Meteorological drought in Bangladesh: assessing, analysing and hazard mapping using SPI, GIS and monthly rainfall data

This study focused on assessing and analysing meteorological drought characteristics of Bangladesh based on rainfall, standardized precipitation index (SPI) and geographic information system (GIS). SPI and monthly rainfall time series dataset for the period of 1971–2010 were used to define the drought years and severity. GIS techniques, along with inverse distance weighted interpolation, were used to determine the spatial pattern of drought. Drought occurrences with severity were analysed based on 3-month (SPI-3 January and SPI-3 April) and 6-month (SPI-6 April) time scales. Drought occurrence maps were generated in GIS environment by summarizing the percentage of drought occurrence for each category and for each time scale. For drought hazard mapping, a drought hazard index was computed from 34 observation stations using analytical hierarchy process, weighted sum method and drought occurrence with different severities at different time scales. Afterwards, index values were interpolated and classified into four hazard levels viz. low, moderate, high and very high. This study pointed out that 1972, 1978, 1981, 1982, 1995, 1997, 1999, 2004, 2006 and 2010 were the most drought-affected years since 1971, and 1972, 1978, 1982, 1995, 1999 and 2006 were the worst drought years based on severity. In the last two decades, Bangladesh had high numbers of severe and extreme droughts. Drought occurrences showed that during the study period, comparatively moderate drought occurred more frequently than severe and extreme. The time scale SPI-3 January was more prone to severe drought occurrence while the time scale SPI-3 April was more prone to extreme drought occurrence. The northern, north-western, western, south-western and central parts were the most drought-prone areas of the country in terms of occurrence and severity. Low annual and seasonal rainfall, high variability in rainfall and climate change impacts, and particularly increased maximum temperatures greatly influence droughts in Bangladesh. On the other hand, drought hazard maps of SPI-3 January, SPI-3 April and SPI-6 April showed that high and very high hazardous areas were located in the north-west, west and south-west parts of the country. The Rajshahi, Dinajpur, Rangpur, Bogra, Kushtia were the most drought-prone districts (under very high hazard zone) of the country. The districts Jamalpur, Pabna, Jessore, Khulna, Mymensingh and Tangail were also identified as drought hazardous districts (under high hazard zone). Thus, these parts of the country require urgent intervention on a priority basis to mitigate drought impacts.