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Rural Focus Ltd.Tel:+254 (020) 2309900/ 733-679125
P.O. Box 1011, Nanyuki 10400, Kenya
www.ruralfocus.com
VES SITES SELECTION MODEL FOR
GROUND WATER ANALYSIS AND
MAPPING
VES SITES SELECTION MODEL FOR GROUND WATER ANALYSIS AND
MAPPING
BY
A CASE STUDY OF TURKANA COUNTY, KENYA
NJENGA WAINAINA JOHN ESTHER MAXWELL BARASA
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INTRODUCTION• Water is essential for
life.
• Increased cases of
Water stress.
• Diminishing Surface
Water.
• Ground water
exploration is an
expensive
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STUDY AREA• Turkana County is an ASAL
county in Kenya with nomadic
pastoralism as major
economic activity and recently
oil exploration.
• The climate is hot (21-37oC)
and dry (150mm to 400mm
annual rainfall).
• As a water stressed area,
underground water has been
explored as a solution to the
water shortages.
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GROUND WATER RESEARCH METHODOLOGY
• PRELIMINARY SURVEY; Involves
detailed desk study of existing
ground water sources
occurrence like springs ,
previous works and talking to
the community.
• ANALYZING TOPOGRAPHY; from
remote sensing data and other
spatial data to inform on
potential occurrence of ground
water e.g. performing NDVI,
study the geological formations
of the area and the areas
physiography.
• HYDRO-GEOPHYSICS; Involves
measuring the electrical
resistivity of various formations
to ascertain the water
availability in them.
ABEM Tetrameter SAS 1000 with 600m take out cables
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GROUND WATER OCCURENCE
Ground water occurrence <> permeability + porosity local geological formations
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DATA SOURCES
• Geological Maps Of Kenya From The Ministry
Of Mining.
• Geological Map Of Kenya With Structural
Contours.
• ASTERGDEM V2 30m Resolution Elevation
Model.
• Past Works And Reports
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ANALYSIS WORKFLOW
• Data Geo-referencing
• Data Projections
• Data Mosaicking
• Database Schema Creation
• Data Digitization and attributing
Data Pre-processing
• Digital Elevation Model Processing
• Creation of Basement Depth Raster
• Creation of Basement Elevation Model
• Data Reclassification
Raster Processing
• Overlay Weight influence determination.
• Perform Analysis
• Visual Inspection.
• Select VES Sites
Weighted Overlay Analysis
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RESULTS & DISCUSSIONS
THE RESULTS OF THE DATA
PREPROCESSING:
1. Mosaicked geological
maps.
2. Vector geological
formations data.
3. Digital basement contours
with values of depth from
the surface
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RASTER PROCESSING RESULTSTurkana County Hill shade Depicting Hills and Plains Turkana County Basement Elevation Model Structure
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RASTER PROCESSING RESULTS
Turkana County Reclassified Geology Depicting Suitability to Store Ground Water
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RASTER PROCESSING RESULTS
Turkana County Reclassified Basement Depicting Suitability to Store Ground WaterLegend
Lake Turkana
Depth To the Basement
1, (Above 600m) (Least Suitable)
2, (500m - 600m)
3, (400m - 500m)
4, (0-50m)
5, (300m - 400m)
6, (50m - 100m)
8, (200m - 300m)
9, (150m -200m) (Most Suitable)
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WEIGHTED OVERLAY ANALYSIS RESULTSSuitability map depicting suitable areas to perform
VES analysis
Selected Sites To perform Vertical Electric Sounding (VES)
Survey
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0
20
40
60
80
100
120
Total
Sum of Z by Results
Results from VES analysis on selected
Sites from the Suitability Model
VERTICAL ELECTRIC SOUNDING (VES) RESULTS
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CONCLUSION & RECOMMENDATIONS
• The suitability model as a blueprint for future groundwater
exploration using GIS analysis.
• Other factors that control groundwater occurrence and movement
such as fracturing, fault zones grain size and sorting of particles were
not included.
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END RURAL FOCUS LTD
JOHN ESTHER,
GEOSPATIAL ANALYST, CARTOGRAPHER
WORK: +254 (0) 20 444 0149
MOBILE:+254 71 884 2584
EMAIL: [email protected]
WEBSITE: www.ruralfocus.com