Agricultural Drought in Bangladesh - Monitoring and Predicting Agricultural Drought: A Global Study - page 316

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46

Kh arif Drought
Kharif has always been the major cropping season in the country because
of the abundant availability of rainfall during this season. The season
usually begins in July and ends in mid-October. Aman is the dominant
crop of this season, which is usually harvested in December. Currently, the
transplanted variety of Aman is grown over 60% of all cultivable lands
throughout the country. From the viewpoint of the livelihood strategy of
the majority of the people, Aman is the key crop, a failure of which poses
serious threats to the food security of poor households. Unfortunately,
such an important crop reaches its reproductive stage when the available
moisture is significantly reduced. This leads to high moisture stress for the
standing crops, especially during the last one and a half months before the
harvest. Intensity of drought increases with long periods without rainfall
coupled with high temperatures from late October to the end of November.
Supplementary irrigation reduces the risk of Kharif drought signifi-
cantly, especially during flowering stages. Given the intricate river net-
works throughout the country and the fact that most of the croplands are
located in the floodplains, it is possible to cope with Kharif drought if
there are adequate surface flows in the river systems during the postmon-
soon months. In the absence of adequate surface flows, it is also possible
to offer supplementary irrigation to overcome moisture stress, depending
on the availability of groundwater resources.

[316

Line
——
-0.2
——
Norm
PgEn

[316

Ra bi Drought
The drought problem in Bangladesh perhaps reaches it peak during the
Rabi season that extends from mid-October to early April. December, Jan-
uary, and February are the months with negligible rainfall across the 1.75
million ha of the combined catchment area of the Ganges-Brahmaputra-
Meghna (GBM) river systems in the eastern Himalayan region (Ahmad et
al., 1994). As a result, river flows are at their minimum. From March to
early April, the temperatures shoot up rapidly, particularly during the day.
These conditions lead to high potential evapotranspiration (PET), causing
acute moisture stress in the topsoils. When residual moisture can no longer
support the standing crops, drought develops and adversely affects crop
production. The land with very poor moisture-holding capacity, found in
the Barind tract, faces the worst consequences of drought during the Rabi
season.
Drought severity during the Rabi season can be determined by the length
of growing period (LGP). If the LGP in an area is very short (about 80-90
days), the area is likely to suffer very severe drought. With an increase of
LGP by 10 days, the drought severity class changes from very severe to
severe, from severe to moderate, from moderate to slight, and slight to no
drought (Iqbal and Ali, 2001). Figure 24.2 presents the drought-affected
regions of Bangladesh for the Rabi season. Iqbal and Ali (2001) categorized