Assessment of Surface Water Potential to Manage Frequent Drought Disaster (A Case of Dhas District in Borana Zone of Oromia Region, Ethiopia)
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Date
2019-06
Authors
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Journal ISSN
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Publisher
Addis Ababa University
Abstract
The study was conducted in Dhas district, which is located in Borana Zone of
Oromia region; geographically it is situated 4.00
o
-4.39
o
N and 38.39
o
-39.46
o
E with
altitude range of 1082 – 1666m a.m.s.l. Total area of the district is 3,183.22km
2
; its
length from West to East is 120 Km and width from South to North is 41km.
There is not any river and gauging station in the district; the study was conducted
aiming at estimation of surface water potential of the district and evaluation of its
sufficiency for managing of drought disaster in the district. The surface water
potential assessment of the district was conducted using SCS model with the aid of
remote sensing and GIS. The assessment output was contextualized with the study
finding of Genale Dawa integrated Master plan study (Dhas district is located in
Dawa sub-basin; finding from separate analysis of Dawa sub-basin was referred).
For the recent land use/ land cover information of Dhas district; satellite images
were downloaded from USGS (United States Geological Survey) website with
acquisition dates of December 2018, and the image processing was done using
ERDAS Imagine 2015. With the aid of HEC-GeoHMS tool that is specifically
designed in the ArcGIS environment to process geospatial data, the curve number
was generated using the required information (hydrologic soil group, DEM, LULC
map).
The district was divided in to twelve sub-watersheds using Global mapped
software, and direct runoff estimation was done for each sub-watershed
separately; the summation of direct runoff from each sub-watershed was made to
get the total direct runoff amount of the district. Thirty years daily grid rainfall data
that was collected from NMA was used for the estimation of the direct runoff.
Estimation of runoff volume was computed for all thirty years period, and the
estimated minimum and maximum runoff volume were found to be 8Mm
3
and
361Mm
3
respectively. Twenty years of forecast was made to estimate the major
requirements in the district. Human and livestock’s water requirement estimation
based on the population sized of 2039 was computed to be 10Mm
3
/ year.
The abundant of estimated runoff volume was evaluated, whether it is enough or
not to satisfy the major water requirements in terms of managing the frequent
drought disaster. As the analysis shows, Dhas district is having sufficient surface
water potential that can be developed for managing of the frequent drought
disaster in the district.
This study was conducted focusing only on the available surface water potential of
the district, and its sufficiency for managing of the drought disaster in the district.
Its finding is also expected to be an entry point for development of the resource in
the large scale. But for its implementation, it needs further feasibility and detail
studies.
Description
Keywords
Surface Water, Drought Disaster, Assessment