Groundwater protection strategy

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Groundwater protection strategy

• Troels Kærgaard Bjerre
• Odense Water
• GroPro International Conference
• ATV JORD OG GRUNDVAND
• KLARSKOVGAARD
• 15. - 17. september 2008

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Agenda

• Odense Water
• Background
• Groundwater protection strategy of Odense Water
• Conclusions
• Perspectives

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Odense
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Facts and figures about Odense Water

• Approximately 2600 common water utilities in
  Denmark with total abstraction of approximately
  400 mill. m³/year.
• Odense Water is one of the biggest water utility
  with a abstraction permission of 13,8 mill.
  m³/year.
• Groundwater abstraction on 7 wellfields.
• 42 abstraction wells (25 to 100 m deep).
• Geological setting Glacial deposits on a
  basement of paleocene chalk and marl.
• Aquifers Glacial sand- and graveldeposits and to
  a small extend paleocene chalk.

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Major threats towards the wellfields of Odense
Water

• Quantitative threats
• Urbanization
• Environmental targets
• Climate change
• Qualitative threats
• Pesticides
• Chlorinated solvents
• Other org. haz. subst.
• Nitrate
• Chloride
• Hardness (Ca and Mg)
• Arsenic

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Why is groundwater protection a hot issue in
Denmark?

• 99 of the drinking water in Denmark comes from
  groundwater!
• The National Groundwater Policy of Denmark!
• Action plans for groundwater protection!

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The National Ground Water Policy of Denmark

• Objectives
• Production of drinking water should be based on a
  decentralized abstraction structure.
• Protection against exploitation of groundwater.
• Production of drinking water should be based on
  clean ground water no advanced treatment.
• Protection against ground water pollution.
• Water abstraction should be balanced against
  nature and surface water objectives.

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Action plans for groundwater protection

• State authorities carry out a detailed
  hydrogeological investigation of the ground water
  ressources in Denmark.
• The investigations are financed by tax on
  abstraction permissions
• From 1999 - 2006 1.054 mill. kr. (140 mill.
  Euro).
• The results are used by local authorities as the
  foundation of action plans for ground water
  protection.

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Ground water protection at the wellfields of
Odense Water

• At present a detailed hydrogeological
  investigation are being carried out by the state
  authority in cooporation with Odense Water
• The results of the investigation is expected by
  2009 and forth
• The first groundwater protection plan is expected
  in 2010
• Meanwhile we are getting prepared for the
  effort..

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Groundwater protection strategy of Odense Water

• Proactive role in ground water protection
• Basis for cooporation with authorities
• Framework for our future investments in ground
  water protection
• The aim is cost-effective investments in ground
  water protection for the benefit of our consumers
  and their descendants

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Groundwater protection strategy of Odense Water
Headlines

• General actions (geographically unspecific)
• coorporation with environmental authorities
• communicating the need for groundwater protection
• protection of interests through The Danish Water
  and Wastewater Association
• education
• etc.
• Specific actions (geographically specific)
• based on an detailed hydrological investigation
• detailed zonation of catchments (areas of
  interest)
• program of measures

!
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Premises for specific actions

• Centralized wellfields - considerable ground
  water abstraction help to ensure
  cost-effectiveness in ground water protection.
• Sustainable ground water abstraction - minimizes
  deterioration of the ground water quality due to
  exploitation. Consideration of vulnerable nature.
  
• Optimized abstraction strategy - minimizes human
  and natural threats towards groundwater quality
  on the wellfields.
• Up to date waterworks - high technical standard
  minimizes the risks of polluting the drinking
  water from source to consumer.

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Subdevision of the catchments Focus

• Ground water recharge
• Ground water vulnerability (nitrate)
• Travel time (based on numerical modelling and
  particle tracking)

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Subdivision of the catchments Terminology
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Travel time

• Negative correlation between transportation time
  and risk of contamination.
• Transportation time separates the near from the
  distant catchment.
• Near catchment Zone 1-3
• Distant catchment Zone 4-6
• Why use travel time in the aquifer instead of
  total travel time?
• Why 25 years?

Life expectancy map
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Why 25 years?

• Inspired by Dutch and Canadian practice.
• Exclusion of particles trapped in aquitards and
  inclusion of the hydrologically active parts of
  the saturated zone.
• General assumptions and experiences with
  degradation, dispersion, diffusion and dilution
  of organic hazardous substances in groundwater.
• Butit is a rather pragmatic solution that
  works quite well in the hydrogeological setting
  of Denmark.
• It is certainly a big step in the right direction
  towards cost-effective investments in groundwater
  protection, but it is not rocket science.

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Wellhead protection zones (BNBO)

• BNBO1 Travel time less than 1 year.
• BNBO2 Travel time between 1 and 2 years.
• Differentiation of groundwater protection near
  abstraction wells.
• Why?
• Not all threats in the proximity of the
  wellfields are equal.

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Wellhead protection zones (BNBO)
1 year
2 years
25 years
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Conclusions

• The measures are well known and well tested in
  Denmark. But the combination of measures and
  areas of interest calls for attention.
• A detailed subdivision of the catchments based on
  knowledge about groundwater recharge, aquifer
  vulnerability and travel time.
• The use of travel time through introduction of
  differentiated wellhead protection and the 25
  year boundary distinguish the strategy from
  common practice in Denmark.
• The use of travel time in the groundwater
  protection strategy gives more attention to the
  threats towards the wellfields.

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Perspectives

• Well Vulnerability A Quantitative Approach for
  Source Water Protection, Ground Water, vol. 44,
  nr. 5, p. 732 742 by Frind, E.O., Molson, J.W.
  and Rudolph, D.L.
• Integration of travel time in the vulnerability
  assessment.
• Aquifer vulnerability 3D groundwater
  protection.
• Well vulnerability 4D groundwater protection.
• This knowledge is of great importance when..
• prioritizing the groundwater protecting actions
  in a cost-effective manner.
• planning hydrogeological surveys.

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• It is time the thoughts behind the concept well
  vulnerability gains more attention in Denmark
  like the well established concept aquifer
  vulnerability.
• Because..at the end of the day a drinking water
  producer shall be more concerned about the
  consumers than the aquifers.

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Thank you for your attention!