Agricultural Drought in Indonesia - Monitoring and Predicting Agricultural Drought: A Global Study - page 331

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drought. On average, the total area affected per year by drought is 200,000
ha for rice, 26,000 ha for maize, 10,000 ha for soybeans, and 6,000 ha for
peanuts (Ditlin, 2000).
In extreme drought years, the drought-affected area increases signifi-
cantly. For rice, for example, the total affected area could go up to 900,000
ha, while for maize, soybeans, and peanuts, it could go up to 86,000,
38,000 and 23,000 ha, respectively (Ditlin, 2000). This chapter discusses
briefly the causative factors of drought, drought monitoring systems, and
drought mitigation for the agricultural sector in Indonesia.

C ausative Factors of Drought
A significant decrease in rainfall, especially during the dry season, causes
serious damage to crops. There are many factors affecting rainfall variabil-
ity in Indonesia.

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Ty pes of Rainfall

There are three types of rainfall within Indonesian region (Boerema, 1938).
The first type is monsoon rainfall, which peaks in December. The second is
equatorial rainfall, characterized by two monthly rainfall peaks in March
and October. The third is a “local” type with a monthly rainfall peak in
July-August (figure 26.1).
According to Boerema (1938), monsoon rainfall can be categorized into
two groups (types A and B) that are prevalent in southern Indonesia.
Types A and B indicate a clear distinction between a dry and a wet season
throughout the year. Type A shows a longer dry period (eastern part of
Indonesia, Nusa Tenggara islands) and is drier overall compared to type B
(Java, South Sumatra, and South Sulawesi). The region with type A rainfall
experiences severe drought more frequently. In general, rainfall variation
is larger in the dry season (April-September) compared to the wet season
(October-March).
Type C (local type), which differs from the types A and B, is located
mainly in the eastern equatorial part of Indonesia (e.g., Maluku and So-
rong). Wet seasons of this type are between April and September, while
dry seasons are between October and March. However, the dry periods of
this type are not as dry as those of type A or even type B. As a result, the
total rainfall in a year is relatively high.
Equatorial-type rainfall can be divided into two groups, types D and E.
Type D covers the west coast of North Sumatra with no pronounced dry
season, and rainfall increases slightly around March and October. Type E
covers the west coast of South Sumatra with uniform distribution of rainfall
throughout the year.
The length of the wet season varies from as long as 280-300 days to as
short as 10-110 days. The seasonal rainfall during the wet season varies
from as high as 4115 mm to as low as 640 mm. The early onset and the

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