ves sites selection model for ground water analysis
TRANSCRIPT
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
Impe
rmea
ble la
yers
=
confi
ning l
ayer
whe
re w
ater
is tra
pped
abov
e &
below
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 & 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
RASTER PROCESSING RESULTSTurkana County Hill shade Depicting Hills and Plains
Turkana County Basement Elevation Model Structure
RASTER PROCESSING RESULTSTurkana County Reclassified Geology Depicting Suitability to Store Ground Water
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)
WEIGHTED OVERLAY ANALYSIS RESULTSSuitability map depicting suitable areas to perform VES analysis
Selected Sites To perform Vertical Electric Sounding (VES) Survey
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
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.
