Groundwater Potential Evaluation Based on Integrated GIS and Remote sensing Technqiues, in Bilate River Catchment:South Rift Valley of Ethiopia
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Date
2010-06
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Addis Ababa Universty
Abstract
Groundwater is occurring within different hydrogeology environment, geologic formations
and topographic settings that the factors mainly control the groundwater distribution and
development for different purposes. A systematic evaluation of groundwater is essential for the
proper utilization and management of this precious natural resource. Integrated GIS
(geographic information system) and remote sensing are efficient techniques in groundwater
studies; in facilitate better data analysis and their interpretations of groundwater potential
controlling parameters. In the present study, an attempt has been made to delineate and
classify possible groundwater potential zones in the Bilate River catchment of the south
Ethiopian rift escarpment, found in SNNPR using integrated remote sensing and GIS
techniques. The thematic layers considered in this study are lithology,
geomorphology/landform, drainage density, lineament density, rainfall, soil, slope and land
use/ land cover were prepared using the Landsat ETM+ imagery and ArcGIS software. All the
thematic layers were then assigned weights according to their relative importance in
groundwater occurrence and the corresponding normalized weights were obtained based on
the Saaty's analytical hierarchy process. These weights were applied in linear summation
equation to obtain a unified weight map containing due weights of all input variables. The
thematic layers were finally integrated using ArcGIS and IDRIS software to produce a
groundwater potential zone map of the study area. Thus, four different groundwater potential
zones were identified, namely 'high, 'moderate’,' low’ and 'poor'. The high potential zones
correspond to alluvial plains, lacustrine sediments, the fracture valleys, and valley fills, which
coincide with the low slope and high lineaments density areas .The eastern portion and some
small patches in the northern and valley escarpment of Bilate River of the study area fall
under moderate groundwater potential zone. The low zones mainly comprise structural hills
and escarpments which contributes high run-off .On the other hand, Poor groundwater
potential zones are present in the mountain peaks, plateaus and escarpments with steep cliff,
where low fractured undifferentiated peralkaline Dino formation, obsidian and pitch stone
exist. The resulted groundwater potential zoning map validated based on existing water
sources point data of the study area. Finally, it is concluded that the integrated GIS and
remote sensing techniques are very efficient and useful for the identification of groundwater
potential zones.
Key words: Bilate River, Groundwater potential, GIS and remote sensing, western
escarpment, thematic maps
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Keywords
Bilate River, Groundwater potential, GIS and remote sensing, Western escarpment, Thematic maps