the Mae Nam Nan. These dams, both of which
have associated hydroelectric power-generating facilities,
impound water at two large reservoir locations in the Chao Phraya
Basin. Other World Bank-financed projects were also carried out
in this basin during the 1970s, and by the end of the decade
nearly 1.3 million hectares had controlled water flow in the
rainy season, and about 450,000 hectares had it in the dry
season.
The Chao Phraya Basin's natural features, as well as its
size, made it the most important area for irrigation development.
The topography and water systems of the Northeast, by contrast,
were not well suited to large-scale irrigation projects (except
on the Mekong River, which would involve major resettlement
problems). Controlled irrigation potentially could encompass
about 10 percent of the Northeast's 3.5 million hectares of
paddy. Beginning in the 1960s, the Royal Irrigation Department,
founded in 1904 and largely responsible for development and
maintenance of the country's main irrigation systems, constructed
6 large and about 200 small dams in the region. The associated
irrigation system contained design defects, and in the mid-1970s
improvement was undertaken with World Bank assistance. Part of
the irrigable area was receiving water in the early 1980s, but
completion of necessary additional work was not anticipated
before the late 1980s, at which time about 160,000 hectares would
have irrigation throughout the year.
Irrigation work also began in the 1960s in the Mae Nam Mae
Klong Basin, which contained nearly 400,000 irrigable hectares of
paddy. Regulated wet-season irrigation was furnished during the
1970s for roughly 175,000 hectares. A multiple dam completed in
the late 1970s and a distribution system under way in the 1980s
was expected to provide adequate water for double cropping on
over 250,000 hectares. Small irrigation projects also were
started in the 1960s in the South, on the east coast where more
than 500,000 of the region's 600,000 hectares of paddy were
located. About 75,000 hectares had supplementary wet-season
water, and work under way in the 1980s in the Mae Nam Pattani
Basin was expected eventually to serve about 52,000 hectares.
Data as of September 1987
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