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A review of droughts on the African continent: A geospatial and long-term perspective

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This paper presents a comprehensive review and analysis of the available literature and information on droughts to build a continental, regional and country level perspective on geospatial and temporal variation of droughts in Africa. The study is based on the review and analysis of droughts occurred during 1900–2013, as well as evidence available from past centuries based on studies on the lake sediment analysis, tree-ring chronologies and written and oral histories and future predictions from the global climate change models. Most of the studies based on instrumental records indicate that droughts have become more frequent, intense and widespread during the last 50 years. The extreme droughts of 1972–1973, 1983–1984 and 1991–1992 were continental in nature and stand unique in the available records. Additionally, many severe and prolonged droughts were recorded in the recent past such as the 1999–2002 drought in northwest Africa, 1970s and 1980s droughts in western Africa (Sahel), 2010–2011 drought in eastern Africa (Horn of Africa) and 2001–2003 drought in southern and southeastern Africa, to name a few. The available (though limited) evidence before the 20th century confirms the occurrence of several extreme and multi-year droughts during each century, with the most prolonged and intense droughts that occurred in Sahel and equatorial eastern Africa. The complex and highly variant nature of many physical mechanisms such as El Niño–Southern Oscillation (ENSO), sea surface temperature (SST) and land–atmosphere feedback adds to the daunting challenge of drought monitoring and forecasting. The future predictions of droughts based on global climate models indicate increased droughts and aridity at the continental scale but large differences exist due to model limitations and complexity of the processes especially for Sahel and northern Africa. However, the available evidence from the past clearly shows that the African continent is likely to face extreme and widespread droughts in future. This evident challenge is likely to aggravate due to slow progress in drought risk management, increased population and demand for water and degradation of land and environment. Thus, there is a clear need for increased and integrated efforts in drought mitigation to reduce the negative impacts of droughts anticipated in the future.
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Hydrol. Earth Syst. Sci., 18, 3635–3649, 2014
www.hydrol-earth-syst-sci.net/18/3635/2014/
doi:10.5194/hess-18-3635-2014
© Author(s) 2014. CC Attribution 3.0 License.
A review of droughts on the African continent:
a geospatial and long-term perspective
I. Masih1, S. Maskey1, F. E. F. Mussá1,2, and P. Trambauer1
1UNESCO-IHE, Institute for Water Education, P.O. Box 3015, 2601 DA Delft, the Netherlands
2Eduardo Mondlane University, Faculty of Engineering, Av. de Moçambique km 1.5, C. Postal 257, Maputo, Mozambique
Correspondence to: I. Masih (i.masih@unesco-ihe.org)
Received: 31 January 2014 – Published in Hydrol. Earth Syst. Sci. Discuss.: 6 March 2014
Revised: 14 August 2014 – Accepted: 14 August 2014 – Published: 17 September 2014
Abstract. This paper presents a comprehensive review
and analysis of the available literature and information on
droughts to build a continental, regional and country level
perspective on geospatial and temporal variation of droughts
in Africa. The study is based on the review and analysis of
droughts occurred during 1900–2013, as well as evidence
available from past centuries based on studies on the lake
sediment analysis, tree-ring chronologies and written and
oral histories and future predictions from the global climate
change models. Most of the studies based on instrumental
records indicate that droughts have become more frequent,
intense and widespread during the last 50 years. The ex-
treme droughts of 1972–1973, 1983–1984 and 1991–1992
were continental in nature and stand unique in the available
records. Additionally, many severe and prolonged droughts
were recorded in the recent past such as the 1999–2002
drought in northwest Africa, 1970s and 1980s droughts in
western Africa (Sahel), 2010–2011 drought in eastern Africa
(Horn of Africa) and 2001–2003 drought in southern and
southeastern Africa, to name a few. The available (though
limited) evidence before the 20th century confirms the occur-
rence of several extreme and multi-year droughts during each
century, with the most prolonged and intense droughts that
occurred in Sahel and equatorial eastern Africa. The complex
and highly variant nature of many physical mechanisms such
as El Niño–Southern Oscillation (ENSO), sea surface tem-
perature (SST) and land–atmosphere feedback adds to the
daunting challenge of drought monitoring and forecasting.
The future predictions of droughts based on global climate
models indicate increased droughts and aridity at the conti-
nental scale but large differences exist due to model limita-
tions and complexity of the processes especially for Sahel
and northern Africa.
However, the available evidence from the past clearly
shows that the African continent is likely to face extreme
and widespread droughts in future. This evident challenge
is likely to aggravate due to slow progress in drought risk
management, increased population and demand for water and
degradation of land and environment. Thus, there is a clear
need for increased and integrated efforts in drought mitiga-
tion to reduce the negative impacts of droughts anticipated in
the future.
1 Introduction
Drought is a recurrent climatic phenomenon across the
world. It affects humanity in a number of ways such as caus-
ing loss of life, crop failures, food shortages which may lead
to famine in many regions, malnutrition, health issues and
mass migration. It also causes huge damage to the environ-
ment and is regarded as a major cause of land degradation,
aridity and desertification. The impacts of droughts are wit-
nessed at a range of geographical scales. For instance, in-
dividual families or communities may lose their livelihoods
and source of water, subject to acute food shortages and
health issues and the country’s economy may be severely im-
pacted. The available estimates on drought impacts suggest
that, during the period 1900–2013, there were 642 drought
events reported across the world resulting in a huge toll to
humanity, killing about 12 million people and affecting over
2 billion (EM-DAT, 2014). The total economic damages are
estimated at USD135billion (Table 1).
Published by Copernicus Publications on behalf of the European Geosciences Union.
3636 I. Masih et al.: A review of droughts on the African continent
Table 1. Overview of a number of droughts and their impact across
the world during 1900–2013.
# of # of # of Damage
Continent events people killed people affected (×103USD)
Africa 291 847143 362225799 2920 593
Americas 134 77 69505 391 50 471 139
Asia 153 9663 389 1 707 836 029 44251 865
Europe 42 1200 002 15 488 769 25 481309
Oceania 22 660 8034 019 12 303 000
Total 642 11711 271 2163 090 007 135 427 906
Source: EM-DAT: the International Disaster Database. Centre for Research on the
Epidemiology of Disasters-CRED; http://www.emdat.be/database (last access: 13 January
2014).
Drought remains a major disaster causing huge damages to
humanity, the environment and the economy, despite making
considerable progress on monitoring, forecasting and mitiga-
tion of droughts across the world. The lack of desired level
of success could be attributed to many reasons. Drought is
a complex phenomenon, which varies every time in terms
of its onset, intensity, duration and geographical coverage.
The capacity of people facing this hazard may be limited to
avoid adverse impacts compounded by shortcomings in gov-
ernment capacity (e.g. financial, institutional and political) to
provide short-term relieve and install long-term drought miti-
gation measures. There is an urgent and dire need to progress
on various fronts of drought mitigation such as early warning
and forecasting, building the resilience of the societies, short-
term relief efforts, long-term planning and capacity building
(e.g. Calow et al., 2010; Clarke et al., 2012; Dondero, 1985;
Falkenmark and Rockström, 2008; GFDRR, 2011; IFAD,
2010, 2011a, b; Logar and van den Bergh, 2013; Mishra and
Singh, 2010; Msangi, 2004; Sehmi and Kundzewicz, 1997;
Tadesse et al., 2008; Tøttrup et al., 2012; UNISDR, 2004,
2010; Vicento-Serrano et al., 2012; Vogel et al., 2010; World
Bank and GFDRR, 2010).
Understanding gained from detailed analysis of historic
drought events offers enormous possibilities to carry out bet-
ter drought management planning and to mitigate impacts
of droughts (Vicente-Serrano et al., 2012). A sound science-
based geospatial analysis of the past drought events and their
causes can facilitate the improvement of drought mitigation
and preparedness plans. This can also help with determin-
ing the spatial and temporal variability of drought hazard and
the vulnerability of water resources, vegetation systems and
society to drought. The analysis of historical droughts can
provide information on deficits in water demand and likely
impacts on water resources and environment, which is es-
sential for drought risk reduction, planning new projects and
reviewing the existing ones. Such studies can also provide
necessary information on the periodic nature of droughts and
their relationship with increasing water demand or climate
change (Mishra and Singh, 2010). Moreover, the outlook of
the current and future drought events in the historic context
could facilitate in applying low-risk and long-term plans to
use, conserve and sustain water and other natural resources
(Touchan et al., 2008). The current efforts by the scientific
community in this direction are very limited and require fur-
ther attention (Mishra and Singh, 2010; Touchan et al., 2008;
Vicente-Serrano et al., 2012; Vogel et al., 2010). The avail-
able scientific studies do not provide enough geospatial and
long-term temporal coverage of past drought events at global
and continental levels. However, the increasing number of
available studies offers great opportunity to conduct such
an analysis. The major focus of this paper is to review the
available literature in the context of Africa where impacts of
droughts are more severe and result in significant loss of life,
negative effects on people and damages to the economy and
environment. Most countries in Africa also lack the neces-
sary capacity and resources to make required progress to ad-
dress this catastrophic hazard (e.g. GFDRR, 2011; Tadesse
et al., 2008; Vogel et al., 2010).
A recent global review on droughts and aridity by
Dai (2011) indicated that large-scale droughts have fre-
quently occurred during the past 1000 years across the globe.
This review briefly reported a few of these severe and multi-
year droughts in North America, China and Africa, but does
not provide the detailed review of the historic droughts
across the world. For Africa, the focus was on the severe,
widespread and prolonged droughts that occurred during
1970s and 1980s in western Africa (Sahel region). The study
mainly focused on aridity changes from 1950 to 2008 and
provided foresight for the 21st century. One of the impor-
tant conclusions of this paper is that the global aridity and
drought areas have increased substantially during the 20th
century and attributed to widespread drying since 1970s over
Africa, southern Europe, East and South Asia, eastern Aus-
tralia and many parts of the northern mid–high latitudes. The
aridity trends are projected to continuously increase in the
21st century. However, the study of Sheffield et al. (2012)
shows that drought patterns have been increasing over last
60 years, though not as alarming as usually projected. Mishra
and Singh (2010) conducted a comprehensive review on
drought concepts and a critical evaluation of the most widely
used indicators for drought assessment. But the review re-
mains limited in terms of description of the historic droughts
and only briefly mentions few of them with their main im-
pacts. For Africa, the study only enlisted the severe droughts
in Sahel that occurred during 1910s, 1940s, 1960s, 1970s
and 1980s. These droughts caused huge socio-economic and
environmental impacts in this semi-arid region resulting in
massive-scale migration, famine and environmental degrada-
tion (desertification), especially during the last two drought
episodes. The study noted that growing demand for water,
limited sources of water and changes in spatio-temporal pat-
terns of climate are aggravating the drought impacts in the
world.
There are a growing number of studies addressing vari-
ous drought related issues for Africa. Most of these studies
Hydrol. Earth Syst. Sci., 18, 3635–3649, 2014 www.hydrol-earth-syst-sci.net/18/3635/2014/
I. Masih et al.: A review of droughts on the African continent 3637
focused on a specific region, i.e. southern Africa (e.g. Clarke
et al., 2012; Cornforth, 2013; Dube and Jury, 2000, 2002,
2003; Green, 1993; Jager et al., 1998; Manatsa et al., 2008;
O’Meagher et al., 1998; Richard et al., 2001; Unganai and
Kogan, 1998; Vogel et al., 2010), Sahel (western Africa) (e.g.
Giannini et al., 2008; Govaerts and Lattanzio, 2008; Kasei
et al., 2010; Lebel et al., 2009; Lodoun et al., 2013; Traore
and Fontane, 2007; Zeng, 2003), eastern Africa (Horn of
Africa) (e.g. Anderson et al., 2012; Dutra et al., 2013; Syroka
and Nucifora, 2010) and northwestern Africa (e.g. Touchan
et al., 2008, 2011). There are few studies which attempt to
cover more than one region (e.g. Calow et al., 2010; Her-
weijer and Seager, 2008; Rojas et al., 2011; Naumann et al.,
2012; Tadesse et al., 2008; Verschuren, 2004). These and
many other studies are comprehensively reviewed and dis-
cussed in the following sections. Most of them investigate
one or more drought related subjects i.e. the study of a spe-
cific drought event or historic droughts in a country or re-
gional perspective, methodological developments on drought
indicators, causes of droughts, forecasting and early warning
systems, impact analysis and drought risk reduction, drought
planning and management and capacity building. None of
them provide a long-term analysis of droughts considering
past, present and future perspective at the continental scale.
There are a growing number of continental and global data
sets on drought. For instance, there are specific continental
drought monitoring and forecasting systems that deal with
specific drought related information in real time as well as
historical data. The examples are the African drought mon-
itor: http://hydrology.princeton.edu/adm (Sheffield et al.,
2013) and the DEWFORA African drought observatory:
http: edo.jrc.ec.europa.eu/dewfora/ (Barbosa et al., 2013).
Moreover, the EM-DAT database (http://www.emdat.be/
database) provides information on historic droughts recorded
across the world along with their impacts. Significant ad-
vances have been made on the global-scale estimation of
various drought-related indicators (e.g. standardized precip-
itation and evaporation index, SPEI) (Vicento-Serrano et al.,
2012). Several remote-sensing-based data and products have
been developed over time (e.g. Rojas et al., 2011; Sheffield et
al., 2013). These efforts have resulted in significant increase
in the scientific literature and databases, which can facilitate
continental-scale analysis of droughts in terms of severity,
spatial and temporal coverage.
The main objective of this study is to review available in-
formation and literature and conduct a detailed geospatial
and long-term analysis of droughts across the African con-
tinent. We examine the major causes of droughts reported in
the literature and present findings and important discourses
on drought trends (including frequency, intensity and geospa-
tial coverage), temporal variability, desiccation (aridity) and
causes of drought.
Figure 1. Map of the African continent with country names and
rainfall patterns. (Data source: ERA-Interim corrected with GPCP
v2.1; period: 1979–2010. See Trambauer et al. (2014) for detailed
explanation).
2 Materials and methods
2.1 Study area
This study focuses on the entire African continent. How-
ever, analysis and discussion is also presented in the regional
and country perspectives. It is important to note the dif-
ferences in grouping various countries in different regions.
For instance, EM-DAT groups African countries into north-
ern, middle, southern, eastern and western Africa). On the
other hand, many regional studies are focused on Sahel (in-
cludes countries in western Africa between Sahara desert and
Guinea coast rainforest, about 18 to 15N), Horn of Africa
(Ethiopia, Somalia, Kenya), equatorial eastern Africa and
southern Africa. The special reference to countries in a given
region is made wherever deemed necessary. In this study, the
continent is grouped into northern, western (Sahel), eastern,
middle and southern Africa (Table 2).
The rainfall depicts very high spatial and temporal vari-
ability across the African continent (Fig. 1). Northern Africa
receives very low rainfall and has a desert climate. The high-
est rainfall occurs in middle African countries and some
countries along with west coast of West Africa. These coun-
tries have (sub)-humid climatic characteristics. The highest
spatial and temporal variability of rainfall is found across
most of the countries having a semi-arid climate within west-
ern, eastern and southern Africa. Variations within a coun-
try are also important to note, for instance, the eastern part
of Ethiopia receives much less rainfall (semi-arid) com-
pared to the Ethiopian Highlands (sub-humid) in the west-
ern part. There are distinct differences in intra-annual vari-
ability across the regions. Southern Africa receives most of
the rainfall during October–March, whereas Sahel rainfall is
www.hydrol-earth-syst-sci.net/18/3635/2014/ Hydrol. Earth Syst. Sci., 18, 3635–3649, 2014
3638 I. Masih et al.: A review of droughts on the African continent
Figure 2. Geospatial coverage of extreme droughts of 1964–1965,
1972–1973, 1983–1984 and 1991–1992 indicated by 12 months
SPEI (October to September). (Data source: global SPEI database
available at http://sac.csic.es/spei/database.html, version 2.2 re-
trieved in January 2014.)
concentrated during July–August summer monsoon period.
Most countries in the Horn of Africa and equatorial eastern
Africa receive rainfall in two seasons: October–December
(short rainfall season) and March–May (long rainfall season).
Northwestern Africa receives most of the rainfall during
October–April.
2.2 Data and methods
The main data and information sources for this study are
collected from the literature (e.g. published, peer and non-
peer reviewed, unpublished sources). More than 100 litera-
ture sources were studied in detail, after initially skimming
over 500 articles searched from relevant international jour-
nals (individual journals and search engines), African jour-
nals, donor reports and other sources. The list of reviewed
material is not exhaustive, though an effort has been made to
conduct compressive coverage.
The global data set on droughts from EM-DAT website
(http://www.emdat.be/database) were accumulated for the
available period 1900–2013. This data set provides coun-
try/regional/continental level estimates on drought events,
people killed and affected and economic damage. Addition-
ally, a global database on SPEI was used to analyse droughts
with the aim to substantiate the findings of this review (http:
//sac.csic.es/spei/home.html). It is acknowledged that a num-
ber of drought indicators are available, each with its own
Figure 3. Geospatial coverage of selected droughts 1910–1911,
1931–1932, 1940–1941 and 1948–1949 indicated by 12 months
SPEI (October to September). (Data source: global SPEI database
available at http://sac.csic.es/spei/database.html, version 2.2 re-
trieved in Jan 2014.)
strengths and weaknesses (e.g. Mishra and Singh, 2010; Dai,
2011; Zargar et al., 2013). For example, the decile index
(Gibbs and Maher, 1967) is easy to compute; however, it re-
quires a long time series of data to have accurate results. With
the Palmer Drought Severity Index (PDSI) (Palmer, 1968),
abnormality of agricultural droughts can be identified and it
also shows historical aspects of current conditions. The dis-
advantage of this method is that it depends on soil moisture
data and its properties which are often very difficult to assess,
especially at a larger spatial scale and in spatially distributed
manner. The widely used standardized precipitation index
(Mckee et al., 1993; Zargar et al., 2011) seems to have ad-
vantages because it is a simple method that requires few data
(only precipitation) for its computation. The SPEI is a widely
used drought indicator which uses precipitation and poten-
tial evapotranspiration for its computation. It has the ability
to monitor onset, intensity and duration of drought. The indi-
cator is very suitable to study geospatial and temporal varia-
tion of drought including the impact of global warming. This
indicator is primarily related to meteorological drought and
does not offer as such estimates on agricultural, hydrologi-
cal and socio-economic aspects of droughts, though it could
be seen as a proxy to these droughts as eventually they are
caused by the deficit in precipitation. The detail discussion on
various drought indicators and their comparative basic con-
cepts and various perceptions on drought can be found in the
Hydrol. Earth Syst. Sci., 18, 3635–3649, 2014 www.hydrol-earth-syst-sci.net/18/3635/2014/
I. Masih et al.: A review of droughts on the African continent 3639
literature (e.g. Dai, 2011; Mishra and Sing, 2010; Ntale and
Gan, 2003; Smakhtin and Schipper, 2008; UNISDR, 2004;
Zargar et al., 2011).
3 Results and discussion
3.1 Geospatial and temporal pattern of droughts during
1900–2013
The summary of the selected literature reviewed is presented
in Table 2, indicating drought years, geographical location
and key relevant findings. While preparing this Table, an ef-
fort was made to avoid duplication of similar studies and
yet provide geospatial and temporal coverage. Another im-
portant consideration was to examine important discourses
most relevant to the topic of this paper. There are a rapidly
growing number of studies on various drought related is-
sues, especially during the last decade. The available stud-
ies cover most parts of Africa, though coverage is low for
middle Africa which is understandable as in this region cli-
mate is humid and droughts are not as catastrophic as in the
other regions. Meteorological drought remains the main sub-
ject of most studies followed by agricultural drought. Studies
examining hydrological droughts and the impacts of human
uses of water on the assessment and intensification of these
droughts are limited.
Table 3 provides a summary of the drought events recorded
in the EM-DAT database along with the number of people
killed and affected and estimated economic damage. This
widely used database provides very useful information for
this study. However, caution is required while using it for
a specific purpose due to several reasons. First, the avail-
able information underestimates the total number of drought
events per country and consequent impacts. Generally, a
much lower number of droughts are recorded for many coun-
tries (e.g. Morocco, Tunisia, Algeria, Sudan, Zimbabwe and
South Africa) for the period 1900–2013, which prohibits for-
mulating a century-scale picture of drought patterns for these
countries. The information before 1960s is not available for
most of the countries. Similarly, no information is available
for many recorded drought events on the number of people
killed and affected and economic damage. Thus, aggregated
values of these indicators, which are often used, give much
lower estimates of drought effects. Second, in the aggrega-
tion of the number of events, the method used by EM-DAT
and many users takes a country level perspective. In this way,
a drought event occurred during one year in many countries
in a region is counted more than once. This should be prop-
erly examined, especially when studying the region with sim-
ilar climatic regimes. In the scientific literature, regional and
multi-year droughts are often referred as one drought event
(Table 2). This difference limits a straightforward compari-
son of the droughts given in Tables 2 and 3.
38
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
Dec-01
May-05
Oct-08
Mar-12
Aug-15
Jan-19
Jun-22
Nov-25
Apr-29
Sep-32
Feb-36
Jul-39
Nov-42
Apr-46
Sep-49
Feb-53
Jul-56
Nov-59
Apr-63
Sep-66
Feb-70
Jul-73
Nov-76
Apr-80
Sep-83
Feb-87
Jul-90
Nov-93
Apr-97
Sep-00
Feb-04
Jul-07
Nov-10
Moderate Dry
Severe Dry
Extreme Dry
1
Figure 4. Fraction of the African continent under different drought conditions computed from 2
the 12 month SPEI dataset. (Data source: Global SPEI database available at 3
http://sac.csic.es/spei/database.html, version 2.2 retrieved in May 2014). Note: Moderate dry 4
(-1.5 < SPEI < -0.5); Severe Dry (-2.0 < SPEI < -1.5); Extreme Dry (SPEI < -2.0). 5
Figure 4. Fraction of the African continent under different drought
conditions computed from the 12 month SPEI data set. (Data
source: global SPEI database available at: http://sac.csic.es/spei/
database.html, version 2.2 retrieved in May 2014). Note: moder-
ate dry (1.5<SPEI <0.5); severe dry (2.0 <SPEI<1.5);
extreme dry (SPEI<2.0).
A number of inferences are drawn from the analysis of
the available data and scientific evidence reviewed in this pa-
per (Tables 2 and 3). The frequency, intensity and geospa-
tial coverage of droughts have significantly increased across
the entire African continent during the second half of the
1900–2013 period. This inference is supported by studies
conducted at continental scale (e.g. Dai, 2011, 2013) as
well as by most of the regional and country level studies
(e.g. Ouassou et al., 2007; Touchan et al., 2008, 2011, Elagib
and Elhang, 2008; Kasei et al., 2010; Manatsa et al., 2008;
Richard et al., 2001). The available data (though limited in
temporal coverage) from EM-DAT also supports this obser-
vation (Table 2).
This point is further substantiated by Figs. 2, 3 and 4. The
drought shown in Figs. 2 and 3 were reported by most of
the reviewed literature and thus were chosen for the illus-
tration. Figure 2 shows the geospatial coverage of the four
most extreme droughts which occurred during past 50 years.
Three out of these four droughts (1972–1973, 1983–1984
and 1991–1992) were most severe and could be regarded
continental in nature as they spanned over many sub-regions
and covered wide areas of the African continent; none of the
previous droughts during 20th century were as wide spread
and intense in comparison to these (Fig. 3). Figure 4 shows
the area of the African content under different drought cate-
gories based on SPEI data analysis conducted in this study.
On this data, the widely used non-parametric Spearman Rank
test (e.g. Masih et al., 2011) was applied to test the statistical
significance of the trends. The results revealed a statistically
significant increase (at 99% significance level) in the area
under all categories of drought (e.g. moderate, severe and ex-
treme droughts) for the African continent during 1901–2011.
Figure 4 exhibits these findings and the visual inspection also
indicates the increasing trend in the geospatial extent of the
African continent under drought.
www.hydrol-earth-syst-sci.net/18/3635/2014/ Hydrol. Earth Syst. Sci., 18, 3635–3649, 2014
3640 I. Masih et al.: A review of droughts on the African continent
Table 2. Summary of the selected literature reviewed in this study.
Reference Drought enlisted by region/country/basin during 1900
to 2013 Remarks
Northern Africa
Ouassou et al. (2007) Morocco: 1904–1905, 1917–1920, 1930–1935, 1944–
1945, 1948–1950, 1960–1961, 1974–1975, 1981–1984,
1986–1987, 1991–1993, 1994–1995, 1999–2003
The study shows that droughts of 1944–1945, 1982–1983, 1994–1995 and 1999–2000 were
the driest agricultural seasons. Most severe hydrological droughts were 1980–1981, 1985–1986,
1991–1992, 2000–2001, 2002–2003. This study describes the institutional change in drought man-
agement in Morocco with progress, though slow, from crisis management to more risk manage-
ment.
Touchan et al. (2011) Northern Africa – Morocco, Algeria and Tunisia: 1945–
1946, 1981–1982, 1999–2000 The study uses tree-ring chronologies to investigate climate of northern Africa and have con-
structed Palmer Drought Severity Index (PDSI) for Morocco, Algeria and Tunisia back to
AD 1179. The later half of the 20th century emerged as the driest among last nine centuries.
Touchan et al. (2008) Northwestern Africa Algeria and Tunisia: 1920s,
1940s, 1945, 1999–2002 The study uses tree-ring chronologies to investigate climate of northern Africa and has constructed
PDSI for Algeria and Tunisia for the period AD1456–2002. The study mentions 19 droughts
occurred during 20th century compared to 12–16 droughts per century during earlier periods.
However, specific years or decades in which they occur are not given. The multi-year drought of
1999–2002 is the most severe in the last five centuries.
Elagib and Elhang (2011) Sudan: 1969–1970, 1972–1973, 1979–1985, 1990–
1991, 2002–2008 The study examines the drought episodes in Sudan using PDI drought index estimated from rain-
fall and temperature of 14 stations across Sudan for the period 1940s to 2008. The study shows
several multi-year droughts after 1970s and suggested intensifying drought evidence. El Niño is a
major driver of droughts in Sudan.
Western Africa
Dai (2011) Western Africa – Sahel: 1970s, 1980s These droughts were attributed to a southward shift of the warmest SSTs in the Atlantic and
warming in the Indian Ocean.
Druyan (2011) WesternAfrica – Sahel: 1970s, 1980s No trend in future droughts in Sahel in late 21st century. Some studies say wet and some dry
conditions.
Giannini et al. (2008) Western Africa – Sahel: 1970s, 1980s The study investigates the droughts in Sahel during 1970s and 1980s using global climate models.
The results suggest that the origin of these droughts is global in scale and external to the region.
These droughts are attributed to warming of tropical oceans, especially the pacific and Indian
Oceans, superimposed on an enhanced warming of the Southern Hemisphere compared to the
Northern Hemisphere most evident in Atlantic. Land surface changes, driven by precipitation
changes and also anthropogenic activities, may have acted to amplify these droughts.
Kasei et al. (2010) Western Africa – Burkina Faso, Ghana, Mali, Togo,
Volta Basin: 1961, 1970, 1983, 1984, 1992, 2001. Using rainfall data of 1961 to 2005, intensity, extent and recurrence frequencywas estimated using
SPI as a drought indicator. The 1983–1984 drought was most severe covering 90% of the basin
area. Akosomombo lake recorded lowest flows during 1983. The study show that dry years have
become more frequent and occur at shorter intervals. Areal coverage of drought has also increased.
Mishra and Singh (2010) Western Africa – Sahel: 1910s, 1940s, 1960s, 1970s,
1980s The study reviews drought concepts and provides a critical evaluation of the most widely used
indicators for drought assessment. But the review remains limited in terms of description of the
historic droughts and only briefly mentions few of them with their main impacts and recommends
further work in this direction.
Lebel et al. (2009) Western Africa – Sahel: 1970s, 1980s A wealth of data is collected under AMMA-Catch case sites in Mali, Niger and Benin on land sur-
face processes and atmospheric dynamics. This will help in better understanding the interactions
between atmospheric, oceanic and terrestrial systems enabling a better understanding and
prediction of rainfall in this region.
Shanahan et al. (2009) Western Africa – Lake Bosumtwi, Ghana: 1970s Sahel
drought The study indicates that the severe droughts of Sahel in 1970s is not anomalous in the context
of past three millennia and monsoon is capable of longer and more sever future droughts. The
findings are based on sediment analysis from Lake Bosumtwi in Ghana.
Zeng (2003) WesternAfrica – Sahel: Late 1960s onward. The study shows lower rainfall in Sahel since 1960s but the exact drought years are not men-
tioned. The study focuses on reviewing the existing evidence on causes of droughts in Sahel. The
study shows that combination of various factors are responsible for droughts in Sahel and are not
yet fully understood and thus could not be adequately predicted. Therefore, a combination of im-
proved climatic predictions, sensible land use practices and green house gas emission reductions
are very important for the future of this region.
Eastern Africa
Anderson et al.(2012) Eastern Africa: 2010–2011 drought in Ethiopia, Soma-
lia and Kenya The study demonstrated the usefulness of remotely sensed data and hydrological modelling for
tracking the progression and severity of drought.
Dutra et al. (2013) Horn of Africa: 2010–2011 in Ethiopia and Somalia The study shows that droughtwas caused by lack of rainfall inboth the October–December (short
rainfall) and March–May (long rainfall) seasons. The drought was attributed to La Niña
conditions. This drought was well forecasting by the European Centre for Medium-Range Weather
Forecasts (ECMWF) forecasting system.
Hastenrath et al. (2007) Eastern Africa – Kenya: 2005 Drought was attributed to increased pressure in the west and accelerated westerlies (wind)
anomalies
Ntale and Gan (2003) Eastern Africa – Kenya and Tanzania: 1949–1950. The study reviewed various drought indicators and compared the performance of the PDSI,
Bhalme–Mooley Index (BMI) and standardized precipitation index (SPI). Different indicators may
yield different drought results. SPI was recommended for eastern Africa.
Rulinda et al. (2012) Eastv Africa – Burundi, Kenya, Rwanda, Tanzania,
Uganda: 2005–2006 Analyzed spatial propagation of vegetative drought during September 2005 to April 2006 using
10-day NOAA AVHRR images. The drought reached peak in January 2006.
Tierney et al. (2013) Eastern Africa – Horn of Africa: 2010–2011 This drought was regarded as the worst during the past 60 years. The study concluded that the
Indian Ocean SSTs are the primary influence on East African rainfall over multi-decadal and
perhaps longer timescales.
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I. Masih et al.: A review of droughts on the African continent 3641
Table 2. Continued.
Reference Drought enlisted by region/country/basin during 1900
to 2013 Remarks
Southern Africa
Belbase and Morgan (1994) Southern Africa – Botswana: 1978–1979, 1982–1987,
1991–1992. The case study highlights the salient features of the relatively successful drought management
experience in Botswana.
Manatsa et al. (2008) Southern Africa Zimbabwe: 1902–1903, 1911–
1916, 1926–1927, 1941–1942, 1963–1964, 1972–1973,
1982–1984, 1986–1987, 1991–1992
The study identified droughts in Zimbabwe based on SPI estimation from the regionally averaged
rainfall for the period 1900–2000. The moderate to severe droughts are noted here, with 1991–
1992 as the most extreme drought of the 20th century. The study indicate that El Niño–Southern
Oscillation (ENSO) alone is not a sufficient predictor of droughts; furthermore, it shows that the
March–June extreme positive Darwin sea level pressure anomalies are ideal additional candidate
for drought monitoring and forecasting in Zimbabwe and southern Africa.
Msangi (2004). Southern Africa: 1902, 1909–1911, 1917–1918, 1921–
1922, 1925, 1929, 1933–1934, 1939–1940, 1953, 1969,
1972–1973, 1976, 1980–1982, 1984–1985
Information on drought years and respective country is not given. The study mainly focused on
analyzing the drought management efforts by international and regional organizations, national
institutions and NGOs and communities. The study stressed the need for adopting people centred
mitigation measures and calling for informed global action as the success lies with people in the
south and those in the north.
Mussá et.al. (2014) South Africa, Crocodile River catchment: 1945, 1951,
1958, 1966, 1970–1971, 1978, 1983–1984, 1992–1995
and 2003–2004
The main focus of the study is to analyze whether groundwater can be used as an emergency
source of water in cases of severe droughts in the Crocodile catchment. The study used the SPI
and SRI drought indicators to identify meteorological and hydrological droughts, respectively. It
implies that the 1992–1995 drought was the most severe one in the last 70 years where the upper
and lower areas of the catchments were the most affected.
Richard etal. (2001) Southern Africa: 1951, 1960, 1964, 1965, 1968, 1970,
1973, 1982, 1983, 1987 Droughts were not referred per country. The study focused on analyzing droughts from 1950
to 1988 during the summer rainfall period January–March. Droughts during 1970–1988 period
were intense and widespread compared to those during 1950–1969. The ENSO was the main
governing factor for droughts during 1970–1988 (though not always), whereas regional oceanic
and atmospheric anomalies (e.g. southwest Indian Ocean SST) were the main causes.
Rouault and Richard (2005) Southern Africa (south of 10S): 1906, 1916, 1924,
1933, 1949, 1970, 1983, 1984, 1992, 1993, 1995, 1996,
2002, 2003, 2004.
The study discussed these droughts and corresponding area under them at an aggregated level of
the African continent. Country or regional estimates are not available. SPI estimates for the period
1900–1999 are used. The ENSO (El Niño conditions) was attributed to 8 out of these 12 droughts
occurred during 20th century. The area of the African continent under drought has significantly
increased, especially after 1980s.
Vogel et al. (2010) Southern Africa: 1982–1993, 1991–1992, 1994–1995,
2001–2003 This study stresses the need for learning from past drought events to better manage the future. The
response to drought and general management options practiced in Southern African Development
Community (SADC) countries are reviewed, in special reference to indicated droughts.
More than one region
Calow et al. (2010) 2002–2003, 2004–2005 and 2005–2006 droughts in
Ethiopia; 1991–1992 drought in Lesotho, Malawi,
South Africa, Zimbabwe and Ghana.
The study shows the impacts of droughts on groundwater resources and consequently on water
supply security. The communities enter into a spiral of water insecurity when shallow ground-
water supplies fail and additional demand on remaining resources causes mechanical failures.
Declining access to food and access to safe water are interrelated, but the later usually receive less
attention in drought management. Groundwater can act as buffer during droughts by increasing
the coverage of groundwater supplies to rural communities underpinned by sound hydrological
and socio-economic information.
Couttenier and Soubeyran (2013) Sub-Saharan Africa: 1980s. No country or year specific information presented, though droughts in Sudan in 1980s and in
Uganda during 1980s and 2003–2005 are linked to civil war. Overall, the link between drought
and civil war was described as weak.
Rojas et al. (2011) Morocco: 1992, 1995, 1997; Tunisia and Algeria: 1999–
2002; Sahel: early–mid 1980s; Ethiopia and Kenya:
1984 and 2000; Ethiopia, Eritrea and Somalia: 1987;
Southern Africa: 1982–1983 and 1991–1992 (most
countries).
The study examined the major droughts that occurred on the African continent during 1980–2010.
The study proposed that the mixed Vegetation Health Index (VHI), estimated using remote-sensing
data (AVHRR) is a promising agricultural drought monitoring indicator and was able to track
major droughts during 1981–2009 reported in the selected literature.
Tadesse et al. (2008) Sub-Saharan Africa: 1972–1974 and 1984–1985 (Sahel
and East Africa), 1992–1993 (southern Africa), 2000–
2002 (Horn of Africa)
Droughts resulting in severe food shortages and famine are mentioned. The need for moving
from a crisis management to risk management approaches is stressed and the use of the available
drought and food security monitoring tools is recommended to reduce the impacts of droughts.
Vicente-Serrano et al. (2012) Ethiopia, Sudan and Sahel region: 1974; Zimbabwe;
1990–1991; Kenya: 1999–2001; Many countries: 1984;
Congo River: 1960s, 1970s; Orange River:1980s, 1990s
The study demonstrated how the development of drought information systems based on geospa-
tial technology, that combines static and real-time information could improve the possibilities of
drought mitigation in Africa.
Most African countries observe single and multi-year
droughts when seen from purely hydro-climatic point of
view. For instance, a number of severe droughts that occurred
in northern and southern Africa during the 20th century are
comparable to those observed in eastern and western Africa
where comparatively more droughts are reported in litera-
ture and available databases (Tables 2 and 3). However, dis-
tinct geospatial and temporal patterns exist in the drought
episodes mainly driven by the diverse nature of the climate
and drought inducing physical mechanisms (discussed later
in this paper). It can be inferred from the studies reviewed
in this paper (Table 2) that the multi-year and prolonged
droughts are more common in Sahel compared to any other
regions (e.g. Mishra and Singh, 2010; Rojas et al., 2011). In
contrast, studies for the eastern Africa report mostly very se-
vere seasonal droughts often not spanning over many years
(e.g. Dutra et al., 2013).
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3642 I. Masih et al.: A review of droughts on the African continent
Table 3. Summary of drought events recorded for 1900–2013 in EM-DAT database.
# of # of # of Economic damage
Region/countries Drought years events people killed people affected (USD×103)
Overall African Continent 291 847 143 362225 799 2920 593
North Africa 18 150 012 31 153 400 900 100
Algeria 1981, 2005 2 12 0 0
Morocco 1966, 1971, 1983, 1984, 1999 5 0 412 000 900100
Tunisia 1977, 1988 2 0 31 400 0
Sudan 1980, 1983, 1987, 1990, 1991, 1996, 1999, 2009, 2012 9 150 000 30 710 000 0
Middle Africa 25 3058 11 379800 84 500
Angola 1981, 1985, 1989, 1997, 2001, 2004, 2012 7 58 4 443900 0
Cameroon 1971, 1990, 2001, 2005 4 0 586 900 1500
Central Africa Republic 1983 1 0 0 0
Chad 1910, 1940, 1966, 1969, 1980, 1993, 1997, 2001, 2012 9 3000 5 456000 83 000
Congo 1983 1 0 0 0
Sao Tome et Principe 1983 1 0 93 000 0
Zaire/Congo Dem Rep 1978, 1983 2 0 800000 0
West Africa 94 170 012 74 500 255 507 354
Benin 1969, 1980 2 0 2 215000 651
Burkina Faso 1910, 1940, 1966, 1969, 1976, 1980, 1988, 1990, 1995, 1998, 2001, 2011 12 0 8 413290 0
Cape Verde Is 1900, 1910, 1920, 1940, 1946, 1969, 1980, 1992, 1998, 2002 10 85000 40 000 0
Cote d’Ivoire 1980 1 0 0 0
Gambia The 1910, 1940, 1968, 1969, 1976, 1980, 2002, 2012 8 0 1 258000 700
Ghana 1971, 1977, 1980 3 0 12 512 000 100
Guinea 1980, 1998 2 12 0 0
Guinea Bissau 1910, 1940, 1969, 1980, 1980, 2002, 2006 6 0 132000 0
Liberia 1980 1 0 0 0
Mali 1910, 1940, 1966, 1976, 1980, 1991, 2001, 2005, 2006, 2010, 2011 11 0 6 927000 0
Mauritania 1910, 1940, 1965, 1969, 1976, 1978, 1980, 1993, 1997, 2001, 2010, 2011 12 0 7 398 907 59 500
Niger 1903, 1906, 1910, 1940, 1966, 1980, 1988, 1990, 1997, 2001, 2005, 2009, 2011 13 85000 23 655 058 0
Nigeria 1981 1 0 3 000000 71 103
Senegal 1910, 1940, 1966, 1969, 1976, 1979, 1980, 2002, 2011 9 0 8 399000 374800
Togo 1971, 1980, 1989 3 0 550000 500
East Africa 122 523 561 220 892229 371 900
Burundi 1999, 2003, 2005, 2008, 2009, 2010 6 126 3062 500 0
Comoros 1981 1 0 0 0
Djibouti 1980, 1983, 1988, 1996, 1999, 2005, 2007, 2008, 2010 9 0 1 188008 0
Eritrea 1993, 1999, 2008 3 0 5 600 000 0
Ethiopia 1965, 1969, 1973, 1983, 1987, 1989, 1997, 1998, 1999, 2003, 2005, 2008, 2009, 2012 15 402 367 66 941879 92 600
Kenya 1965, 1971, 1979, 1983, 1991, 1994, 1996, 1999, 2004, 2005, 2008, 2010, 2012 13 196 47 200 000 1500
Madagascar 1981, 1988, 2000, 2002, 2005, 2008 6 200 3 515290 0
Malawi 1987, 1990, 1992, 2002, 2005, 2007, 2012 7 500 21 578 702 0
Mauritius 1999 1 0 0 175000
Mozambique 1979, 1981, 1987, 1990, 1998, 2001, 2003, 2005, 2007, 2008, 2010 12 100068 17 757 500 50000
Rwanda 1976, 1984, 1989, 1996, 1999, 2003 6 237 4 156 545 0
Somalia 1964, 1969, 1973, 1980, 1983, 1987, 1988, 1999. 2004, 2005, 2008, 2010, 2012 13 19 673 13 183 500 0
Tanzania Uni Rep 1967, 1977, 1984, 1988, 1990, 1996, 2003, 2004, 2006, 2011 10 0 12 737 483 0
Uganda 1967, 1979, 1987, 1998, 1999, 2002, 2005, 2008, 2010 9 194 4 975000 1800
Zambia 1981, 1983, 1990, 1995, 2005 5 0 4 173 204 0
Zimbabwe 1981, 1990, 1998, 2001, 2007, 2010 6 0 14822 618 51 000
Southern Africa 32 500 24 300115 1 056739
Botswana 1965, 1968, 1970, 1981, 1990, 2005 6 0 1 344900 3000
Lesotho 1968, 1983, 1990, 2002, 2007, 2011 6 0 2 736 015 1000
Namibia 1981, 1990, 1995, 1998, 2001, 2002, 2013 7 0 1 114200 51 000
South Africa 1964, 1980, 1981, 1986, 1988, 1990, 1995, 2004 8 0 17 475000 1 000000
Swaziland 1981, 1984, 1990, 2001, 2007 5 500 1 630 000 1739
The geospatial spread of drought depicts large variation
within a country or a basin, beside regional heterogeneity.
This point is clearly indicated by Figs. 2 and 3 and also
highlighted by other studies (e.g. Anderson et al., 2012;
Moeletsi and Walker, 2012; Mussá et al., 2014; Rojas et al.,
2011; Rulinda et al., 2012; Trambauer et al., 2014). The in-
creasingly available information and tools based on remote
sensing, analysis of global climatic data sets (e.g. global
SPEI products) and hydrological and climatic modelling of-
fer great opportunity to identify these geospatial differences
and drought hot spots. For instance, a remote-sensing-based
study by Rojas et al. (2011) identified hot spots regions
at sub-national level depicting higher probabilities of fac-
ing agricultural droughts. The studies indicate that the semi-
arid and sub-humid regions of Africa are the most drought
prone regions (e.g. World Bank and GFDRR, 2010). These
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I. Masih et al.: A review of droughts on the African continent 3643
countries are highly vulnerable to drought owing to high
climatic variability and also due to other reasons such as
poverty, high dependency on rainfed agriculture and weak
infrastructure to manage resources and recover from disas-
ters. Moreover, vulnerability to drought varies per country.
For instance, the economic impact of the 1991–1992 drought
was much higher on the GDP of Malawi and Zimbabwe
compared to South Africa and Botswana (Benson and Clay,
1998). The lowest negative impacts in Botswana on peo-
ple’s livelihoods and food security during drought periods of
1982–1987 and 1992 were mainly attributed to a small and
largely accessible national population, availability of domes-
tic and international resources, existence of rural infrastruc-
ture, government commitment, district-level capacity and a
timely and fairly comprehensive food security and nutrition
monitoring system (Belbase and Morgan, 1994).
There is increasing availability of drought monitoring and
forecasting tools for decision making which can provide real-
time monitoring and forecasting of drought across the region
(e.g. Tadesse et al., 2008; Anderson et al., 2009; Dutra et
al., 2013; Vicente-Serrano et al., 2012). However, the use of
these tools in decision making is still limited and could be
promoted. For instance, despite inherent uncertainties in the
available drought monitoring and forecasting systems, the
2010–2011 drought in the Horn of Africa was well predicted
by European Centre for Medium-Range Weather Forecasts
(ECMWF). But this information was not timely used for bet-
ter preparedness and mitigation of the drought, which finally
caused heavy toll affecting about 12 million people (Dutra et
al., 2013).
3.2 Past, present and future pattern of droughts
There are few studies available to date which offer possi-
bility of comparing droughts observed during 1900–2013
(instrumental era) with those witnessed in the past cen-
turies. This comparison is important as African climate dis-
plays high decadal and century-scale variability. The work of
Touchen et al. (2008, 2011) provides a long-term perspective
on droughts in northwestern Africa (Morocco, Algeria and
Tunisia). They used tree-ring records to construct the PDSI
for the period AD 1179 to 2002. These studies reveal that the
frequency of occurrence of a single drought event was 12 to
16 times per century before the 20th century, which was in-
creased to 19 during the 20th century. The most severe multi-
year drought occurred during 1999–2002, whereas 1847 and
2002 were identified as the driest single years with PDSI val-
ues of 3.74 and 3.90, respectively. The latter half of the
20th century is seen as the driest period in the last nine cen-
turies. This shift to drier conditions was attributed to anthro-
pogenic climate change.
A number of researchers studied historic droughts in
Africa based on lake sediment analyses. Evidence from the
sediment analysis of the Lake Bosumtwi, Ghana, indicated
several prolonged periods of drought during the last three
millennia, most recent ones around 200 to 300 years ago
(Shanahan et al., 2009). Comparing 1970s droughts in Sa-
hel with earlier drought episodes that occurred during the
past three millennia, they concluded that more severe and
prolonged droughts were recorded in the past centuries. Ver-
schuren et al. (2000) investigated droughts over the pe-
riod AD900 to 2000 based on sediment analysis of Lake
Naivasha, Kenya, in equatorial eastern Africa. The period
AD1000 to 1270 (Medieval Warm Period) was found to be
the driest one over the last 1100 years. Additionally, dry
conditions were found around AD1380–1420, 1560–1620
and 1760–1840 during relatively wet period of AD1270–
1850 (Little Ice Age). These drought episodes were more
severe than recorded droughts in the 20th century. Bessems
et al. (2008) noted extreme droughts in equatorial eastern
Africa about 200 years ago based on the sediment analysis of
three lakes (Chibwera and Kanyamukali in western Uganda,
and Baringo in central Kenya). The authors, Verschuren et
al. (2000) and Bessems et al. (2008), compared their find-
ings with the available evidence from the cultural history of
eastern Africa and found consistency between two sets of
observations.
Endfield and Nash (2002) described the discourse on long-
term desiccation of the African continent emerged during
19th century. Their study is based on the analysis of the
missionary documents from southern Africa (Botswana and
South Africa). The authors constructed a chronology of intra-
decadal climatic variability for the period 1815–1900 and
showed that the major multi-year droughts occurred in 1820–
1827, 1831–1835, 1844–1851, 1857–1865, 1877–1886 and
1894–1899. The study inferred that the discourse on long-
term desiccation evolved during this period was merely trig-
gered by these episodes of droughts rather than underpinned
by long-term climatic deterioration. Nevertheless, the dis-
course on desiccation still remains an important subject in
the current drought research. The evidence presented in the
previous section pointed out to the increased aridity and in-
tensification of droughts, especially during the second half
of the 20th century (e.g. Dai, 2011; Elagib and Elhang,
2008; Kasei et al., 2010; Ouassou et al., 2007; Manatsa et
al., 2008; Touchan et al., 2008, 2011; Richard et al., 2001).
Dai (2013) predicted the likelihood of increased droughts
and aridity over central and southern Africa during the 21st
century. On the contrary, the Sahel region may receive more
rainfall. Large uncertainties exist in these findings and thus
require caution in making regional or continental conclu-
sions. Druyan (2011) reviewed 10 studies which are based
on the simulations of atmosphere–ocean global climate mod-
els on future climate of Sahel. Some studies projected wet-
ter conditions and some projected more frequent droughts,
thus, no consensus was observed. The large uncertainties
and differences in these predictions were attributed to model
limitations and complexity of many physical mechanisms
governing the precipitation trends.
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3644 I. Masih et al.: A review of droughts on the African continent
3.3 Causes of droughts
Drought is a part of natural climatic variability on the African
continent, which is quite high at intra-annual, inter-annual,
decadal and century timescales (e.g. Nicholson, 2000). Many
studies attempted to investigate the natural causes that could
be associated with droughts in Africa (Caminade and Terray,
2010; Dai, 2011, 2013; Dutra et al., 2013; Giannini et
al., 2008, 2013; Hastenrath et al., 2007; Herweijer and
Seager, 2008; Jury et al., 1996; Kerr, 1985; Lebel et al.,
2009; Manatsa et al., 2008; Nicholson, 2000; Richard et al.,
2001; Shanahan et al., 2009; Tierney et al., 2013; Vicente-
Serrano, 2012; Zeng, 2003). Some of them also focus on an-
thropogenic factors, such as climate change, aerosol emis-
sions, land use practices and resulting land–atmosphere in-
teractions, contributing to drought inducing mechanisms
(e.g. Dai, 2011, 2013; Hwang et al., 2013; Lebel et al., 2009;
Zeng, 2003). The review of these studies revealed that there
are a number of factors contributing to inducing drought con-
ditions. However, despite regional differences in the factors
causing droughts in a specific region, El Niño–Southern Os-
cillation (ENSO) and SSTs are regarded major influencing
factors across the continent. For instance, Nicholson (2000)
demonstrates that ENSO, SST and land–atmospheric feed-
back are the major governing factors on the rainfall variabil-
ity in Africa. The author states that these factors alone or in
combination can change the atmospheric dynamics and cir-
culation patterns, for instance, causing changes in the Hadley
and Walker circulations or upper level jet streams.
Droughts in southern Africa occur most of the time dur-
ing the warm phase of ENSO (El Niño Southern Oscilla-
tion). Nicholson and Kim (1997) studied the correlation be-
tween precipitation and ENSO in the Pacific. They found that
among the 20 extreme rainfall events analyzed, 15 events
appeared to be modulated by the ENSO. Their results sug-
gest that the southern part of Africa is negatively correlated
with warm ENSO. Phillips et al. (1998) studied the possi-
bility of using ENSO predictions to reduce the risks asso-
ciated with rainfall variability in agricultural production in
Zimbabwe. The analysis showed that during the El Niño
phase, a decrease on the precipitation was noticed, which
is in agreement with the findings of Nicholson and Kim
(1997). Rouault and Richard (2005) studied the temporal and
spatial extent of the drought in South Africa based on the
SPI (standardized precipitation index) from 1900 to 2004.
Their results show that 8 out of 12 droughts detected coin-
cide with El Niño years, which confirms the strong relation-
ship between the ENSO and the droughts events in southern
Africa. However, some studies point to the fact that the oc-
currence of droughts during El Niño years does not always
happen, as there are many other local and global factors in-
fluencing the drought phenomenon. Richard et al. (2001) ex-
amined droughts during 1950 to 1988 in southern Africa.
They found that droughts during 1970–1988 were intense
and widespread compared to those during 1950–1969. The
El Niño was the main governing factor for droughts dur-
ing 1970–1988; however, this observation requires caution
because droughts may not occur during El Niño periods,
i.e. as happened during 1925–1926 and 1997–1998. For
the droughts during 1950–1969, regional oceanic and atmo-
spheric anomalies (e.g. southwest Indian Ocean SST) were
named as the main causes. Manatsa et al. (2008) suggested
that El Niño alone is not a sufficient predictor of droughts
in southern Africa. They recommend that March to June ex-
treme positive Darwin sea level pressure anomalies are ideal
additional candidate for drought monitoring and forecasting
in Zimbabwe and southern Africa.
Contrary to southern Africa, eastern Africa faces droughts
during cold phase of ENSO (La Niña). For instance, Dutra et
al. (2013) indicated that strong La Niña event was the main
cause of 2010–2011 drought in the Horn of Africa. Lott et
al. (2013) investigated whether the 2010–2011 drought was
caused by human intervention or not. They did not find any
evidence of human activities on this event and also attributed
this with La Niña events. Tierney et al. (2013) also sug-
gested that the recent drought in the Horn of Africa, was
partly due to the prevailing La Niña conditions in the tropi-
cal Pacific. On the other hand, Hasternath et al. (2007) argue
that the low rainfall in this region occurs during fast west-
erlies which are usually accompanied by anomalously cold
waters in the northwestern and warm anomalies in the south-
eastern extremity of the equatorial Indian Ocean basin. This
mechanism was found to be responsible for 2005 drought
in the Horn of Africa. Tierney et al. (2013) suggested that
the Indian Ocean drives rainfall variability in eastern Africa
by altering the local Walker circulation. Moreover, it is ar-
gued that warming of the central Indian Ocean accelerated
by greenhouse gas and aerosol emissions after the latter half
of the 20th century are correlated with the decline in pre-
cipitation over eastern Africa (Funk et al., 2008; Williams
and Funk, 2011). These studies suggested that warming of
the central Indian Ocean drives changes in the local Walker
circulation causing reduction in the seasonal rainfall and in-
ducing drought conditions in the region.
Droughts in Sahel are caused by an array of com-
plex processes and feedback mechanisms. Caminade and
Terray (2010) stated that conditions that favour lower sum-
mer rainfall in Sahel are when Atlantic Ocean north of equa-
tor is cool and south of the equator is warm, El Niño events
and increased vertical thermal stability from a warming tro-
posphere. Most of the studies on Sahel droughts concur that
the recent severe droughts in Sahel were caused by the ocean
warming (southward warming gradient of the Atlantic ocean
and steady warming of the Indian Ocean) and a southward
shift of inter-tropical convergence zone (ITCZ) (Caminade
and Terry, 2010; Dai, 2011; Giannini et al., 2008; Janicot et
al., 1998; Kerr, 1985; Lebel et al., 2009; Zeng, 2003). The
land–atmosphere feedbacks through natural vegetation and
land cover change are also important factors. Anthropogenic
contribution in land use change altering the land surface
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I. Masih et al.: A review of droughts on the African continent 3645
feedback mechanisms is also seen as a factor. Some stud-
ies were done with the objective of examining whether the
climate in the Sahel region is sensitive to land use changes
or not. For instance, Zheng and Eltahir (1997) investigated
the interaction between vegetation and climate in the Sahel
region by means of simulations of the West African mon-
soons with a simple zonally symmetric model. Their results
show that the impacts of land cover changes in the Sahel re-
gion along the border with Sahara are insignificant. However,
deforestation along the southern coast of West Africa can
cause significant reduction of the rainfall and effect on the
monsoon circulation. Several studies suggested aerosol emis-
sions were an important driver of the recent Sahel droughts
(e.g. Desboeufs et al., 2010; Hwang et al., 2013; Moulin and
Chiapello, 2004; Prospero and Lamb, 2003). Furthermore,
human induced green house gas emission is also considered
as a contributory factor to oceans warming (e.g. Dai, 2013).
Despite recognition of these anthropogenic factors, their rel-
ative contribution compared to natural factors in inducing Sa-
hel droughts is debated and regarded as a secondary factor.
The limited studies are available on causes of droughts in
northwestern Africa. The North Atlantic Ocean SST does
have an influence on rainfall variability in the region but
this relationship is rather weak and could not explain ma-
jor droughts in the region (Li et al., 2003; Touchan et al.,
2011). Similarly, ENSO is seen as a potential factor, but a
strong relationship is not demonstrated by ENSO for mod-
ulating droughts in this region (Esper et al., 2007; Touchan
et al., 2008). The North Atlantic Oscillation (NAO) indicates
variable influence on the rainfall in the region, with negative
correlation with western parts but no correlation with east-
ern parts (Touchan et al., 2011). However, no relationship is
found between NAO and droughts in the region. Touchan et
al. (2011) argued that anthropogenic green house gas emis-
sion is an important factor causing drying in this region. The
review of these studies suggested that the causes of droughts
in northwestern Africa are not well established and require
further research.
4 Conclusions
The climate of the African continent exhibits large geospa-
tial and temporal variability. Droughts are recurrent features
varying from lack of rain in one season or up to one or more
years. The vulnerability to droughts is high due to poverty,
large dependency on rainfed agriculture and other factors.
Therefore, droughts continue to incur a heavy toll to peo-
ple, animals, environment and economy. The planning and
management of droughts requires a paradigm change shift-
ing from crisis management to risk management. Compre-
hensive studies on historic drought events could significantly
guide better planning and mitigation strategies of droughts.
There is a significantly increasing number of scientific stud-
ies and information on various aspects of drought. However,
these studies do not provide a long-term and/or continental-
scale perspective. This study is a first of its kind to build such
a perspective on droughts in Africa with the aim on conduct-
ing geospatial and long-term analysis of the droughts. The
study is underpinned by a comprehensive review of avail-
able information and scientific literature and analysis of the
EM-DAT and SPEI data sets.
The analysis of droughts during 1900–2013 indicated that
droughts have intensified in terms of their frequency, sever-
ity and geospatial coverage over the last few decades. The
droughts that occurred in 1972–1973, 1983–1984 and 1991–
1992 were most intense and widespread. All of the re-
gions witnessed severe droughts in the last few decades,
for instance, the 2010–2011 drought in East Africa (Horn
of Africa), 1999–2002 drought in North Africa, 2001–2003
drought in southern Africa and persistent droughts in Sa-
hel during 1970s and 1980s. Few studies are available
to construct drought chronologies before the 20th century.
However, studies based on lake sediment analysis indicated
episodes of severe droughts prolonged for decades and even
centuries in the past over West and equatorial eastern Africa,
which are also documented in the cultural histories of these
regions. The studies underpinned by tree-ring chronologies
in northwestern Africa indicated quite a number of moderate
to severe droughts in the past, about 12–16 events per century
which has increased to 19 during the 20th century. Southern
Africa also faced several single and multi-year droughts dur-
ing the 19th century, as indicated by the analysis of mission-
aries’ correspondence.
Drought predictions based on the global climate models
simulations show varying results and thus remain uncertain
for most of the African continent. However, the results of
simulation models suggested a high likelihood of increased
droughts in central and southern Africa. Despite consider-
able improvements in these models, they are still not able
to accurately represent the large number of complex fac-
tors responsible for causing the droughts across various re-
gions of the continent (e.g. ENSO and SSTs, wind and pres-
sure anomalies, land–atmospheric feedback mechanisms).
Their complex interactions induce uncertainty in the drought
predictions.
The available evidence from the past clearly shows that
the African continent is very likely to face extreme and
widespread droughts in the future. The vulnerability is likely
to increase due to fast growing populations, increasing wa-
ter demands and degradation of land and environmental re-
sources. Addressing such a daunting and evident challenge
calls for much more serious and committed action from com-
munities, governments, regional bodies, international orga-
nizations and donors than what is witnessed at present. This
review advances available information and scientific under-
standing of the droughts in Africa.
www.hydrol-earth-syst-sci.net/18/3635/2014/ Hydrol. Earth Syst. Sci., 18, 3635–3649, 2014
3646 I. Masih et al.: A review of droughts on the African continent
Acknowledgements. This study was carried out in the scope of
the DEWFORA (improved drought early warning and forecasting
to strengthen preparedness and adaptation to droughts in Africa)
project which is funded by the Seventh Framework Programme for
Research and Technological Development (FP7) of the European
Union (grant agreement no: 265454).
Edited by: F. Pappenberger
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Droughts are widespread natural hazards and in many regions their frequency seems to be increasing. A finer resolution version (0.05° x 0.05°) of the continental scale hydrological model PCR-GLOBWB was set up for the Limpopo river basin, one of the most water stressed basins on the African continent. An irrigation module was included to account for large irrigated areas of the basin. The finer resolution model was used to analyse droughts in the Limpopo river basin in the period 1979-2010 with a view to identifying severe droughts that have occurred in the basin. Evaporation, soil moisture, groundwater storage and runoff estimates from the model were derived at a spatial resolution of 0.05° (approximately 5 km) on a daily time scale for the entire basin. PCR-GLOBWB was forced with daily precipitation, temperature and other meteorological variables obtained from the ERA-Interim global atmospheric reanalysis product from the European Centre for Medium-Range Weather Forecasts. Two agricultural drought indicators were computed: the Evapotranspiration Deficit Index (ETDI) and the Root Stress Anomaly Index (RSAI). Hydrological drought was characterised using the Standardized Runoff Index (SRI) and the Groundwater Resource Index (GRI), which make use of the streamflow and groundwater storage resulting from the model. Other more widely used drought indicators, such as the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evaporation Index (SPEI) were also computed for different aggregation periods. Results show that a carefully set up process-based model that makes use of the best available input data can successfully identify hydrological droughts even if the model is largely uncalibrated. The indicators considered are able to represent the most severe droughts in the basin and to some extent identify the spatial variability of droughts. Moreover, results show the importance of computing indicators that can be related to hydrological droughts, and how these add value to the identification of droughts/floods and the temporal evolution of events that would otherwise not have been apparent when considering only meteorological indicators. In some cases, meteorological indicators alone fail to capture the severity of the drought. Therefore, a combination of some of these indicators (e.g. SPEI-3, SRI-6, SPI-12) is found to be a useful measure for identifying hydrological droughts in the Limpopo river basin. Additionally, it is possible to make a characterisation of the drought severity, indicated by its duration and intensity.
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Global climate change has received much attention worldwide in the scientific as well as in the political community, indicating that changes in precipitation, extreme droughts and floods may threaten increasingly many regions. Drought is a natural phenomenon that may cause social, economical and environmental damages to the society. In this study, we assess the drought intensity and severity and the groundwater potential to be used as a supplement source of water to mitigate drought impacts in the Crocodile River catchment, a water-stressed sub-catchment of the Incomati River catchment in South Africa. The research methodology consists mainly of three parts. First, the spatial and temporal variation of the meteorological and hydrological drought severity and intensity over the catchment were evaluated. The Standardized Precipitation Index (SPI) was used to analyse the meteorological drought and the Standardized Runoff Index (SRI) was used for the hydrological drought. Second, the water deficit in the catchment during the drought period was computed using a simple water balance method. Finally, a groundwater model was constructed in order to assess the feasibility of using groundwater as an emergency source for drought impact mitigation. Results show that the meteorological drought severity varies accordingly with the precipitation; the low rainfall areas are more vulnerable to severe meteorological droughts (lower and upper crocodile). Moreover, the most water stressed sub-catchments with high level of water uses but limited storage, such as the Kaap located in the middle catchment and the Lower Crocodile sub-catchments are those which are more vulnerable to severe hydrological droughts. The analysis of the potential groundwater use during droughts showed that a deficit of 97 Mm3 yr-1 could be supplied from groundwater without considerable adverse impacts on the river base flow and groundwater storage. Abstraction simulations for different scenarios of extremely severe droughts reveal that it is possible to use groundwater to cope with the droughts in the catchment. However, local groundwater exploitation in Nelspruit and White River sub-catchment will cause large drawdowns (> 10 m) and high base flow reduction (> 20%). This case study shows that conjunctive water management of groundwater and surface water resources is the necessary to mitigate the impacts of droughts.
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Drought by itself does not lead to famine. That requires severe economic weakness, very poor national and/or external response and/or war. In practice, mass starvation does not happen in Africa in the absence of war. However, the degree of hunger and, perhaps even more, the speed of affected household livelihood recovery depend heavily on domestic and international strategic responses. The present standard donor political economy of response to crisis is one-off, short term, not incorporating livelihood rehabilitation or future vulnerability reduction. Further, it is usually managed in a way fragmenting national response and frequently decapacitating national structures. This 'Good Samaritan' approach provides no link back to 'normal development' which also tends to exclude post drought reconstruction by livelihood rehabilitation. National responses vary in coherence, degree of sophistication, capacity and relationship to sustaining or rehabilitating livelihoods. In part this reflects governing coalition political priorities - in the absence of war even a very poor state can mount programmes averting mass migration and famine (e.g. Tanzania). Both normative and efficiency criteria suggest more coherent/nationally owned responses within ongoing donor and national emergency response structures; greater expedition in action to avert people being forced to leave their homes, and building livelihood rehabilitation and future vulnerability reduction components into drought responses as integral components.
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Climatic determinants of summer drought over southern Africa are studied using statistical correlations and simulations from a general circulation model (GCM) experiment. An index of normalised departures of February rainfall over northern South Africa is correlated with regional patterns of outgoing longwave radiation (OLR) and sea surface temperature (SST). Significant correlations are sustained between SST in the central Indian Ocean and February rainfall at lags 0 to -9 months (< -0.5). The dynamical link is through the southward advance and intensity of the Indian monsoon trough. The mechanisms connecting the Indian Ocean with southern African drought are explored using the CSIRO4 GCM. A positive SST anomaly is imposed in the central basin and a simulation is performed. Comparisons with a control run yield significantly reduced continental rainfall. Results indicate that anomalous warming of SST in the central Indian Ocean anticipate and sustain drought over southern Africa.
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This article examines available methods for assessing all types of drought costs, including both damage costs and costs arising from adopting policy measures to encourage mitigation of, and adaptation to, droughts. It first discusses damage costs, distinguishing between direct, indirect and non-market costs. Then it examines the suitability of existing methods for estimating drought costs in different economic sectors, their underlying theoretical assumptions, complementarity between different methods, and conditions relevant for their application. The latter include precision, ability to deal with future climate change risks, data needs and availability, and required financial and human resources. The article further considers potential policies for drought mitigation and adaptation and different cost types associated with them. It ends with providing recommendations for good practices regarding the use of methods as well as drought mitigation and adaptation policies.
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Drought is one of the major environmental disasters in southern Africa. In recent years, the damage from droughts to the environment and economies of some countries was extensive, and the death toll of livestock and wildlife was unprecedented. Weather data often come from a very sparse meteorological network, incomplete and/or not always available in good time to enable relatively accurate and timely large scale drought detection and monitoring. Therefore, data obtained from the Advanced Very High Resolution Radiometer (AVHRR) sensor on board the NOAA polar-orbiting satellites have been studied as a tool for drought monitoring and climate impact assessment in southern Africa. The AVHRR-based vegetation condition index (VCI) and temperature condition index (TCI) developed recently were used in this study because in other parts of the globe they showed good results when used for drought detection and tracking, monitoring excessive soil wetness, assessment of weather impacts on vegetation, and evaluation of vegetation health and productivity. The results clearly show that temporal and spatial characteristics of drought in southern Africa can be detected, tracked, and mapped by the VCI and TCI indices. These results were numerically validated by in situ data such as precipitation, atmospheric anomaly fields, and agricultural crop yield. In the later case, it was found that usable corn yield scenarios can be constructed from the VCI and TCI at approximately 6 (in some regions up to 13) weeks prior to harvest time. These indices can be especially beneficial when used together with ground data.