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 TermDefinition Aquifer Pollution Vulnerability sensitivity to contamination, determined by the natural intrinsic characteristics of geological strata forming the overlying confining beds or vadose zone of the aquifer concerned Groundwater Pollution Hazard probability that groundwater in an aquifer will become polluted to concentrations above WHO drinking-water guidelines when a given subsurface contaminant load is generated at the land surface Groundwater Pollution Risk threat posed by hazard to human health due to pollution of a specific groundwater supply source, or to an ecosystem, due to pollution of a specific natural aquifer discharge.

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 1.Rural water supply 2.Urban- and Peri-urban settlements 3.Groundwater Protection Zones

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

Rural Water Supply (contd.) Gyau-Boakye, P. et. al. (2008) High levels of nitrate and coliforms in hand-dug wells in Ghana Adalena, S. et. al. (2008) 33 % of 2200 wells in Nigeria have nitrate values above 45 mg NO 3 /L Agyekum, W.A. et al. (2008) 38 % of water from boreholes in a district in Ghana have nitrate concentrations above 45 mg/L

Contamination sources dirty water at well head recirculating into the well McDonold et. al. (2005)

Contamination sources (contd.) Pollution from animal faeces

Protection measures  Proper well construction can significantly improve water quality  Well location upstream/away from pit latrines, waste dumps and cemeteries around well with proper drainage  Concrete platforms around well with proper drainage  Animals must be kept away by a  Animals must be kept away by a fence

Protection measures (contd.) Concrete platforms around the well Proper well construction Fencing to keep away animals

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).

Retention of solids Nitrates Viruses Pathogens Infiltration of liquids Source: Nkhuwa 2006 Polluted groundwater Source: GTZ (Werner) 2005 Contamination sources

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)

 Improvement of on-site sanitation through reuse of faecal matter (dry toilets – ecosan). Dehydrating toilets Source: CSIR 2004 Strategies to improve pollution situation in Peri-urban areas (contd.)

Source: BGR 2008 Wastewater treatment  Improvement of on-site sanitation through use of low cost wastewater treatment. Strategies to improve pollution situation in Peri-urban areas (contd.)

Land-use activities commonly responsible for groundwater pollution in the Urban areas. The Urban Environment

Contamination sources to water supply points in Urban areas

Wastewater drain – Accra, Ghana

Contamination sources to water supply points… (contd.) Fuel spillage from a tanker that a petrol station in Lusaka. Non-aqueous phase liquid contamination

Pollution sourceType of contaminant Agricultural Activitynitrates; ammonium; pesticides; faecal organisms In-situ Sanitationnitrates; faecal organisms; trace synthetic hydrocarbons Gasoline Filling Stations & Garages benzene; other aromatic hydrocarbons; phenols Solid Waste Disposal ammonium; salinity; some halogenated hydro-carbons; heavy metals Dry Cleaningtrichloroethylene; tetrachloroethylene Sewage Sludge Disposal nitrates; various halogenated hydrocarbons; lead; zinc Leather Tannerieschromium; various halogenated hydrocarbons; phenols Common grdwater contaminants and associated pollution sources

Remedialmeasures 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.  What treatment is applied to the groundwater before it is piped to consumers?

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.

Thin vadose zone & shallow water-table provides less natural attenuation,  prone to pollution. Vulnerability of aquifer to pollution Vulnerability of aquifer to pollution (contd.)

Deeper and confined aquifers have much greater natural protection by the overlying ground. Vulnerability of aquifer to pollution (contd.)

Pollution Pathways by Sanitation Vulnerability of aquifer to pollution (contd.)

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

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? (contd.)

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

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

Zone II – Protects drinking water source against pathogenic micro­biological constituents bacteria, viruses, parasites. Groundwater protection (contd.) Well I II III Groundwater Flow Direction Zone 1 – Protects well/spring from direct contamination Zone III – Protects against contamination affecting drinking water source over long distances (for chemical substances, which are non- or hardly degradable)

Grdwater Protection Zones :  need regulatory embedding  need public awareness  need Monitoring  usually imply landuse restrictions to balance competing user-interests. Groundwater protection (contd.)

Who should promote groundwater pollution protection? The ultimate responsibility for groundwater pollution protection lies with relevant government agency......

Thank you for your attention

 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 – Waste Management Role Play

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.