A new early warning drought index for Ethiopia

International Journal on Environmental Sciences, 2020

This research is intended to characterize drought intensity, duration, and areal extent of meteorological drought in the Awash River basin. Using rainfall data and evapotranspiration data is useful to determine the spatial distribution and characteristics of drought and understanding the characteristics is important for monitoring and establishing an early warning system. Reconnaissance Drought Index (RDI) was used for the identification of drought conditions, Mann-Kendall test is used for determining the trend, and ArcGIS is used to analyze the areal extent of drought in the Awash River Basin. The basin is affected by mild, moderate, severe, and extreme drought in different years. The duration of dry months ranges between 1- 4 months. Severity is increasing in the upper and middle Awash basin. There is also an aerial shift of extreme drought from the lower basin to the upper and middle part of the basin. The worst drought in recorded in 2015 by its intensity, duration, and areal extent.

International Journal of Climatology, 2003

This study analysed and modified (where necessary) the properties of three drought indices: the Palmer drought severity index (PDSI), the Bhalme-Mooley index (BMI) and the standardized precipitation index (SPI). We modified the original PDSI's recursive formula, potential runoff, and Z index, which produced more realistic results than the original PDSI (designed for the USA) for East Africa. We improved the SPI by first using a plotting position formula designed for the Pearson type III (P3) distribution to transform the smoothed precipitation data into non-exceedance probabilities, which we then transformed into standard P3 variates by the regional flood index method. The modified SPI depicted East Africa's drought conditions more accurately than the original SPI. Using the three indices and East Africa as a case example, we identified eight assessment criteria to determine the most appropriate index for detecting drought events on a regional basis. BMI produced results that are highly correlated to those of the modified PDSI, which suggested that precipitation alone could explain most of the variability of East African droughts. Furthermore, among the three indices, SPI is more appropriate for monitoring East African droughts because it is more easily adapted to the local climate, has modest data requirements, can be computed at almost any time scale, provides relatively consistent power spectra spatially, has no theoretical upper or lower bounds, and is easy to interpret.

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...

This research is intended to characterize drought intensity, duration, and areal extent of meteorological drought in the Awash River basin. Using rainfall data and evapotranspiration data is useful to determine the spatial distribution and characteristics of drought and understanding the characteristics is important for monitoring and establishing an early warning system. Reconnaissance Drought Index (RDI) was used for the identification of drought conditions, Mann-Kendall test is used for determining the trend, and ArcGIS is used to analyze the areal extent of drought in the Awash River Basin. The basin is affected by mild, moderate, severe, and extreme drought in different years. The duration of dry months ranges between 1-4 months. Severity is increasing in the upper and middle Awash basin. There is also an aerial shift of extreme drought from the lower basin to the upper and middle part of the basin. The worst drought in recorded in 2015 by its intensity, duration, and areal extent.

Natural Hazards, 2017

The Niger River basin is drought-prone, and farmers are often exposed to the vagaries of severe weather and extreme climate events of the region. Spatiotemporal characteristics of drought are important for its mitigation. With 52 years of gauged-based monthly rainfall, the study investigates the potentials of Standardized Precipitation Index (SPI) as standard measure for meteorological drought, its characterization, early warning systems and use in weather index-based insurance. Gamma probability distribution type 2, which best fits the rainfall frequency distribution of the region, was used for the transformation of the skewed rainfall data to derive the SPI. Results showed 9, 5, 5 and 6 drought events of severe to extreme intensities occurred in the headwaters of the basin, inner delta, middle Niger, and lower Niger sub-watersheds, respectively. Their magnitudes were in the range 1-5, 2-6, 2-8 and 2-7, respectively. Spatially, results further showed that the 1970s and 1980s drought events were dominantly of moderate (SPI values-1 to-1.49) and severe (SPI values-1.5 to-1.99) intensities, respectively, with sporadic cases of severe to extreme drought intensities occurring in 1970s and extreme to exceptional intensities in the 1980s. Further investigations show that 3-month SPI indicated 85% of variance in the standardized cereal crop yield, which suites well as weather index insurance Electronic supplementary material The online version of this article (

Earth systems and environment, 2018

The aim of this study was to model the relationship between Land Surface Temperature (LST), Normalized Difference Vegetation Index (NDVI), Vegetation Condition Index (VCI), Temperature Condition Index (TCI), Vegetation Health Index (VHI), and Standardized Precipitation Index (SPI) at 3-month timescale in Raya and its environs, Northern Ethiopia. This study answered how NDVI and LST, VCI and TCI, SPI and VHI are related. It also explained better drought indices for meteorological and agricultural drought monitoring. MOD11A2 LST Terra, eMODIS NDVI, and monthly rainfall data of the tropical applications of meteorology using satellite and ground-based observations (TAMSAT) were used. The data were analyzed using a simple linear regression model. The results revealed that the mean LST was high (i.e., between 39.6 and 41.29 °C), while NDVI was poor and unhealthy (i.e., below 0.27) in the lowland area due to unfavorable moisture condition than the mid and highland areas. The regression result indicated that NDVI and LST have a relatively strong negative and significant relationship (R 2 /P = 0.40/0.01 to R 2 /P = 0.62/0.00) in all districts of the study area. This study also reported that there is a positive and significant relationship between VCI and TCI (R 2 /P = 0.38/0.02 to R 2 /P = 0.63/0.00) in all districts of the study area. Furthermore, this study found that the relationship between SPI and VHI is positive and significant (R 2 /P = 0.36/0.02 to R 2 /P = 0.60/0.00) in all districts of the study area. The SPI and VHI indices are suitable for monitoring the incidence of meteorological and agricultural drought. This study may help to improve the understanding of both meteorological and agricultural drought indices relationships.

International Journal of Climate Change Strategies and Management

Purpose The purpose of this paper is to investigate the patterns and trends of drought incidence in north east highlands of Ethiopia using monthly rainfall record for the period 1984-2014. Design/methodology/approach Standard precipitation index and Mann – Kendal test were used to analyze drought incident and trends of drought occurrences, respectively. The spatial extent of droughts in the study area has been interpolated by inverse distance weighted method using the spatial analyst tool of ArcGIS. Findings Most of the studied stations experienced drought episodes in 1984, 1987/1988, 1992/1993, 1999, 2003/2004 and 2007/2008 which were among the worst drought years in the history of Ethiopia. The year 1984 was the most drastic and distinct-wide extreme drought episode in all studied stations. The Mann–Kendal test shows an increasing tendencies of drought at three-month (spring) timescale at all stations though significant (p < 0.05) only at Mekaneselam and decreasing tendencies a...

Pure and Applied Geophysics

This study aims to investigate the standardized precipitation evapotranspiration index (SPEI) using the monthly observed and gridded Climate Research Unit (CRU) dataset across 13 stations in Ethiopia during the period 1970–2005. SPEI is computed at a 4-month timescale to represent drought during the Belg (February–May) and Kirmet (June–September) seasons separately, and at an 8-month timescale to represent the drought during these two seasons together (February–September). The results show that there are extremely strong correlations (R ≥ 0.8) between the estimated precipitation values from CRU and the observed values, with root mean square error (RMSE) of 4–99 mm and mean percentage error (MPE%) of −30 to 73% at most stations. For temperature and SPEI, the CRU shows almost strong correlations (0.6 ≤ R < 0.8), while the dominant values of RMSE and MPE are 0.7–5 °C and −22 to 26%, respectively, for temperature and 0.28–0.96 and −49 to 55%, respectively, for SPEI during the three s...

Drought [Working Title], 2022

Drought is a complex natural disaster unlike flood, which covers a large area when it occurred. This review was conducted on hydrological drought analysis and monitoring status in Ethiopia by reviewing the master plan of eight major river basins and previous research related to drought. A total of 24 article papers was reviewed and it is found that hydrological drought analysis studies cover only 8.33% of all of the river basins in Ethiopia. Researchers in the region have focused primarily on meteorological drought (37.5%) rather than hydrological and agricultural drought analysis. Although Ethiopia has long been dependent on rainfed agriculture for its economy and remains the primary livelihood of the population, the Ethiopian government has begun focusing on transitioning to an industrial economy, placing pressure on the water resource. In a region plagued by drought, drought analysis, and monitoring, drought early warning systems and effective mitigation measures are still limite...

The Ethiopian Journal of Social Sciences, 2021

Droughts originate from deficiency in precipitation over extended periods of time and affect approximately 60% of the world's population. They are the major obstacle to viable rain-fed agriculture. The study was undertaken to investigate the magnitude, frequency and trends of drought incidents in lowlands of the Borana Zone, southern Ethiopia from 1987 to 2017. Coefficient of variation, standard precipitation index, Mann-Kendal test, and Drought Index Calculator were used to analyse the rainfall data. The SPI for the main rainy season, short rainy season and annual period were computed.