1. 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

2. INTRODUCTION
• Water is essential
for life.
• Increased cases of
Water stress.
• Diminishing
Surface Water.
• Ground water
exploration is an
expensive

3. 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

4. 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
ABEM Tetrameter SAS 1000 with 600m take
out cables

5. GROUND WATER OCCURENCE
Ground water occurrence <> permeability + porosity local geological formations

6. 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

7. 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

8. 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

9. RASTER PROCESSING RESULTS
Turkana County Hill shade Depicting Hills
and Plains
Turkana County Basement Elevation Model
Structure

10. RASTER PROCESSING RESULTS
Turkana County Reclassified Geology Depicting Suitability to Store Ground
Water

11. RASTER PROCESSING RESULTS
Turkana County Reclassified Basement Depicting Suitability to Store Ground
Water
Legend
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)

12. WEIGHTED OVERLAY ANALYSIS RESULTS
Suitability map depicting suitable areas to
perform VES analysis
Selected Sites To perform Vertical Electric
Sounding (VES) Survey

13. 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

14. 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.

15. END
JOHN ESTHER,
GEOSPATIAL ANALYST, CARTOGRAPHER
MOBILE:+254 71 884 2584
EMAIL: johnestaar@gmail.com