Remote Sensing and Gis Based Characterization of Agriculturral Drought Conditions in North Wollo Zone Amhara Regional State, Ethiopia
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Date
2017-01
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Addis Ababa Universty
Abstract
Drought is the most complex but least understood of all natural hazards. Major food
production in Ethiopia, especially in the Amhara Region, North Wollo Zone, is almost fully
dependent on rain-fed agriculture and the area is often hit by periodic droughts. This
drought causes serious economic, social, food security and environmental problems. Arid
climatic conditions in North Wollo Zone are characterized by erratic rainfall and successive
drought years together with high rate of moisture deficiency has adversely affected the
agricultural production levels. Thereby increases drought risk. In this study, the
Standardized Precipitation Evaporation Index (SPEI), Normalized Difference Vegetation
Index (NDVI) and Vegetation Condition Index (VCI), were applied to characterize the
agricultural drought conditions in North Wollo Zone from 2000 to 2015. Correlation
analysis was performed between NDVI and SPEI, rainfall and NDVI, VCI and rainfall and
NDVI and Crop Yield Anomaly and SPEI and Crop Yield Anomaly. SPEI values were
interpolated to get the spatial pattern of meteorological based drought. Ground based crop
yield data was used to evaluate the drought monitoring index. Finally, the combined drought
severity map was generated by overlaying the agricultural and meteorological drought
severity maps. The results showed that there was good correlation between rainfall and
NDVI (r=0.71), VCI and Rainfall (r = 0.77), NDVI and SPEI (r=0.82) and NDVI and Crop
Yield anomaly, (r=0.78) and SPEI and Crop Yield Anomaly (r=8.3). Analysis result of
Spatial pattern of long term seasonal average rainfall and NDVI from 2000 to 2015 years,
showed that there was a large variation during the main cropping season and the
corresponding NDV1 values was also almost similar. The minimum and maximum rainfall
observed during this period was found to be 250 to 599 mm where it indicates a large
variation in distribution of rainfall in all the weather stations. This might be the effect of
altitude among other factors. The drought severity was analyzed from 2000 to 2015 based on
satellite and climate data. The two years 2005 and 2015 were considered as drought years
and 2009 and 2013 were taken as slight-drought years. The extent of drought severity was
increased by increasing time scale. The combined risk map showed that approximately 5% of
the area has slight risk, 42.5 % of the area faced by very severe risk, 19.5 % of the area
considered as moderate risk and 33 % area face severe risk within the study area. It can be
seen severe drought year from 2000 to 2015 because it has received low rainfall at 2005
and 2015. Hence, it is concluded that, the study area was affected by severe drought in year
2005 and 2015 and slight drought in 2009 and 2013 and the drought monitoring indices
results almost similar with ground truth data result of crop yield. Drought from socioeconomic
aspect has not been studied. Besides, delineating areas under drought risk
relevancy of risk assessment can be made more meaningful when the human population as
well as livestock population under risk will be assessed. Therefore, it is recommended to
include the socio-economic data to better understand the vulnerability factors.
Keywords: Agricultural drought, Meteorological drought, SPOT, NDVI and SPEI
Description
Keywords
Agricultural drought, Meteorological drought, SPOT, NDVI and SPEI