Map 3.8. Rainfall-based Indicators of HYV Aman Production Numerical Risk Assessment Map in 9 Selected Regions (Great Districts) of Bangladesh

Source: Authors.

69. 
    Bogra and Rajshahi appear as acutely vulnerable to water deficit. In particular, Rajshahi HYV Aman rice production appears as sensitive to rainfall shortage in April, suggesting a high vulnerability to erratic rainfalls and dry spells during the seedling and/or transplating periods. Similarly, Bogra exhibits acute sensitivity to water deficit during April but also presents “mild” vulnerability during May; suggesting a more spread seedling/transplanting period.
    
70. 
    Jessore and Faridpur HYV Aman productions appear as “mildly” sensitive to rainfall-deficit-driven stress. Specifically, Jessore Aman yields respond negatively to deficit rainfall during May, June, and July. In addition to being consistent with the BARC risk map that classifies the Jessore region as “moderately” vulnerable during the Kharrif period, this result also reflects the rainfall season’s historic temporal distribution (figure 3.9) that shows a later monsoon onset in Jessore than in other regions in Bangladesh. Likewise, Faridpur Aman production appears to be more vulnerable to May rainfall deficit.
    
71. 
    The southern area of the northeastern Districts of Patuakhali and Sylhet, bordering Bengal Bay, are markedly vulnerable to acute excess rainfall. In effect, as shown in the Bangladesh isohyets map (map 3.7), while Sylhet is situated in the highest precipitation region of Bangladesh (receiving over 5,000 mm of rainfall annually), the Patuakhali region is also one of the regions receiving higher rainfall (over 3,000 mm annually). Sylhet HYV Aman production appears as particularly vulnerable to excess rainfall during July, which is during the monsoon’s peak rainfall period. In effect, severe rainfall can impinge upon the highly sensitive yield-formulating reproductive stage of rice. On the other hand, the rice production in Patuakhali is acutely vulnerable to excessive rainfall in April, during the transplanting period.
    
72. 
    In the analysis, Rangpur stands out as the only District where HYV Aman rice production is vulnerable to both deficit and excess rainfall. However, the cultivation is found to be exposed to these different rainfall-driven risks during distinct time periods. On the one hand, the selected indicators show a “mild” vulnerability to deficit rainfall during May and June (the monsoon rainfall peak period), which coincides with the water-stress-sensitive reproductive stage. On the other hand, the Aman cultivation appears as “acutely” vulnerable to excess water stress during October. Excessive rainfall during this grain maturing and/or harvesting period can cause grain germination or rotting, both reducing yields.
    
73. 
    The indicator-based, rainfall-driven production-risk-assesssment approach allows a meaningful capturing of the risk deriving from a single weather parameter. Nevertheless, this method also presents constraints as exemplified in the three Disitricts where the risk assessment was “inconclusive.” For the purpose of studying the feasibility of weather-index insurance, this highlights the need to carry out more detailed analyses at the sub-District level in order to undertstand the more localized effect of weather on crop production. The climatic profile of the three Districts chosen for this study is presented below. The result of the detailed indicator analysis for rice production in each of these areas is presented in chapter 4.
    

74. 
    The present study focused in three Districts in order to characterize and study the weather-driven rice production risk. The Districts are Dinajpur, Bogra, and Pabna.
    
75. 
    Figure 3.12 shows the monthly temperature variation, which is similar in the three studied areas. The average maximum temperature reaches a peak of 34.1°C in April (before the Aman transplanting period) before dropping below 32°C at the end of June and reaching a minimum of 24.7°C T_max in January. On the other hand, with an average of 20.3°C, the minimum temperatures stay above 20°C from April to November and reach an annual low of 11.1°C in January).
    

Source: Authors.

76. 
    Dinajpur, Bogra, and Pabna are, from north to south, situated in the northwestern region of Bangladesh. With an average annual rainfall of 1,866 mm, the northern District of Dinajpur receives higher rainfall than Pabna and Bogra, which receive annual average rainfall of 1,590 mm. and 1,542 mm, respectively (figure 3.13 A, B and C).
    

Source: Authors

77. 
    Although receiving a higher rainfall of 270 mm more than Pabna and Bogra, Dinajpur’s monthly and annual rainfalls are also more erratic.³⁸ Nevertheless, in spite of the slightly higher rainfall and more intra- and interannual rainfall variability, Dinajpur in general is not characterized as a flood-prone area in Bangladesh; only a northern third of the District is classified as low “flash flood” prone.
    
78. 
    Instead, Dinajpur’s data suggest more exposure to rainfall deficit. In particular, the monsoon onset period of April–May displays the highest rainfall variability among the three studied Districts (figure 3.13 C). This period coincides with the transplanting of Aman rice. However, according to the drought risk mapping carried out by BARC,³⁹ the pre-Kharif period (March to the end of May) is less drought-prone than the Kharif period (June–October). While during the pre-Kharif period, the District ranges from “slightly” to “moderately” drought-prone from the northeast to the southwest, with a pocket of “severely” drought-prone in the Dinajpur-Sadar Upazila, the District is characterized uniformly as “moderately” to “severely” drought-prone from June to October.
    
79. 
    With an annual average rainfall of 1,590 mm, Pabna’s precipitation level is lower than Dinajpur (figure 3.13 B). Rainfall is somewhat more variable than the two other Districts studied during the monsoon’s peak period of June and July (figure 3.13 C).
    
80. 
    The Ganges-bordering area of the District is classified by BARC as “severely” (in the south, river border area) to “moderately” prone to river flooding. The pre-Kharif period is classified as uniformly “moderately” drought prone, but with pockets in the northwest and the west of “severely” drought-prone areas. On the other hand, the District is uniformly classified as “not” to “moderately” drought-prone during the Kharif period,
    
81. 
    While Bogra has overall lower but more stable intra- and interannual precipitations, the monsoon season’s second peak rain in September in Bogra is more pronounced than in the two other studied Districts (figure 3.13 B and C). Concerning drought risk, the rainfall data indicate, in contrast with Pabna and Dinajpur, that the District is subject to higher rainfall variation in Kharif than in the pre-Kharif period.
    
82. 
    The East Jamuna river-bordering area of the District is classified by BARC as a “severely” to “moderately” river-flood-prone area, while the east of the District is not classified as flood prone. From the northeast to the southwest and during the Kharif monsoon period, the District is classified as ranging from “slightly” to “moderately” drought prone with small patches of “severely” drought prone areas in the centre of the District. Another half of the area in the eastern and the western parts of the District are uniformly classified as “slightly” and “moderately” drought-prone areas with no “severely” drought prone areas during the pre-Kharif period.