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Wells
Wells
1
Marco Bruni, seecon international gmbh
Wells
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Included in the SSWM Toolbox are materials from various organisations and sources. Those materials are open source. Following the open-source concept for capacity building and non-profit use, copying and adapting is allowed provided proper acknowledgement of the source is made (see below). The publication of these materials in the SSWM Toolbox does not alter any existing copyrights. Material published in the SSWM Toolbox for the first time follows the same open-source concept, with all rights remaining with the original authors or producing organisations.
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The contents of the SSWM Toolbox reflect the opinions of the respective authors and not necessarily the official opinion of the funding or supporting partner organisations.
Depending on the initial situations and respective local circumstances, there is no guarantee that single measures described in the toolbox will make the local water and sanitation system more sustainable. The main aim of the SSWM Toolbox is to be a reference tool to provide ideas for improving the local water and sanitation situation in a sustainable manner. Results depend largely on the respective situation and the implementation and combination of the measures described. An in-depth analysis of respective advantages and disadvantages and the suitability of the measure is necessary in every single case. We do not assume any responsibility for and make no warranty with respect to the results that may be obtained from the use of the information provided.
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Wells
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Contents
1. Introduction
2. How Can Wells Optimise my Local Water System?
3. Prospecting for Groundwater Sources
4. Different Types of Wells and their Characteristics
5. Basic Design and Construction Principles
6. Operation and Maintenance
7. Applicability
8. Advantages and Disadvantages
9. References
3
Wells
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Variability of the Groundwater Table
4
1. Introduction
Source: SMET & WIJK (2002)
Infiltration of water into an aquifer during the wet season
Infiltration of water into an aquifer during the dry season
Wells
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Groundwater Withdrawal from Wells by Means of Buckets or Pumps
5
1. Introduction
Source: IWMI (n.y.); NE (n.y.); WATER CHARITY (n.y.); BAUMANN (2011)
PumpsPumps
Rope & BucketRope & Bucket
Source: http://www.flickr.com/photos/foodforthepoor/6100218694/sizes/z/in/photostream/ [Accessed: 17.05.2012]
Wells
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Health Aspects
6
2. How Can Wells Optimise my Local Water System?
Source: BAUMANN (2011)
A properly constructed well can improve a community’s water supply substantially.
High quality drinking water
High quality drinking water
No or just minor purification
required
No or just minor purification
required
Many low-cost and low-tech digging and
drilling options available
Many low-cost and low-tech digging and
drilling options available
Wells
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Where Should I Look for Groundwater?
• Villagers and members of the neighbouring communities can be a good source of information on the presence of shallow groundwater.
• Also, certain types of vegetation (e.g. banana plants, bulrushes, sugar can, date palms) can indicate presence of groundwater (COLLINS 2000).
• Often, existing wells in close proximity indicate the presence of groundwater.
• If technical equipment is available, test borings can give detailed information on the groundwater level.
7
3. Prospecting for Groundwater Sources
Source: http://thumbs.dreamstime.com/thumblarge_553/1288894832745DF3.jpg [Accessed: 18.05.2012]
Wells
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Two Main Types of Wells
8
4. Different Types of Wells and their Performance
Dug WellsDug Wells Drilled WellsDrilled Wells
Diameter: +/- 1.2mLength: 3 – 20m
Diameter: +/- 50mmLength: 10 – 50m (200m)
Wells
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Location
• Wells should not be constructed close to potential sources of contamination, e.g. pit latrines, livestock farming, fuel/pesticide/ fertiliser storage, etc.
• Well should be located in close proximity to the actual point of water use
9
5. Basic Design and Construction Principles
Source: BUCHANAN et al. (2010)
Wells
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Dug Well: Elements
10
5. Basic Design and Construction Principles
Source: SMET & WIJK (2002)
Well HeadWell Head
Well ShaftWell Shaft
IntakeIntake
Wells
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Dug Well: Excavation
• Excavation is done manually with pick and shovel
• Lining is most often necessary to protect the well from collapsing and preventing subsequent contamination of the well
• Materials for lining: prefabricated concrete rings, stones, bricks, masonry, etc.
11
5. Basic Design and Construction Principles
Source: : http://cloud.globalgiving.org/pfil/7109/Handdug_Well2_Grid7.jpg [Accessed: 14.03.2011]
Wells
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Drilled Well: Drilling
a) Basic hand-drilling techniques
b) High-tech machine-drilling
12
5. Basic Design and Construction Principles
Source: http://www.nigerwaterforlife.org/images/upload/IMAG0010.jpg [Accessed: 27.03.2012]
Source: http://i01.i.aliimg.com/photo/v0/106324951/water_well_drilling_and_borehole_rig_machine.jpg [Accessed: 17.05.2012]
Wells
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Drilled Well: Drilling – Many Different Techniques
a) Basic Hand-drilling techniques
b) Machine-drilling
13
5. Basic Design and Construction Principles
Source: ELSON & SHAW (1995)
Source: WURZEL (2000)
Augering
Jetting
Sludging
Percuss
i
on
Machine-
drillin
g
Wells
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Drilled Well: Completion
Completion of a well involve construction of a:
•Well casing (prevents the well from collapse and seepage of contaminants).
•Well screen (holds back sediments while allowing water to infiltrate the well)
•Gravel pack (prevents the well screen from becoming clogged)
•Sanitary seal & head works (prevents surficial contamination)
14
5. Basic Design and Construction Principles
Source: WATERAID (2008)
Wells
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Well Protection
• Wells and aquifers are susceptible to contamination. Contaminants can either enter from the opening or from the sides of the excavation.
• Water source protection involves: Interdiction of all activities that can potentially cause
contamination close to the well (e.g. pit latrines, livestock farming, fuel/pesticide/ fertiliser storage, etc)
• Wellhead protection involves: Drainage Surficial seal: an apron Impermeable lining (dug wells) or
casing (drilled wells) Securing functioning of the pump
15
5. Basic Design and Construction Principles
Source: NABUUR (n.y.)
Wells
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Dug Well
16
• Structural maintenance includes: Checking the apron for cracks, Securing the inspection cover, Improving the yield by
deepening or removing infiltrated sand particles, and the Maintenance of the lifting device.
• Equally, securing hygienic operation is essential. This involves: Protection and cleaning of the area (e.g. fencing and
covering), Checking water quality and disinfecting if necessary, Monitoring the effects of withdrawal on environment
and surrounding areas, and Educating water users in proper operation of the well.
6. Operation and Maintenance
Wells
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Drilled Well
17
• Drilled wells are easy to operate and basically not in need for maintenance.
• However, as a drilled well always include a manual or mechanised pump, maintenance of the lifting is critical!
6. Operation and Maintenance
Source: http://www.edgeoutreach.com/sites/edgeoutreach.com/files/HaitiHPRTrainers.jpg [Accessed: 18.05.2012]
Wells
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Drilled Well Drilled Well
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• Can serve as a water supply for a rural community, depending on the performance
• Low-tech solution particularly for rural communities
• Can serve as water supply for single households, for small rural communities as for more urban areas, depending on the size of the well (depth & diameter).
• Manual drilling is applicable in alluvial soils up to 40 metres.
• A pump must be available and frequently maintained
7. Applicability
Wells
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Dug Well
19
Advantages:•High degree of involvement of the local community during the whole process
•Under supervision, no skilled workers are required
•Simple equipment sufficient for both construction and maintenance
•Low cost for construction and O&M
•Involvement of private sector possible (local well diggers)
•Yield can be increased after construction
•Reservoir included (large diameter)
Disadvantages:•Long construction phase
•Dangerous excavation
•Motorised pump (power source) often required to lower the water table during construction
•Application restricted to regions with rather soft geological formation and relatively high groundwater levels
•Alteration of groundwater level can adversely affect the surrounding environment
•High susceptibility for contamination
•People (i.e. children) can fall in if the well is uncovered
8. Advantages and Disadvantages
Wells
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Drilled Well
20
Advantages:•Quicker and cheaper to sink than hand-dug wells
•Less susceptible to contamination
•No dewatering during sinking required
•Less lining material required
•Safer in construction and use
•The well itself needs barely maintenance
•Many simple drilling techniques available suiting many geological conditions
Disadvantages:
•Skilled staff and experts required for drilling
•Pump required, which needs appropriate operation and maintenance
•Lower yield than hand-dug wells (smaller diameter)
•Overexploitation may lead to adverse effects on the environment
•Arsenic pollution may occur
•More technical equipment and skills necessary for construction
•No integrated storage capacity / recharge during periods of low abstraction
8. Advantages and Disadvantages
Wells
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21
9. ReferencesBAUMANN, E. (2011): Low-cost Hand Pumps. St. Gallen: Rural Water Supply Network (RWSN). URL: http://www.rwsn.ch/documentation/prcollector.2009-04-05.2482958002/skatdocumentation.2011-07-01.0268979788/file [Accessed: 02.04.2012].
BUCHANAN, B.; DE LA CRUZ, N; MACPHERSON, J.; WILLIAMSON, K. (2010): Water Wells that Last for Generations. Edmonton: Alberta Agriculture and Rural Development. URL: http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/wwg404 [Accessed: 23.04.2012].
ELSON, B.; SHAW, R. (1995): Simple Drilling Methods. Leicestershire: Water, Engineering and Development Centre (WEDC), Loughborough University. URL: http://www.lboro.ac.uk/well/resources/technical-briefs/43-simple-drilling-methods.pdf [Accessed: 21.03.2012].
IWMI (n.y.): Diesel pump in operation. Colombo: International Water Management Institute (IWMI). URL: http://awm-solutions.iwmi.org/motorized-pumps.aspx [Accessed: 25.04.2012].
NABUUR (n.y.): Protected dug well in Uganda. Amersfoort: Nabuur. URL: http://www.nabuur.com/en/village/nakyerongosa/project/task/integrated-community-managed-water-hygiene-and-sanitation-improvem [Accessed: 15.03.2012].
NE (n.y.): Solar Water Pump. Lahore: National Engineers (NE). URL: http://www.ne.com.pk/uploads/images/Gallery/pump/DSCN0054.jpg [Accessed: 26.04.2012].
SMET, J. (Editor); WIJK, C. van (Editor) (2002): Small Community Water Supplies: Technology, People and Partnership: Groundwater Withdrawal - Chapter 10. The Hague: International Water and Sanitation Centre (IRC). URL: http://www.irc.nl/page/1917 [Accessed: 29.02.2012].
WATERAID (2008): Technology Notes. London: Wateraid. URL: http://www.wateraid.org/documents/plugin_documents/technology_notes_2008.pdf [Accessed: 12.03.2011]
WATER CHARITY (n.y.): Deep-well hand piston pump including apron and drain in Wallalan, Upper Badibu District, Gambia. Crestline: Water Charity. URL: http://appropriateprojects.com/images/jorgensen/7.jpg [Accessed: 02.04.2012].
WURZEL, P. (2001): Drilling Boreholes for Handpumps. St. Gallen: Swiss Centre for Development Cooperation in Technology and Management (SKAT). URL: http://www.skat.ch/publications/prarticle.2005-09-29.5069774463/prarticle.2006-11-02.5180575226/skatpublication.2006-11-02.0404244520/file [Accessed: 22.03.2012].
Wells
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22
“Linking up Sustainable Sanitation, Water Management & Agriculture”
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