Analysis of Meteorological Drought using Standardized Precipitation Index (SPI) and Reconnaissance Drought Index (RDIst) at Bilate basin, Southern Ethiopia

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Abstract Background: Drought Indices has an important role to assess drought over the surfaces of the Earth. Drought is one of the most complex and severe catastrophes in the study area that causes damage in different ways. The main objective of this study is to assess the spatiotemporal variation of meteorological drought using Reconnaissance Drought Index (RDIst) and Standardized Precipitation Index (SPI) in Boricha District. The study used the long-term gridded rainfall and temperature data in six stations covering the period of (1985-2016). The spatial distribution of drought was mapped using ArcGIS 10.3 spatial analysis tool and interpolated using Inverse Distance Weight (IDW) method.Results: The spatiotemporal variation of meteorological drought was analyzed by using both SPI and RDIst at seasonal and annual timescale. In spring season two extreme droughts were observed in station-2 and 3 with the same SPI value of (-2.26). During summer season in station-3 extreme drought was detected with SPI values of (-2.32), in station-4 one extreme drought was observed with SPI values of (-2.14). In 12 month RDIst time scale, one extreme drought was identified in station-4 during 2012 with RDIst value of (-2.25), and in station-6 one extreme drought has been occurred during 2009 with RDIst value of (-2.23). The study area was affected by drought of slight/mild to extreme droughts at all time scale. MK trend test indicates the tendency of drought was decreased and statistically insignificant in spring and annual timescales except station-1 (12 months SPI) in the study period of (1985-2016). The temporal correlation analysis of SPI and RDIst was applied with the correlation coefficient at seasonal (spring, summer) and annual timescale (r = 0.99) and it’s significant at P = 0.01 levels was achieved, which indicates very strong positive correlation. Conclusion: The study area was more affected by meteorological drought. There is no a station without drought in all parts of the district. The substantial parts of the district are under severe and extreme drought risk, calling for an immediate intervention by the regional and federal disaster risk preparedness and natural resource office to save people and Natural resource.

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