Rural Focus Ltd.Tel:+254 (020) 2309900/ 733-679125

P.O. Box 1011, Nanyuki 10400, Kenya

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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

INTRODUCTION• Water is essential for

life.

• Increased cases of

Water stress.

• Diminishing Surface

Water.

• Ground water

exploration is an

expensive

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.

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

GROUND WATER OCCURENCE

Ground water occurrence <> permeability + porosity local geological formations

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

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

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

RASTER PROCESSING RESULTSTurkana County Hill shade Depicting Hills and Plains Turkana County Basement Elevation Model Structure

RASTER PROCESSING RESULTS

Turkana County Reclassified Geology Depicting Suitability to Store Ground Water

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)

WEIGHTED OVERLAY ANALYSIS RESULTSSuitability map depicting suitable areas to perform

VES analysis

Selected Sites To perform Vertical Electric Sounding (VES)

Survey

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

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.

END RURAL FOCUS LTD

JOHN ESTHER,

GEOSPATIAL ANALYST, CARTOGRAPHER

WORK: +254 (0) 20 444 0149

MOBILE:+254 71 884 2584

EMAIL: johnestaar@gmail.com

WEBSITE: www.ruralfocus.com