groundwater in big cities, use, consequences, impacts of climate change and response options karen...
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Groundwater in big cities, use, Groundwater in big cities, use, consequences, impacts of climate consequences, impacts of climate change and response optionschange and response options
Karen G. VillholthKaren G. VillholthGroundwater Specialist, Senior ResearcherGroundwater Specialist, Senior Researcher
GEUSGEUS, Geological Survey of Denmark and Greenland, Geological Survey of Denmark and GreenlandCopenhagen, DenmarkCopenhagen, Denmark
FAU Conference 2000FAU Conference 2000CCopenhagen Business School, Denmark, May 15, 2008openhagen Business School, Denmark, May 15, 2008
Groundwater development in selected countries
0
50
100
150
200
250
1940 1960 1980 2000
Gro
un
dw
ater
wit
hd
raw
al, c
ub
ic k
m/y
ear
India
USA
China
Bangladesh
Pakistan
Mexico
W.Europe
Tunisia
South Africa
Sri Lanka
Vietnam
Spain
Ghana
Ref: Shah, 2004
Importance of GW for citiesImportance of GW for cities
• Groundwater is the main source of Groundwater is the main source of domestic-potable water supply in most domestic-potable water supply in most European countries (European countries (Water Economy Water Economy Prospects for 1990 and 2000, Prospects for 1990 and 2000, 1982)1982)
• In general, GW is the primary source for In general, GW is the primary source for domestic water supply and hence domestic water supply and hence significant for most citiessignificant for most cities
• Quantity-wise, GW use for cities is less Quantity-wise, GW use for cities is less than the use in agriculturethan the use in agriculture
Reasons and advantages of Reasons and advantages of using groundwater for citiesusing groundwater for cities
• Surface water exhausted or pollutedSurface water exhausted or polluted
• New drilling and pumping technologyNew drilling and pumping technology
• Groundwater is generally of a good, Groundwater is generally of a good, reliable and constant quality and reliable and constant quality and temperature suitable for drinking water temperature suitable for drinking water with no or little pre-treatmentwith no or little pre-treatment
• Groundwater can be developed Groundwater can be developed incrementally and with less capital incrementally and with less capital investmentinvestment
Feature Groundwater resources and aquifers
Surface water resources and reservoirs
HYDROLOGICAL CHARACTERISTICSHYDROLOGICAL CHARACTERISTICS
Storage volumeStorage volume Large to very large small to moderate
Resource areasResource areas relatively unrestricted restricted to water bodies
Flow velocitiesFlow velocities very low moderate to high
Residence timesResidence times decades/centuries weeks/months
Drought propensityDrought propensity generally low generally high
Evaporation lossesEvaporation losses low and localized high for reservoirs
Resource assessmentResource assessment high cost and significant uncertainty lower cost and often less uncertainty
Abstraction impactsAbstraction impacts delayed and dispersed immediate
Natural qualityNatural quality generally (but not always) high variable
Pollution vulnerabilityPollution vulnerability variable natural protection largely unprotected
Pollution persistencePollution persistence often extreme mainly transitory
SOCIO-ECONOMIC FACTORSSOCIO-ECONOMIC FACTORS
Public perception of resourcePublic perception of resource unconnected and replenishable limited, aesthetic
Development costDevelopment cost generally modest often high
Style of developmentStyle of development mixed public and private largely public
Knowledge of resource and Knowledge of resource and importanceimportance
Sparse, use underestimated, impacts disregarded
well-developed, use well-documented
Groundwater Surface water
Pre-development
Post--development (T1)
Post--development (T2)
Impact in response to changeImpact in response to change
Example from Dhaka, Example from Dhaka, BangladeshBangladesh
Δ=22%
Δ=30m over 30 years
GWL decline, example from GWL decline, example from ChinaChina
Hydrograph depicting water-table elevations beneath Luancheng Agro-Ecological Research Station (Chinese Academyof Sciences), Luancheng County, Hebei Province, 1974-2002.
Δ=20m over 35 years
Dramatic changes of depression cones Dramatic changes of depression cones in Cangzhouin Cangzhou
6-1973
6-2000
6-1995
2-1981
mm
Saltwater intrusionSaltwater intrusion• Inflow of saltwater into freshwater aquiferInflow of saltwater into freshwater aquifer
• Origin of saltwater:Origin of saltwater:– Seawater in coastal areasSeawater in coastal areas– Geological saline deposits in deeper formationsGeological saline deposits in deeper formations– Influx or accumulation from irrigated Influx or accumulation from irrigated
agricultureagriculture
In coastal areas there is a In coastal areas there is a natural balance between salt natural balance between salt and freshwater and freshwater
fresh groundwater
ground surface
saline groundwater
seaphreatic water table
zone of diffusion
im pervious layer
Subsidence, impactsSubsidence, impacts
• Gives problems for infrastructure, Gives problems for infrastructure, buildings, pipelinesbuildings, pipelines
• Flooding and drainage patterns Flooding and drainage patterns changedchanged
• Causes secondary GW contamination Causes secondary GW contamination from breakage of underground pipes from breakage of underground pipes and tanks and tanks
What is subsidence?What is subsidence?Before After
Example of subsidence,Example of subsidence,San Joaquin ValleySan Joaquin Valley
GWL
Landsurface level
Relation btw. subsidence and Relation btw. subsidence and GWL declineGWL decline
Groundwater pollution Groundwater pollution sourcessources
GW pollution riskGW pollution riskPollution risk
low
high
high
Load is high, but vulnerability is low
Vulnerability high, but load is low
UrbanizationUrbanization
• Generally, urbanization decreases the Generally, urbanization decreases the recharge to aquifers (pavements, storm water recharge to aquifers (pavements, storm water drainage)drainage)
• However, depending on the primary source of However, depending on the primary source of water supply and the means of discharging water supply and the means of discharging wastewaters, GWLs may be affected differentlywastewaters, GWLs may be affected differently
Climate changeClimate change
• There is accumulating evidence that the climate There is accumulating evidence that the climate is changing on a global scaleis changing on a global scale
• Exact effects not known as well as the speed, Exact effects not known as well as the speed, extent and local distribution of themextent and local distribution of them
• Some effects seem inevitable:Some effects seem inevitable:– Water level rises due to global warmingWater level rises due to global warming– More variability and unpredictability in climate and more More variability and unpredictability in climate and more
‘extreme’ events‘extreme’ events– Dry regions becoming drierDry regions becoming drier
• Effects compounded by other human influences Effects compounded by other human influences (e.g. intensive water exploitation)(e.g. intensive water exploitation)
• Most vulnerable areas: Arid areas, big coastal Most vulnerable areas: Arid areas, big coastal cities, large tropical deltascities, large tropical deltas
Climate change on GW in Climate change on GW in citiescities
• GW can be a drought prevention strategy but GW can be a drought prevention strategy but only to a certain extentonly to a certain extent
• GW over-abstraction and flooding can occur at GW over-abstraction and flooding can occur at the same timethe same time
• Energy intricately linked to GW exploitationEnergy intricately linked to GW exploitation• CC exacerbate existing problems of GWCC exacerbate existing problems of GW
Post-Modern Water Post-Modern Water BalanceBalance
Changes in Water Availability
Precipitation Change
Increased Valuation/Economic
Breakpoints
Water Contamination
Trans-boundaryDisputes
Salt-water
intrusion
Virtual Water ImportsAnd Exports
Increased Water Demand for Agriculture, People and Ecosystems
Changes in Water Availability
Precipitation/Recharge Change
Cost-Effective WaterTreatment andConservationTechnologies
Ground Water Contamination
Trans-boundary
Flows
Salt-water
intrusion
Virtual Water ImportsAnd Exports
Increased Pumpage to Meet Domestic, Agricultural, Industrial and
Ecosystem Demands
Baseline situation
0
Availability and accessibility of adequate quality groundwater greatly exceeds small dispersed demand
Registration of wells required, together with maps of occurrence of usable resources
Incipient stress an
1
Growth of aquifer pumping, but only few local conflicts between neighbouring abstractors
Simple management tools (e.g. appropriate well-spacing according to aquifer properties)
Significant stress
2
Abstraction expanding rapidly with impacts on natural regime and strong dependence of stakeholders on ressource
Regulatory framework needed, based on comprehensive assessment
Unstable development
3
Excessive abstraction with irreversible aquifer deterioration and stakeholder conflicts
Regulatory framework with demand managemnt and/or artificial recharge urgently needed
Stable development
4
High-level of abstraction, but sound balance between stakeholder interests and ecosystem needs
Integrated management with high-level of user self-regulation, aquifer monitoring and assessment
timeTot
al a
bstr
actio
n
Num
ber
of
wel
lsSustainable level of
ressource development with acceptalbe impacts
under present conditions
Some response optionsSome response options
• More focus on GW, monitoring, permits, More focus on GW, monitoring, permits, • GW mgt. as an integral part of IWRMGW mgt. as an integral part of IWRM• Combine demand and supply mgt.Combine demand and supply mgt.• Awareness of general public => genuine Awareness of general public => genuine
stakeholder participation in groundwater stakeholder participation in groundwater protectionprotection
• Capacity building => Research into mgt. => Capacity building => Research into mgt. => informed mgt.informed mgt.
• Advocacy at the policy level => importance of Advocacy at the policy level => importance of GW acknowledged and incorporated into policies GW acknowledged and incorporated into policies and institutionsand institutions
• Climate change a driver for GW emphasisClimate change a driver for GW emphasis• No blanket policyNo blanket policy