Delineation of Groundwater Potential Zones of Upper Tumet Catchment, Menge Area, Western Ethiopia Using Remote Sensing and Gis
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Date
2007-07
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Addis Ababa Universty
Abstract
Low success rate of drilling productive wells is one of the challenges encountered in
hard rock environment. The use of remote sensing data for the evaluation of
groundwater resource in conjunction with ancillary ground information in GIS
environment is becoming an effective method for the improvement of groundwater
development success rate. In the present research thematic layers generated from
satellite images, existing maps and field survey results were integrated in Geographic
Information System (GIS) environment to delineate the groundwater potential zones
in upper Tumet catchment, Menge area. Factor maps generated from satellite images
include lineament, thermal lineament, soil moisture and vegetation anomaly and land
use (lu)/land cover (lc) whereas those derived from existing maps were slope,
drainage density and lithology. The zone of weathering thematic layer was generated
from water point inventory data and Vertical Electrical Sounding (VES) survey
interpretation results. In order to drive groundwater indicator parameters from satellite
images, image pre-processing, enhancements and classifications were performed
and various false color composite images were generated. Geologic and topographic
maps were digitized and GIS analysis performed to drive thematic layers from
existing maps. Field work was conducted for inventorying water points, to do VES
survey and to collect point information for geometric rectification and ground truth.
Information for 49 water points was gathered and 13 VES surveys were done. The
collected ground truth was used during image classification. Data derived from
different sources were reclassified to common scale and weighted. Multi-criteria
evaluation using pairwise comparison matrix was used for weighting and ranking the
thematic layers. In order to arrive at the groundwater prospect map raster based GIS
modeling was conducted using Weighted Linear Combination (WLC) method. The
resulting groundwater prospect map has five classes; namely Excellent, Very good,
Good, Moderate and Poor. The model result revealed that large part of the study area
has poor groundwater potential. The resulting model was evaluated using water point
inventory data and the result was found to be in good agreement with the model
output.
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Keywords
Tumet Catchment, Menge Area