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Uncertainty Based Assessment of Drought Using Standardized Precipitation Index-A Case Study
Drought is a recurrent extreme hydrological event occurring almost every year in Bangladesh. Particularly, the northwest region of the country has been severely affected by the frequent occurrence of droughts. Standardized Precipitation Index (SPI) is the most widely used index for meteorological drought assessment because of its modest data requirements and ease of use. However, SPI's reliability in drought assessment has been questioned due to the presence of uncertainty in its computational process. Although past studies have identified various sources of uncertainty, only a few have explored their influence on drought calculation. Therefore, the aim of this study is to identify the sources of uncertainty in SPI based drought assessment and analyze their effects on drought characteristics. The current study is demonstrated through two selected climate stations, namely Bogra and Ishurdi, located in the northwest region of Bangladesh. Two probability distribution functions, such as gamma and log-normal distributions, are used to calculate SPI over 6-, 12-, and 24-month time scales. The maximum likelihood method is adopted to find parameters for the distribution functions, and Run's theory is employed to determine the drought characteristics. The results indicate that the uncertainty in the SPI calculation is greater at smaller time scales and usually decreases with the increase in time scale and length of data series. It is also evident from the results that the standard gamma distribution performs similarly to the log-normal distribution at larger time scales. This demonstrates that the log-normal distribution can be adopted as a viable alternative to the standard gamma distribution for drought assessment in the study area. The results also show that the uncertainty greatly affects extreme droughts; the higher the SPI value, the greater the chances of uncertainty. It is also found that the sources of uncertainty greatly impact the characteristics and categorization of the drought. The current study thus concludes that a correct and reliable assessment of drought using SPI can be achieved by considering diverse sources of uncertainty and their impacts on the drought assessment.
Uncertainty Based Assessment of Drought Using Standardized Precipitation Index-A Case Study
Drought is a recurrent extreme hydrological event occurring almost every year in Bangladesh. Particularly, the northwest region of the country has been severely affected by the frequent occurrence of droughts. Standardized Precipitation Index (SPI) is the most widely used index for meteorological drought assessment because of its modest data requirements and ease of use. However, SPI's reliability in drought assessment has been questioned due to the presence of uncertainty in its computational process. Although past studies have identified various sources of uncertainty, only a few have explored their influence on drought calculation. Therefore, the aim of this study is to identify the sources of uncertainty in SPI based drought assessment and analyze their effects on drought characteristics. The current study is demonstrated through two selected climate stations, namely Bogra and Ishurdi, located in the northwest region of Bangladesh. Two probability distribution functions, such as gamma and log-normal distributions, are used to calculate SPI over 6-, 12-, and 24-month time scales. The maximum likelihood method is adopted to find parameters for the distribution functions, and Run's theory is employed to determine the drought characteristics. The results indicate that the uncertainty in the SPI calculation is greater at smaller time scales and usually decreases with the increase in time scale and length of data series. It is also evident from the results that the standard gamma distribution performs similarly to the log-normal distribution at larger time scales. This demonstrates that the log-normal distribution can be adopted as a viable alternative to the standard gamma distribution for drought assessment in the study area. The results also show that the uncertainty greatly affects extreme droughts; the higher the SPI value, the greater the chances of uncertainty. It is also found that the sources of uncertainty greatly impact the characteristics and categorization of the drought. The current study thus concludes that a correct and reliable assessment of drought using SPI can be achieved by considering diverse sources of uncertainty and their impacts on the drought assessment.
Uncertainty Based Assessment of Drought Using Standardized Precipitation Index-A Case Study
Lecture Notes in Civil Engineering
Arthur, Scott (editor) / Saitoh, Masato (editor) / Hoque, Asiful (editor) / Rabby, M. F. (author) / Adhikary, S. K. (author)
International Conference on Advances in Civil Engineering ; 2022 ; Bangladesh, India
Proceedings of the 6th International Conference on Advances in Civil Engineering ; Chapter: 10 ; 115-125
2024-01-12
11 pages
Article/Chapter (Book)
Electronic Resource
English
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