Comparison of the performance of six drought indices in characterizing historical drought for the upper Blue Nile Basin, Ethiopia

Comparison of the performance of six drought indices in characterizing historical drought for the upper Blue Nile Basin, Ethiopia

Bayissa, Y.A. (IHE Delft Institute for Water Education; University of Nebraska–Lincoln)
Maskey, Shreedhar (IHE Delft Institute for Water Education)
Tadesse, Tsegaye (University of Nebraska–Lincoln)
van Andel, Schalk Jan (IHE Delft Institute for Water Education)
Moges, Semu (Addis Ababa Institute of Technology (AAiT))
van Griensven, Ann (IHE Delft Institute for Water Education; Vrije Universiteit Brussel)
Solomatine, D.P. (TU Delft Water Resources; IHE Delft Institute for Water Education; Russian Academy of Sciences)

2018-03-01

The Upper Blue Nile (UBN) basin is less-explored in terms of drought studies as compared to other parts of Ethiopia and lacks a basin-specific drought monitoring system. This study compares six drought indices: Standardized Precipitation Index (SPI), Standardized Precipitation Evaporation Index (SPEI), Evapotranspiration Deficit Index (ETDI), Soil Moisture Deficit Index (SMDI), Aggregate Drought Index (ADI), and Standardized Runoff-discharge Index (SRI), and evaluates their performance with respect to identifying historic drought events in the UBN basin. The indices were calculated using monthly time series of observed precipitation, average temperature, river discharge, and modeled evapotranspiration and soil moisture from 1970 to 2010. The Pearson’s correlation coefficients between the six drought indices were analyzed. SPI and SPEI at 3-month aggregate period showed high correlation with ETDI and SMDI (r > 0.62), while SPI and SPEI at 12-month aggregate period correlate better with SRI. The performance of the six drought indices in identifying historic droughts: 1973–1974, 1983–1984, 1994–1995, and 2003–2004 was analyzed using data obtained from Emergency Events Database (EM-DAT) and previous studies. When drought onset dates indicated by the six drought indices are compared with that in the EM-DAT. SPI, and SPEI showed early onsets of drought events, except 2003–2004 drought for which the onset date was unavailable in EM-DAT. Similarly, ETDI, SMDI and SRI-3 showed early onset for two drought events and late onsets in one-drought event. In contrast, ADI showed late onsets for two drought events and early onset for one drought event. None of the six drought indices could individually identify the onsets of all the selected historic drought events; however, they may identify the onsets when combined by considering several input variables at different aggregate periods.

Comparison of indices
Drought assessment
Drought indices
Upper Blue Nile

http://resolver.tudelft.nl/uuid:45a960f4-a8bd-407c-8548-a5150578ddd1

https://doi.org/10.3390/geosciences8030081

Geosciences (Switzerland), 8 (3)

Institutional Repository

journal article

© 2018 Y.A. Bayissa, Shreedhar Maskey, Tsegaye Tadesse, Schalk Jan van Andel, Semu Moges, Ann van Griensven, D.P. Solomatine