WASH Cluster – Groundwater Development and Drilling
GWD1
Session Plan
GWD1 – Occurrence
Timetable
GWD1 - Occurrence
GWD2 GWD3 - Identifying
GWD4 - Developing
Characteristics of
Potential
Groundwater Sources
Groundwater Systems Groundwater Sources
60 mins
1 hour 45 mins
40 mins
1 hour 45 mins
GWD5 - Protecting
Groundwater Sources
1 hour 10 mins
Session-at-a-Glance
Session Activities
What is Groundwater?
Approx. Time
10
Geology and Aquifer types
20
CASE STUDY 1:
10
EXERCISE 1: Mapping
20
Instructional Activity
Plenary discussion with
power point slides
Discussion with slides
Review of case study and
discussion
handouts and mapping
exercise (10mins), review
of discussion (10)
1hr
Session Aims

To provide an understanding of how groundwater occurs in nature and how this can influence
the location of potential groundwater sources and the means of developing the source
Session Objectives
By the end of the session participants will be able to:

Describe what groundwater is

List different geological features and how they influence the flow of groundwater through
the subsurface

Describe concepts of permeability - aquifers and aquitards

Describe groundwater flow through aquifers
Session Materials

Computer and projector

Flip chart paper and pens

Bucket of sand and block of concrete

Handouts:
- TABLE OF ROCK TYPES AND POROSITY
- Case study 1 description
- Map and activity description for Exercise1
Key Learning Points
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WASH Cluster - Groundwater Development and Drilling



GWD1
Different ground conditions require different investigation techniques and potential for
supplying an adequate water supply
Groundwater is not always available in sufficient volumes for emergency needs
Some sources of groundwater are difficult to access
Facilitator Guidance
Outlined in detail in the session plan
Session plan
Trainer: Write objectives on the notes sheet on flip chart paper stuck
on wall and refer to them during the session
This is to show that groundwater is a valuable resource world wide
Trainer to point to the place on the map where the training is taking
place
Ask participants if they know what the groundwater situation is there.
Trainer:
Get a jar filled with stones or sand and half fill with water – preferably
water coloured blue, red or green
Point out from the slide and the water filled jar that:
Groundwater is like the coloured water stored within rocks
The water table is the top of the zone completely saturated
with water (top of the coloured zone)
Layers of rock containing groundwater are referred to as
AQUIFERS – this is a fundamental concept
TRAINER NOTE:
Question participants on types of rocks
Igneous, sedimentary and metamorphic
Refer to slide
There are many types of rocks – therefore many types of aquifers
Trainer to bring local rock samples if available and ask participants to
try and identify what they are and where they come from in the area
Explain that we want to discuss rock types because the rock type
influences the way in which groundwater occurs
Session Plan – GWD1
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WASH Cluster - Groundwater Development and Drilling
GWD1
Make the point that there has been a massive amount of money
spent and failures in programs where the rock types and the
groundwater occurrence are not understood and drilling has
gone on unsuccessfully regardless
Trainer: Note the two ways in which particles that make up rocks
(and therefore aquifers) are organised
Use local rock specimens to show this difference. The next
Hand out: TABLE OF ROCK TYPES AND POROSITY
The next 14 slides could be run as a group activity where each group
is given an aquifer category from table (4 groups) and they have
10mins to prepare a poster explaining formation, draw the
arrangement and explain porosity.
This is for reference because many different rock types that people
may encounter are listed
The few most common rock types are shown in the following slides.
Present the slides
Igneous and metamorphic rocks
– Interlocking crystals
– Generally hard
Use the slides to show how different rocks occur in the field
Point out that:
Crystalline rocks (such as granite and metamorphic rocks in this slide)
do not have much porosity
The way that these rocks hold groundwater is in FRACTURES – water
is not held between mineral particles
Trainer
Q: How is basalt formed?
A: solidifying lava flows from volcanoes
Basalt Forms a common aquifer – how ?
On slides point out the fractures in basalt which store water and make
it an aquifer
Trainer explain that
Drill core covering a vertical profile of basalt – even within a few
metres, there is great variation in rock type. It is why some bores in
basalt are dry and other have high groundwater production
The vesicles are generally not interconnected. the porosity in basalts
is largely through cracks and fractures
Session Plan – GWD1
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WASH Cluster - Groundwater Development and Drilling
GWD1
Trainer: Looking at sedimentary rocks as aquifers
Display a lump of concrete / aggregate and a bucket / jar of loose
sand or loose mixed sand and pebbles
Which is the hardest – Why?
Note that the basic components of both are sand and gravel – the
aggregate is bound together by cement
Q: Which would be better aquifers – the cemented concrete or the
loose sand? Why?
A: Loose sand because pores are open
Note that the same
unconsolidated rocks
occurs
in
nature
with
consolidated
and
Show that the sandstones in this photo are very closely packed (like
the cement above ) and so have lower porosity than uncemented sand
Trainer:
Note the photo of coarse river gravel
Comment on the large open pore volume - compare with consolidated
pebble rock ( conglomerate)
Q: Which of these would hold the most water? Why?
A: the coarse gravel because of the open pore space
Point out that:
Sedimentary layers can be:
very extensive and flat like in the Grand Canyon in USA (on the left)
or
tilted by earth movements (right photo)
Refer to the photo in the slide,
Note:
the sand and gravel in the vertical face and the sand in the foreground
–these are not strongly cemented and would form reasonably good
aquifers
Session Plan – GWD1
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WASH Cluster - Groundwater Development and Drilling
GWD1
Trainer:
Comment that Limestone is often a very productive aquifer Refer to next two slides
Trainer:
Point out cavities in the rock and at larger scale the caves in the next
slide
Limestones can occur in areas described as “Karst” landscapes
Trainer :
Summarise the way rocks are grouped into three types of aquifer as
on the slide
Trainer:
Suggest that this slide is only used by trainers who have a
reasonable understanding of hydrogeology.
If used, show that the way the different rocks occur, some aquifers
overlie each other or are pushed against each other
It is a diagrammatic cross section like you might see on a geological
map and shows how different rocks may be found in nature.
Eg it shows that:
A: some consolidated sedimentary rocks are strongly tilted
into folds (as shown in slide)
B: consolidated sedimentary rocks that are not so strongly
tilted (have relatively flat layering) can rest on older rocks and
their thickness is often known . (shown in Grand Canyon
photo)
C:
flat unconsolidated deposits generally rest on top of
consolidated sedimentary rocks – they are generally younger
and their distribution and thickness is often known. In the
figure they show lenses of gravel, sand and clay which is often
how these sediments occur
D: volcanic rocks originate at depth and erupt via volcanoes at
the ground surface, and sometimes are interlayered with
sedimentary rocks
Session Plan – GWD1
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WASH Cluster - Groundwater Development and Drilling
GWD1
E:
granites shave been intruded into rocks such as
consolidated sediments and can occur at depth or are exposed
at the ground surface when erosion occurs
F: Faults (large fractures in the earth’s crust resulting from
large earth movements) can push different rock types against
each other
TRAINER:
Q:
Why is it useful to know the rock type when sourcing
groundwater?
General discussion, then finalise by referring to the slide
CASE STUDY OF EASTERN CHAD:
Hand out Case study notes
Trainer:
Work through the summary and figures
Participants to read details of the case study at a later time privately
Exercise 1:
DESCRIPTION
HANDOUT
OF
GEOLOGICAL
MAP
and
ACTIVITY
This is to give participants an appreciation of the way geological
information is presented and how they might use the geological map
to search for groundwater sources
See detailed handout notes for the trainer
TRAINER:
Refer to flip chart - which objectives have been met??
Session Plan – GWD1
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WASH Cluster - Groundwater Development and Drilling
GWD1
Notes for the facilitator: Exercise 1:
There are 8 different groupings of rocks shown in the map legend– participants to recognise that
there are different rocks mapped in each group (eg sandstone, sand, conglomerate)
Group
Rock types
Extent of group
Likely fractures and
Rank for water
porosity
bearing (Aquifer)
in the group
potential
1
granite
and
granodiorite
Extent
large
isolated
blocks
scattered
across
Isolated
fractures
in
Low
in
Low
crystalline rock
the region
2
gneiss
and
schist
Covers
a
large
area in the west
Isolated
fractures
crystalline rock
of the region
3
sandstone,
Covers
a
large
shale
areas
in
the
along the layering of
May be higher rank
eastern
part
of
these sediments. Note
in faulted zones
the region – note
numerous faults in the
that there are
eastern
and
slate
Possible
fractures
part
Low -Medium
which
may indicate zones of
intense
fracture
porosity
4
conglomerate,
Relatively limited
Probably
sandstone
distribution in the
and cemented so most
consolidated
and shale
centre of the area
likely
porosity
Low –Medium
is
fractures
5
sandstone,
Discontinuous
Contains
sand
patches
presumably
and
conglomerate
sand
cemented
so
Medium
not
and
has
granular porosity
6
Basalt
Extensive
linear
zones
Basalts
have
potentially
dense
fractures
Medium-High
Note the photos of
the
basalt
with
fractures etc
7
clay,
sand
and gravel
Extensive
and
Contains
gravel
and
High
continuous in the
sand as well as the
(this will depend on
north east
clays – so there are at
how much gravel
least some zones with
and sand there is)
high porosity
Remember that
sedimentary
deposits are layered
8
sand,
gravel
and clay
Very
limited
extent –in narrow
ribbons
Has
high
porosity
granular
Medium -High because it is narrow,
there may not be
much aquifer
material to store
large amounts of
Session Plan – GWD1
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WASH Cluster - Groundwater Development and Drilling
GWD1
water – note the
wadi cross section
More information would be:
 How thick is the layered sedimentary deposit in group7
 How well cemented or consolidated are the sedimentary layers in 4, 5
 Is there any scoria in the basalt area (group6)
Session Plan – GWD1
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