International Journal of Applied Earth Observation and Geoinformation 13 (2011) 309–321
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Spatial and temporal assessment of drought in the Northern highlands of Ethiopia
, Anne van der Veen
, Ben Maathuis
Faculty of Geo-Information Science and Earth Observation, University of Twente, P.O. Box 217, 7500 AA Enschede, The Netherlands
Department of Water Resources, Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, P.O. Box 217, 7500 AA Enschede, The Netherlands
Received 1 October 2010
Accepted 14 December 2010
With the development of global changes, researchers from all over the world increasingly pay attention
to drought detection, and severe droughts that may have resulted from climate change. In this paper,
spatial and temporal variability of drought is evaluated based on precipitation data and remotely sensed
images. The standard precipitation index (SPI) and vegetation condition index (VCI) are used to evaluate
the spatial and temporal characteristics of meteorological and vegetative drought in Tigray, Northern
Ethiopia. Based on the drought critical values of SPI and VCI deﬁning drought, the spatial and temporal
extent of droughts in the study area is established. We processed 396 decadal images in order to produce
the multi-temporal VCI drought maps. The results of the SPI and VCI analysis reveal that the eastern
and southern zones of the study region suffered a recurrent cycle of drought over the last decade. Results
further show that there is a time lag between the period of the peak VCI and precipitation values obtained
from the meteorological stations across the study area. A signiﬁcant agreement was observed between
VCI values with the current plus last two-months of precipitation. The study demonstrates the utility of
the vegetation condition index in semi-arid and arid regions.
© 2010 Elsevier B.V. All rights reserved.
Although the name “Water Tower of Africa” has been given to
Ethiopia, the country is one of the Horn of Africa countries that is
highly vulnerable to drought. The country’s main economic activ-
ity, agriculture, is overwhelmingly dependent on the timely onset,
amount, duration and distribution of rainfall. An incident of drought
generally implies substantial and extended deviation from the nor-
mal rainfall pattern, which affects crop production and vegetation
In Ethiopia drought is a frequently recurring phenomenon. It is
the single most important climate related natural hazard impact-
ing on the country from time to time. Historical drought events
reveal that Ethiopia frequently faces drought and famine. In the
past nine centuries there were about 30 major drought episodes.
Of these drought episodes 13 of them are known to have covered
the entire nation and they were reported as severe. From 1970
onwards, drought hit the country at least once in every 10 years
during the last years the event is becoming even more frequent.
It is now recurring every two or three years at different levels
of intensity (Margaret, 2003). In recent years the spatial extent
and frequency of droughts have both increased causing signiﬁcant
water shortages, economic losses and adverse social consequences.
Corresponding author. Tel.: +31 63 4467 893; fax: +31 53 4874 575.
E-mail address: firstname.lastname@example.org (T. Gebrehiwot).
Climatic conditions during drought years are characterized by
either almost total failure of rainfall or a late or too early onset of
inadequate rainfall during both the short and the main rainy sea-
sons locally known as “Belg” and “Kiremit”. A continuous dry spell
or poor rainfall in successive years hinders ground-water recharge
and imparts stress on ground-water resources leading to severe
water deﬁcit in many parts of the region during both the wet and
the dry seasons.
The droughts of the last decades have produced a complex
impact, which spans many sectors of the economy, especially the
agriculture sector. Droughts of the year 1984–1985 took the lives
of an estimated one million people, destroyed crops, contributed to
the death of animals, and threatened the lives of millions of people
with starvation. The drought caused the then biggest famine affect-
ing an estimated 5.8 million people forcing them to be dependent
on food hand-outs or food aid (Benson, 1998). As a result, a consid-
erable part of the society proved vulnerable to famine that in turn
caused a deep-seated destitution. The recent drought of 2002–2003
with affected 13.5 million people showed once more the magnitude
and the proportion of the problem (Wagaw et al., 2005).
The chronology of Ethiopian drought history further indicates
that most of the drought and food crisis events have been geo-
graphically concentrated in two broad zones of the country. The
ﬁrst consist of the central and northern highlands, stretching from
northern Shewa through Wello and Tigray, and the second consists
of low-lying agro-pastoral lands ranging from Wello in the north,
through Hararghe and Bale to Sidamo and Gamo Gofa in the south
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