WASH Cluster – Emergency Training GWD GWD5 1 1 Groundwater Development and Drilling Session 5...
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Transcript of WASH Cluster – Emergency Training GWD GWD5 1 1 Groundwater Development and Drilling Session 5...
![Page 1: WASH Cluster – Emergency Training GWD GWD5 1 1 Groundwater Development and Drilling Session 5 Protecting Groundwater Sources.](https://reader035.fdocuments.us/reader035/viewer/2022062809/5697c0271a28abf838cd66af/html5/thumbnails/1.jpg)
GWD5 1
WASH Cluster – Emergency Training GWD
1
Groundwater Development and Drilling
Session 5
Protecting Groundwater Sources
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GWD5 2
WASH Cluster – Emergency Training GWD
Session Aims
2
•Demonstrate the potential impacts on groundwater that may affect security of the water source,
•Discuss systems that must be put in place to determine whether the water supply is able to be sustained for on-going use, and
•Demonstrate what issues need to be understood for on-going use
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GWD5 3
WASH Cluster – Emergency Training GWD
Question 1: What are some of the risks to the use of groundwater for emergency water supply?
Key Risks to Groundwater
3
•Reduction of groundwater availability / Depletion of aquifer yield due to excessive drawdown, sustainability, interference from other bores •Water quality impacts - contamination in the catchment and near the bore -eg salt water intrusion, latrines, other pollutants•Protection of the bore itself -eg animals, agricultural runoff, dirty equipment, including vandalism•Contamination from up-gradient contaminants, salt water intrusion•Set up costs, time lags, proper investigation and design•Costs of pumping, maintenance of pumps and fuel supply•Interruption to power or fuel supply (related to well infrastructure and delivery–session GWD4)
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GWD5 4
WASH Cluster – Emergency Training GWD
QUIZ 2:• What factors will affect the amount of
water that can be extracted from a well? • What will happen if the well is pumped at
too high a rate
• What happens when the pump stops?
• Does this apply to all wells?
• What might the long term effect of this be?
Reduced Yield from a Well
4
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GWD5 5
WASH Cluster – Emergency Training GWD
Relevance to Emergency
• Reduction of flow from well or spring related to the balance between the amount of water removed from an aquifer and the amount that recharges.
• Unless there is adequate seasonal recharge into the aquifer, the volume of groundwater stored in the aquifer will be reduced - ultimately unsustainable supply.
• If extraction is too great on a particular day, the yield of the well on that day may drop off
• Changes due to pumping drawdown and recovery due to recharge need to be carefully monitored to make sure supply is maintained
Reduction in Availability
5
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GWD5 6
WASH Cluster – Emergency Training GWD
Groundwater potentially protected by being below the surface
Potability can be influenced by:– Natural variations in salinity– Naturally occurring chemicals – Man-induced contamination
Water Quality Effects
6
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GWD5 7
WASH Cluster – Emergency Training GWD
• Salinity – Potable (<1000mg/L) based on palatibility
• Turbidity– Can be serious in hand dug wells and
poorly constructed drilled wells
• Dissolved Iron– Unpleasant taste and colour
• Dissolved Carbonate / bicarbonate– Unpleasant taste, precipitation on pipes
Naturally occurring quality issues
7
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GWD5 8
WASH Cluster – Emergency Training GWD
• High Fluoride and Arsenic occur in some groundwaters
• Can be naturally occurring • Can be detrimental to health • Tend to be due to long term exposure
– but requires careful assessment
Natural Toxicants
8
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GWD5 9
WASH Cluster – Emergency Training GWD
Contamination by Humans
9
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GWD5 10
WASH Cluster – Emergency Training GWDMicrobiological contamination
10
The bacterium Escherichia.coli is found in the intestines of warm blooded animals,
- present in the faeces of humans
Latrines can be a source of contamination with E.coli –
Bacteria and viruses have relatively short lives in groundwater
Latrine siting is important - not in the groundwater flow path
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GWD5 11
WASH Cluster – Emergency Training GWDMicrobiological contamination
11
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GWD5 12
WASH Cluster – Emergency Training GWD
Protection of Well surrounds
12
Poorly maintained well head at pumping well with pathway for contamination down the well, Osire Refugee Camp, Namibia
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GWD5 13
WASH Cluster – Emergency Training GWD
Protection of Well surrounds
13
Filthy surrounds to shallow well and likely contamination introduced to a well by rope.
Note the broken hand pump has compromised the security of the well head. To access the well buckets are used. Gassire, Eastern Chad
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GWD5 14
WASH Cluster – Emergency Training GWD
Protection of Well surrounds
14
Sanitary well conditions at the well head but a contamination source (pig pens) is immediately behind the fence (Nias, Indonesia, 2006).
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GWD5 15
WASH Cluster – Emergency Training GWD
• Emergency can cause additional demand – Increased drawdown on existing wells – Over-extraction pressure on the aquifer
• Too many people at a well (eg open well) can lead to contamination
Maintenance of Aquifers and Well Infrastructure
15
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GWD5 16
WASH Cluster – Emergency Training GWDRepairing and disinfecting wells
16
Litter in well after Tsunami, Band Aceh, Indonesia
Rubbish removed from the base of an open well during well rehabilitation, Gassire, Chad
After rubbish removal, disinfection with a chlorine solution
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GWD5 17
WASH Cluster – Emergency Training GWD
Refurbishing well surrounds
17
Original unsanitary well surrounds,
Rehabilitated apron with drainage point bottom left.
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GWD5 18
WASH Cluster – Emergency Training GWD
Repair of deep wells
18
Deep wells can be degraded by:•Microbiological contamination – can be disinfected with chlorine solution•Casing and screen corrosion – repair or replacement•Build up of bacterial slime (fouling) on screens– chemical treatments
Treatment / repair of existing wells needs careful assessment and specialist inputs
•Not a focus for first phase emergencies.
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GWD5 19
WASH Cluster – Emergency Training GWD
Spring Protection
19
Dedicated buckets and collection cell, Nias,Indonesia
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GWD5 20
WASH Cluster – Emergency Training GWD
Monitoring
• QUIZ 2: MONITORING QUIZ
• Why monitor?
• What to consider in a monitoring program
• What type of information is collected for a groundwater source?
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GWD5 21
WASH Cluster – Emergency Training GWD
Monitoring
Monitoring of water level, usage and quality is important
fundamental to record and store the data
Data must be looked at and used to make best use of the groundwater resource
Monitoring groundwater levels in new water supply well