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Groundwater Quality and Protection. defining strategies and setting priorities. Learning Objectives. To assess and identify threats and pollution hazards to groundwater quality To discuss ways of protecting groundwater from pollution. Definition of common groundwater pollution terms.

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groundwater quality and protection

Groundwater Quality and Protection

defining strategies and setting priorities

learning objectives
Learning Objectives
  • To assess and identify threats and pollution hazards to groundwater quality
  • To discuss ways of protecting groundwater from pollution.
slide4

How do aquifers become polluted?

  • When contaminant load (effluent discharge and/or leachate):
  • is inadequately controlled/disposed of.
  • exceeds natural attenuation capacity of underlying soils and strata.
  • groundwater merits protection because
  • it provides vital source of potable water supply
outline of presentation
Outline of Presentation
  • Rural water supply
  • Urban- and Peri-urban settlements
  • Groundwater Protection Zones
rural water supply
Rural Water Supply
  • Currently 53 % of Africa‘s rural population is without access to safe water (AfDB 2009)
  • „Safe drinking water“ is predominantly from hand-dug-wells and drilled wells with hand pumps
  • Frequent reports in literature indicate elevated nitrate levels and bacterial contamination
contamination sources

McDonold et. al. (2005)

Contamination sources

dirty water at well head recirculating into the well

contamination sources contd
Contamination sources (contd.)

Pollution from animal faeces

protection measures
Protection measures
  • Proper well construction can significantly improve water quality
  • Well location upstream/away from pit latrines, waste dumps and cemeteries
  • Concrete platformsaround well with proper drainage
  • Animals must be kept away by a fence
protection measures contd
Protection measures (contd.)

www.ualberta.ca/~xcle/img/pump.jpg

Proper well construction

www.wateraid.org/images/cm_images/pump-web.jpg

Concrete platforms around the well

Fencing to keep away animals

http://rehydrate.org/dd/img2/su312.jpg

peri urban settlements
Peri-urban settlements

Present situation in Peri-urban settlements in Africa:

  • Uncontrolled settlement
  • Predominant use of on site-sanitation
  • Uncontrolled waste dumping
  • Water supply predominantly from dug wells or water ponds
  • Extensive contamination by nitrate, nitrite, ammonia, and faecal bacteria
  • Frequent outbrake of water-borne diseases (cholera).
contamination sources13
Contamination sources

Retention of solids

Infiltration of liquids

Pathogens

Polluted groundwater

Nitrates

Viruses

Source: Nkhuwa 2006

Source: GTZ (Werner) 2005

strategies to improve pollution situation in peri urban areas
Strategies to improve pollution situation in Peri-urban areas
  • Connection to public water supply (piped water system)
  • Connection to sewerage system
  • No realistic short term solution (high investment costs)
slide15

Dehydrating toilets

Source: CSIR 2004

Strategies to improve pollution situation in Peri-urban areas (contd.)

  • Improvement of on-site sanitation through reuse of faecal matter (dry toilets – ecosan).
slide16

Wastewater treatment

Source: BGR 2008

Strategies to improve pollution situation in Peri-urban areas (contd.)

  • Improvement of on-site sanitation through use of low cost wastewater treatment.
land use activities commonly responsible for groundwater pollution in the urban areas
Land-use activities commonly responsible for groundwater pollution in the Urban areas.

The Urban Environment

slide20

Contamination sources to water supply points… (contd.)

Fuel spillage from a tanker that overturned @ a petrol station in Lusaka.

Non-aqueous phase liquid contamination

slide23

Groundwater Protection

    • Common approach worldwide:
    • Protection of water resources by Groundwater Protection Zones (GPZ) – to be discussed in detail later
  • General aim:
  • To Protect drinking water resources in the groundwater contribution zone, upstream of a well/spring, from pollution.

Remedial

measures

  • What treatment is applied to the groundwater before it is piped to consumers?
vulnerability of aquifers to pollution
Vulnerability of aquifers to pollution

Threats to groundwater pollution are a function, among others, of:

  • Thickness & properties of overlying soil (vadose zone)
  • Depth to water-table.
vulnerability of aquifer to pollution contd
Vulnerability of aquifer to pollution (contd.)
  • Thin vadose zone &shallow water-table provides less natural attenuation,

prone to pollution.

vulnerability of aquifer to pollution contd26
Vulnerability of aquifer to pollution (contd.)
  • Deeper and confined aquifers have much greater natural protection by the overlying ground.
pollution pathways by sanitation
Pollution Pathways by Sanitation

Vulnerability of aquifer to pollution (contd.)

how can groundwater pollution hazard be assessed
How can groundwater pollution hazard be assessed?
  • from the hydrogeological characteristics of the overlying material.
      • used to produce a vulnerability index that can be mapped
      • a variety of vulnerability assessment tools may be used e.g.: DRASTIC method
how can groundwater pollution hazard be assessed contd
How can groundwater pollution hazard be assessed? (contd.)

DRASTIC

  • D - depth to water
  • R - net Recharge
  • A -aquifer media
  • S - soil media
  • T - topography
  • I -impact of vadose zone
  • C - hydraulic conductivity
how can groundwater pollution hazard be assessed contd30
How can groundwater pollution hazard be assessed? (contd.)

Pollution Hazard Assessment

When map of potl contaminant load overlain on aquifer vulnerability map, it will provide a map of groundwater pollution hazard.

groundwater protection
Groundwater protection

Its General aim:

  • To protect drinking water resources in the groundwater contribution zone upstream of the well/spring from pollution.

Common approach worldwide involves:

  • Protection of water resources by employing Groundwater Protection Zones (GPZ)
    • Zone I – Immediate Protection Zone
    • Zone II – Inner Protection Zone
    • Zone III – Outer Protection Zone
groundwater protection contd
Groundwater protection (contd.)

Zone 1 –Protects well/spring from direct contamination

Zone II – Protects drinking water source against pathogenic micro­biological constituents bacteria, viruses, parasites.

Groundwater Flow Direction

II

III

I

Well

Zone III – Protects against contamination affecting drinking water source over long distances (for chemical substances, which are non- or hardly degradable)

groundwater protection contd33
Groundwater protection (contd.)

Grdwater Protection Zones :

  • need regulatory embedding
  • need public awareness
  • need Monitoring
  • usually imply landuse restrictions to balance competing user-interests.
who should promote groundwater pollution protection
Who should promote groundwater pollution protection?

The ultimate responsibility for groundwater pollution protection lies with relevant government agency......

exercise waste management role play
Exercise – Waste Management Role Play
  • You are required to improve waste management / effluent disposal in the capital city in your country. Participants divide into stakeholders: Water/Groundwater managers; Waste Disposal companies; Industry discharging effluent; Citizen Groups; Politicians.
  • The water managers must propose sweeping reforms to improve all aspects of waste management in the city for the purpose of protecting quality of groundwater (& surface water). The other stakeholders should raise queries about the impact of the changes on them, & make objections/suggestions to the water managers.
  • Preparation: 20 minutes
  • Debate: 40 minutes.
exercise
EXERCISE
  • Purpose:To share experience of groundwater quality problems.
  • Activity:Break into groups of 4 or 5. 1 hour.
  • Each group to Identify a common groundwater quality problem in one of your countries.
  • Discuss the nature & scale of the problem – is it anthropogenic or natural?
  • How is the problem being managed and who is responsible for the management?
  • What have been the aims of the management and how successful has it been?
  • What would you need to change to improve the situation?
  • Report back: 15 minutes per group.