Observed meteorological drought trends in Bangladesh identified with the Effective Drought Index (EDI)

Abstract

Countries dependent on small-scale agriculture, such as Bangladesh, can be vulnerable to the effects of climate change and variability. Changes in the occurrence and severity of drought are an important part of this issue and form the subject of this paper. We examined the characteristics of meteorological drought occurrence and severity using the Effective Drought Index (EDI), including the drought events, drought chronology, onset and ending of drought, consecutive drought spells, drought frequency, intensity and severity, using North-Bengal of Bangladesh as a case study. The rainfall and temperature dataset of the Bangladesh Meteorological Department (BMD) for the study region throughout 1979–2018 is utilised. The trends of drought are detected by using the Mann-Kendall test and Sen Slope estimation. We evaluated the performance of EDI using the Standardized Precipitation Index (SPI), historical drought records and rice production. This study finds that seasonal and annual droughts have become more frequent over the period studied in all seasons except the pre-monsoon. In addition, the largest decrease in seasonal EDI is found in the monsoon, both in the Teesta floodplain and Barind tract regions. In the decades prior to the late 2000s, a drought spell typically starts between March and May (±15 days) and ends with the monsoonal rainfall in June/July. In the years since the late 2000s, monsoon and post-monsoon droughts spells have significantly increased. Overall, the peak intensity of droughts are higher in the Barind tract than in the Teesta floodplain, and the frequency and severity of moderate to severe drought are increasing significantly in the Barind tract. The drought frequency has increased by at least 10% in North Bengal of Bangladesh over the periods of 1979–2018. Though EDI is strongly correlated with the SPI index, our analysis shows that, surprisingly, rice production is actually decoupled from meteorological drought (as identified by the EDI and SPI). Hence, this research suggests that there are other significant influences on rice yield beyond meteorological drivers. This could include effects from differing irrigation infrastructure, technology and management strategies in the study regions. Challenges to agricultural production may be exacerbated in coming years, should the identified increasing meteorological drought trends continue. Data AvailabilityThe data that support the findings of this study are available on request from the corresponding author.