Monitoring Agricultural Drought in South Korea - Monitoring and Predicting Agricultural Drought: A Global Study - page 387

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Norm
* PgEn

Fig ure 30.1 Nineteen climate zones of South Korea and seven climate zones of North Korea
(Choi and Yun, 1989).

categorized as drought-risk areas at transplanting stage based on the ratio
of evaporation to precipitation (Choi and Yun, 1989).
About 157,000 ha (8% of Korea's arable land) is damaged by climate
disasters every year, costing about half a billion dollars for mitigation.
Table 30.1 shows areas affected by severe droughts during the 1960s. The
most severe drought occurred in 1968. Drought also occurred in 2001. In
spring, even a small rain deficit can cause agricultural damage due to the
high demand for water for rice transplanting. Every spring, there is at least
some level of water shortage. However, the most severe drought generally
occurs during summer.

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C auses of Drought Occurrence
D rought occurs due to restricted irrigation, lack and uneven distribution
of precipitation in any season, late onset of rainy season, and occurrence of
dr y spells. Agricultural water use is the largest component (45%) of total
di rect water use in Korea (MOCT, 2001). Sometimes agricultural water
us age is curtailed to meet the urban and industrial water demands, and as
a result drought may occur.
The pressure distribution of the marine tropical air mass, polar air mass,
or continental air mass determines the amount of precipitation in summer
se ason. When one of the air masses is excessively strong or weak such that
th e high pressure system is centered over the Sea of Ohkotsk and not over
th e northern Pacific Ocean, a drought begins (Park and Schubert, 1997).