Abstract:
Drought is an insidious natural hazard that results from a deficiency of precipitation from
normal conditions such that when it is extended over a season or longer period of time to meet
the demands of human activities and the environments. A single drought analysis technique is
not adequate, for Borkena river catchment there was no comparative study, instead
combinations of techniques integrated together have been found preferable. Therefore, this
study aimed to compare four drought analysis techniques and recommend suitable method for
the study area. For this study; the comparison among Standardized Precipitation Index (SPI),
Reconnaissance Drought Index (RDI), Rainfall Anomaly Index (RAI) and Precipitation
Deciles Index (PDI) drought analysis techniques have been inspected to determine the
relation. DrinC software was adopted for the analysis using rainfall as input for SPI, RAI and
PDI techniques and both rainfall and PET for RDI to get output. Daily meteorological data
were collected from NMA for 1987-2017 and annual time series scales used in the analysis.
The compared results showed that all drought analysis techniques have positive correlation
and very strong relation among SPI, RDI, RAI and PDI with values of R2 greater than 0.8
except Majete station. SPI and RDI drought analysis techniques showed very strong positive
correlation relation and even they have strong correlation at Majete station with R2= 0.604.
This implies that for selected stations only SPI and RDI showed strong correlation. The
comparison result based on drought classes and frequency showed SPI and RDI perform
almost similar as compared to other selected drought analysis techniques to determine
drought frequency and drought classes. These lead to say SPI and RDI are the best techniques
than other selected drought analysis techniques for the area. Therefore; it is advisable to use
SPI and RDI for further study about drought condition for the study area.
