Agriculture Reference
In-Depth Information
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Table 25.1
Spatial distribution of drought occurrence in Thailand
Drought severity class (% area)
Total
area (km
2
)
Region
Severe
Moderate
Slight
None
Source
Northeast
168,854
68
17
9
6
OEPP/KU (1996)
North
169,756
1
7
82
10
OEPP/IWB Siam-Tech. (1998)
Central
104,319
4
57
33
6
OEPP/TRTI (1999)
South
71,040
Incidence of drought reported
SU (1997)
but not quantified
=
=
OEPP
Office of Environmental Policy and Planning, TRTI
Thailand Research and Technology
=
Ins
titute, and SU
Songkhla University.
[325
D
rought Index
A
drought index,
D
, is also used to monitor drought conditions in Thai-
la
nd. The index is based on various variables that are given different
w
eights and scores (table 25.2) to compute the index (Eiumnoh, 2000)
:
Line
——
12.
——
Norm
PgEn
i
n
S
ij
W
i
D
=
[25.1]
i
n
W
i
w
here
W
i
is the weight for the
i
th
input variable, and
S
ij
is the score for the
j
th
class of the
i
th
variable.
D
ranges from 1 to 42 for slight drought, from
43 to 84 for moderate drought, and exceeds 84 for severe drought.
[325
A
gricultural Drought Warning System
Although there are numerous departments that routinely collect data rel-
evant to drought monitoring, there is no integrated system for drought
monitoring or early warning at national level. Recently, the Ministry of
Agriculture and Cooperative has taken an initiative and has proposed an
early warning system for agricultural drought based on a better coordina-
tion among different departments and organizations. The proposed system
operates in two modes: time-warning mode and event-warning mode, as
illustrated in figure 25.2.
The time-warning mode is a long-term drought warning system based
on meteorological and physical data. The Department of Meteorology pro-
vides weather information throughout the year. Particularly in the dry sea-
son, the department predicts drought for different parts of the country.
The Department of Land Development provides the information on current
land use, land use changes, and soil types. This mode evaluates the seasonal
as well as monthly weather conditions during the hot and dry season and
helps identify the potential drought-prone areas and their drought sever-
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