Groundwater in Lusaka - A Resource in Need of Protection
Transcript of Groundwater in Lusaka - A Resource in Need of Protection
Groundwater in LusakaGroundwater in LusakaG ou d ate usa aG ou d ate usa a-- A Resource in Need of Protection A Resource in Need of Protection --
Roland Bäumle & Levy MusetekaREPUBLICOF ZAMBIA
yFringilla Lodge, Feb 8th, 2011
Presentation OutlinePresentation Outline
1. Groundwater Pollution
2. Groundwater Protection
3. Vulnerability3. Vulnerability
4. Lusaka Groundwater Systems
5. Groundwater Chemistry and Quality in Lusaka
6. Conclusions
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World wide fresh water resources = 35 Mio. km3
Lakes 0 26% Rivers
Fresh groundwater
0,26% Rivers 0,0057%
Wetlands 0,033%Unsaturated soil 0,05%g
30,1% Atmosphere 0,04%
,
Ice and snow ( + glaciers and permafrost)( + glaciers and permafrost)
68,8%Source: Water for People, Water for Life – UN World Water
Development Report (WWDR); UNESCO 2003.REPUBLICOF ZAMBIA
Relevance of groundwater
Groundwater:
• worldwide most important resource for drinking water supply(nearly 60% of all drinking water worldwide is abstracted from groundwater,in arid and semi-arid zones up to 100% ! )
• in many countries used for agricultural irrigation(over 50% in Bangladesh, India and Iran; ca. 30% in Argentina, Mexico,and Pakistan; nearly 20% in China karst aquifers)and Pakistan; nearly 20% in China karst aquifers)
• secure water supply(natural protection against pollution important storage function during dry season)(natural protection against pollution, important storage function during dry season)
• relatively cheap to develop for rural water supply (local resource low development costs no sophisticated pipeline system needed(local resource, low development costs, no sophisticated pipeline system needed, in most cases no or only minor treatment costs)
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Groundwater Pollution in Urban AreasLand use activities commonly responsible for groundwater pollutionLand-use activities commonly responsible for groundwater pollution in the urban areaHow do aquifers become polluted?
When contaminants (effluents, discharge or leachate) are inadequately controlled and disposed of orexceed natural attenuation capacity of underlying soils and strata
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Common g/water contaminants & associated pollution sources
Pollution source Type of contaminantPollution source Type of contaminant
Agricultural Activity nitrates; ammonium; pesticides; faecal organisms
In-situ Sanitationnitrates; faecal organisms; trace synthetic hydrocarbonshydrocarbons
Gasoline Filling Stations & Garages
benzene; other aromatic hydrocarbons; phenolsStations & Garages
Solid Waste Disposal
ammonium; salinity; some halogenated hydro-carbons; heavy metalsDisposal carbons; heavy metals
Dry Cleaning trichloroethylene; tetrachloroethylene
Sewage Sludge nitrates various halogenated hydrocarbons lead Sewage Sludge Disposal
nitrates; various halogenated hydrocarbons; lead; zinc
chromium; various halogenated hydrocarbons; REPUBLICOF ZAMBIALeather Tanneries
chromium; various halogenated hydrocarbons; phenols
Peri-urban settlements
Present situation in many peri-urban settlements :Uncontrolled settlementPredominant use of on site-sanitationPredominant use of on site-sanitationUncontrolled waste dumpingWater supply predominantly from shallow wells or open water y yponds
Extensive contamination by nitrate,nitrite, ammonia, and faecal bacteria
Frequent outbreak of water-bornediseases (diarrhea, cholera).
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Contamination Pathway
Retention of solids
I fil i f li id
Soil:
Pathogens
Infiltration of liquids
P ll t d d tHigh water l l Nitrates
Viruses
Polluted groundwaterlevel:Short cut
Source: GTZ (Werner) 2005Source: GTZ (Werner) 2005
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Pathogenic germs
Unaffected groundwater is free of pathogenic germsUnaffected groundwater is free of pathogenic germsand is in good bacteriological conditions≈ 50 days of underground passage is sufficient to virtually kill all harmful bacteria
Empirical correlation of the so-called“50-day line”
Time in days
Mortality Rate in %REPUBLICOF ZAMBIA
Mortality Rate in %
Groundwater Protection
Protection of water resources by employing G/w Protection ZonesProtection of water resources by employing G/w Protection ZonesZone 1 – Immediate Protection ZoneProtects well/spring from direct contamination
WellI II III
Groundwater Flow Direction
contamination
Well
Zone III – Outer Protection ZoneZone II – Inner Protection ZoneProtects drinking water source against pathogenic constituents
Protects against contamination affecting drinking water source over long distances (for chemical substances REPUBLIC
OF ZAMBIA
g p gbacteria, viruses, parasites.
long distances (for chemical substances, which are non- or hardly degradable)
Protection ZonesGroundwater Protection Zones around well fields (public sector)Groundwater Protection Zones around well fields (public sector)
Graded protection and controlled use –To protect drinking water resources supplied from groundwater
Protection zone I has the highest priority(area directly surrounding the production well)
upstream of the well/spring from pollution.
Protection zone II:no groundwater pollutants and no industry
(area directly surrounding the production well)
and no industry, no untreated wastewater
Protection zone III
Zone III
limited use, construction/housing limited
Catchment areaCatchment Boundary
Zone II
Zone ICatchment BoundaryCatchment area
Integrated Water ResourcesManagement (IWRM)
BoundaryZone I
Well
Boundary
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Groundwater Protection Zones
Need regulatory embeddingNeed public awarenessNeed monitoringUsually imply land use restrictions to balance
ti i t tcompeting user interests.
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Definition of Vulnerability
Term Definition
S iti it t t i ti d t i d b th t lAquiferVulnerability
Sensitivity to contamination, determined by the naturalintrinsic characteristics of geological strata forming the overlyingconfining beds or vadose zone of the aquifer concerned
Threats to groundwater pollution are a function of:g pThickness & properties of overlying soilDepth to the water tableInfiltration rates and othersInfiltration rates, and others
A variety of vulnerability assessment tools may be used, e.g.: DRASTIC, PI methods
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How can groundwater pollution hazard be assessed?
Vulnerability Assessment
DRASTICDRASTICD - Depth to waterR N t R hR - Net RechargeA - Aquifer mediaS S il diS - Soil mediaT - TopographyI I f d I - Impact of vadose zoneC - hydraulic Conductivity
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Vulnerability Map
The ultimate goal of a vulnerability map is the subdivision of anThe ultimate goal of a vulnerability map is the subdivision of an area into several units showing the different degree of vulnerability.
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Lusaka Groundwater system in perspectiveLusaka Groundwater system in perspective
Lusaka is capital of Zambia with population of [at least] 1.3 million people with population growth rate of 3.7% per annum.Water supply coverage by municipal Service Provider (LWSC) is at 68%Water supply coverage by municipal Service Provider (LWSC) is at 68%. LWSC pumps 52% of water supply from groundwater. 48% comes from Kafue River 45km from Lusaka.
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Challenges
Karstic aquifer system characterized by shallow water tables andKarstic aquifer system characterized by shallow water tables and epikarstic zone extending between 5 and 25m Unregulated groundwater abstractiong gIncrease in unsafe disposal of solid and liquid waste in highly karstified aquiferS ll l iSmall-scale quarryingLow sanitation coverage of 17%
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Program to Develop Aquifer Management StrategyWater Quality Assessment
Hydrogeological InvestigationsG
Water Quality AssessmentPollution source/ risk
detectionVulnerability assessment
Groundwater balanceResource
t
Groundwater Information Groundwater Information System
Water point database
y
Remote SensingassessmentGroundwater
Modelling
Water point databaseHydrometric & water
quality monitoringGIS/Thematic Mapping
Remote SensingLand useKarst features &
geological structuresGIS/Thematic Mapping
D l t f d t
geological structures
Development of a groundwater management strategy
C lt tiR i P t ti Z i
Management guidelines
Consultative Process
Review Protection Zoning
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gg
Lusaka Groundwater SystemsPlateau of 3 000 sq km covering Lusaka City and adjacent parts ofPlateau of 3,000 sq.km covering Lusaka City and adjacent parts of Mwembeshi and Chongwe catchments
Quartzite & Schist
1. Main aquifer hosted by marbles of the Lusaka Dolomite – fast flowing GWLusaka Dolomite fast flowing GW
2. Subordinate aquifers within marbles of the Cheta formation located to the north and south – fast flowing GW
3. Minor Aquifers developed in schists and quartzites of the Cheta and Chunga formations and within alluvial deposits –l GW fl d filt tiREPUBLIC
OF ZAMBIA slower GW flow and more filtration
Lusaka Groundwater Systemsgroundwater flows (like surface water) from the higher (potential / water table) togroundwater flows (like surface water) from the higher (potential / water table) to the lower (potential / water table) Regional flow (shown here) but locally it can differ due to pumping of boreholes
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Some Past Water Quality studies conducted on the Lusaka Aquifers
ECZ, Lusaka Groundwater Contamination Assessment Project 2003. Concentrated ona) Libala Tipping sitea) Libala Tipping site. b) Leopard’s Hill –c) Lusaka industrial area )
UNEP, Assessment of pollution Status and Vulnerability of Water Supply Aquifers of African cities, 2005
Th t i t t t lit bl i th j t fThe most important water quality problem in the project areas of John Laing and Misisi is faecal pollution together with the associated disease-causing organisms Water from boreholes is less affected by bacteriological problems than that from shallow wells Conductivity and nitrate generally show elevated levels duringConductivity and nitrate generally show elevated levels during the dry season and lower concentrations during the wet season, probably resulting from dilution due to increased saturation in the aquiferREPUBLIC
OF ZAMBIA aquifer
Chemical Results GW Quality in Lusaka-Apr/May 2010
Piper DiagramResults groupedResults grouped
according to lithology and nitrate content
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ConclusionsUntreated wastewater from households and industry infiltrate into theUntreated wastewater from households and industry infiltrate into the soil and endanger aquifers and thus the drinking water supplyThe Lusaka Aquifer management strategy will depend on thorough assessment of:assessment of:
Groundwater potentialCurrent pollution statusPotential risks and vulnerability of the Lusaka groundwater system
Development of suitable management concepts that take specific situation in and around Lusaka into account
Thus decentralized sanitation and wastewater treatment concepts are some alternatives that could be usedThe concept of protection zones, the separation of abstraction, renewalThe concept of protection zones, the separation of abstraction, renewal and catchment area is essential for sustainable drinking water supplyIntegrated concepts can help in the long run to save considerable investments in water treatment and supply schemes as well as forinvestments in water treatment and supply schemes as well as for health services
Successful implementation will rely on institutional framework and capacitiesREPUBLIC
OF ZAMBIAcapacities