VES SITES SELECTION MODEL FOR GROUND WATER ANALYSIS
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Transcript of VES SITES SELECTION MODEL FOR GROUND WATER ANALYSIS
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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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Impe
rmea
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yers
=
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ayer
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re w
ater
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e &
below
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 & DISCUSSIONSTHE 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 RESULTSTurkana County Reclassified Geology Depicting Suitability to Store Ground Water
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RASTER PROCESSING RESULTSTurkana County Reclassified Basement Depicting Suitability to Store Ground Water
LegendLake Turkana
Depth To the Basement1, (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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Total0
20
40
60
80
100
120
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.