WASH Cluster – Emergency Training
GWD
Groundwater Development
and Drilling
Session 4
Developing Groundwater Sources
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WASH Cluster – Emergency Training
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Session Aims
• Provide guidance on appropriate methods of
developing groundwater resources.
• Clarify understanding of the development of
groundwater by wells, boreholes, spring
enhancement
• Discuss excavation and drilling techniques
appropriate to hydrogeological conditions.
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WASH Cluster – Emergency Training
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Wells and Bores
• Wells are holes in the ground that
intersect groundwater and enable
groundwater to be brought to the surface
• Holes are dug by hand or by drilling
machine
• Walls of the hole usually supported
• Depth depends on aquifer type, available
yield
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Drilling techniques
• How do you……?
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Types of wells
Shallow well
• Hand dug
• Unconfined water
table aquifer
• Groundwater
recovered by hand
or low rate suction
pump
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Types of wells
Deep well
• Machine drilled
• Confined and
unconfined aquifers
• Groundwater
recovered by pump
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Well installation methods
• Hand excavation / boring
• Hand drilling
– incl augering and jetting
• Machine drilling
– Rotary, percussion, down hole hammer
• Drilled wells
– Reach greater depths
– Penetrate wider range of rocks
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WASH Cluster – Emergency Training
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Hand completed wells
• Hand augering a small hole
– install narrow casing - tube well
• Hand digging larger diameter (~1m diam)
• Ground must be soft enough to penetrate
• Shallow water table required
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WASH Cluster – Emergency Training
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Application of hand completed wells
• Likely in the very first phase of an
emergency
– equipment can be mobilised quickly
– produced from available materials
• Relatively low cost
• Often local expertise available
• Can be labour intensive
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WASH Cluster – Emergency Training
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Hand Auger drilling
• VIEW Video of hand augering:
http://www.youtube.com/watch?v=qq0p
_WPwSZo
• Affordable Water Well Drilling in Sierra
Leone - Fresh Hope Ministries
International 7min
http://www.youtube.com/watch?v=UYay92UMwM
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Shallow hand auger wells
A
C
B
D
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Hand dug Groundwater wells
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WASH Cluster – Emergency Training
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Lining of Hand Dug wells
From Oxfam Manual on Hand Dug Well Equipment
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Completion of Hand dug wells
Simple open holes,
no protection from contamination
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Sanitary surrounds with hand pump
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Bore Drilling
• Drilling equipment and technique is
affected by:
– rock type(s) encountered
– depth to groundwater
– aquifer pressure
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Hand operated drilling
•Narrow diameter (< 100mm diam) bores
•Casing installed to construct tube wells (narrow
diameter production wells).
VIEW YOUTUBE FILES
Shallow percussion:
http://www.youtube.com/watch?v=N3CUnUrMo6s&feature=related
Shallow percussion in Senegal:
http://www.youtube.com/watch?v=VWaTBNt0n9o&feature=related
Deep well in Dhaka slums 200ft (>60m) deep:
http://www.youtube.com/watch?v=nIvgg6QTKj4
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WASH Cluster – Emergency Training
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Jetting Techniques
Use water pressure forced down a drill pipe through a nozzle to penetrate the soil
Need a source of water and pump to provide the pressure
Source: Water for the World, Constructed Jetted Wells,
Technical Note No RWS 2.C.3
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Jetting Techniques
Use water pressure forced down a drill pipe through a nozzle to penetrate the soil
Need a source of water and pump to provide the pressure
20m deep jetted well, near Matatuto, Timor Leste
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Jetting Videos
A jetting operation in Ethiopia:
http://www.youtube.com/watch?v=cHu5yFQn660&feature=related
Jetting in Indonesia:
http://www.youtube.com/watch?v=D-pmZe2aQuY&feature=related
A backyard well in USA :
http://www.youtube.com/watch?v=FbGUV7GQpMM&feature=fvw
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Machine Drilling
Advantages
• Can reach great depths
• Can penetrate wide
range of rock types
• Can produce high
yielding wells
•
•
•
•
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Disadvantages
Expensive
Require highly skilled
crews
Can have long lead time
from set up to
completion
May be privately or Govt
owned and not available
for an emergency
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Percussion Rigs
crushes the rock under the weight of a tool dropped down the hole on a
length of cable
Suitable for unconsolidated and soft formations
Relatively slow
VIDEO: of cable tool operation
:http://www.youtube.com/watch?v=vEIyPhQdqrw&feature=related
Application in the Philippines:
http://www.youtube.com/watch?v=mXAS0UUc7Ek&feature=related
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WASH Cluster – Emergency Training
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Rotary Rigs
Can drill to great depths (1000+ m)
Drill bits attached to the end of a
segmented string of steel drilling
rods
As the drilling rods rotate, the bit
grinds through the soil and rock
Air, water or drilling mud used as a
circulation fluid to remove cuttings
of rock and soil
Photo of Rotary rig, with drill bit and drilling rods visible – white tubing is PVC casing to be installed in the bore.
Photo courtesy GHD Pty Ltd
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Rotary Rigs
• VIDEO of a mud rotary rig
http://www.youtube.com/watch?v=ZVlzCs3686s
• Some rotary rigs require no mud and are powered by air
to activate the drilling bit. This is shown on the
following video:
http://www.youtube.com/watch?v=Qa0SL6h3pF8&feat
ure=related
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Constructing a Well
• In most drilled wells, the
walls need support
• Wells are cased with
lengths of factory-made
pipe
• Casing can be steel or
plastic (Eg PVC, PE, ABS)
• Holes in very strong rock
sometimes not cased
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Installation of plastic casing in rotary drilled
bore, Photo Courtesy GHD Pty Ltd
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Constructing a Well
Highest flow from an aquifer into a drilled well is ?
through the most permeable zones
Identified through:
Drill cores
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“Cuttings” pushed to surface
during drilling
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Opening the well to the Aquifer
•Cased wells need to have a screen to
allow water to flow from the aquifer into
the well
•Screens are a length of slotted or
perforated pipe
•Typically PVC, steel or stainless steel
•Screens often have a filter pack to
improve inflow to the well
•Wells drilled in stable rock sometimes
are not cased and have no screen –
termed “open hole”
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Positioning Screens in a well
from Nkhoma and Baumle, (2007)
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Display of constructing a well
Insert narrow pipe /
plastic bottle
Casing
Drilled
Bore
(Plastic
bottle)
Soil mixed
with flour
Flour to seal
Gravel pack
AquiferScreen
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Typical Well construction
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Summary of Types of Wells
Modified From Wikepedia
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Well Development
•Well development is undertaken after
installing casing, screen and gravel pack
•Improves well efficiency
•Involves surging or jetting water or air in and
out of the well screen to clean out residual
drilling fluid.
•May take several days.
•Well developed wells have lower pump
costs, longer pump life – sand and mud
passing through screen damages pumps
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WASH Cluster – Emergency Training
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Groundwater pumping effects
Neighbouring
Bores
Drawdown
Drawdown
Available Drawdown
Drawdown
Radius of Influence
Static or pre-pumping
w ater level
Drawdown
Creek
Cone of
depression
Aquifer
Pump
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WASH Cluster – Emergency Training
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Test pumping of wells
• Completed after well development
• Tests the potential pumping rate and
resulting drawdown
• Assists in determining :
– Long term pumping rate and water level
– Size of pump
– Impact on surrounding wells or environment
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WASH Cluster – Emergency Training
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Pumping tests
• Step drawdown test
– short periods of pumping at progressively higher rates
and measuring drawdown in the well
– helps work out achievable pumping rate
• Constant rate test
– Pumping at constant rate (could be for days or weeks)
– Measure drawdown in well and nearby “observation”
wells
– Helps assess pumping impacts on the aquifer under
different pumping scenarios
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WASH Cluster – Emergency Training
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Specific Capacity of a Well
• Measures ratio of drawdown to pumped
flow rate
• Allows a check of well efficiency
• Helps indicate bore deterioration eg
blocked screens
• Reduced capacity (greater drawdown to
pumping rate) indicates reduced well
efficiency
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WASH Cluster – Emergency Training
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Relevance to an Emergency
• Groundwater can be developed quickly in some
situations – eg springs, shallow wells, available
drilling equipment
• Existing deep wells may be available
– Could be included in emergency water supply
solution
– Need to understand capacity, condition, constraints
on use
• Potential for future development later in
emergency
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WASH Cluster – Emergency Training
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Springs
•May be harvested in a number
of ways
•Should always be protected
from degradation.
Spring being protected, Zaire - S House / WEDC
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From Oxfam technical brief
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WASH Cluster – Emergency Training
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Springs
A protective box that enables:
•collection of water by hand
•discharge to a tap for collection
at the spring
•discharge downhill by
distribution pipe .
Spring box with discharge pipe leading down hill, Nias, Indonesia
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WASH Cluster – Emergency Training
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Estimating volume of
groundwater available
Q:How you might work out how much
groundwater is available?
A: Factors to be considered
•Area where rainfall might occur on aquifer
•When does it rain
•Will all of the rainfall enter the aquifer?
•The rock type
•Flows of existing bores / springs
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